Building and method for erecting a building

Abstract

The building (E) includes zones (ZW) with walls (5) and a structure (1) that comprises: prefabricated columns (2); prefabricated girders (3); prefabricated floor elements (4); wherein the columns (2) have a rectangular transversal cross-section; and the column (2) is hidden in the thickness of the wall (5); and / or placed at the junction of two walls (5) forming an angle between them, so that the construction of the building (E) can be particularly fast and without props.

Description

[0001] BUILDING AND METHOD FOR ERECTING A BUILDING

[0002] TECHNICAL FIELD

[0003] The invention focuses on the field of buildings that include a large number of walls, including fagades and interior partition walls, such as residential buildings, hospitals, hotels, etc.; and on how to make their structural system compatible with this large number of walls while consuming a minimum of useable area.

[0004] STATE OF THE ART

[0005] There is currently a wide variety of materials and structural solutions for building construction. However, none of the existing solutions optimally combines the existing options when the aim is to achieve the following features at the same time: i) low cost, ii) high construction speed, iii) high structural efficiency (i.e. efficient use of materials), iv) high structural resilience, v) high durability, vi) hiding the structure within architectural elements, such as the walls of the building. In order to analyse the listed features (i, ii, iii, iv, v, vi) for each of the different materials and structural types currently existing for the formation of building structures and how they are combined, all of them will be analysed from 5 perspectives:

[0006] a) Material of the structural members

[0007] b) Type of vertical structure (columns, walls), according to their cross-section

[0008] c) Type of vertical structure (columns, walls), according to number of the number of storeys and of the material

[0009] d) Type of girder, according to the material

[0010] e) Type of girder, according to the cross-section [only for prefabricated concrete]

[0011] f) Type of girder, according to connection with columns

[0012] g) Type of floor

[0013] a) Material of the structural members

[0014]

[0015]

[0016] b) Type of vertical structure (columns, walls), according to their cross-section

[0017] &

[0018]

[0019] c) Type of vertical structure (columns, walls), according to number of storeys and of the material

[0020]

[0021]

[0022] d) Type of girder, according to the material

[0023]

[0024] e) Type of girder, according to the cross-section [only for prefabricated concrete]

[0025]

[0026] f) Type of girder, according to connection with columns

[0027] &

[0028]

[0029] g) Type of floor

[0030] &

[0031] &

[0032]

[0033] &

[0034] &

[0035] &

[0036]

[0037] In each of the 8 table charts above [a) to g)], the different materials and / or structural types most commonly used in construction have been indicated in the left column and the right columns have been used to assess to what extent the different materials and / or structural types are good according to the criteria described at the beginning [i) to vi)].

[0038] To ease the reading of the table charts, in the right columns, the highest values in the evaluations of each material and / or structural solution, according to criteria (i) to (vi), have been highlighted using bold type. As a summary, in the left column, the material and / or structural solution that stands out in a greater number of criteria (i) to (vi), has been highlighted also using bold type.

[0039] Summarizing the results of the table charts, we see that the most optimal combination of materials and structural elements according to criteria (i) to (vi) is the following:

[0040] a) Material for structural elements, which best meets criteria (i) to (vi): Prestressed concrete (prefabricated)

[0041] b) Type of vertical structure (columns, walls), according to cross section, which best meets criteria (i) to (vi): Rectangular column or wall

[0042] c) Type of vertical structure (columns, walls), according to number of heights and material, which best meets criteria (i) to (vi): Prefabricated multi-storey column (precast concrete) d) Type of girder, according to material, which best meets criteria (i) to (vi): Prestressed concrete (prefabricated)

[0043] e) Type of girder, according to cross section [only for prefabricated concrete], which best meets criteria (i) to (vi): Rectangular down-dropping girder (narrow web) and T downdropping girder (narrow web)

[0044] f) Type of girder, according to connection with pillars, which best meets criteria (i) to (vi):

[0045] Fixed girder - column junction

[0046] g) Type of slab, which best meets criteria (i) to (vi): Precast hollow core slabs with deep grooves or protrusions on top face & in situ topping (completely fixed floor).

[0047] There are currently no structural solutions for buildings that meet all of these features, for the following reasons:

[0048] • Despite the advantages of prefabricated concrete and especially prestressed elements, the construction of buildings using this type of structural members is still very unusual today in most countries.

[0049] • This is because the know-how on the design of prefabricated structures is currently concentrated in a small number of designers, usually the manufacturers of prefabricated products themselves. This is because training in the design of prefabricated (prefabricated) structures is not included in the curriculum of almost any faculty of architecture or architectural engineering. However, it is more common for industrial engineering and civil engineering faculties to include training in this field. • As a conseguence, the construction of architectural buildings using this type of elements is still very unusual today. Indeed, construction with prefabricated elements today is basically limited to industrial buildings construction, certain public infrastructure buildings (schools, hospitals) and certain large-scale buildings (stadiums, shopping malls, etc.).

[0050] Although some public infrastructure and large-scale buildings are designed using prefabricated elements, the design of prefabricated elements is basically in the hands of manufacturers, who have their design teams made up of engineers, who either do not have the appropriate architectural sensitivity or cannot invest their working time in designing solutions that meet the needs of architects.

[0051] However, the largest number and volume of buildings currently constructed worldwide are residential buildings (by far, if we compare it to any other type of building). Beyond residential, buildings such as hotels, offices, hospitals and schools are also common. With some exceptions (which are indicated below), all these types of buildings share several features:

[0052] • These are buildings designed by architects, or with architectural design criteria.

[0053] • These are multi-storey buildings (except for some residential buildings and schools) • These are buildings with many interior partition walls (except for office buildings). The interior partitions in these buildings, include a significant number of walls that will hardly need to be demolished or modified throughout the useful life of the building. For example, walls that separate one dwelling from another in a multi-family building; walls that separate hotel or hospital rooms, etc.

[0054] In these sort buildings, it would be beneficial to be able to use prefabricated concrete structures, since they are very cheap structures (i), very quick to build (ii), might be designed with an efficient use of materials (iii), might be designed for high structural resilience (iv), with high durability (v) and might be designed with a good capacity to hide the structure (vi), so that it does not interfere with the architectural design.

[0055] However, in buildings that need to be designed according to architectural criteria these features have not been met until now, mainly because architects have not been inclined to design with prefabricated elements due to their lack of training in this field, and because manufacturers have not approached the needs of architects either, as they have mainly industrial engineers and civil engineers in their design teams.

[0056] In buildings such as office buildings, large zones of the interior of the building have no partition walls. Also, in almost any building (including housing buildings, hotels, hospitals, etc) there’s at least some zones that are free of interior partition walls, such as reception calls, corridors, etc. So, in office buildings and in those zones of all other buildings that are free of interior partition walls, it is often demanded by architects that ceilings are flat of almost flat. Having flat ceilings in those areas is an important feature to architectural design because in these areas it is very common that facilities’ ducts or cables (electricity supply, water supply, gas supply and I or HVAC ducts) have to be arranged right under the structural floor. The need to place such facilities right under the structural floor normally enters in direct conflict with the optimization of the cost of the structure. This is because, most the times, the cheapest floors can be achieved when floors are supported on beams that have large down-drops under the soffit of the floor. Such beams with deep down-drops, thus, typically conflict with the need to place the mentioned facilities ducts or cables.

[0057] Besides, in such zones free of walls, it is usual that architects design spaces including suspended ceilings (= dropped ceilings) so as to hide the mentioned facilities and also to hide the structural floors. So, when in such spaces the structure includes beams with large downdrops such beams may conflict with the suspended ceilings, and having an aesthetic impact.

[0058] Also, when structural designers and inventors design structural solutions that are new, they often focus mainly in the structural soundness of the solution in its most general meaning. Structures designed after this approach may be very efficient in terms of structural capacity and soundness. However, when one thinks in detail that any structure has to be built (= needs an erection process), and also that the structure is among the first parts of the building that are erected, it comes up that during the transitory time that is the erection process two specific situations happen that may no longer happen once the building has been completed:

[0059] • During the erection process some parts and / or materials of the structure are incomplete and thus they are unstable. Those parts and materials need temporary means (props, shoring, formers, molds, scaffolds, screws, pins, etc) to hold them in place until these parts and materials reach their final condition, and they also need heavy machinery (cranes, trucks, etc) to move them around, as structural parts and materials are often very heavy.

[0060] • During the erection process of the structure the definitive walls (fagades, partitions) and railings are normally not in place. As a consequence, there are serious risks that workers at the job may fall down the structure and hurt themselves or third parties or even put lives in risk. That is why temporary railings, nets or other similar means need to be arranged around the structure to prevent those risks. Suck security means need to be arranged on the structure under construction itself, so the structure need to be ready to accommodate the connections these security means to the structure.

[0061] However, the specific loading situations that happen under construction and the specific details that should be considered in the structure in order to accommodate the connections with the temporary security means are most of the times overlooked by structural designers and inventors of structural systems.

[0062] DESCRIPTION OF THE INVENTION

[0063] The present invention describes buildings and methods for erecting buildings in which the structures are formed using prefabricated self-supporting elements, and therefore the construction can be particularly fast and without props, and in which the prefabricated structures include columns, girders and floor elements, which are at the same time particularly efficient from a structural point of view and very slender, so that the columns and girders can be hidden in the walls (facades and partition walls). Furthermore, the use of floors formed by particularly slender floor elements fixed with moment- resistant junctions to the beams allows the beams and walls to have smaller sections because they support lighter floor structures and because the fixed junctions of slabs to the beams make the whole structure more resistant to horizontal forces (wind, earthquake, etc.). As a result of it all, lighter structures with larger spans are possible, leading to buildings with cheaper foundations, because fewer foundation units are required and / or each foundation supports less load than in a conventional building.

[0064] The present invention is particularly useful for buildings or areas of buildings where there are many walls or partition walls. Its application can also be useful for buildings or areas of buildings where there are not many (or no) partition walls. This is because there is always the possibility, thanks to the invention, that the columns and / or the girders are hidden within the fagade walls of the perimeter of the building.

[0065] In the current document, the term girder will be used, and eventually beam may be used as a synonym. Girder means here a linear structural member of primary importance, which works under one-way flexure, and it is directly supported on vertical structural members (columns or walls). The girder is also a member typically supporting structural members of secondary importance, which also work under one-way flexure. These structural members of secondary importance are named here as floor elements, or sometimes floor members. Floor members supported on girders, depending on the sort of structural system, may either be flat members (often called slabs or planks) or linear members (often called beams, joists or purlins) that are typically spaced, and support non-structural members (often called floor blocks or formers).

[0066] Note how generally speaking the term ‘beam’ sometimes is used to refer to the primary structural member (girder) or to the linear secondary structural member (joist) . That is why, in this document, the term girder is preferred over beam, that could lead to more confusion.

[0067] The term one-way floor systems will be used, being the one-way floor systems formed by girders (primary structural member) and slabs (flat secondary floor system). That is why, the systems described here should not be confused with two-way floors.

[0068] Also, the term self-supporting one-way structural members, will be referred to as girders (for the linear primary members) and floor elements (for the flat secondary members). A self-supporting linear structural element must be understood here as a member that is designed to be supported only at its two ends and is able to span from these two ends without the need of props, shoring or formers during the construction process, during which the self-supporting element will have to endure notable increases of load. For example, a self-supporting girder will be able to withstand, without shoring, the weight of the floor slabs supported on it, the weight of the fresh concrete poured on the slabs and the girder to form the topping, and the weight of the workforce and other auxiliary machinery and materials needed during the erection process. A self-supporting floor element should be understood in the present document as a hollow core slab able to withstand its weight, the weight of the topping and the weight of the workforce and machinery without the need of props or shoring.

[0069] Thus, the self-supporting prefabricated floor elements referred to in the present document must not be confused with that kind of small floor elements (such as floor blocks and the like) that are placed one by the other in the direction of the span to function as formers or as part of the structure once that concrete has been poured after them, but that during the erection process need formers and / or props, as these small members are not able to span for themselves from one end to the other to primary structural members such as walls, columns or girders.

[0070] In this document, the term linear applied to one-way structural elements refers to elements where one dimension, typically one horizontal, is much larger than the two others. This larger dimension runs along what is called the axis of the member, and the distance from the two ends of the axis is called the span. The two other dimensions of the member are used to define the cross-section.

[0071] In this document, the term planar applied to one-way structural elements refers to elements where one dimension, typically one horizontal, is much larger than the two others, being this one called the span. Of the two other dimensions, again there is always one clearly larger than the other, being the larger one the horizontal. Thus, the smallest dimension is always the vertical one, so called depth.

[0072] In this document, the term prefabricated structural member can be considered as equivalent to industrialized structural member. This is, any structural member that has been produced away of the construction job, typically in a factory or a shop, and that is transported to the job job as a finished or almost finished component, ready to be assembled, by means of minor operations, to other structural components or to other parts of the structure formed at the job job. Thus, the term prefabricated must not be understood as restricted to one material, such as concrete. A prefabricated structural member may also be made, for example, of steel or timber.

[0073] To overcome the shortcomings described in the state of the art, in a first aspect of the present invention is a building including zones with walls and including a structure that comprises: - prefabricated columns made of reinforced concrete;

[0074] - prefabricated girders supported at their ends on the columns; and

[0075] - prefabricated floor elements supported at their ends on the girders;

[0076] wherein the columns have a rectangular transversal cross-section such that in the crosssection of these columns the direction of the depth coincides with the largest size of the transversal cross-section and the width direction coincides with the smallest size the transversal cross-section, such that in those zones having walls, the rectangular columns of the building are:

[0077] embedded within a wall, the column being hidden in the thickness of the wall, with the direction of the depth of the column being parallel to the direction of the wall; and / or placed at the junction of two walls forming an angle between them, with the direction of the depth of the column being parallel to the direction of one of the walls and the direction of the other wall being transversal to the depth of the column, such that the column is embedded in the thickness of the wall parallel to the depth of the column; being the thickness of each of the walls respectively larger than the corresponding dimensions of the web of the respective girders and being each dimension of the respective walls larger than the smallest dimension of the cross-section of the respective columns for those columns which direction of the depth coincides with the direction of the wall.

[0078] A building with a structure that uses prefabricated structural members has a number of advantages, both regarding the erection process and the overall cost and efficiency of the structure:

[0079] • Prefabricated structural members will typically be delivered to the job as completed components and their assembly will typically be completed with only a few operations (screwing, welding, pouring reduced amounts of concrete or grout, etc.). Thus, workforce requirement at the job will be reduced, and the erection process of the structure may be rapid.

[0080] • Prefabricated structural members may be designed to be self-supporting, and may not need shoring.

[0081] • In industrially produced structural members, dimensional control is much superior.

[0082] Placement of perforations, junctions of members, cuts, and shapes in general can be guaranteed with tighter geometric tolerances. This allows for less material consumption, which is cheaper and more sustainable.

[0083] • Working at a shop or factory also allows to work for longer times, leading to higher production outputs. This is because weather conditions (extreme temperatures, rain, snow, wind, etc.) do not affect as much the production of the workforce as they do at the construction site, typically at the open air.

[0084] • Working at the shop or factory allows to use heavy and / or precision machinery, and powerful cranes to lift heavy loads.

[0085] • Working at the shop or factory makes it easier recover waste materials and recycle them.

[0086] Furthermore, a building with a structure that uses prefabricated concrete structural elements has a number of advantages in comparison to a concrete structure entirely cast in place. These advantages are mainly regarding the erection process and the overall cost of the structure:

[0087] • Prefabricated concrete structural members can be designed to be self-supporting. This will allow to place them at the job without using props or shoring, and without waiting for the concrete to harden to continue the erection of the structure. As a result, the erection process of the structure is accelerated. Also, the lack of props under the structural floors will allow that the placement of other non-structural components of the building can be done earlier, leading to a speeding up of the overall structure.

[0088] • In prefabricated concrete structural members, dimensions of members and the position of reinforcements within members can be much better controlled, given that dimensional tolerances in the production of concrete structural members at the shop are much smaller than dimensional tolerances of concrete members cast at the job. In structural members produced at the shop dimensions may be tighter, allowing for smaller cover of reinforcements and, when necessary, for connections more congested with reinforcement.

[0089] • In prefabricated concrete structural members, as concrete is produced at the shop, higher concrete quality is more easily feasible and controllable, as concrete is usually produced at the same factory where prefabricated members are produced. Typically, concretes produced at the factory of precast structural members are a 50% to a 200% stronger than concretes used to erect structures at the job, that typically use ready-mix concretes produced in plants away from the job. These higher strength concretes used in prefabricated members allow to use less steel and / or less concrete in the cross sections of members that mainly function under compressive loads (such as columns or walls). Also, the concretes used at the shop tend to use smaller aggregates, and may also use more fluid mixes (even self-consolidating mixes), than the mixes used at the job. This allows that prefabricated structural members can be more congested with reinforcement, if required, and it also guarantees a larger durability of precast members as compared to cast at the job members, because complete concrete covering of reinforcement is better guaranteed when small aggregate and / or fluid mixes are used.

[0090] • Prefabricated concrete members designed to work under flexure (girders, slabs, etc.) may be produced with optimal cross sections that are normally costly to produce at the job, as they ask for special formers that are not economically efficient for jobs cast in place. For example, hollow core slabs may be used as floor members, instead of solid slabs cast at the job (that consume a lot of material, and are very heavy), or waffle slabs cast in the job (that have a T cross-section which is less efficient in terms of cross section than a hollow core slab, that has an I cross-section). More or less, the same stands for girders and beams. Girders poured at the job with geometries other than rectangular are normally costly.

[0091] • In prefabricated concrete members designed to work under flexure (floor elements, girders) it is easy and cheap to introduce prestress forces, whereas prestressing concrete cast at the job structures asks for far more workforce and dimensional control, leading to more expensive structures. Using prestress in prefabricated members has several advantages:

[0092] o It allows to use much less steel than in reinforced (not prestressed) structures cast at the job, as prestressing steel has 3 times the strength of passive steel (deformed bars), and thus the amount of steel may be reduced by 3. o Prestressing concrete members designed to work under flexure (floor elements, girders) allows to reduce concrete consumption, as the depth of prestressed members may be reduced around 1 / 3 as compared to equivalent nonprestressed members.

[0093] • While it is true that prestressing at the job (using post-tensioning) may be apparently advantageous over prefabricated prestressed members, where prestressed reinforcement is typically only placed at the bottom face of the member, precast prestressed members designed as described in this document (including negativemoment reinforcements placed at the job both for girders and for floors) has interesting advantages over post-tensioned members (girders and floors) poured at the job: o Prestressed reinforcement embedded in precast has the advantage that it typically asks for less bottom cover than post-tensioning, given that posttensioning ducts have relatively large sections (which causes the upwards movement of the center of gravity of bottom prestressed reinforcement during the tensioning process) and also posttensioning ducts ask for much larger covers than prestressed reinforcement.

[0094] o In precast prestressed members where passive top reinforcement is placed at the job, fixity is achieved, and deflections are well controlled, allowing for precast prestressed members fixed at their ends to have depths very similar (or even smaller) than those required for post-tensioned members cast in place. o As precast prestressed members do not include prestressed reinforcement at their top face, or it is only required for erection phases but not in service phases, and the top passive reinforcement is embedded in a layer of concrete poured at the job, the result is a composite member, where the top part is a conventional reinforced concrete layer, where crack control requirements do not apply. So, at the top face of these composite (semi-prestressed) members, cracks in concrete are allowed. Whereas, for members post-tensioned at the job the need to control cracking both at the top and the bottom fibers of the member, will typically ask for additional prestressed reinforcement only to control cracks at the top, as negative moments are typically larger than positive moments. Also, top faces of post-tensioned members are typically very congested with passive and active reinforcement, causing post-tensioning tendons to have large top covers in these areas, making those tendons less effective.

[0095] Additionally, the fact that a column is rectangular, and that its smallest dimension (width) is less than the thickness of the wall with which it is aligned with, so that it can be hidden into the wall, has at least 6 advantages, 2 of an architectural nature and 4 of a structural nature:

[0096] • Architectural advantages:

[0097] o Unlike other columns that are placed next to walls, columns that are narrower than the walls have the advantage that the wall does not show a protrusion in the position of the column. This allows for the space in the room to be more usable, for example because furniture can be placed more easily next to the wall, even in the area where the column is.

[0098] o By placing columns inside the walls in those zones of buildings where walls are present, offers the chance of not placing columns in the middle of open spaces (e.g. inside a living room). Of course, this is only feasible in the case that the distances between the walls that may hide the columns are short enough for the floor elements to span over the distance between walls. Thus, by eliminating columns located in the middle open spaces, useable area is gained in the building.

[0099] • Structural advantages:

[0100] o In terms of resistance to horizontal actions (wind, earthquake, etc.) that are parallel to the largest dimension of the column (the depth), rectangular columns perform better than square or circular columns under the same gravity loads. o In terms of fire resistance, the fact that a column is narrower than the wall it is hidden in, has the advantage that the column is more protected against fire on its long faces and can therefore withstand more intense and / or longer-lasting fires. And regarding its short faces, since these are entirely embedded in the thickness of the wall, they may be considered as not exposed to fire at all. Thus, a rectangular and narrow column that is hidden in a wall is mainly exposed to fire on its long sides and not on its short sides. This makes the fire performance of this kind of column similar to that of structural walls, and much better than the fire performance of square columns, where the fire heats the column on all four sides, and, as a consequence, the corner reinforcements tend to heat up very quickly. In columns where fire heats two sides of the member forming a corner (such as in square columns that cannot be properly hidden in walls), the designer of the structure must add large coverings to corner reinforcements, and by so doing adding thickness to the column.

[0101] o As for durability, narrow columns that can be hidden in walls have a longer lifespan and / or require less covering on their reinforcements, thanks to the additional protection offered by the material of the wall that covers the column. o Given that this sort of hidden columns behaves particularly well against fire and in terms of durability, and therefore their reinforcements can have reduced coverings, their structural performance under normal loads improves. This is because thanks to small covers, reinforcements have a greater lever arm in the smallest dimension, which is the weakest. This feature allows the consumption of materials in the column to be optimized.

[0102] Moreover, the fact that girders have a web that is smaller than the width of the wall that has the same axis as the corresponding beam has various architectural and structural advantages (which are difficult to separate from each other):

[0103] • Architectural and structural advantages:

[0104] o The narrow web of the beam can be completely hidden inside the wall and has no architectural presence, so it will not be visually bothersome, nor will it be a nuisance when placing furniture next to the wall where the beam hides in. o As the beam is hidden inside the wall and it is not a visual or functional nuisance in the architectural design, the depth of the beam can be relatively large under the floor if this is convenient for structural reasons. The fact that the beam may have a large depth makes it particularly efficient at a structural level and, therefore, economical, because it consumes few materials.

[0105] o The structural efficiency of the beam also allows the beam to be light (by using little concrete) which in turn facilitates its transport, lifting, and assembly on site. A structure that includes this type of narrow-web beams along with narrow rectangular columns (smaller than the corresponding walls that have parallel axis) allows for the formation of frames with a notable rigidity in their plane, especially if the junction between beams and columns is designed to be fixed. These frames provide the building with great strength and stability against horizontal forces in the direction of these frames; which is advantageous compared to structures with rectangular columns and / or flat slabs, without suspended beams.

[0106] The use of this type of narrow frames also has several advantages compared to structures entirely supported by prefabricated concrete walls, which are currently a trend in the market:

[0107] • The use of these narrow and stiff frames consumes much less material than the use of prefabricated concrete walls. This is because concrete walls use much more concrete and more steel.

[0108] • The use of narrow frames such as those described above allows to erect the structure of the building using fewer and lighter structural members than when the structure is erected with prefabricated concrete walls.

[0109] • By using narrow frames inside the walls, in areas where there are no columns or girders, this is in the part of the walls placed under the depth of the beam, and between columns, where building services (plumbing, electric wiring, etc.) can be embedded inside the wall. Also, their position may be modified or new services may be added in subsequent renovations of the building, providing the building with flexibility. Whereas, in the case of erecting the vertical supports made of reinforced concrete walls (precast or not), placing building services is very difficult, and it makes it then almost impossible to add new services or to modify the position of embedded services in the wall in subsequent renovations, given that those new embedments would mean carving in a structural member, causing vibrations and noise as well as new checks of the structural integrity of the building.

[0110] • By using narrow frames, in the event of a deep renovation of the building it would be possible to demolish the walls that surround the narrow frames to eventually allow the merger of the two rooms located on either side of the frame (and the old wall). Whereas, in the case of a building using concrete walls in the partition walls between useable spaces, in the event of a renovation these walls will not be available for demolition, causing the building to be much less flexible for future uses.

[0111] In some embodiments the floor elements are prefabricated and / or self-supporting.

[0112] When self-supporting prefabricated floors elements are used to form structural floors, the advantage is that their assembly does not require the use of props and, therefore, the speed of construction can be much greater for three reasons:

[0113] • Their structural capacity is such that they can support not only their own weight but also the weight of workers and machinery on them and the weight of fresh concrete poured on them to form the topping.

[0114] • It is not necessary to wait for the concrete poured on site on the slabs to completely harden before continuing to build the structure of the upper levels. Only 1 or 2 days after pouring the concrete of the topping its surface will normally be enough for workers to operate on it for the construction of upper levels.

[0115] • As there are no props, work can be done under the slabs immediately after they have been assembled.

[0116] In addition, self-supporting floor elements are usually several times longer than they are wide, as they are designed to rest directly on the beams (or walls) located at the two ends of the span covered by the self-supporting floor members. These elements are therefore typically long and large, and the assembly of a structural floor using this type of elements requires only a small number of assembly operations. This type of element should not be confused with small-sized prefabricated floor elements (usually with all three dimensions under 1 m) which are not self-supporting, i.e. they are not capable of supporting themselves during the assembly phase over the entire span from one beam to another, or from one vertical support (column or wall) to another. Therefore, these small prefabricated or industrialized floor elements (which in some cases only function a way to lighten the floor and, in some cases, can contribute to the strength of the structural floor) need to be supported by props and / or formwork during the roof construction phase, as they only integrated into the final structural after bottom reinforcements have been placed along with a certain volume of in-situ concrete poured over all these elements. In the structures including these small non-self-supporting elements, the props and / or formwork cannot be removed until the in-situ concrete has completely hardened. Therefore, the construction of floors with this type of small industrialized elements results in a much slower and more labor-intensive floor construction than construction made with the long and large self-supporting elements described in the present invention.

[0117] In some embodiments the walls are walls including fagades and main partition walls.

[0118] Here main partition wall should be understood as those interior partition walls that separate useable units that will only very improbably be merged, such as partition walls separating two dwellings in a multi-housing building, or partition walls separating two hotel rooms. These main partition walls will also typically thicker than secondary or interior partition walls, that are thinner and are much likely be removed or modified in case of a major reform of the useable unit. Thus, this embodiment, where columns and girders are aligned with walls that are facades and main partition walls, has the advantage of giving the building more flexibility in the event of a major renovation of the interior layout, where interior (or secondary) partition walls (such as walls separating sleeping rooms, the kitchen, the bathroom, etc.) will likely be torn down and replaced by other partitions for a new layout. In other words, when columns and beams are hidden in fagades and main partition walls, that is, walls placed in the perimeter of useable units; in case of modification of the interior layout, there will be more useable space, as columns will not “appear” at potentially inconvenient places at the interior of a useable unit.

[0119] In some embodiments the partition walls have a thickness between 15 cm and 25 cm.

[0120] These thicknesses can generally be considered as particularly reduced and it is difficult, when building a structure with in-situ concrete, steel or wood, to achieve columns with thicknesses under these values and / or beams with a web narrower than these dimensions. However, with prefabricated concrete, thanks to the precision with which work is carried out in the factory and the good structural behavior of reinforced concrete against buckling, it is possible to achieve columns and beams with these reduced dimensions.

[0121] Furthermore, having partition walls with these dimensions is very practical in terms of architectural design, because these thicknesses are usually sufficient to include in the partition walls all the materials necessary to achieve a proper separation of two spaces that must be thermally and acoustically independent.

[0122] In some embodiments, at least one of the prefabricated columns is placed with the direction of its depth being transverse to the direction of the depth of the rest of the columns of the building.

[0123] Having rectangular columns in the same building with their depth in perpendicular (or substantially transverse) directions is very advantageous because it will provide the building with good stiffness against horizontal forces in 2 transverse directions, which is equivalent to saying that the building will be able to have good horizontal stiffness against horizontal forces in any direction. This is because the forces resisted by columns arranged in two transverse directions can be combined to respond to horizontal forces in any direction.

[0124] In some embodiments the prefabricated columns have one or several of the following features: a) the prefabricated columns are made in one piece with a total height corresponding to the height of several floor levels of the building; b) the column includes corbels protruding beyond the rectangular plan of the column, meant for supporting the prefabricated girders, including such corbels a vertical protruding reinforcement, as a part of the erection anti-torque system of the prefabricated girder; d) the column includes at the level of each floor of the building a horizontal duct having an elongated cross-section, such that the largest dimension is placed vertically, and the longitudinal axis of the duct being horizontal and parallel to the direction of the depth of the prefabricated column, being such duct crossed by negative-moment reinforcement of the girder running through and along the duct, being the reinforcement placed at the job, and being the duct filled with cementitious material poured at the job;

[0125] e) the column includes at its top, at the junction with the column of the level above, at least two levelling devices;

[0126] f) the column includes at its top, at the junction with the prefabricated column of the level above, vertical ducts embedded in the column, arranged in such positions that allow for the insertion of vertical reinforcements protruding from the bottom of the prefabricated column above; g) the column includes vertical reinforcements protruding from its bottom, for the insertion of those reinforcements in vertical ducts embedded in the support below, being this support below either the prefabricated column below or the foundation of the column, being such ducts filled with cementitious material with limited shrinkage placed at the job.

[0127] The fact that columns have the height of several floors, this is that columns are multi-storey, has several advantages in terms of cost and erection speed. When columns are multi-storey erection is faster, because the number of elements to be assembled is smaller.

[0128] Another advantage of multi-storey columns is that the number of column-to-column junctions will be reduced, and this will typically mean costs reductions, as junctions in these members typically mean special devices and / or using high-strength grout to properly splice vertical reinforcements. Thus, minimizing the number of splices will typically mean cost cuts.

[0129] However, there’s also two limitations associated to using multi-storey columns. On the one hand, the total length and weight of these columns has to be carefully looked at, because the transportation and handling capacity of machinery may limit the number of storeys that a column can have. Considering these limitations, the range of storeys will often be between 2 and 5. On the other hand, when columns are multi-storey, beams must be interrupted at every junction with the column, and the bearing of the beam cannot be solved by placing the beam on top of the column. Instead, some sort of corbel is typically required.

[0130] That is why, in this embodiment, it is convenient that, at the level of each floor, concrete corbels protrude out of the floorplan of the column. The fact that the corbels are made of concrete, and not of steel, makes them cheaper.

[0131] The fact that the corbels include a vertical protruding reinforcement is particularly convenient as, when the beam (that includes a vertical duct to accommodate this vertical protruding reinforcement) is placed on the corbel, the duct including the vertical bar will be filled with grout, leading to junction beam-to-column junction able to resist to sort of critical forces:

[0132] • It will be part of a system, made of reinforcement and concrete or mortar, that as a whole is able to resist torque moments, preventing the beam to rotate due to torque both during the erection process and during the service of the structure.

[0133] • It will be part of a system, made of reinforcement and concrete or mortar, that as a whole is able to transmit positive moments of the beam to the column, and eventually to the beam placed at the other side of the column. In other words, a system able to transmit tensions of the bottom reinforcement of the beam into the column, through the corbel.

[0134] When prefabricated column is multi-storey, in order to allow the girders supported on this column to resist negative moments, that is, moments that cause tensions at the top face of the girders, it is very convenient that the negative reinforcement placed on a certain girder is continuous with the negative reinforcement of the girder in the span next to it, this is the girder placed at the other side of the column. So that the beams that are placed at both sides of a column can share the same negative reinforcement rebars, it is very convenient that the prefabricated column includes a horizontal duct that allows the passage of this negative reinforcement through the column. But, given that both the beams and the columns are particularly narrow, the negative reinforcement of beams will often ask for several rebars that can hardly be placed one beside the other. Instead, it is much more convenient that these negative-moment rebars of beams are “piled” vertically, this is placed one on top of the other rather than one beside the other. So, an embodiment of the invention where columns include at the level of each floor (= storey) a horizontal duct with an elongated cross-section, such that the largest dimension is vertical, is advantageous as it allows to pass through it the shared negative reinforcements, formed by several bars piled vertically, of the girders placed at one side and the other of the column.

[0135] The mentioned negative reinforcements of the girders may be included in the hoops formed by the stirrups protruding from the top of the girders. These negative reinforcements will typically come to the job, being loose within the protruding hoops. Once the girders are placed at each side of the column, and supported on the corbels, a worker will slide the negative reinforcements trough the horizontal duct in the column and into the hoops protruding from the top of the beam placed at the other side of the column.

[0136] After all the precast floor elements are placed, and the concrete of the topping is poured, the horizontal ducts passing through the columns will typically not be properly filled, because the concrete of the topping will normally not be appropriate in terms of aggregate size and consistency to properly fill that duct. Moreover, the concrete used for the toppings of the floors will typically have lower specified strength than the columns have. That is why in this duct will more conveniently be filled with low-shrinkage, high strength grout placed after the hardening of the topping.

[0137] Anyhow, having this duct filled with cementitious material will improve the durability of the negative-moment reinforcement passing through it.

[0138] It is particularly convenient that at the junction of two columns placed one on top of the other, the column above can be properly levelled, so as to guarantee that it is perfectly vertical. The best way to guarantee that is that on top of a column where another column is going to be placed, levelling devices exist. A minimum of two devices will be enough in order to guarantee levels in two faces of the column. Levelling devices, normally formed by steel plates, screws and nuts, are expensive, so their number should be minimized if the minimum cost of the structure is aimed.

[0139] However, it is common practice to use large amounts of certain particular sorts of levelling devices that not only function as levellers but also as splices of the vertical bars of the columns that are joined. Using this approach, will normally make columns very expensive, due to a large number of splicers-levellers will be needed.

[0140] In order to avoid large amounts of splicers-levellers, this embodiment reduces the number of levellers to a minimum of two, and these are not necessarily used also as splices. Instead, the splice of each vertical rebar of the column may be done, very cheaply, by means of vertical ducts placed at the top of the bottom columns, in such a position that coincides with vertical reinforcements protruding from the bottom of the prefabricated column above. For a proper splicing, the ducts will be filled with a cementitious material, normally high-strength low-shrinkage grout. Also, for a proper splice, the reinforcement protruding from the bottom of the columns above and inserted in the ducts that will be filled with cementitious material, beside the vertical ducts placed at the top of the columns below, will be the upper ends of the vertical reinforcement of the column (reaching the top of the column). Thus, the reinforcement of the top and bottom column will be placed in parallel along a bond length.

[0141] An analogous solution is as well cheap and guarantees the verticality of columns, for the junction of the foundation and the bottom end of a column supported on that foundation.

[0142] In some embodiments, those of the prefabricated girders that have their longitudinal axis parallel to the direction of the depth of the corresponding column or columns where each girder is supported, the girders have the corresponding width of the web not larger than the smallest dimension of the corresponding columns.

[0143] The fact that the width of the web is smaller than the thickness of the column is advantageous because it is a way to guarantee that the web of the beam will be entirely hidden in the thickness of the wall.

[0144] In some occasions, for the column to be hidden in the wall, the wall may need to increase locally its thickness, but this may only cause limited architectural inconveniencies. However, having to increase the thickness of the whole wall due to a thick web of the girder (beam) is more inconvenient in terms of architecture, as it would reduce excessively the useable area. That is why, keeping the thickness of the web of the girder (beam) not larger (or even smaller) than the thickness of the wall is advantageous in terms of architecture, especially in those cases where the columns need to be slightly thicker than the average of the wall.

[0145] In some embodiments, the prefabricated girders have a cross-section in the shape of a T, where the top part of the girders has a width larger than the web, thus forming a head of width, such that the top part of the cross-section has two flanges, one at each side of the web, that make it easier for the prefabricated and self-supporting floor elements to be supported on both sides of the top of the girders.

[0146] In this embodiment, the ‘head’ of the beam has three main advantages:

[0147] • It provides the beam with a larger moment of inertia, which makes the beam less deformable; which makes the beam more efficient and leads to a reduction of materials consumption.

[0148] • It causes the center of gravity of the cross-section of the girder to move upwards, thus leading to a larger effectivity of bottom prestressed reinforcement. This makes the beam more efficient and leads to a reduction of materials consumption.

[0149] • It allows for an easy bearing of the floor elements on both sides of the girder, despite the very narrow web of the girder. In some embodiments, prefabricated girders include a vertical duct at each of their ends, as well as a steel plate including a perforation placed on top of the vertical duct, as a part of the erection anti-torque system together with the vertical reinforcement protruding out of the corresponding corbel connected to the prefabricated column.

[0150] This embodiment allows to complete the antitorque system of the beam very fast, as it is only required to screw a nut at the top of the vertical reinforcement protruding from the corbel. This way, it is not necessary to fill the duct with grout -which is currently the most conventional method- to get the anti-torque system in operation. Thus, the beam can be loaded with floor elements without waiting for the grout to harden, and construction can be accelerated.

[0151] In some embodiments, girders, at their junction with a column have a cantilevered protrusion that has a cross section similar to that of the flange, and extends along all the dimension of the column and next to the vertical face of the column, forming a lintel that facilitates the support of the prefabricated and self-supporting floor elements during the erection phase, and the cantilevered protrusion functions also as a part of the erection anti-torque system.

[0152] This embodiment has the advantage that the cantilevered protrusion (or lintel) works as a part of the anti-torque system during the erection process, to prevent the beam from twisting or turning when it is loaded from only one side. This anti-torque system functions when floor elements are placed only (or in a larger number) on the flange of the girder that does not extend to form a cantilevered protrusion (or lintel). In such a case, the cantilevered protrusion (or lintel) gets in contact with the long vertical face of the column, so that the turning or twisting of the girder is prevented.

[0153] However, the turning or twisting of the girder is not prevented in the opposite direction. That may happen in the event that floor elements are placed only (or in a larger number) on the flange of the beam that includes the cantilevered protrusion (or lintel). In the event of such a torque moment, the anti-torque system is based on another mechanism, based on the reinforcement vertically protruding from the corbel, that is embedded in a vertical duct of the girder, filled with cementitious material.

[0154] As it has just been explained, in this embodiment the anti-torque system based on the reinforcement vertically protruding from the corbel only works under tension for torques in one direction and it does not work under tension but under shear for torque moments in the other direction. As a consequence, it is not necessary that the reinforcement that protrudes vertically from the corbel is centered in the width of the corbel (as it is necessary when the anti-torque system is required to work under tension for torque moments in either direction). Thus, the protruding vertical reinforcement from the corbel may embedded in the corbel in a position that is decentered, this is moved towards the face of the column that stands opposite to the side where the cantilevered protrusion is in contact with the lateral face of the column. Decentering in such a way the protruding vertical reinforcement, will allow this anti-torque system to withstand larger torque moments in the direction that it is operational. Thus, this is an additional advantage of having a girder that includes a cantilevered protrusion (or lintel).

[0155] In some embodiments, the cantilevered protrusion (or lintel) is tightly connected to the column with a screw, guaranteeing the contact of the cantilevered protrusion and the vertical face of the column, and thus forming an anti-torque system.

[0156] This embodiment has three main advantages:

[0157] • Firstly, the tight screwed junction improves significantly the torque strength of the antitorque system in several ways:

[0158] o The tight screwing guarantees the contact of the cantilevered protrusion and the column, thus guaranteeing that there is a proper transmission of compression between the two members, when the torque moment tends to cause a turning of the girder that produces that contact and compression. Having the contact guaranteed by the screw before the torque moment actually enters in action, is a way to prevent that accidental separation between the two members either prevents the actual contact or requires a relevant (and undesired) rotation of the girder before contact happens.

[0159] o The screwing also has the advantage that it allows the junction of the column and the cantilevered protrusion to resist tensions. This is advantageous as it allows to resist torque moments of the opposite sign. This is, torque moments tending to separate the cantilevered protrusion from the column. So, this connection allows that the column to girder connection is able to resist torque moments in any of the two directions.

[0160] • Secondly, screwing the cantilevered protrusion to the column, allows the screw to withstand vertical loads. Thus, the cantilevered protrusion, after being screwed to the column, will no longer be cantilevered, or the cantilever will be very much reduced. This will very much reduce the risk that the cantilevered protrusion breaks or suffers excessive deflection when it is loaded with the weight of the gravity loads transferred by the floor that is supported on the cantilevered protrusion. • Finally, this screwed connection is also able to resist horizontal shear forces, and this allows that tensions may be transferred trough the cantilevered protrusion into the girder, thus allowing to anchor the beam to the column and transfer a certain amount of negative moment of the girder into the column. This increases the stiffness and strength of the column-to-girder junction.

[0161] In an embodiment, the position of the horizontal screw has to be well adjusted to prevent the collision with other reinforcements of the column, that is typically a densely reinforced member. In those girder-column junctions that happen at a level where there is also a column-to-column junction, the congestion of reinforcement may cause difficulties placing the horizontal screw. This problem should not exist when the girder-column junction does not coincide with a column-to-column junction.

[0162] In some embodiments, on the ends of each couple of prefabricated girders, at their junction with a column, lintels are supported on the flanges of the girders, being the length of the lintels approximately the same as the dimension of the column.

[0163] This embodiment allows for a straightforward way to solve the problem of how to support floor elements that cannot be supported on the girder, due to the fact that the girder is interrupted at the column. This embodiment is also easier to produce industrially than an embodiment based on prefabricated columns including corbels in all four faces: two corbels for girders and two corbels for floor elements.

[0164] Thanks to this embodiment, also the production of girders is simplified, when compared to the embodiment where beams include cantilevered protrusions functioning as lintels.

[0165] In some embodiments, the floors supported on the girders are formed by a combination of the following elements:

[0166] a) A multiplicity of prefabricated and self-supporting floor elements with a rectangular and elongated floor plan including reinforcement near its bottom face, being such reinforcement parallel to the major dimension of the floor element, and including on the top planar face of the floor element grooves or protrusions with a depth not smaller than the coarse aggregate of the cementitious material placed at the job to form a topping layer on the prefabricated and self-supporting floor elements, and having these grooves or protrusions a width not smaller than 1 ,5 times the depth, being the width the dimension parallel to the major dimension of the floor element.

[0167] b) Reinforcement to resist negative moments of the floor placed at the job, placed transversely to the girder that supports the floor elements, and being the negative-moment reinforcement extending over the top planar face of the floor elements, and being the reinforcement embedded in the topping layer.

[0168] c) Topping layer formed with cementitious material poured at the job, covering the top planar face of the prefabricated and self-supporting floor elements, the girders and the reinforcement placed at the job, being the size of the coarse aggregate of the cementitious material not larger than the depth of the grooves or protrusions included on the superior planar face of the prefabricated and self-supporting floor elements.

[0169] d) Having the prefabricated and self-supporting floor elements a geometry of their lateral faces such that a cavity is formed along the junction between each pair of floor elements, having such cavity a geometry that it allows for cementitious material placed at the job while forming the topping layer to enter the cavity and fill it with the same cementitious material and being solidary with the topping layer.

[0170] A building after this embodiment is advantageous for a number of reasons:

[0171] • The floor elements described in a) are particularly advantageous, because they are self-supporting, this is, they do not need shoring or props during construction. Thus, during construction, they can be directly supported at their ends on the girders, and they will be able to resist their weight, the weight of the fresh concrete of the topping, the weight of workers and machinery, all without need of propping or shoring. This kind of floor elements will typically use prestressed reinforcement at their bottom face, which will increase their structural performance and, thus facilitate their being self-supporting.

[0172] • The combination of features a), b) and c) will allow floors to resist negative moments, despite the detrimental effect of differential shrinkage on horizontal shear strength on the interface of the precast concrete and the cast in place concrete. Differential shrinkage occurs due to the fact that when the fresh concrete of the topping is poured on the prefabricated floor elements, when the latter ones have already experienced a large part of their total shrinkage, as most of the shrinkage occurs at early ages of the precast concrete (when the precast concrete is setting at the shop). Thus, as the concrete of the topping sets and shrinks, it tends to slide on the upper planar surface of the prefabricated floor element. This tendency to sliding, greatly reduces the horizontal shear strength at the interface of the two concretes (the precast, and the cast at the job). The very deep grooves or protrusions on the upper planar face of the prefabricated floor elements, where the aggregate of the topping is not larger than the depth of the grooves or protrusions, has the advantage that is guarantees aggregate interlock. This means that the aggregate of the cast in the job concrete can be completely beared by and pushing (compressing) -this is locked- on the aggregate of the precast concrete. This sort of pushing (compressing) of the aggregate of the cast- in-place concrete on the aggregate of the precast concrete typically happens as a result of the horizontal shear forces, such as those caused by flexure moments along the span floor element. These horizontal shear forces occur as a consequence of the tendency that flexure forces cause of layers (or fibers) of a cross-section to slide one on top of each other. As mentioned, differential shrinkage tends to harm the capacity of the material (concrete) to break under horizontal shear, but aggregate interlocking (produced thanks to deep grooves or protrusions), prevents the detrimental effects of differential shrinkage, this is, it prevents horizontal shear strength loss. Thus, thanks to the very strong connection between the two layers (precast and cast in the job) that prevents them from sliding, the negative-moment reinforcement can be advantageously embedded in the concrete of the layer, and thus allow the floor finally formed (by the precast floor elements, the concrete of the topping and the negativemoment reinforcement) to form continuous floors. This is, floors where two spans of floor elements can transmit negative moments across the girder on which they are supported. Thanks to achieving effective floors continuity, structural performance of floors is very much improved, and the thickness of floors can be reduced to around 30%, as compared to the depth of floors where floor elements are only positive-moment resistant, this they function as simply supported (or pinned-pinned), which is currently the common practice. Thus, being able to use thinner floors thanks to these features (a, b, c), the weight of floors is reduced a well as their cost. As the weight of floors is reduced, the girders supporting these floors can be built cheaper (using less steel and / or concrete). Also, columns and foundations of the building can be reduced, thus leading to an overall cost reduction. As well, using less material in the whole structure will lead to more sustainable structures.

[0173] • The performance of the structure versus horizontal loads (wind, earthquake) is improved, because thanks to the proper and solid connection between the precast floor elements and the topping, as well to thanks to the continuity of floors (this is, their negative-moment strength) the whole thickness of floors (and not only the topping) may function as a diaphragm for the building at the level of each floor.

[0174] • The fact that floors are lighter, this is also advantageous for construction in structures that have to be designed to undergo earthquakes, as a lighter structure will produce reduced horizontal forces induced by the shaking of the building.

[0175] • Regarding feature d) it is important to guarantee that adjacent floor elements will work together under flexure, as they deform as a sole member. This is because filling the lateral cavity with concrete (or other cementitious material) makes it to work as a shear key. These shear keys are particularly necessary in the floors of this embodiment, where floor elements are thinner, and thus might be more affected by concentrated loads than floors formed by thicker elements.

[0176] In some embodiments, reinforcement is placed to resist positive moments in the zone where prefabricated and self-supporting floor elements are supported, that is, reinforcements are placed transversally to girders, on top of the girders and placed in bottom part of the cavities formed between the lateral faces of each pair of prefabricated and self-supporting floor elements, being the cavities filled with cementitious material placed at the job when forming the topping layer.

[0177] This embodiment allows floors, at their junction with girders, to resist moments reversal. This is, floors can resist positive moments at their bearing of girders. This happens thanks to the fact that positive-moment reinforcement is placed at the bottom of the cavities (or shear keys) and it is properly anchored on the girder or beyond it into the shear key of the floor span at the other side of the girder. The capacity of floors to resist significant positive moments at their bearings on beams is a feature that allows these structures to be particularly resilient (strong) under extreme horizontal loads (high speed wind and strong seismic forces).

[0178] The floors of the present invention are designed to function in continuity, this is to resist large negative moments under gravity loads. This feature, as explained above, already is a very good mechanism to resist horizontal forces on the structure, as large negative moments on the bearings, already are a very good mechanism to prevent moment reversals. Moment reversals only happen under considerable horizontal forces that produce such large positive moments at the junctions, that these positive moments are larger than the negative moment caused by gravity loads. This only happens when the number of stories is considerable (8 storeys or beyond, in areas of moderate seismic action). In those cases where inversion moment may happen even on floors designed for continuity, having the feature of this embodiment (positive moment reinforcement placed in the shear keys) allows floors to contribute as a part of the horizontal resistance mechanism of the whole building; because floors do not only function as a diaphragm but they also contribute through their flexure stiffness, both under positive and under negative moments.

[0179] The design of the junction of the prefabricated girders and the floor elements, such that the web of the girder does not protrude upwards higher than the top face of the flanges of the girder, on top of which the floor elements are supported, makes it particularly easy, during the erection process, to place at the job the positive moment reinforcement of the floor, by simply laying this reinforcement at the cavity (shear key) formed between the lateral faces of each pair of floor elements.

[0180] A second aspect of the present invention is a method for erecting a building as previously described, which comprises the following steps:

[0181] - constructing foundations embedded in the ground, leaving vertical ducts embedded at the top of the foundations, arranged in positions that allow for the insertion of vertical reinforcements protruding from the bottom of the prefabricated column that has to sit on each foundation and also embedded at the top of each foundation at least two levelling devices arranged to allow for the levelling of the corresponding prefabricated column,

[0182] - placing each column on top of its corresponding foundation, arranging it such that vertical reinforcements protruding from the bottom of the prefabricated column enter in the vertical ducts embedded in each corresponding foundation without the need of props to sustain de columns,

[0183] - levelling each column using the levelling devices embedded in the foundation,

[0184] - pouring cementitious material with limited shrinkage to completely fill the vertical ducts embedded in the top part of each foundation so that the vertical reinforcements protruding from the bottom of each column get connected to the corresponding foundation after the hardening of the cementitious material with limited shrinkage,

[0185] - placing the girders on the corbels protruding of the corresponding columns, including each girder, the corresponding negative-moment reinforcement on the top of the beam, inside of its out-propping stirrups, and free for movement,

[0186] - connecting the girders with the corbels and / or directly with the columns by means of the antitorque system, without the need of props to sustain the columns or the girders,

[0187] - placing prefabricated self-supporting floor elements, including grooves or protrusions on their superior planar face, directly on the corresponding girders, without the need of props to sustain the columns, the girders or the floor elements,

[0188] - sliding of the negative-moment reinforcement of each girder through the out-propping stirrups of the beam, through the horizontal duct of the corresponding column, and through the out-propping stirrups onto the girder placed at the other side of the column,

[0189] - placing the reinforcement to resist the negative moments of the floor such that the reinforcement extends over the top planar face of the floor elements placed at each side of each girder,

[0190] - placing formers locally around each girder-column junction,

[0191] - placing a reinforcement mesh all over the floor elements and pouring a topping layer all over the floor elements, the girders, and the girder-column junctions, being the topping layer formed with cementitious material with coarse aggregate not larger than the depth of the grooves or protrusions included on the superior planar face of the prefabricated self-supporting floor elements,

[0192] - repeating an analogous sequence to erect the rest of the structure of the building,

[0193] - while the structure is being built or after it has been completed, erecting the walls of the building supported on the structure.

[0194] In an embodiment of the invention, rectangular columns are erected coinciding with the direction and position of walls, the walls are erected covering and hiding the columns as well as covering and hiding the web of the corresponding girders.

[0195] In an embodiment of the invention, the method comprises a final step of erecting the building’s parts and services until the total completion of the whole building.

[0196] The method of the present invention has the same advantages as the ones explained for the first aspect of the invention.

[0197] Present invention also describes buildings in which the prefabricated structures include columns, girders and floor elements, which are at the same time particularly efficient from a structural point of view and very slender, so that the girders have flanges with small downdrops that allow for ceilings to be flat. Also, the structures of the buildings of the invention are designed considering not only the stability and security of the structure once the structure has been fully completed, but also are designed to allow for the structure to be easy to erect and secure for the workers during the erection as well as allowing for each of the structural components to be stable during the erection process, and not only once the whole structure has been completed.

[0198] In the current document the term ceiling is used to describe the inferior surface of the structure of the building, including the bottom face (or soffit) of the floor elements and including also the bottom face (of soffit) of the girders. In this document the term flat ceiling does not mean that the ceiling is completely flat and even. It rather means that the ceiling is almost flat. This means that the soffit (= bottom face) of the girder may be some cm under the soffit (=bottom face) of the floor elements, but the difference in level between the two soffits is relatively reduced as compared to the large spans covered by the floor elements. As a consequence, the ceiling, when looked at as a whole, it looks relatively flat.

[0199] In the current document the term aspect ratio refers to the relation (or ratio) of the two most different sides of a planar shape. For example, in a rectangular cross-section the aspect ratio is always the division of the smallest dimension by the largest dimension.

[0200] In the current document is repeated several times the expression “vertical dimension that is more than 50 times smaller than the span of the floor elements”. This has to be understood as: “vertical dimension” < 50 ■ “span of the floor elements”. To put it in a more mathematical way, if we replaced “vertical dimension” by DD and “span of the floor elements” by SF, this could be written as DD < 50- SF.

[0201] To overcome the shortcomings described in the state of the art, in a third aspect of the present invention is a building including zones with flat ceiling, without partition walls and including a structure that comprises:

[0202] - prefabricated columns made of reinforced concrete;

[0203] - prefabricated girders supported at their ends on the columns; and

[0204] - prefabricated floor elements supported at their ends on the girders;

[0205] wherein the columns have a cross-section with an aspect ratio between 1 and 0,3 and the girders have bottom flanges that down-drop under the soffit of the prefabricated floor elements a vertical dimension that is more than 50 times smaller than the span of the floor elements supported on the girders.

[0206] In a zone of a building without partition walls, architects will normally search that the structure is the least apparent possible, and that it does not obstruct much the space.

[0207] Having columns with an aspect ratio between 1 and 0,3 means that columns may either be round or square (both cross sections have an aspect ratio of 1) or have a cross-section with a geometry not tto far from being square (in the worst case, least square, the shortest dimension would be 0,3 times de largest dimension of the cross-section). As mentioned, in such open zones of a building, having columns with an aspect ratio of 1 (or close to that) is desirable. Also, in that zones of buildings it is desirable that columns are away from one another. Using the structures described in the current invention is then particularly advantageous, given the high efficiency of the floor elements (that are typically prestressed and function in continuity, resisting positive and negative moments). Their high efficiency allows for the columns the be placed at a larger distance from one another than much other conventional structures, where there is no prestressing of the floor elements and / or where there is no floor continuity (resistance to both positive and negative moments).

[0208] Also, in those zones of the buildings that have no partition walls, facilities (electricity, water, gas, HVAC, etc) may need to be arranged on the ceiling, thus, it is interesting that the ceiling is as flat as possible. In the structures here described, the bottom flange of the girders has a very reduced down-drop, which is particularly convenient. A down-drop of the bottom flange 50 times smaller than the span of the floor elements is already reduced. However, the embodiments described below, may allow to even larger ratios reaching bottom flanges 100 or more times smaller than the span. With the embodiments described below, typical spans of floor elements range between 6 m to 16 m, and the vertical dimension of the flange of the girder ranges from 6 to 16 cm. Thus, it is not unusual to have a down-drop with a vertical dimension between 100 and 150 times smaller than the span of the floor elements.

[0209] In some embodiments the reinforcement of each of the bottom flanges of the girder is formed by a continuous U-shaped reinforcement, being all of this continuous U-shaped reinforcement included in a diagonal plane that is both perpendicular to the cross-section of the girder and, for each flange, parallel to a line starting close to the bottom and most exterior corner of that flange and passing tangent to the point where the top horizontal face of the flange contacts de web of the girder.

[0210] Girder provided with such reinforcements at their bottom flanges allow for very shallow bottom flanges (=flanges with reduced down-drop) and are particularly easy and cheap to produce at the factory. The flanges can be particularly shallow compared to the flanges of the state of the art. This is because in the flanges of girders of the state of the art, a large thickness is required to properly placed all the reinforcement conventionally placed in each flange. This is because in the flanges of girders of the state of the art are typically reinforced as members under flexure asking for reinforcement on both faces (top and bottom) of the flange. Beyond that, proper cover is required for both reinforcements (top and bottom of the flange). Moreover, to reach a proper bonding of these top and bottom reinforcements they are bent at their end. Thus, normally this top and bottom reinforcement end up forming a closed hoop included in a plane parallel to the cross-section of the girder, and the minimum distance between the two reinforcements ends up being controlled by the minimum interior radius of bending of the rebar, and such radius of bending is controlled by the radius of the rebar itself. So, the depth of the flanges of a girder of the state of the art can hardly have a depth under 20 cm.

[0211] However, the reinforcement described in the current embodiments is able to overcome the current limitations, and have much shallower bottom flanges, that may be even only 5 cm deep. This is achieved in the first place because the bottom flanges of this embodiment are not reinforced as bending members but rather like elements that do not bend and need to be analyzed by the method of strut and tie. This is because the slenderness (cantilever span I thickness) of the bottom flanges of girders is small enough for flexure not to exist. This absence of flexure is even more real in thick bottom flanges (like those of the girders of the state of the art), and it is still true of the bottom flange of the girders of the current embodiments. For the computation of such slenderness, the span of the cantilever of the flange is accounted for from the face of the web of the girder to the point of application of the load (=the center of the bearing pad on which the floor element is supported on the bottom flange).

[0212] In the strut and tie analysis performed of the loaded bottom flange, a tie is formed that has a diagonal direction included in a plane that is both perpendicular to the cross-section of the girder, and is parallel to a line starting close to to the bottom and most exterior corner of that flange and passing tangent to the point where the top horizontal face of the flange contacts de web of the girder. Placing reinforcement in this plane allows to withstand the tensions on the tie of the strut and tie model. Thus, there is no need to place reinforcement parallel to the top face of the flange.

[0213] Finally, to reach a proper bonding of the reinforcement under tension (the one resisting the force on the tie) there is no need to bend that reinforcement in a plane that is parallel to the cross-section of the girder. Instead, the rebar can be bent within the diagonal plane that is perpendicular to the cross-section of the girder. This has the great advantage that the radius of bending of the rebar resisting the tension is not leading to an increase of the depth of the bottom flange of the girder.

[0214] Thus, a continuous U-shaped reinforcement placed in the mentioned diagonal plane is a particularly efficient reinforcement for the bottom flange, and still allows for the depth of the flange to be very reduced.

[0215] The fact that the U-shaped reinforcement is continuous it also makes it very convenient in terms of production, as a long portion of the flange of the girder can be reinforced with only one piece of reinforcement. Also, the U-shaped reinforcement can be designed so that it does not conflict with the vertical stirrups (=shear reinforcement) of the web of the beam. When the U-shaped reinforcement is designed in such a way, it can be mounted very easily, and allow for a fast production.

[0216] In some embodiments the reinforcement of each of the bottom flanges of the girder is formed by a series of hooks spaced along the length of the beam, and being each of these hooks welded to a bent steel plate that covers the top horizontal face of the bottom flange and the lateral vertical face of the web of the girder, running this bent steel plate all along the girder, and being each of these hooks included in a plane parallel to the cross-section of the girder and, including each of the hooks a long leg forming a diagonal line included in a diagonal plane that is both perpendicular to the cross-section of the girder and, for each flange, parallel to a line starting close to the bottom and most exterior corner of that flange and passing tangent to the point where the top horizontal face of the flange contacts de web of the girder.

[0217] This embodiment shares several features with the prior embodiment (such that bottom flanges can be designed using the stud and tie model, and thus optimized), however it has its own set of advantages and disadvantages when compared to the prior embodiment. En terms of its advantages, the flange can be done particularly shallow, thanks to the collaboration of the steel bent plate. This plate, also allows for the top corner of the flange to be straight, as it is reinforced by the flange and there is no risk that the concrete in the very corner cracks and ends splitting from the rest of the flange. The steel plate also functions as a former during the production in the factory, and thus there is not a specific need for the precaster to invest in a former to produce these girders.

[0218] Also, in terms of the advantages, this solution allows to place a prestressed reinforcement at the corner of the flange, inside the welded hook.

[0219] In terms of the disadvantages of this solution, as compared to the previous embodiment: this solution asks both for both a steel plate and for welding, which are both expensive. Thus, the prior embodiment, advantageously, will allow for cheaper girders with shallow bottom flanges, than the current embodiment.

[0220] In some embodiments the girders have top flanges that down-drop under the soffit of the prefabricated floor elements a vertical dimension that is more than 50 times smaller than the span of the floor elements supported on the girders.

[0221] Putting it in another way, in some embodiments, in zones with flat ceiling and with walls and including a structure that comprises:

[0222] - prefabricated columns made of reinforced concrete;

[0223] - prefabricated girders supported at their ends on the columns; and

[0224] - prefabricated floor elements supported at their ends on the girders;

[0225] characterized in that the columns have a rectangular transversal cross-section such that in the cross-section of these columns the direction of the depth coincides with the largest size of the transversal cross-section and the width direction coincides with the smallest size the transversal cross-section, such that in those zones having walls, the rectangular columns of the building are:

[0226] embedded within a wall, the column being hidden in the thickness of the wall, with the direction of the depth of the column being parallel to the direction of the wall; and / or placed at the junction of two walls forming an angle between them, with the direction of the depth of the column being parallel to the direction of one of the walls and the direction of the other wall being transversal to the depth of the column, such that the column is embedded in the thickness of the wall parallel to the depth of the column the thickness of each of the walls being respectively larger than the corresponding dimensions of the web of the respective girders and being each dimension of the respective walls larger than the smallest dimension of the cross-section of the respective columns for those columns which direction of the depth coincides with the direction of the wall. And being the girders provided with top flanges that down-drop under the soffit of the prefabricated floor elements a vertical dimension that is more than 50 times smaller than the span of the floor elements supported on the girders.

[0227] The sort of girders described in both embodiments is advantageous in zones of the building where there are walls that can hide the webs of the beams, and still are zones of the building where it is interesting for the architectural design to have shallow flanges of the girders. This is, that the top flanges of the girders, that may come out of the walls, have a reduced downdrop that has little effect in aesthetics or space available on the ceiling to place facilities.

[0228] In some embodiments the where girders have the web reinforced split into two groups of hoops spaced along the axis of the girder, being one of the groups formed by interior hoops that are entirely embedded in the precast concrete of the girder, having each interior hoop a vertical dimension approximately equal to the vertical dimension of the girder, and being the other group of hoops formed by top exterior hoops, having each top exterior hoop a part protruding out of the precast concrete of the girder and another part embedded in the precast concrete of the girder.

[0229] This embodiment has a number of advantages when compared to those girders, of the state of the art, where the hoops of the web of the of the girder are in one piece, this is, the hoop goes from the very bottom to of the web of the precast concrete girder to the top face of the concrete poured in the job over the girder. The hoops of the girders of the state of the art, that have just been described, given that a part of the same hoop is interior to the web of the girder and a part of the hook is out of the girder, the top part of the precast web of the girder typically does not have transversal reinforcement.

[0230] In the embodiment here described, where one of the group of hoops is entirely embedded in the precast concrete, these hoops provide the girder with a much-increased strength against torque moments. This is a key feature to prevent that the girder is damaged during the erection process, when the girder is only formed by its precast concrete cross-section and has not had its cross-section complete by the concrete poured at the job. During the erection process large torque moments act on the precast girder, caused by the uneven loading on the girder due to placing floor elements only on one side of the girder, which is a typical and very convenient way to erect these sorts of precast structures.

[0231] Another advantage of not having the interior hoops separated from the exterior hoops is that the amount and spacing of interior hoops can be different from the amount and spacing of the exterior hoops. It has been found that, it is very frequent that exterior hoops are more frequently required than interior hoops. This is due to the need to place reinforcement to resist horizontal shear forces. Resisting such horizontal shear forces is key to prevent that the girder breaks in two, splitting the top part (cast in the job, where negative-moments reinforcements are embedded) from the bottom part (precast, where the positive-moments reinforcements are embedded). Thus, intensifying exterior hoops without the need to intensify the interior hoops, allows to interior hoops, allows to reduce the consumption of steel while keeping reinforcement placed there where it is really needed.

[0232] In some embodiments, girders have the top flanges reinforced by a continuous U-shaped reinforcement included in a horizontal plane included within the top flanges of the girders.

[0233] This kind of reinforcements has advantages that are to a large extent analogous to the advantages described for the continuous U-shaped reinforcement used to reinforce the bottom flange of girders that have bottom flanges described above. The main advantage in the current embodiment is, again, that the U-shaped reinforcement allows for shallow flanges, as this U-shaped reinforcement allows to have all the reinforcement required in the flange (the tension reinforcement) placed in on sole plane, a horizontal plane in this case. In this case, the corbel formed by the top flange is particularly not slender when considered as a cantilever in the transverse direction of the girder. Given its reduced slenderness, is does not bend, and it can be studied as a stiff member it typically studied, through the strut and tie method. Analysing its behaviour by this means, a horizontal tie is formed, and its tension is well resisted by placing reinforcement in a horizontal plane. Such reinforcement is properly bonded thanks to the fact that it is bent also within that horizontal plane, and does not need to bend out of this plane (for example in a plane parallel to the cross-section of the girder) which would lead to the need of increasing the depth of the top flange of the girder.

[0234] In some other embodiments the prefabricated columns include one or several of the following features:

[0235] a) The column has its junction with the column above at a height several tens of centimetres away from the closest floor placed under this junction and several centimetres away from the closest floor placed above this junction;

[0236] b) The column includes corbels protruding beyond the cross-section of the column, meant for supporting floors for one or several of the levels through which the column such that the corbel is connected to the column with uninterrupted reinforcements coming out of the cross-section of the column;

[0237] c) The column includes corbels protruding beyond the cross-section of the column, meant for supporting floors for one or several of the levels through which the column such that the corbel is connected to the column with reinforcements coming out of the cross-section of the column, being each reinforcement interrupted at the level of the face of the vertical column by a threaded steel cap;

[0238] d) The column includes one or more threaded steel cap on a vertical face facing a girder, being each threaded steel cap intended to receive a bolt to fast an anti-torque bracket during the erection process;

[0239] e) The column includes a horizontal duct with a rectangular cross-section that crosses the column to allow for the passing of negative-moment reinforcement of the girder, such that the top face of the rectangular cross-section is placed several centimetres above the top face of the topping layer, and so allows for the pouring of cementitious material in the horizontal duct after the topping layer has hardened;

[0240] The feature a) of this embodiment, placing the column-to-column junction several tens of centimetres away from the level of the floors (above and below the junction), has the advantage that the mentioned column-to-column junction is placed away from areas normally congested with reinforcement (the level of the floors), as at these levels, the reinforcement of the corbels for girders and the corbels for floor elements fill the core of the column with steel rebars, and also the negative-moment reinforcement placed at the job crosses the column through a horizontal duct. The coexistence of all these elements (horizontal reinforcements of corbels, negative-moment reinforcement and horizontal duct) with vertical the vertical ducts, vertical lap reinforcement and levelling devices at the column-to-column reinforcement is very difficult and requires working with high precision, not easy to reach even in the controlled conditions of a factory. Thus, having the column-to-column junction several tens of centimetres away from the level of any floor is clearly beneficial.

[0241] The feature b) of this embodiment, corbels for the floor elements with uninterrupted reinforcement, allows for an easy and cheap way to form corbels for the floor elements, there where the concrete of that corbel can be poured when precasting the column.

[0242] In most columns girders are supported on the column on opposite faces, thus the corbels for those girders (that are relatively large and strongly reinforced) need to be placed at those opposite faces. Given that columns are most of the times produced laying on a horizontal former (or on the floor), typically corbels are particularly hard to pour on the face that is placed in contact with the bottom former. Thus, normally, large corbels (such as the corbels for the girders) are placed at the sides of the column when concrete is poured. This leaves the top face of the column to pour the concrete while the bottom face is used as a former. In such an arrangement, after the beginning of the hardening of the concrete of the column (some hours), the top face is ready for a second pour. At this point, the corbel for the floor elements with uninterrupted reinforcement can be poured, because the uninterrupted reinforcement can be arranged to be embedded in the core of the column and with a part coming out of the core of the column, that will be covered in concrete to form the mentioned corbel for the slab, in that second pour. Thus, this corbel can be produced with cheap conventional means, and little work effort.

[0243] This sort of corbels for floor elements is particularly important for columns that have one long dimension, such as the columns described above that are designed to be hidden in walls. Typically, the short dimension of such columns is where the girders are supported on relatively large and reinforced corbels, whereas the long dimension of such columns is where slabs are to be supported on corbels lightly reinforced.

[0244] The feature c) of this embodiment, corbels for the floor elements with interrupted reinforcement, is also convenient to be to easily produce corbels to support floor elements, particularly as these corbels only need a light reinforcement. This embodiment with interrupted reinforcement makes it easy to form a corbel on the face that is in contact with the bottom former where the face normally needs to be totally flat, so reinforcement protruding from this face is not convenient. In a column with such interrupted reinforcement, threaded caps (or similar means) may be used to allow for an ulterior connection of the piece of reinforcement cantilevering out of that face of the column. The placing of such reinforcements coming out (cantilevering) will typically be done as a stage prior to pouring the concrete of that corbel. This operation will typically be done after the hardening of the concrete of the column and it lifting and turning to allow for the addition of the mentioned reinforcement and pouring of the concrete of that corbel.

[0245] Despite this sort of corbel is slightly more expensive than the one described in the feature b), the corbel described in the feature c) is still very cheap, as the threaded caps or couplers are not so expensive, and they will not be required in large numbers, as the reinforcement of this sort of corbel is low.

[0246] The feature d) of this embodiment, threaded steel caps embedded in the face of the column, allows for the use of these caps to allow for an easy bolding of a temporary anti-torque bracket during the erection process. This sort of bracket allows to connect tightly the girder to the column, and thus allowing to have a fixed connection of the end of the girder against torque moments. This prevents that the girder twists around its bearing on the corbel and potentially falls down and hurts someone or damages other parts of the structure under construction.

[0247] Preventing this sort of twisting is an important measure during erection. But as this sort of risk exists only during the erection process it is rational to use temporary means to control that risk rather than measures that will stay in the structure in long term. Thus, providing the column with such steel threaded caps that allow for the bolding of a temporary anti-torque bracket, also allow for an easy unbolting of the temporary anti-torque bracket, in order to reuse it for the next girder-to-column temporary connection. This capacity to reuse the anti-bracket by easily bolting and unbolting it, allows to very much reduce the cost of the means to guarantee the stability of the girder during construction, by removing the need for props placed under the girder to prevent its twisting.

[0248] The feature e) of this embodiment, the horizontal duct that is higher than the topping, is advantageous to guarantee a proper filling of the horizontal duct. This sort of horizontal duct is typically designed with smallest possible cross-section (especially in the horizontal and dimension of the duct transverse to its length). This small horizontal dimension is normally only some millimetres larger than the diameter of the negative-moment reinforcements that have to go through the column, but not larger because otherwise it would excessively weaken the cross-section of the precast column. Thus, the narrowness of the horizontal duct, normally makes it virtually impossible that it is properly filled with the concrete used to form the topping poured on the precast floor elements. This is because the coarse aggregate of that topping will typically be around 10 mm or more, and such a large coarse aggregate will not fit between the negative-moment reinforcement and the sides of the duct. Additionally, the filling of the duct with such a material (concrete placed at the job) is typically not desirable as the concrete poured at the job (for the topping) will most of the times have a strength lower than the strength of the concrete used for the precast columns. So, preventing the filling of the duct with the concrete of the topping is, indeed, desirable. Thus, this embodiment allows to easily fill the duct with a cementitious material placed at the job, after the hardening of the topping. The fact that the top face of the horizontal duct is above the level of the top face of the topping, lets a sort of small window at the bottom of the column, right over the topping, that is easy to fill with a high-strength fluid cementitious material with very small coarse aggregate, that is able to completely fill the gaps in the duct.

[0249] In some other embodiments the girders supporting an edge of a floor and / or self-supporting floor elements include a tab protruding vertically that has its top face higher than the top face of the topping layer.

[0250] The fact that girders and / or floor elements are provided with such tabs, allows for two key advantages. On the one hand, the erection process becomes much easier and convenient, as it makes unnecessary to place perimeter formers at the job, which would, in turn, as for props to hold that formers in place. All this is costly, and time consuming in the job. It also uses a considerable amount of workforce for a small a mount of steel and concrete placed at the job in these perimeters, which is particularly inefficient and costly.

[0251] In the other hand, having such verticals, allows for an easy installation of security means, such as railings or other more appropriate solutions that protect the perimeter of the structure under construction and prevent the falling of the workers out of the structure of the building. It must remember that at this stage of construction of the building, the fagades typically do not exist yet, as fagades will be placed later on in the process, and typically will be supported by the structure that is at this point under erection (thus, supported on the columns and / or on the floors). Given that during the erection of the structure, the fagade is not there, temporary security means to protect the perimeter of the structure are key, and it is good to have them placed in a convenient way, such by holding those perimeter protections on the mentioned vertically protruding tab.

[0252] In some embodiments girders include at their ends, on their top face, a threaded steel cap intended to receive a bolt to fast an anti-torque bracket during the erection process.

[0253] This embodiment functions along with the embodiment of the threaded steel caps embedded in the vertical face of the column (feature d) of column mentioned above). Thus, thanks to the threaded steel caps mentioned in the current embodiment, combined with the steel threaded caps in the columns, it becomes easy and fast to bolt and un bolt the temporary anti-torque bracket during the erection process. All this allows to prevent the use of props in the job to prevent the twisting of the beams during the erection. BRIEF DESCRIPTION OF THE DRAWINGS

[0254] To complete the description and in order to provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate embodiments of the invention, which should not be construed as a restriction of the scope of the invention, but merely as an example of how the invention can be carried out. The drawings comprise the following figures:

[0255] Figure 1 shows a state-of-the-art square column that is placed centered on a wall.

[0256] Figures 2a and 2b show a column of the building of the present invention.

[0257] Figure 3a shows a building, comprising columns and walls of two subclasses: fagades and partition walls.

[0258] Figure 3b shows the structure of the building shown in figure 3a, overlapped with the walls: partition walls, and fagades.

[0259] Figure 3c shows a detail of some of the walls and the structural members, this is, columns and webs of girders of figure 3b.

[0260] Figure 4 shows a detail of two variants of the relation of the dimensions of the column and the wall.

[0261] Figures 5a and 5b show a detail of two variants of the relation of the web of the girder and the wall.

[0262] Figure 6a shows a variant of an embodiment of the anti-torque system where a transverse cross-section of the beam supported on the corbel, and supporting floor elements on the flanges of the beam.

[0263] Figure 6b shows an embodiment of the anti-torque system, particularly a longitudinal section of the beam, showing a profile of the column and the corbel.

[0264] Figure 6c shows an embodiment of the anti-torque system, particularly a top view of the beam, showing the steel plate. Figure 7 shows the functioning of the anti-torque system.

[0265] Figure 8 shows a multi-storey column of 3 storeys height, including: corbels with vertical reinforcement; girders supported on the corbels; horizontal ducts crossing the multi-storey column at the level of each floor of the building; vertical ducts embedded in the foundation where are embedded the vertical reinforcements protruding from the bottom of the multi-storey column; vertical ducts embedded in the top part of the multi-storey column that is also the column below; the column above, having vertical reinforcements protruding from its bottom and embedded in the vertical ducts placed at the top of the column below.

[0266] Figures 9 and 10 show the junction where two girders are supported on an intermediate level (storey) of a multi-storey column, and where floor elements are supported on the girders.

[0267] Figure 11 shows a vertical section parallel to the width of the column and the junction of the column with the second floor.

[0268] Figure 12 shows a solution for the junction of the column below and the column above.

[0269] Figure 13 shows a transverse cut across the junction

[0270] Figures 14, 15, 16a, 16b and 16c show the anti-torque system based on cantilevered protrusions that are an extension of the flange of the girders.

[0271] Figures 16a, 16b and16c show the geometry of members and the forces involved in the antitorque system involving a cantilevered protrusion combined with a vertical reinforcement protruding from the corbel.

[0272] Figures 17a and 17b show the geometry of members and the forces involved in the anti-torque system involving a cantilevered protrusion combined with a vertical reinforcement protruding from the corbel and a horizontal screw connecting the cantilevered protrusion with the column.

[0273] Figure 18 shows two possible embodiments of prefabricated lintels to support the prefabricated floor elements in the zone beside the long side of the cross-section of the column (2), in order to avoid the need to produce the columns including corbels on these sides.

[0274] Figure 19 shows the junction of prefabricated floor elements on a girder, including: several models of prefabricated floor elements including grooves and protrusions on the upper planar face of the floor elements; negative reinforcement on the floor elements , connecting the floor elements at both sides of the girder to provide moments’ continuity; positive moments reinforcements placed at the bottom of the cavity between floor elements, providing the floors with positive-moment strength at the floor-girder-floor junction.

[0275] Figure 20 is a 3D view of a structure where the main structural components can be seen, including multi-storey prefabricated columns, girders and self-supporting prefabricated floor elements.

[0276] Figure 21a shows a 3D drawing of a building including a zone without partition walls and a zone with flat ceiling thanks to having girders with bottom flanges with reduced down-drop.

[0277] Figure 21b shows a plan view of the building depicted in Figure 21a.

[0278] Figure 21c shows a 3D drawing of the building shown in Figure 21a, but in Figure 21c the view is looking upwards, so that the flat ceiling is visible.

[0279] Figure 22a and 22b show the cross-section of a girder with a bottom flange with a reduced down-drop including continuous U-shaped reinforcement to reinforce each flange.

[0280] Figure 22c shows a plan view of the beam showed in Figure 22a.

[0281] Figure 23a shows the cross-section of a girder with a bottom flange with a reduced down-drop including for each flange, steel hooks welded to a bent steel plate.

[0282] Figure 23b shows a plan view of the beam showed in figure 23a

[0283] Figure 24 shows a prefabricated column connected to the column of the level above, where the junction between the columns is placed at a height between two floor levels rather that coinciding with one floor level.

[0284] Figure 25 shows a detail of a junction placed at a height between two floor levels.

[0285] Figure 26 shows an elevation of a column with two models of corbels to support floors.

[0286] Figures 27a, 27b and 27c show a girder connected to a column through a temporary antitorque bracket. Figure 28 shows self-supporting floor elements including a tab protruding vertically able to contain the concrete of the topping layer.

[0287] Figure 29a shows a girder supporting an edge of a floor, including a tap protruding vertically than contains the concrete of the topping layer poured at the job.

[0288] Figure 29b shows a girder similar to that in 29a but without the protruding tab

[0289] Figures 30a and 30b show a girder bearing self-supporting floor elements by means of top both flanges that have a very reduced down-drop

[0290] Figure 31a shows a 3D view of a girder similar to the one in Figure 29b.

[0291] Figure 31b shows a top view of the girder showed in figures 31a and 29b. In this figure 31b can be clearly seen the continuous U-shaped reinforcement that reinforces the top flange.

[0292] Figure 31c shows a 3D view, displaying reinforcement, of a girder similar to that showed in figure 30

[0293] Figure 31 d shows a top view of the girder showed in figure 31c. The continuous U-shaped reinforcement that reinforces the top flange can be seen.

[0294] Figure 32 shows a cross-section of a girder with bottom flanges with very reduced down-drop, displaying the strut and tie diagram of forces.

[0295] Figure 33a shows the strut and tie diagram of forces on the top flange of a girder similar to the one showed in Figure 29b

[0296] Figure 33b shows the strut and tie diagram of forces on the top flange of a girder similar to the one showed in Figure 30

[0297] Figures 34a and 34b show columns including a horizontal duct with its top face placed well above the top face of the concrete topping, and displaying also different models of corbels and of girders being supported by the column.

[0298] Figure 35 shows the cross-section of a girder of the state of the art, with bottom flanges, displaying the reinforcement in those bottom flanges. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0299] The following description is not to be taken in a limiting sense but is given solely for the purpose of describing the broad principles of the invention. Next embodiments of the invention will be described by way of example, with reference to the above-mentioned drawings, showing apparatuses and results according to the invention.

[0300] Concerning the numbering of the figures, take the following as an example: In figure 2a, all reference names and reference numbers are followed by an additional number or subindex 1 (bi, hi, 21, ei, h, ti), whereas in figure 2b, all reference names and reference numbers are followed by an additional number or subindex 2 (b2, h2, 22, e2, h, t2).

[0301] This is a way of expressing that the definition of the features (dimensions, direction, etc.) of each column is done in relation to the features (dimensions, direction, etc.) of the corresponding wall. This is the column and the wall that correspond to each other share the same number (or subindex). This way of writing is used because in a certain building it is very usual to have a multiplicity of walls, each having its own thickness and direction, and still for each column of girder, features can be defined that are valid for each column in relation to the wall associated to it, which is here referred as its ‘corresponding’ wall.

[0302] That is why, in this text in some cases the concept of correspondence of dimensions, direction, etc., of a group of columns and / or girders with their corresponding walls is expressed using numbers or subindex placed after the number of the element, dimension, etc. For example, while the reference name of the column is 2, and the reference name of wall is 5, to express that in a group of columns and walls of a building, each column has a certain feature in relation with is ‘corresponding’ wall, this is expressed by adding a series of numbers, finished in ‘n’, meaning, the number n of different elements (columns and their corresponding walls) may be any number, as high as necessary. This is written as follows: columns 21, 22, 23... 2n correspond to walls 51 , 52, 53... 5n.

[0303] A first aspect of the present invention is a building E, which can be seen in figures 3a and 3b. The building E comprises zones ZWwith walls 5 and a structure 1 that comprises:

[0304] - prefabricated columns 2 made of reinforced concrete;

[0305] - prefabricated girders 3 supported at their ends on the columns 2; and

[0306] - prefabricated floor elements 4 supported at their ends on the girders 3;

[0307] wherein the columns 2 have a rectangular transversal cross-section such that in the crosssection of these columns 2 the direction of the depth h coincides with the largest size of the transversal cross-section I and the width direction b coincides with the smallest size the transversal cross-section t, such that in those zones ZW having walls 5, the rectangular columns 2 of the building E are:

[0308] embedded within a wall 5, the column 2 being hidden in the thickness of the wall 5, with the direction of the depth h of the column 2 being parallel to the direction of the wall 5; and / or

[0309] placed at the junction of two walls 5 forming an angle between them, with the direction of the depth h of the column 2 being parallel to the direction of one of the walls and the direction of the other wall being transversal to the depth h of the column 2, such that the column 2 is embedded in the thickness of the wall parallel to the depth h of the column 2

[0310] being the thickness e1 , e2, e3...en of each of the walls 51 , 52, 53...5n respectively larger than the corresponding dimensions w1, w2, w3...wn of the web of the respective girders 31, 32, 33...3n and being each dimension e1, e2, e3...en of the respective walls 51, 52, 53...5n larger than the smallest dimension t1 , t2, t3...tn of the cross-section of the respective columns 21, 22, 23...2n for those columns which direction of the depth h coincides with the direction of the wall 5.

[0311] Beyond the advantages described above for this invention, next are explained some additional advantages, that are illustrated in figure 1 (state-of-the-art column) compared to figures 2a and 2b (columns of the present invention).

[0312] As it can be seen in figure 1, showing a conventional column (column of the state of the art), the size of the column is larger than the thickness of the wall, the corners of the column are particularly exposed to heat H in case of fire Fl. This is particularly harmful for the reinforcement placed at a corner of the column, as heat H affects it coming from two faces of the column. This sort of column will typically ask for a large cover of the reinforcement in order to prevent fire from affecting the rebars at the corners.

[0313] Figures 2a and 2b, show how columns 2 according to the invention are affected by heat H produced from fire Fl. In both variants of the invention heat H only affects the column 2 from one face. This is well known to slow the penetration of heat into the column 2. Thus, cover can be reduced.

[0314] The short faces of the column 2 are not affected by the heat H, as these faces are protected by the wall. That is why cover of reinforcement at these short faces is particularly reduced in the drawings. In figure 2a, the reinforcement in the long face is also reduced, in comparison to that in figure 2b. This is because the column in 2a has a width ti smaller than the thickness ei of the wall. This allows that the column 2 is completely embedded in the wall, so that the material of the wall covers the column 2. The material of the wall covering the column 2 may be, for example, plasterboard, which is particularly good as a heat insulator in case of fire. That is why in the column 2 in figure 2a the reinforcement has a reduced cover in all 4 faces of the column 2, compared to the cover showed in figure 1, and cover of the reinforcement placed by the long face in figure 2b. When comparing figures 1, 2a and 2b it has to be considered that these are figures that are drawn at the same scale. So, covers can directly be measured on the drawing and compared, to make it clear that in those cases where the face of the column 2 is properly protected, the cover is reduced.

[0315] The same that is illustrated in figures 1, 2a and 2b for columns 2 regarding the improvements in their fire-resistance performance, also stands for girders 3. The fact that girders webs are entirely embedded in walls is advantageous in case of fire, and allows to use reduced cover for reinforcement in the girders 3 according the invention as compared to the larger covers that are needed for conventional girders, that are not embedded in walls.

[0316] According to a preferred embodiment, illustrated in figure 20, the floor elements 4 are prefabricated and / or self-supporting.

[0317] According to a preferred embodiment, illustrated in figures 3a and 3b, the walls 5 are walls including fagades 5f and main partition walls 5d.

[0318] According to a preferred embodiment, partition walls 5d have a thickness between 15 cm and 25 cm.

[0319] According to a preferred embodiment, illustrated in figures 3a and 3b, where at least one of the prefabricated columns 2 is placed with the direction of its depth h being transverse to the direction of the depth h of the rest of the columns 2 of the building E.

[0320] In the drawings it is obvious that not all the columns 2 are parallel, as the interior partition walls 5d are not parallel. Some of the walls 5 are almost parallel, and are slightly oblique to each other. Also, some of the walls 5 clearly perpendicular (or transverse) to others. This is a typical feature in most buildings, as most buildings have at least a perimetral enclosure, that is, the fagade. Taking advantage of the fact that some interior walls 5d are perpendicular or oblique to others, and to the fact that some of the facades 5f also are perpendicular to other walls 5, several of the columns 2 are placed in directions perpendicular or clearly transverse to other walls 2.

[0321] According to a preferred embodiment, illustrated in figures 8, 9, 10, 11, 12 and 13, the prefabricated columns 2 have one or several of the following features:

[0322] a) The prefabricated columns 2 are made in one piece with a total height corresponding to the height of several storeys of the building E: multi-storey columns 2m;

[0323] b) The column 2 includes corbels 6 protruding beyond the rectangular plan of the column, meant for supporting the prefabricated girders 3, including such corbels a vertical protruding reinforcement AG, as a part of the erection anti-torque system ATS of the prefabricated girder 3;

[0324] d) The column 2 includes at the level of each storey of the building E that it passes through, a horizontal duct VH having an elongated cross-section, such that the largest dimension vd is placed vertically, and the longitudinal axis dl of the duct VH being horizontal and parallel to the direction of the depth h of the prefabricated column 2, being such duct VH crossed by negativemoment reinforcement of the girder NRB running through and along the duct VH, being the reinforcement NRB placed at the job, and being the duct VH filled with cementitious material poured at the job;

[0325] e) The column 2 includes at its top, at the junction with the column 2 of the storey above 2s, at least two levelling devices LD;

[0326] f) The column 2 includes at its top, at the junction with the prefabricated column 2 of the storey above 2s, vertical ducts VVS embedded in the column 2, arranged in such positions that allow for the insertion of vertical reinforcements AVS protruding from the bottom of the prefabricated column above 2s;

[0327] g) The column 2 includes vertical reinforcements AVS protruding from its bottom, for the insertion of those reinforcements in vertical ducts VVS embedded in the support below S, being this support below either the prefabricated column 2 below 2i or the foundation F of the column 2, being such ducts VVS filled with cementitious material with limited shrinkage LSC placed at the job.

[0328] In figure 10 it can be seen how the horizontal duct VH has its top face slightly above the top face of the topping T. This is a feature that is advantageous, as it allows to completely fill the horizontal duct VH with a low shrinkage cementitious material LSC after the concrete topping T has hardened, given that the concrete of the topping T will typically use a coarse aggregate that is too large to fit in the horizontal duct VH that will normally be very narrow (as it can be seen in figure 11). According to a preferred embodiment, illustrated in figure 3b, the prefabricated girders 31, 32, 33...3n that have their longitudinal axis parallel to the direction of the depth h of the corresponding column or columns 21, 22, 23...2n where each girder 31, 32, 33...3n is supported, the girders 31, 32, 33...3n have the corresponding width of the web w1, w2, w3...wn not larger than the smallest dimension t1, t2, t3...tn of the corresponding columns 21, 22, 23...2n.

[0329] In figure 3b, girders 3 with webs narrower than the column 2 are illustrated, and the width of the webs is numbered as w11 , w31 , w41 , w61.

[0330] According to a preferred embodiment, illustrated in figures 5a, 5b, and 18, the prefabricated girders 3 have a cross-section in the shape of a T, where the top part of the girders 3 has a width larger than the web w, thus forming a head of width C, such that the top part of the crosssection has two flanges A, one at each side of the web, that make it easier for the prefabricated and self-supporting floor elements 4 to be supported on both sides of the top of the girders 3.

[0331] According to a preferred embodiment, illustrated in figures 6a, 6b, 6c and 7, prefabricated girders 3 include a vertical duct VVB at each of their ends, as well as a steel plate SP including a perforation placed on top of the vertical duct VVB, as a part of the erection anti-torque system ATS together with the vertical reinforcement AG protruding out of the corresponding corbel 6 connected to the prefabricated column 2.

[0332] According to a preferred embodiment, illustrated in figures 11, 14, 15a, 16a, 16b and 16c, prefabricated girders 3, at their junction with a column 2 have a cantilevered protrusion BL that has a cross section similar to that of the flange A, and extends along all the dimension I of the column 2 and next to the vertical face of the column CV, forming a lintel BL that facilitates the support of the prefabricated and self-supporting floor elements 4 during the erection phase, and the cantilevered protrusion BL functions also as a part of the erection anti-torque system ATS.

[0333] In figure 11 it can be seen how this sort of solution is advantageous, as it prevents from having to fabricate the columns 2 including corbels on the long sides of the columns 2. This is advantageous, because producing columns 2 with corbels on the four faces is normally challenging and tends to be expensive.

[0334] Figures 16a, 16b, 16c illustrate in more detail how functions the anti-torque system of this embodiment. This system typically designed to resist torque moments differently in one direction than in the other. This is, the anti-torque system works very differently clockwise and counterclockwise.

[0335] Observing the drawings we can see on figure 16a that a load W of a floor element 4 placed on the left flange A of the girder 3 -called WL- will cause a counterclockwise torque moment Ti,uthat equals W, or WL, times ei, where ei is de distance between the axis of the load WL and the axis of the bearing surface of the girder 3, this is, the axis of the corbel 6. The torque moment Ti,uis an unbalancing moment that will tend to make the girder 3 turn around its bearing, the corbel 6, and eventually fall off.

[0336] To counteract this, in figure 16b is depicted the anti-torque system involving the cantilevered protrusion BL. This system is based in activating a couple of horizontal forces: a shear force F2,V on the vertical reinforcement AG protruding of the corbel, and a compression force F2,cof the same magnitude on the face of the column CV, produced by the ‘pushing’ of the cantilevered protrusion BL on the column 2. This couple of parallel and equal forces, spread a distance e2 produces a balancing torque moment T2,B.

[0337] However, this anti-torque system only functions for torque moment in one direction: counterclockwise.

[0338] Thus, as a complement, to control the effects of those torque moments in the opposite direction (clock-wise), a different anti-torque system is used in this embodiment: the one based on the vertical protruding reinforcement AG of the corbel (explained in figure 16c). Given that the sense of this torque moment Ta,uis a known, the position of the vertical reinforcement AG can be optimized to resist a higher torque moment. So, it can be moved laterally to the most appropriate position, this is, the side opposite to the flange A of the girder 3 that extends with a cantilevered protrusion BL. Placing the protruding reinforcement AG further away from the side of the cantilevered protrusion increases the lever arm e4 of the couple of balancing forces F4,C; F4.t, and thus increases the torque balancing capacity of this solution.

[0339] Besides, figures 15 and 16b also make it clear that for the anti-torque system ATS based on the cantilevered protrusion BL to function properly, compression needs to be transmitted from the cantilevered protrusion BL to the vertical face CV of the column 2. That is why it is essential that the cantilevered protrusion BL is to be in contact with the vertical face CV of the column 2. According to a preferred embodiment, illustrated in figures 13, 14, 15b, 17a and 17b, the cantilevered protrusion BL is tightly connected to the column 2 with a screw LF, guaranteeing the contact of the cantilevered protrusion BL and the vertical face CV of the column 2, and thus forming an anti-torque system ATS.

[0340] Observing figure 17a, despite that the vertical protruding reinforcement AG is placed at the centre of the corbel 2, it can be seen that it describes an anti-torque system against counterclockwise torque moments almost identical to that described in figure 16b. The only difference is that an additional small compressive force F’2,ccan be supported by the steel angle SA united to the cantilevered protrusion BL that is used to fix the screw LF to the column 2. This provides a slightly superior torque strength to this embodiment as compared to the embodiment described in figure 16b.

[0341] However, for clockwise torque moments, the anti-torque system ATS described in figure 17b is substantially different to that described in figure 16c, even if in both cases the unbalancing torque moment Ta,uis virtually the same. In figure 17b, the mechanism described has similarities similar to that described in figure 17a, but inverting the sign of the moments and couples of forces. The balancing torque moment T4,b is formed by a couple of equal forces F4, one being a shear force F4,v at the bottom of the vertical protruding reinforcement AG and the other one being a tension force F4,v on the screw LF connecting the cantilevered protrusion BL with the column 2.

[0342] One of the main advantages of this embodiment of the anti-torque system ATS when compared to other previously described anti-torque systems is that in this embodiment both of the forces of the couple F2,cand F2,v; F4,tand F4,vproducing the balancing torque moment are horizontal forces. Thanks to that horizontality, the couples of forces can use large lever arms 62, e’2, 64, as the forces of the couple may be placed at the top and at the bottom of the girder 3, that is typically a narrow and down-dropping beam. This large lever arms are not only several times larger than the lever arms (e in figure 7; 64 in figure 16c) in the anti-torque systems using vertical forces, but they are also clearly larger than the lever arms of the unbalancing moments due to eccentricity of the load of the floor elements out of the axis of the corbel. The large lever arm of this embodiments allows that the couple of forces producing the balancing moment can be significantly smaller than the forces producing the unbalancing moment. Thus, this provides a very high torque resistance to the junction defined in this embodiment.

[0343] According to a preferred embodiment, illustrated in figures 18, 11 and 13, the ends of each couple of prefabricated girders 3, at their junction with a column 2, lintels CL are supported on the flanges A of the girders 3, being the length of the lintels CL approximately the same as the dimension I of the column 2.

[0344] Figure 7 illustrates the torque moment caused during the erection process, and the action of the anti-torque system that counteracts the torque moment. During the erection process, the weight W of the floor elements 4, is placed eccentrically in relation to the axis of the bearing of the girder 3, this the axis of the corbel 6 supporting the girder 3. This produces an unbalancing torque moment T, that amounts to weight W times the eccentricity E. This unbalancing torque moment tends to produce the turning of the girder 3 round its bottom, and could eventually lead it to fall laterally. To prevent this from happening, a mechanism has to be put in place that is able to counteract the unbalancing torque moment, with a balancing torque moment. This is achieved by means of the anti-torque system described in this embodiment. The balancing moment is achieved by means of a couple of forces F separated a distance e. The forces are a compression Fcon one side of the top face of the corbel 6 and a tension Fton the vertical reinforcement AG, that retains the girder 3, in this embodiment, by means of the steel plate SP and a nut.

[0345] According to a preferred embodiment, illustrated in figures 5a and 19, the floors supported on the girders 3 are formed by a combination of the following elements:

[0346] a) A multiplicity of prefabricated and self-supporting floor elements 4 with a rectangular and elongated floor plan including reinforcement near its bottom face, being such reinforcement parallel to the major dimension of the floor element 4, and including on the top planar face SF of the floor element 4 grooves G or protrusions P with a depth D not smaller than the coarse aggregate CA of the cementitious material placed at the job to form a topping layer T on the prefabricated and self-supporting floor elements 4, and having these grooves G or protrusions P a width W not smaller than 1 ,5 times their depth D, being the width W the dimension parallel to the major dimension of the floor element 4.

[0347] b) Reinforcement to resist negative moments of the floor NRF placed at the job, placed transversely to the girder 3 that supports the floor elements 4, and being the negative-moment reinforcement NRF extending over the top planar face SF of the floor elements, and being the reinforcement NRF embedded in the topping layer T.

[0348] c) T opping layer T formed with cementitious material poured at the job, covering the top planar face SF of the prefabricated and self-supporting floor elements 4, the girders 3 and the reinforcement placed at the job NRB, NRF, being the size of the coarse aggregate CA of the cementitious material not larger than the depth D of the grooves G or protrusions P included on the superior planar face SF of the prefabricated and self-supporting floor elements 4. d) Having the prefabricated and self-supporting floor elements 4 a geometry of their lateral faces such that a cavity SK is formed along the junction between each pair of floor elements, having such cavity SK a geometry that it allows for cementitious material placed at the job while forming the topping layer T to enter the cavity SK and fill it with the same cementitious material and being solidary with the topping layer T.

[0349] According to a preferred embodiment, illustrated in figure 19, reinforcement is placed to resist positive moments PRF in the zone where prefabricated and self-supporting floor elements 4 are supported, that is, reinforcements are placed transversally to girders 3, on top of the girders and placed in bottom part of the cavities SK formed between the lateral faces of each pair of prefabricated and self-supporting floor elements 4, being the cavities filled with cementitious material placed at the job when forming the topping layer T.

[0350] A second aspect of the invention is a method for erecting a building E as described previously, which comprises a first step of constructing foundations embedded in the ground, leaving vertical ducts VVS embedded at the top of the foundations F, arranged in positions that allow for the insertion of vertical reinforcements AVS protruding from the bottom of the prefabricated column 2 that has to sit on each foundation F and also embedded at the top of each foundation F at least two levelling devices LD arranged to allow for the levelling of the corresponding prefabricated column 2s.

[0351] A second step is placing each column 2 on top of its corresponding foundation F, arranging it such that vertical reinforcements AVS protruding from the bottom of the prefabricated column 2 enter in the vertical ducts VVS embedded in each corresponding foundation F without the need of props to sustain de columns.

[0352] The following steps are levelling each column 2 using the levelling devices LV embedded in the foundation and pouring cementitious material with limited shrinkage LSC to completely fill the vertical ducts VVS embedded in the top part of each foundation F so that the vertical reinforcements AVS protruding from the bottom of each column 2 get connected to the corresponding foundation F after the hardening of the cementitious material with limited shrinkage LSC.

[0353] Then, placing the girders 3 on the corbels 6 protruding of the corresponding columns 2, including each girder, the corresponding negative-moment reinforcement NRB on the top of the beam, inside of its out-propping stirrups, and free for movement.

[0354] The next steps are connecting the girders 3 with the corbels 6 and / or directly with the columns 2 by means of the anti-torque system ATS, without the need of props to sustain the columns 2 or the girders, and placing prefabricated self-supporting floor elements 4, including grooves G or protrusions P on their superior planar face SF, directly on the corresponding girders 3, without the need of props to sustain the columns 2, the girders 3 or the floor elements 4. Later, sliding of the negative-moment reinforcement NRB of each girder 3 through the out-propping stirrups of the beam, through the horizontal duct VH of the corresponding column 2, and through the out-propping stirrups onto the girder 3 placed at the other side of the column 2.

[0355] The following steps are placing the reinforcement NRF to resist the negative moments of the floor such that the reinforcement extends over the top planar face SF of the floor elements 4 placed at each side of each girder 3, placing formers locally around each girder-column junction and placing a reinforcement mesh all over the floor elements 4 and pouring a topping layer T all over the floor elements 4, the girders 3, and the girder-column junctions, being the topping layer formed with cementitious material with coarse aggregate not larger than the depth (D) of the grooves G or protrusions P included on the superior planar face SF of the prefabricated self-supporting floor elements 4.

[0356] The final steps are repeating an analogous sequence to erect the rest of the structure 1 of the building E and, while the structure 1 is being built or after it has been completed, erecting the walls 5 of the building E supported on the structure.

[0357] A third aspect of the present invention is a building E, which can be seen in figures 21a, 21b and 21c, including zones ZWOFC with flat ceiling FC -seen in figure 21c-, without partition walls 5d and including a structure 1 that comprises:

[0358] - prefabricated columns 2 made of reinforced concrete;

[0359] - prefabricated girders 3 supported at their ends on the columns 2; and

[0360] - prefabricated floor elements 4 supported at their ends on the girders 3;

[0361] wherein the columns 2 have a cross-section with an aspect ratio between 1 and 0,3, 2AR, and the girders 3WFC have bottom flanges AB that down-drop under the soffit SO of the prefabricated floor elements 4 a vertical dimension DD that is more than 50 times smaller than the span FS of the floor elements 4 supported on the girders 3.

[0362] In the mentioned figures, 21a, 21b and 21c, all the main features of this embodiment can be seen, as well as the relation that they have in general terms to one another.

[0363] According to a preferred embodiment, illustrated in figures 22a, 22b, 22c, the reinforcement of each of the bottom flanges AB of the girder is formed by a continuous U-shaped reinforcement CUD, being all of this continuous U-shaped reinforcement included in a diagonal plane DP that is both perpendicular to the cross-section of the girder 3WFC and, for each flange AB, parallel to a line starting close to the bottom and most exterior corner of that flange (AB) and passing tangent to the point where the top horizontal face of the flange AB contacts de web of the girder 3WFC.

[0364] In Figure 32 it can be seen a strut and tie diagram on the cross-section of the girder 3WFC with bottom flanges AB. The continuous U-shaped reinforcement CUD functions as a tie. Thus, it resists tensions. A strut (= line of major compressions) is depicted that shows an oblique line from the point of application of the load (center of the bearing pad where the floor element 4 is supported). This strut ends close to the bottom face of the girder. From there the load is “taken” as tension (=tie) by the vertical reinforcement of the shear reinforcement (hoop or stirrup). Thanks to that strut and tie analysis, that clearly applies here given the reduced span-to-depth ratio of the flange (functioning as a small lateral cantilever), it is made clear that this shallow flange does not function as a member under flexure and, thus it does not need to have horizontal flexure reinforcement.

[0365] The reduced down-drop of the flanges of the girder are illustrated in figures 21a, 21b and very specially in figure 21c, where it is obvious how long is the span FS of the floor elements 4 as compared to the very reduced depth DD of the bottom flanges AB of the girder 3WFC.

[0366] Figure 35 also illustrates this embodiment, but as an example of what the current embodiments is able to overcome: the reinforcement of the bottom flange formed by a hoop of reinforcement. In the girder of the state of the art, depicted in Figure 35, it is clear how the same rebar is used to reinforce the top and the bottom face, and the geometry of that bent rebar (diameter and radius of bending) plus the thickness of the top and bottom cover are the parameters that prevent the reduction of the depth of the bottom flange beyond a certain limit.

[0367] The current embodiments clearly overcome the limitations set by the need of reinforcement in two faces and the limitations imposed by the radius of bending of the rebar bent in a plane parallel to the cross-section of the girder.

[0368] According to a preferred embodiment, illustrated in Figures 23a and 23b, the reinforcement of each of the bottom flanges AB of the girder is formed by a series of hooks HK spaced along the length of the beam, and being each of these hooks HK welded to a bent steel plate BP that covers the top horizontal face of the bottom flange AB and the lateral vertical face of the web of the girder, running this bent steel plate BP all along the girder, and being each of these hooks HK included in a plane parallel to the cross-section of the girder 3WFC and, including each of the hooks a long leg DL forming a diagonal line included in a diagonal plane DP that is both perpendicular to the cross-section of the girder 3WFC and, for each flange AB, parallel to a line starting close to the bottom and most exterior corner of that flange AB and passing tangent to the point where the top horizontal face of the flange AB contacts de web of the girder 3WFC.

[0369] In terms of structural analysis, the behavior of this embodiment is similar to that of the previous embodiment. Thus, the strut and tie diagram displayed in Figure 32 can also be applied to this embodiment. And also, the girder of the state of the art displayed in Figure 35 serves as a contrast to what is achievable thanks to this embodiment.

[0370] Also Figures 21a, 21b and especially 21c illustrate how a girder 3WFC, that can be reinforced as in this embodiment, allows to have what is called flat ceiling in this document (see definition above)

[0371] According to a preferred embodiment, illustrated in Figures 21a, 21b and especially 21c the girders 3DFC have top flanges AT that down-drop under the soffit SO of the prefabricated floor elements 4 a vertical dimension DD that is more than 50 times smaller than the span FS of the floor elements 4 supported on the girders 3.

[0372] According to a preferred embodiment, illustrated in Figures 21a, 21b and especially 21c, the building E is including zones ZWFC with flat ceiling FC and with walls 5 and including a structure 1 that comprises:

[0373] - prefabricated columns 2 made of reinforced concrete;

[0374] - prefabricated girders 3 supported at their ends on the columns 2; and

[0375] - prefabricated floor elements 4 supported at their ends on the girders 3;

[0376] wherein the columns 2 have a rectangular transversal cross-section such that in the crosssection of these columns 2 the direction of the depth h coincides with the largest size of the transversal cross-section I and the width direction b coincides with the smallest size the transversal cross-section t, such that in those zones ZW having walls 5, the rectangular columns 2 of the building E are:

[0377] embedded within a wall 5, the column being hidden in the thickness of the wall 5, with the direction of the depth h of the column 2 being parallel to the direction of the wall 5; and / or

[0378] placed at the junction of two walls 5 forming an angle between them, with the direction of the depth h of the column 2 being parallel to the direction of one of the walls and the direction of the other wall being transversal to the depth h of the column 2, such that the column is embedded in the thickness of the wall parallel to the depth h of the column 2

[0379] being the thickness e1 , e2, e3...en of each of the walls 51 , 52, 53...5n respectively larger than the corresponding dimensions w1, w2, w3...wn of the web of the respective girders 31, 32, 33...3n and being each dimension e1, e2, e3...en of the respective walls 51, 52, 53...5n larger than the smallest dimension t1 , t2, t3...tn of the cross-section of the respective columns 21, 22, 23...2n for those columns which direction of the depth h coincides with the direction of the wall 5. And being the girders 3DFC provided with top flanges AT that down-drop under the soffit SO of the prefabricated floor elements 4 a vertical dimension DD that is more than 50 times smaller than the span FS of the floor elements 4 supported on the girders 3.

[0380] According to a preferred embodiment, illustrated in Figures 29, 30 and 31 (including all subindex a, b and c), the girders 3 have the web reinforced split into two groups of hoops spaced along the axis of the girder 3, being one of the groups formed by interior hoops IH that are entirely embedded in the precast concrete of the girder 3, having each interior hoop IH a vertical dimension approximately equal to the vertical dimension of the girder 3, and being the other group of hoops formed by top exterior hoops TEH, having each top exterior hoop TEH a part protruding out of the precast concrete of the girder 3 and another part embedded in the precast concrete of the girder 3.

[0381] As mentioned above, this embodiment allows to guarantee a good torque strength during the erection process, and it also allows to optimize the consumption of hoops, as is dissociates the reinforcement required for torque and shear to the reinforcement required for horizontal shear strength (that is typically high, especially in girders with narrow webs).

[0382] Also Figure 35 illustrates the advantages of this embodiment, as it puts forward how in girders of the state of the art, the lack of a closed hoop in the interior of the precast member leads to a weakness of the girder in terms of torque forces during the erection process.

[0383] According to a preferred embodiment, illustrated in Figures 29, 30 and 31 (including all subindex a, b and c), girders 3 have the top flanges AT reinforced by a continuous U-shaped reinforcement CUH included in a horizontal plane included within the top flanges AT of the girders 3.

[0384] In figures 33a and 33b are showed strut and tie diagrams that put forward that the slenderness of the top flanges AT of these girders 3DFC with top flanges is even smaller than the slenderness of the bottom flanges AB of the girders 3WFC with bottom flanges. This is because in the case of girders with top flanges 3DFC there is no need to leave on top of the flange room to pour concrete in the job, given that this concrete can be poured directly on the web of the girder 3DFC with flanges at the top AT. This is because at the end of each floor element it is required that concrete poured at the job to guarantee the proper contact between concrete parts, and so guarantee the proper transmission of compression forces, when con floor elements function under negative moment bending (that compresses the bottom part of the floor element).

[0385] Thus, the fact that for girders 3DFC with flanges at the top, it es even more obvious that the strut and tie model is an appropriate one to analyse the mechanic behaviour of the small cantilever that the flange is. For this cantilever, using an analysis under flexure would clearly not make sense, as flexure analysis does only apply to elements having a span-to-depth slenderness of 2 to 1, or more. In these figures it can be seen how the tie in the strut and tie model is horizontal. As a result, the continuous U-shaped reinforcement is very adequate for the top flanges. Moreover, it is particularly convenient to install during the production process.

[0386] According to a preferred embodiment, illustrated in several Figures listed below in detail, the prefabricated columns 2 include one or several of the following features:

[0387] a) The column 2 has its junction CJ with the column above 2s placed at a height several tens of centimetres away from the closest floor placed under FU this junction CJ and several centimetres away from the closest floor placed above FA this junction CJ;

[0388] b) The column 2 includes corbels 6FU protruding beyond the cross-section of the column 2, meant for supporting floors for one or several of the levels through which the column 2 such that the corbel is connected to the column with uninterrupted reinforcements UCR coming out of the cross-section of the column;

[0389] c) The column 2 includes corbels 6FI protruding beyond the cross-section of the column 2, meant for supporting floors for one or several of the levels through which the column 2 such that the corbel is connected to the column with reinforcements ICR coming out of the crosssection of the column, being each reinforcement interrupted at the level of the face of the vertical column by a threaded steel cap TSC;

[0390] d) The column 2 includes one or more threaded steel cap TSC on a vertical face CVF facing a girder 3, being each threaded steel cap TSC intended to receive a bolt to fast an anti-torque bracket ATB during the erection process;

[0391] e) The column includes a horizontal duct VH with a rectangular cross-section that crosses the column to allow for the passing of negative-moment reinforcement of the girder NRB, such that the top face of the rectangular cross-section is placed several centimetres above the top face of the topping layer T, and so allows for the pouring of cementitious material in the horizontal duct VH after the topping layer T has hardened.

[0392] The feature a) of the current embodiment is illustrated in Figures 24 and 25. The features b) and c) of the current embodiment are illustrated in Figure 26.

[0393] The feature d) of the current embodiment is illustrated in Figures 27a, 27b and 27c.

[0394] The feature e) of the current embodiment is illustrated in Figures 26, 34a and 34b.

[0395] According to a preferred embodiment, illustrated in Figures 28 and 29a, the girders 3ed supporting an edge of a floor and / or self-supporting floor elements 4 include a tab VT protruding vertically that has its top face higher than the top face of the topping layer T.

[0396] In Figure 28 are showed floor elements 4 including tab VT vertically protruding that acts as a former to contain the concrete of the topping T poured at the job. Also, it is showed how the tab VT can be used to support security means SM, such as the railings in the figure. However, it is obvious that other security means may be arranged taking advantage of the tab or taking advantage of the fact that, as displayed in the drawing the floor element has a flat face and has a solid cross section in the part of the floor element that is close to the tab VT. The fact that the tab has a flat surface and in that zone the section of the slab is solid, would allow to screw, to pin or in other way fix a variety of security means SM to that edge of the structural floor.

[0397] Despite that the tab VT will work well as a concrete container, at the ends of the floor elements 4, there where those floor elements are supported on the girders 3, there may be a discontinuity in the means to contain the concrete poured in the job for the topping T. Thus, in those areas of discontinuity it may be necessary to place some small former, that may be screwed, pinned or in other way fixed to the tabs VT of two floor elements 4.

[0398] According to a preferred embodiment, illustrated in Figures 27a, 27b and 27c, the girders 3 include at their ends, on their top face, a threaded steel cap TSC intended to receive a bolt to fast an anti-torque bracket ATB during the erection process.

[0399] In this text, the term "comprises" and its derivatives (such as "comprising", etc.) should not be understood in an exclusive sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include other elements.

[0400] Obviously, the invention is not limited to the specific embodiments described herein, but also encompasses any variation that may be considered by any person skilled in the art within the general scope of the invention as defined in the claims.

Claims

1. CLAIMS1. Building (E) including zones (ZW) with walls (5) and including a structure (1) that comprises: - prefabricated columns (2) made of reinforced concrete;3.- prefabricated girders (3) supported at their ends on the columns (2); and4.- prefabricated floor elements (4) supported at their ends on the girders (3);5.characterized in that the columns (2) have a rectangular transversal cross-section such that in the cross-section of these columns (2) the direction of the depth (h) coincides with the largest size of the transversal cross-section I and the width direction (b) coincides with the smallest size the transversal cross-section t, such that in those zones (ZW) having walls (5), the rectangular columns (2) of the building (E) are:6.embedded within a wall (5), the column being hidden in the thickness of the wall (5), with the direction of the depth (h) of the column (2) being parallel to the direction of the wall (5); and / or7.placed at the junction of two walls (5) forming an angle between them, with the direction of the depth (h) of the column (2) being parallel to the direction of one of the walls and the direction of the other wall being transversal to the depth (h) of the column (2), such that the column is embedded in the thickness of the wall parallel to the depth (h) of the column (2)]8.being the thickness (e1, e2, e3...en) of each of the walls (51, 52, 53...5n) respectively larger than the corresponding dimensions (w1, w2, w3...wn) of the web of the respective girders (31, 32, 33...3n) and being each dimension (e1, e2, e3...en) of the respective walls (51, 52, 53...5n) larger than the smallest dimension (t1, t2, t3...tn) of the cross-section of the respective columns (21, 22, 23...2n) for those columns which direction of the depth (h) coincides with the direction of the wall (5).

2. Building (E) according to claim 1 , where the floor elements (4) are prefabricated and / or self-supporting.

3. Building (E) according to any of the prior claims, where the walls (5) are walls including fagades (5f) and main partition walls (5d).

4. Building (E) according to any of the prior claims, where partition walls (5d) have a thickness between 15 cm and 25 cm.

5. Building (E) according to any of the previous claims, where at least one of the prefabricated columns (2) is placed with the direction of its depth (h) being transverse to the direction of thedepth (h) of the rest of the columns of the building.

6. Building (E) according to any of the prior claims, where the prefabricated columns (2) have one or several of the following features:14.a) The prefabricated columns (2) are made in one piece with a total height corresponding to the height of several storeys of the building (E): multi-storey columns (2m);15.b) The column (2) includes corbels (6) protruding beyond the rectangular plan of the column, meant for supporting the prefabricated girders (3), including such corbels a vertical protruding reinforcement (AG), as a part of the erection anti-torque system (ATS) of the prefabricated girder (3);16.d) The column (2) includes at the level of each storey of the building (E) that it passes through, a horizontal duct (VH) having an elongated cross-section, such that the largest dimension (vd) is placed vertically, and the longitudinal axis (dl) of the duct (VH) being horizontal and parallel to the direction of the depth (h) of the prefabricated column (2), being such duct (VH) crossed by negative-moment reinforcement of the girder (NRB) running through and along the duct (VH), being the reinforcement (NRB) placed at the job, and being the duct (VH) filled with cementitious material poured at the job;17.e) The column (2) includes at its top, at the junction with the column of the storey above (2s), at least two levelling devices (LD);18.f) The column (2) includes at its top, at the junction with the prefabricated column of the storey above (2s), vertical ducts (VVS) embedded in the column (2), arranged in such positions that allow for the insertion of vertical reinforcements (AVS) protruding from the bottom of the prefabricated column above (2s);19.g) The column (2) includes vertical reinforcements (AVS) protruding from its bottom, for the insertion of those reinforcements in vertical ducts (VVS) embedded in the support below (S), being this support below either the prefabricated column below (2i) or the foundation (F) of the column (2), being such ducts (VVS) filled with cementitious material with limited shrinkage (LSC) placed at the job.

7. Building (E) according to any of the prior claims, where those of the prefabricated girders (31, 32, 33...3n) that have their longitudinal axis parallel to the direction of the depth (h) of the corresponding column or columns (21, 22, 23...2n) where each girder (31, 32, 33...3n) is supported, the girders (31, 32, 33...3n) have the corresponding width of the web (w1, w2, w3...wn) not larger than the smallest dimension (t1, t2, t3... tn) of the corresponding columns (21, 22, 23...2n).

8. Building (E) according to any of the previous claims, where the prefabricated girders (3)have a cross-section in the shape of a T, where the top part of the girders (3) has a width larger than the web (w), thus forming a head of width (C), such that the top part of the cross-section has two flanges (A), one at each side of the web, that make it easier for the prefabricated and self-supporting floor elements (4) to be supported on both sides of the top of the girders (3).

9. Building (E) according to claim 1, where prefabricated girders (3) include a vertical duct (VVB) at each of their ends, as well as a steel plate (SP) including a perforation placed on top of the vertical duct (VVB), as a part of the erection anti-torque system (ATS) together with the vertical reinforcement (AG) protruding out of the corresponding corbel (6) connected to the prefabricated column (2).

10. Building (E) according to claims 7 and 8, where prefabricated girders (3), at their junction with a column (2) have a cantilevered protrusion (BL) that has a cross section similar to that of the flange (A), and extends along all the dimension (I) of the column (2) and next to the vertical face (CV) of the column (2), forming a lintel (BL) that facilitates the support of the prefabricated and self-supporting floor elements (4) during the erection phase, and the cantilevered protrusion (BL) functions also as a part of the erection anti-torque system (ATS).

11. Building (E) according to claims 10, where the cantilevered protrusion (BL) is tightly connected to the column (2) with a screw (LF), guaranteeing the contact of the cantilevered protrusion (BL) and the vertical face (CV) of the column (2), and thus forming an anti-torque system (ATS).

12. Building (E) according to claims 7 and 8 where on the ends of each couple of prefabricated girders (3), at their junction with a column (2), lintels (CL) are supported on the flanges (A) of the girders (3), being the length of the lintels (CL) approximately the same as the dimension (I) of the column (2).

13. Building (E) according to claim 1, where the floors supported on the girders (3) are formed by a combination of the following elements:27.a) A multiplicity of prefabricated and self-supporting floor elements (4) with a rectangular and elongated floor plan including reinforcement near its bottom face, being such reinforcement parallel to the major dimension of the floor element (4), and including on the top planar face (SF) of the floor element (4) grooves (G) or protrusions (P) with a depth (D) not smaller than the coarse aggregate (CA) of the cementitious material placed at the job to form a topping layer (T) on the prefabricated and self-supporting floor elements (4), and having these grooves (G) or protrusions (P) a width (W) not smaller than 1,5 times their depth (D), being the width (W) the dimension parallel to the major dimension of the floor element (4).28.b) Reinforcement to resist negative moments of the floor (NRF) placed at the job, placed transversely to the girder (3) that supports the floor elements (4), and being the negativemoment reinforcement (NRF) extending over the top planar face (SF) of the floor elements, and being the reinforcement (NRF) embedded in the topping layer (T).29.c) Topping layer (T) formed with cementitious material poured at the job, covering the top planar face (SF) of the prefabricated and self-supporting floor elements (4), the girders (3) and the reinforcement placed at the job (NRB, NRF), being the size of the coarse aggregate (CA) of the cementitious material not larger than the depth (D) of the grooves (G) or protrusions (P) included on the superior planar face (SF) of the prefabricated and self-supporting floor elements (4).30.d) Having the prefabricated and self-supporting floor elements (4) a geometry of their lateral faces such that a cavity (SK) is formed along the junction between each pair of floor elements, having such cavity (SK) a geometry that it allows for cementitious material placed at the job while forming the topping layer (T) to enter the cavity (SK) and fill it with the same cementitious material and being solidary with the topping layer (T).

14. Building (E) according to claim 12, where reinforcement is placed to resist positive moments (PRF) in the zone where prefabricated and self-supporting floor elements (4) are supported, that is, reinforcements are placed transversally to girders (3), on top of the girders and placed in bottom part of the cavities (SK) formed between the lateral faces of each pair of prefabricated and self-supporting floor elements (4), being the cavities filled with cementitious material placed at the job when forming the topping layer (T).

15. A method for erecting a building (E) as described in any of the previous claims, which comprises the following steps:33.- constructing foundations embedded in the ground, leaving embedded at the top of the foundations (F) vertical ducts (VVS), arranged in positions that allow for the insertion of vertical reinforcements (AVS) protruding from the bottom of the prefabricated column (2s) that has to sit on each foundation (F) and also embedded at the top of each foundation (F) at least two levelling devices (LD) arranged to allow for the levelling of the corresponding prefabricated column (2s),34.- placing each column (2) on top of its corresponding foundation (F), arranging it such that vertical reinforcements (AVS) protruding from the bottom of the prefabricated column enter in the vertical ducts (VVS) embedded in each corresponding foundation (F) without the need of props to sustain de columns,35.- levelling each column (2) using the levelling devices (LV) embedded in the foundation, - pouring cementitious material with limited shrinkage (LSC) to completely fill the vertical ducts (VVS) embedded in the top part of each foundation (F) so that the vertical reinforcements (AVS) protruding from the bottom of each column (2) get connected to the corresponding foundation (F) after the hardening of the cementitious material with limited shrinkage (LSC), - placing the girders (3) on the corbels (6) protruding of the corresponding columns (2), including each girder, the corresponding negative-moment reinforcement (NRB) on the top of the beam, inside of its out-propping stirrups, and free for movement,36.- connecting the girders (3) with the corbels (6) and / or directly with the columns (2) by means of the anti-torque system (ATS), without the need of props to sustain the columns or the girders,37.- placing prefabricated self-supporting floor elements (4), including grooves (G) or protrusions (P) on their superior planar face (SF), directly on the corresponding girders (3), without the need of props to sustain the columns (2), the girders (3) or the floor elements (4),38.- sliding of the negative-moment reinforcement (NRB) of each girder (3) through the out-propping stirrups of the beam, through the horizontal duct (VH) of the corresponding column (2), and through the out-propping stirrups onto the girder (3) placed at the other side of the column (2),39.- placing the reinforcement (NRF) to resist the negative moments of the floor elements (4) extending over the top planar face (SF) placed at each side of each girder (3),40.- placing formers locally around each girder-column junction,41.- placing a reinforcement mesh all over the floor elements (4) and pouring a topping layer (T) all over the floor elements (4), the girders (3), and the girder-column junctions, being the topping layer formed with cementitious material with coarse aggregate not larger than the depth (D) of the grooves (G) or protrusions (P) included on the superior planar face (SF) of the prefabricated self-supporting floor elements (4),42.- repeating an analogous sequence to erect the rest of the structure (1) of the building (E), - while the structure (1) is being built or after it has been completed, erecting the walls (5) of the building (E) supported on the structure.

16. Building (E) including zones (ZWOFC) with flat ceiling (FC), without partition walls (5d) and including a structure (1) that comprises:44.- prefabricated columns (2) made of reinforced concrete;45.- prefabricated girders (3) supported at their ends on the columns (2); and46.- prefabricated floor elements (4) supported at their ends on the girders (3);47.characterized in that the columns (2) have a cross-section with an aspect ratio between 1 and 0,3 (2AR) and the girders (3WFC) have bottom flanges (AB) that down-drop under the soffit (SO) of the prefabricated floor elements (4) a vertical dimension (DD) that is more than 50 times smaller than the span (FS) of the floor elements (4) supported on the girders (3)17. Building (E) according to claim 16 where the reinforcement of each of the bottom flanges (AB) of the girder is formed by a continuous U-shaped reinforcement (CUD), being all of this continuous U-shaped reinforcement included in a diagonal plane (DP) that is both perpendicular to the cross-section of the girder (3WFC) and, for each flange (AB), parallel to a line starting close to the bottom and most exterior corner of that flange (AB) and passing tangent to the point where the top horizontal face of the flange (AB) contacts de web of the girder (3WFC).

18. Building (E) according to claims 16 where the reinforcement of each of the bottom flanges (AB) of the girder is formed by a series of hooks (HK) spaced along the length of the beam, and being each of these hooks (HK) welded to a bent steel plate (BP) that covers the top horizontal face of the bottom flange (AB) and the lateral vertical face of the web of the girder, running this bent steel plate (BP) all along the girder, and being each of these hooks (HK) included in a plane parallel to the cross-section of the girder (3WFC) and, including each of the hooks a long leg (DL) forming a diagonal line included in a diagonal plane (DP) that is both perpendicular to the cross-section of the girder (3WFC) and, for each flange (AB), parallel to a line starting close to the bottom and most exterior corner of that flange (AB) and passing tangent to the point where the top horizontal face of the flange (AB) contacts de web of the girder (3WFC).

19. Building (E) according to any of the claims 1 to 14, where the girders (3DFC) have top flanges (AT) that down-drop under the soffit (SO) of the prefabricated floor elements (4) a vertical dimension (DD) that is more than 50 times smaller than the span (FS) of the floor elements (4) supported on the girders (3).

20. Building (E) including zones (ZWFC) with flat ceiling (FC) and with walls (5) and including a structure (1) that comprises:52.- prefabricated columns (2) made of reinforced concrete;53.- prefabricated girders (3) supported at their ends on the columns (2); and54.- prefabricated floor elements (4) supported at their ends on the girders (3);55.characterized in that the columns (2) have a rectangular transversal cross-section such that in the cross-section of these columns (2) the direction of the depth (h) coincides with the largest size of the transversal cross-section I and the width direction (b) coincides with the smallest size the transversal cross-section t, such that in those zones (ZW) having walls (5), the rectangular columns (2) of the building (E) are: embedded within a wall (5), the column being hidden in the thickness of the wall (5), with the direction of the depth (h) of the column (2) being parallel to the direction of the wall (5); and / or56.placed at the junction of two walls (5) forming an angle between them, with the direction of the depth (h) of the column (2) being parallel to the direction of one of the walls and the direction of the other wall being transversal to the depth (h) of the column (2), such that the column is embedded in the thickness of the wall parallel to the depth (h) of the column (2)]57.being the thickness (e1, e2, e3...en) of each of the walls (51, 52, 53...5n) respectively larger than the corresponding dimensions (w1, w2, w3...wn) of the web of the respective girders (31, 32, 33...3n) and being each dimension (e1, e2, e3...en) of the respective walls (51, 52, 53...5n) larger than the smallest dimension (t1, t2, t3...tn) of the cross-section of the respective columns (21, 22, 23...2n) for those columns which direction of the depth (h) coincides with the direction of the wall (5). And being the girders (3DFC) provided with top flanges (AT) that down-drop under the soffit (SO) of the prefabricated floor elements (4) a vertical dimension (DD) that is more than 50 times smaller than the span (FS) of the floor elements (4) supported on the girders (3).

21. Building (E) according to claims 1 to 14 or claims 19 to 20 where girders (3) have the web reinforced split into two groups of hoops spaced along the axis of the girder (3), being one of the groups formed by interior hoops (IH) that are entirely embedded in the precast concrete of the girder (3), having each interior hoop (IH) a vertical dimension approximately equal to the vertical dimension of the girder (3), and being the other group of hoops formed by top exterior hoops (TEH), having each top exterior hoop (TEH) a part protruding out of the precast concrete of the girder (3) and another part embedded in the precast concrete of the girder (3).

22. Building (E) according to claims 1 to 14 or claims 19 to 21 where girders (3) have the top flanges (AT) reinforced by a continuous U-shaped reinforcement (CUH) included in a horizontal plane included within the top flanges (AT) of the girders (3).

23. Building (E) according to claims 1 to 14 or claims 16 to 20 where the prefabricated columns (2) include one or several of the following features:61.a) The column (2) has its junction (CJ) with the column above (2s) placed at a height several tens of centimetres away from the closest floor placed under (FU) this junction (CJ) and several centimetres away from the closest floor placed above (FA) this junction (CJ);62.b) The column (2) includes corbels (6FU) protruding beyond the cross-section of the column (2), meant for supporting floors for one or several of the levels through which the column (2) such that the corbel is connected to the column with uninterrupted reinforcements (UCR) coming out of the cross-section of the column;63.c) The column (2) includes corbels (6FI) protruding beyond the cross-section of the column (2), meant for supporting floors for one or several of the levels through which the column (2) such that the corbel is connected to the column with reinforcements (ICR) coming out of the cross-section of the column, being each reinforcement interrupted at the level of the face of the vertical column by a threaded steel cap (TSC);64.d) The column (2) includes one or more threaded steel cap (TSC) on a vertical face (CVF) facing a girder (3), being each threaded steel cap (TSC) intended to receive a bolt to fast an anti-torque bracket (ATB) during the erection process;65.e) The column includes a horizontal duct (VH) with a rectangular cross-section that crosses the column to allow for the passing of negative-moment reinforcement of the girder (NRB), such that the top face of the rectangular cross-section is placed several centimetres above the top face of the topping layer (T), and so allows for the pouring of cementitious material in the horizontal duct (VH) after the topping layer (T) has hardened;24. Building (E) according to claims 1 to 14 or claims 19 to 23 where the girders (3ed) supporting an edge of a floor and / or self-supporting floor elements (4) include a tab (VT) protruding vertically that has its top face higher than the top face of the topping layer (T).

25. Building (E) according to claims 1 to 14 or claims 19 to 24 where the girders (3) include at their ends, on their top face, a threaded steel cap (TSC) intended to receive a bolt to fast an anti-torque bracket (ATB) during the erection process.

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