Device for reinforcing existing structures

Abstract

Reinforcement system applicable to truss-type structures, which supplements the strength of linear elements with insufficient structural capacity (1) and which consists of a linear reinforcement element (2), ultra-high performance concrete elements (3) which transfer the load between the existing structure and the linear reinforcement element (2) with the help of the reliefs (4) of the existing structure and the projections (5) or reliefs of the linear reinforcement element (2) at the nodes of the truss.

Description

TECHNICAL SECTOR

[0001] This invention concerns a system for reinforcing existing structures.

[0002] This system is particularly adapted to truss-type bridge structures and serves to increase the structure's load-bearing capacity.BACKGROUND OF THE INVENTION

[0003] Today, the need to reinforce structures has increased due to the ageing of many structures and the advisability of making them capable of withstanding greater loads than those for which they were originally designed.

[0004] Structural rehabilitation specialists are often faced with the problem of designing a structural reinforcement to improve the load-bearing capacity, either due to an increase in the expected overloads or to deterioration that needs to be compensated for. One of the tools available to these professionals would be to arrange additional linear elements parallel to the structure's original ones, enabling it to bear more load than it could initially bear. In this case, it would be a matter of providing the necessary quantities of steel to achieve the desired resistance capacity. These solutions are normal because the material input is concentrated where it is required. In other words, it has financial and constructional advantages.

[0005] The traditional way of adding this additional material has been to weld steel elements to those originally existing in the structure. There are two problems with this approach. The first is that in old trusses the steel may not be weldable. The second problem is that the nodes of the truss, which is where it is usually advisable to start and finish a reinforcement, are areas with a complex geometry, where stress transfer is complicated, making the solution more expensive.

[0006] Another way of adding the reinforcement elements is by bolting them on, enabling them to be applied to old, reinforced trusses simply by drilling them to then place the new bolts. With this method, the stress transfer at the nodes tends to get even more complicated, as the nodes are already heavily drilled to take the original fixtures.

[0007] When the objective is specifically to repair corrosion, it is often necessary to remove rivets, to remove defective elements, to replace them with new ones, but already fixed with bolts. Such removal of rivets is a specialised and non-standardised operation, and therefore entails risks and uncertainties, which, in turn, makes it costly. Also, if a number of rivets of elements making up the bridge's bracing system need to be removed simultaneously, it may be necessary to shore up the truss.

[0008] In this proposed reinforcement system, the aim is to relieve truss elements of primarily axial stresses and to replace complicated or risky execution methods with others that offer sufficient structural guarantees, while seeking to make only simple modifications to the existing structure.

[0009] Looking at the existing patents worldwide, we have found different solutions that differ from the proposed model in the ways explained below.

[0010] Patent CN109024225A, filed by the University of Hunan (China), proposes an ultra-high performance concrete truss arch whose connections consist of pouring a final segment of concrete, establishing structural continuity also with bars and connectors. This solution differs from the one proposed in that it does not act on an existing structure, the entire structure being new, and therefore all its elements purpose-built. In addition, the connections are not placed on the truss nodes, but outside them.

[0011] Patent CN110630030A, filed by the University of Hunan (China), proposes an ultra-high performance concrete and steel bar reinforcement system that is connected to the existing structure by in-situ pouring. This solution differs from the one proposed in that it does not refer to a truss but rather to beam-type elements providing an improvement in bending, but not in tension or compression. In addition, the connection between the part and the existing structure is continuous along the entire length of the section to be reinforced, it not being possible to identify nodes as such in the existing structure. In addition, it requires the execution of some slits so that it works together with the existing structure, plus some connection bars and other elements that do not match the ones of the proposed system.

[0012] Patent CN111155449A, filed by the University of the Southeast (China), proposes a construction method using a prefabricated notched block to anchor external prestressing tendons. This reinforcement solution differs from the proposed one in that the block is prefabricated, requires the preparation of a notch in the existing structure and in the block, the use of epoxy resin and tie rods to the existing structure to complete the connection.

[0013] Patent CZ36413U1, filed by Pavel Ryjáček and Filip Kramoliš, proposes a reinforcement system consisting of the execution of an ultra-high performance concrete die in the support area of a truss bridge. This reinforcement solution differs from the one proposed in that the system itself does not reinforce the linear elements of the truss and confines itself specifically to reinforcing the node where the truss is supported. Nor do the reliefs of the existing structure in the form of rivets participate in the system, as holes are drilled and bars inserted to establish a monolithic union unrelated to the rivets.

[0014] Patent KR20120120109807A, filed by Choi, Ha Jung, proposes a system for reinforcing the elements of a tubular tube truss by inserting profiles and bars inside the tubes with connectors to improve the bending capacity of the same once they are filled uninterruptedly with concrete. This solution, apart from not being intended for use in an existing structure, differs from the proposed solution in that the concrete fills the linear elements from end to end. In the proposed system, the connection acts only at the nodes of the truss thanks to the ultra-high performance concrete elements, so that the improvement of the element occurs primarily under axial not bending forces. Moreover, as it is not applied on an existing structure, it does not take advantage of the original reliefs, for example, the heads of the rivets and bolts, but rather connectors or drilled plates must be welded specifically to establish a monolithic union, which is precisely one of the difficulties it is aimed to avoid with the proposed system.

[0015] Patent US4691399A, applied for by Kim Jai, B.; Yadlosky, John M., proposes a reinforcement device consisting of supporting arches embedded within the existing truss. Each of these arches includes the elements forming an arched path and, inter alia, a tensioned element joining the two ends of the arch. This reinforcement solution differs from the one proposed in that the reinforcement system is not applied to individual elements of the existing truss, but to the truss as a whole, which completely alters the distribution of stresses between elements. Furthermore, it does not use any type of concrete to make the connections, nor does it take advantage of the reliefs of the structure.

[0016] Patent JP3732468B2, filed by Asahi Engineering KK, refers to a bridge reinforcement structure in which, through auxiliary triangular structural frames, each of which is built at opposite ends of a truss girder or arch girder and a cable stretched between the auxiliary triangular structural frames, an upward direction force is exerted on the truss beam or bowstring beam, thus effectively inducing a load resisting force. This reinforcement solution differs from the one proposed, as the reinforcement system is not applied on individual elements of the existing truss. Furthermore, it does not use any type of concrete to make the connections, nor does it take advantage of the reliefs of the structure.

[0017] Patent JP3597168B2, filed by Asahi Engineering KK, refers to a bridge reinforcement structure in which a cable stretched in the direction of the length of the bridge imposes a uniform upward reaction of said cable in order to improve the bridge's load-bearing capacity. The ends of this cable are connected to the ends of the bridge, and a number of hydraulic jacks installed in the lower part of the bridge, between the cable and the bridge's beams, stretch the cable, imposing a force that reinforces the load-bearing capacity. This reinforcement solution differs from the one proposed, as the reinforcement system is not applied on individual elements of the existing truss. Furthermore, it does not use any type of concrete to make the connections, nor does it take advantage of the reliefs of the structure.EXPLANATION OF THE INVENTION

[0018] This is a structure reinforcement system, specially adapted to truss bridges, consisting of linear metallic elements, in the form of profiles or reinforced sections, bars or tendons, which are arranged parallel to the linear elements of the original structure which require it as they lack load-bearing capacity, especially against axial stresses. To be able to support the existing element along its entire length, these reinforcements must take on load at the nodes that connect them to the rest of the structure and it must also be possible to transfer the loads between the parts in the corresponding magnitude, ideally without altering the distribution of forces inherent to the truss. Instead of using the usual welding or bolting solutions, an ultra-high-performance concrete element is placed to block the movements between the existing elements and the reinforcement at the nodes. This overall arrangement of the system guarantees the stress transfers between the different parts of the truss without any further connection operations.

[0019] A necessary condition for the system to function properly is that the connection between the parts at the nodes is monolithic. This could be achieved by adding connecting pins or other elements against the slippage between the concrete and the steel. In other words, it would be necessary to use welding to fix these anti-slip metal elements in the area of the truss nodes. This system, on the other hand, does not require altering the existing structure by adding connectors, welding or bolting. To achieve this, the reliefs of the existing metal structure are made to work differently than originally planned. Thus, if the structure is riveted, the heads of the rivets are used as relief to achieve the anti-slip effect to stop the concrete slipping in relation to the metal plate. Similarly, if the structure is bolted, the bolt heads or nuts are used. Therefore, no specially designed means of connection are used. Projections or other existing elements at the node could also be used to fulfil this anti-slip function, depending on whether they were originally dimensioned with a sufficient clearance and have sufficient capacity to cope with this additional work.

[0020] On the other hand, new reinforcement elements must be provided with reliefs in the form of ribbed elements or anchor plates that act in a similar way.

[0021] One last issue regarding this invention is that the morphology of existing nodes often prevents continuity of reinforcement. Sometimes there is no such interference, but, if there is, it is easily solved with this system, since the nodes usually have sufficient structural capacity to allow selective drilling in order to create pass-throughs to the linear reinforcement elements which, as they participate in the resistance with predominantly axial forces, have a very small section compared to the section they would need to operate in bending. Therefore, the only direct modification of the existing structure is the opening, if not previously existing, of pass-throughs at the nodes, since the rest of the elements of the system are simply additions.

[0022] All the added elements are placed in position and once the ultra-high performance concrete has been poured, they are solidly joined together, providing just the structural capacity required for the structure, without welding, bolting or direct bonding of the reinforcement parts, thanks to the reliefs on the existing structure.

[0023] The last precaution is to check if the node, which is the only part that has its original internal operation altered, suffers any unacceptable concentration of stresses, which is unlikely, as this alteration is internal to the node, so the stress redistribution is moderate and can be altered or further distributed by making minor adjustments to the geometry of the ultra-high performance concrete element.

[0024] The advantage of the system is that the material input is kept to the minimum necessary to achieve the required resistance capacity. Only the weight of the linear reinforcement elements and the ultra high-strength concrete is added. The latter, due to its high mechanical properties, can be used in a very limited quantity.

[0025] There are also constructive advantages, as this solution can be applied without modifying the original structure beyond any drill holes for the reinforcement to pass through. In addition, the connections to be made on site are achieved by simply pouring the self-forming and normally self-levelling material, which is the ultra-high performance concrete. Drilling and pouring concrete are quick operations. This facilitates construction, as the time spent on site by personnel is limited and road occupation is easier to combine with vehicular traffic.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To add to the description herein and to facilitate a better understanding of the invention's characteristics, a set of drawings is attached as an integral part of the said description, which are illustrative and non-exhaustive, depicting the following: Figure 1.- Shows a perspective view of a truss bridge in which reinforcement by means of the system is possible because the bridge has several elements with insufficient structural capacity. Figure 2.- Shows an elevation view of a truss on which reinforcement by means of the system is possible because the truss has several elements with insufficient structural capacity. Figure 3.- Shows a longitudinal vertical section of the reinforcement applied on a diagonal of a truss by means of the system in the form of a rebar. Figure 4.- Shows a longitudinal vertical section of the reinforcement applied to a segment of the bottom chord of a truss by means of the system in the form of rebars. Figure 5.- Shows a longitudinal vertical section of the end node of the reinforcement applied to the bottom chord of a truss by means of the system in the form of rebars. Figure 6.- Shows a longitudinal vertical section of the bottom node of the reinforcement applied on a diagonal of a truss by means of the system in the form of rebars. Figure 7.- Shows a longitudinal horizontal section of a connection of the system, with the linear reinforcement elements being rebars and the existing structure being riveted. Figure 8.- Shows a horizontal longitudinal section of a connection of the system, the linear reinforcement elements being smooth bars threaded on both ends with anchor plate and nut and the existing structure being riveted. Figure 9.- Shows a longitudinal horizontal section of a connection of the system, the linear reinforcement elements being a closed profile finished in smooth bars threaded on both ends with anchor plate and nut and the existing structure being riveted. Figure 10.- Shows an elevation view of a bolted truss node where two of the elements have insufficient structural capacity. Figure 11.- Shows a longitudinal vertical section of the reinforcement applied at a diagonal and at the bottom chord of a truss by means of the system in the form of rebars. PREFERRED EMBODIMENT OF THE INVENTION

[0027] As can be seen in the figures referred to, the different components of the reinforcement system described in this invention are distributed over the existing structure which has linear elements with insufficient structural capacity (1). There are one or more linear reinforcement elements (2), generally bars, which are parallel to the elements of the existing structure to be reinforced, which may be the upper or lower chord, the diagonals or the vertical uprights. At the ends of the reinforcements and coinciding with the nodes of the truss, there are ultra-high performance concrete elements (3) that are immobilised in their position thanks to the heads or reliefs (4) of the rivets, bolts or nuts on the existing structure, preventing slippage between the concrete and the steel of the existing structure. These solid blocks are made at the connection points of the elements that make up the truss, and which have insufficient bearing capacity, by pouring an ultra-high performance concrete. The choice of this product is due to the high strength and rigidity required. In addition, the reinforcing bars will normally have ribbed projections (5), so they will not slip when a sufficient length of them is embedded in the ultra-high performance concrete node. Furthermore, the bars can be smooth and with anchoring parts at the end and can even, instead of bars, be profiles or plates with an anchoring system for this purpose.

[0028] Therefore, in the proposed system it is not necessary to weld or bolt it onto the original structure. The connection of all the elements is achieved by altering the modus operandi of the existing nuts, rivets or other reliefs which, thanks to their shape, prevent the metal plates slipping in relation to the concrete. Thus, bolts or rivets, which originally transfer the load between the metal plates they connect, transfer the force from the ultra-high performance concrete to the heads of rivets or bolts and, subsequently, to the node's other metal plates.

[0029] To complete the system, it is necessary to have existing or specially constructed pass-throughs (6) at the nodes of the truss so that there is a sufficient length of force transfer between the reinforcement and the existing structure. These pass-throughs will normally be sealed by the concrete, so that the node, even if it has been necessary to drill through it, will have its strength partially restored as the poured concrete has a strength of the same order of magnitude as that of the original steel, at least in compression.

[0030] Once completed, the system works in such a way that the forces are transferred between the reinforcement element and the reinforced element, both parallel, right at the nodes of the truss, so that the global distribution of stresses that normal trusses have due to their internal isostatism is not altered. Therefore, with this system, used passively, there is no disturbance of the internal forces of the truss, which in other methods results in the need to act on other elements. This does not mean that it is not also possible to use the proposed device actively, by stressing the reinforcement element, so that the parallel reinforced element is unloaded, although at the cost of a redistribution of stresses in the rest of the structure.

[0031] Nowadays, truss bridge structure reinforcement projects are usually resolved by welding steel parts onto the existing structure, meaning that welded or bolted connections have to be made on site. If the original bridge is corroded, it may even be necessary to remove damaged plates and replace them with new ones, either by cutting the plate or by removing rivets or bolts. On other occasions, prestressing is applied to unload the structure, although this solution is limited in truss structures to the extent that the compression added by the stressing must not excessively overload any part, which makes it necessary to reinforce the structure by adding more steel parts on top of the existing structure. With this invention, the reinforcement of the existing structure is achieved just in the elements that require it, but without the unwanted need to dismantle plates or parts beforehand, or the difficulty of supplementing them by welding or bolting on new elements. The linear reinforcement elements (2) are joined together by means of ultra-high performance concrete elements (3), but only in the favourable circumstance that there are reliefs and projections that allow the reinforcement-concrete connection to be linked to the concrete-structure connection. Furthermore, in order for the linear reinforcement element (2) to function correctly in tension or compression, the connection must be made right at the nodes of the truss. The linear reinforcement element must also be able to pass through the other elements of the truss without interruption, and therefore, if not present, the necessary pass-throughs (6) must be opened. Afterwards, these pass-throughs can be sealed by the ultra-high performance concrete, which will restore part of the bearing capacity lost when the pass-through is drilled.

Examples

Embodiment Construction

[0027]As can be seen in the figures referred to, the different components of the reinforcement system described in this invention are distributed over the existing structure which has linear elements with insufficient structural capacity (1). There are one or more linear reinforcement elements (2), generally bars, which are parallel to the elements of the existing structure to be reinforced, which may be the upper or lower chord, the diagonals or the vertical uprights. At the ends of the reinforcements and coinciding with the nodes of the truss, there are ultra-high performance concrete elements (3) that are immobilised in their position thanks to the heads or reliefs (4) of the rivets, bolts or nuts on the existing structure, preventing slippage between the concrete and the steel of the existing structure. These solid blocks are made at the connection points of the elements that make up the truss, and which have insufficient bearing capacity, by pouring an ultra-high performance co...

TECHNICAL SECTOR

[0001] This invention concerns a system for reinforcing existing structures.

[0002] This system is particularly adapted to truss-type bridge structures and serves to increase the structure's load-bearing capacity.BACKGROUND OF THE INVENTION

[0003] Today, the need to reinforce structures has increased due to the ageing of many structures and the advisability of making them capable of withstanding greater loads than those for which they were originally designed.

[0004] Structural rehabilitation specialists are often faced with the problem of designing a structural reinforcement to improve the load-bearing capacity, either due to an increase in the expected overloads or to deterioration that needs to be compensated for. One of the tools available to these professionals would be to arrange additional linear elements parallel to the structure's original ones, enabling it to bear more load than it could initially bear. In this case, it would be a matter of providing the necessary quantities of steel to achieve the desired resistance capacity. These solutions are normal because the material input is concentrated where it is required. In other words, it has financial and constructional advantages.

[0005] The traditional way of adding this additional material has been to weld steel elements to those originally existing in the structure. There are two problems with this approach. The first is that in old trusses the steel may not be weldable. The second problem is that the nodes of the truss, which is where it is usually advisable to start and finish a reinforcement, are areas with a complex geometry, where stress transfer is complicated, making the solution more expensive.

[0006] Another way of adding the reinforcement elements is by bolting them on, enabling them to be applied to old, reinforced trusses simply by drilling them to then place the new bolts. With this method, the stress transfer at the nodes tends to get even more complicated, as the nodes are already heavily drilled to take the original fixtures.

[0007] When the objective is specifically to repair corrosion, it is often necessary to remove rivets, to remove defective elements, to replace them with new ones, but already fixed with bolts. Such removal of rivets is a specialised and non-standardised operation, and therefore entails risks and uncertainties, which, in turn, makes it costly. Also, if a number of rivets of elements making up the bridge's bracing system need to be removed simultaneously, it may be necessary to shore up the truss.

[0008] In this proposed reinforcement system, the aim is to relieve truss elements of primarily axial stresses and to replace complicated or risky execution methods with others that offer sufficient structural guarantees, while seeking to make only simple modifications to the existing structure.

[0009] Looking at the existing patents worldwide, we have found different solutions that differ from the proposed model in the ways explained below.

[0010] Patent CN109024225A, filed by the University of Hunan (China), proposes an ultra-high performance concrete truss arch whose connections consist of pouring a final segment of concrete, establishing structural continuity also with bars and connectors. This solution differs from the one proposed in that it does not act on an existing structure, the entire structure being new, and therefore all its elements purpose-built. In addition, the connections are not placed on the truss nodes, but outside them.

[0011] Patent CN110630030A, filed by the University of Hunan (China), proposes an ultra-high performance concrete and steel bar reinforcement system that is connected to the existing structure by in-situ pouring. This solution differs from the one proposed in that it does not refer to a truss but rather to beam-type elements providing an improvement in bending, but not in tension or compression. In addition, the connection between the part and the existing structure is continuous along the entire length of the section to be reinforced, it not being possible to identify nodes as such in the existing structure. In addition, it requires the execution of some slits so that it works together with the existing structure, plus some connection bars and other elements that do not match the ones of the proposed system.

[0012] Patent CN111155449A, filed by the University of the Southeast (China), proposes a construction method using a prefabricated notched block to anchor external prestressing tendons. This reinforcement solution differs from the proposed one in that the block is prefabricated, requires the preparation of a notch in the existing structure and in the block, the use of epoxy resin and tie rods to the existing structure to complete the connection.

[0013] Patent CZ36413U1, filed by Pavel Ryjáček and Filip Kramoliš, proposes a reinforcement system consisting of the execution of an ultra-high performance concrete die in the support area of a truss bridge. This reinforcement solution differs from the one proposed in that the system itself does not reinforce the linear elements of the truss and confines itself specifically to reinforcing the node where the truss is supported. Nor do the reliefs of the existing structure in the form of rivets participate in the system, as holes are drilled and bars inserted to establish a monolithic union unrelated to the rivets.

[0014] Patent KR20120120109807A, filed by Choi, Ha Jung, proposes a system for reinforcing the elements of a tubular tube truss by inserting profiles and bars inside the tubes with connectors to improve the bending capacity of the same once they are filled uninterruptedly with concrete. This solution, apart from not being intended for use in an existing structure, differs from the proposed solution in that the concrete fills the linear elements from end to end. In the proposed system, the connection acts only at the nodes of the truss thanks to the ultra-high performance concrete elements, so that the improvement of the element occurs primarily under axial not bending forces. Moreover, as it is not applied on an existing structure, it does not take advantage of the original reliefs, for example, the heads of the rivets and bolts, but rather connectors or drilled plates must be welded specifically to establish a monolithic union, which is precisely one of the difficulties it is aimed to avoid with the proposed system.

[0015] Patent US4691399A, applied for by Kim Jai, B.; Yadlosky, John M., proposes a reinforcement device consisting of supporting arches embedded within the existing truss. Each of these arches includes the elements forming an arched path and, inter alia, a tensioned element joining the two ends of the arch. This reinforcement solution differs from the one proposed in that the reinforcement system is not applied to individual elements of the existing truss, but to the truss as a whole, which completely alters the distribution of stresses between elements. Furthermore, it does not use any type of concrete to make the connections, nor does it take advantage of the reliefs of the structure.

[0016] Patent JP3732468B2, filed by Asahi Engineering KK, refers to a bridge reinforcement structure in which, through auxiliary triangular structural frames, each of which is built at opposite ends of a truss girder or arch girder and a cable stretched between the auxiliary triangular structural frames, an upward direction force is exerted on the truss beam or bowstring beam, thus effectively inducing a load resisting force. This reinforcement solution differs from the one proposed, as the reinforcement system is not applied on individual elements of the existing truss. Furthermore, it does not use any type of concrete to make the connections, nor does it take advantage of the reliefs of the structure.

[0017] Patent JP3597168B2, filed by Asahi Engineering KK, refers to a bridge reinforcement structure in which a cable stretched in the direction of the length of the bridge imposes a uniform upward reaction of said cable in order to improve the bridge's load-bearing capacity. The ends of this cable are connected to the ends of the bridge, and a number of hydraulic jacks installed in the lower part of the bridge, between the cable and the bridge's beams, stretch the cable, imposing a force that reinforces the load-bearing capacity. This reinforcement solution differs from the one proposed, as the reinforcement system is not applied on individual elements of the existing truss. Furthermore, it does not use any type of concrete to make the connections, nor does it take advantage of the reliefs of the structure.EXPLANATION OF THE INVENTION

[0018] This is a structure reinforcement system, specially adapted to truss bridges, consisting of linear metallic elements, in the form of profiles or reinforced sections, bars or tendons, which are arranged parallel to the linear elements of the original structure which require it as they lack load-bearing capacity, especially against axial stresses. To be able to support the existing element along its entire length, these reinforcements must take on load at the nodes that connect them to the rest of the structure and it must also be possible to transfer the loads between the parts in the corresponding magnitude, ideally without altering the distribution of forces inherent to the truss. Instead of using the usual welding or bolting solutions, an ultra-high-performance concrete element is placed to block the movements between the existing elements and the reinforcement at the nodes. This overall arrangement of the system guarantees the stress transfers between the different parts of the truss without any further connection operations.

[0019] A necessary condition for the system to function properly is that the connection between the parts at the nodes is monolithic. This could be achieved by adding connecting pins or other elements against the slippage between the concrete and the steel. In other words, it would be necessary to use welding to fix these anti-slip metal elements in the area of the truss nodes. This system, on the other hand, does not require altering the existing structure by adding connectors, welding or bolting. To achieve this, the reliefs of the existing metal structure are made to work differently than originally planned. Thus, if the structure is riveted, the heads of the rivets are used as relief to achieve the anti-slip effect to stop the concrete slipping in relation to the metal plate. Similarly, if the structure is bolted, the bolt heads or nuts are used. Therefore, no specially designed means of connection are used. Projections or other existing elements at the node could also be used to fulfil this anti-slip function, depending on whether they were originally dimensioned with a sufficient clearance and have sufficient capacity to cope with this additional work.

[0020] On the other hand, new reinforcement elements must be provided with reliefs in the form of ribbed elements or anchor plates that act in a similar way.

[0021] One last issue regarding this invention is that the morphology of existing nodes often prevents continuity of reinforcement. Sometimes there is no such interference, but, if there is, it is easily solved with this system, since the nodes usually have sufficient structural capacity to allow selective drilling in order to create pass-throughs to the linear reinforcement elements which, as they participate in the resistance with predominantly axial forces, have a very small section compared to the section they would need to operate in bending. Therefore, the only direct modification of the existing structure is the opening, if not previously existing, of pass-throughs at the nodes, since the rest of the elements of the system are simply additions.

[0022] All the added elements are placed in position and once the ultra-high performance concrete has been poured, they are solidly joined together, providing just the structural capacity required for the structure, without welding, bolting or direct bonding of the reinforcement parts, thanks to the reliefs on the existing structure.

[0023] The last precaution is to check if the node, which is the only part that has its original internal operation altered, suffers any unacceptable concentration of stresses, which is unlikely, as this alteration is internal to the node, so the stress redistribution is moderate and can be altered or further distributed by making minor adjustments to the geometry of the ultra-high performance concrete element.

[0024] The advantage of the system is that the material input is kept to the minimum necessary to achieve the required resistance capacity. Only the weight of the linear reinforcement elements and the ultra high-strength concrete is added. The latter, due to its high mechanical properties, can be used in a very limited quantity.

[0025] There are also constructive advantages, as this solution can be applied without modifying the original structure beyond any drill holes for the reinforcement to pass through. In addition, the connections to be made on site are achieved by simply pouring the self-forming and normally self-levelling material, which is the ultra-high performance concrete. Drilling and pouring concrete are quick operations. This facilitates construction, as the time spent on site by personnel is limited and road occupation is easier to combine with vehicular traffic.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To add to the description herein and to facilitate a better understanding of the invention's characteristics, a set of drawings is attached as an integral part of the said description, which are illustrative and non-exhaustive, depicting the following: Figure 1.- Shows a perspective view of a truss bridge in which reinforcement by means of the system is possible because the bridge has several elements with insufficient structural capacity. Figure 2.- Shows an elevation view of a truss on which reinforcement by means of the system is possible because the truss has several elements with insufficient structural capacity. Figure 3.- Shows a longitudinal vertical section of the reinforcement applied on a diagonal of a truss by means of the system in the form of a rebar. Figure 4.- Shows a longitudinal vertical section of the reinforcement applied to a segment of the bottom chord of a truss by means of the system in the form of rebars. Figure 5.- Shows a longitudinal vertical section of the end node of the reinforcement applied to the bottom chord of a truss by means of the system in the form of rebars. Figure 6.- Shows a longitudinal vertical section of the bottom node of the reinforcement applied on a diagonal of a truss by means of the system in the form of rebars. Figure 7.- Shows a longitudinal horizontal section of a connection of the system, with the linear reinforcement elements being rebars and the existing structure being riveted. Figure 8.- Shows a horizontal longitudinal section of a connection of the system, the linear reinforcement elements being smooth bars threaded on both ends with anchor plate and nut and the existing structure being riveted. Figure 9.- Shows a longitudinal horizontal section of a connection of the system, the linear reinforcement elements being a closed profile finished in smooth bars threaded on both ends with anchor plate and nut and the existing structure being riveted. Figure 10.- Shows an elevation view of a bolted truss node where two of the elements have insufficient structural capacity. Figure 11.- Shows a longitudinal vertical section of the reinforcement applied at a diagonal and at the bottom chord of a truss by means of the system in the form of rebars. PREFERRED EMBODIMENT OF THE INVENTION

[0027] As can be seen in the figures referred to, the different components of the reinforcement system described in this invention are distributed over the existing structure which has linear elements with insufficient structural capacity (1). There are one or more linear reinforcement elements (2), generally bars, which are parallel to the elements of the existing structure to be reinforced, which may be the upper or lower chord, the diagonals or the vertical uprights. At the ends of the reinforcements and coinciding with the nodes of the truss, there are ultra-high performance concrete elements (3) that are immobilised in their position thanks to the heads or reliefs (4) of the rivets, bolts or nuts on the existing structure, preventing slippage between the concrete and the steel of the existing structure. These solid blocks are made at the connection points of the elements that make up the truss, and which have insufficient bearing capacity, by pouring an ultra-high performance concrete. The choice of this product is due to the high strength and rigidity required. In addition, the reinforcing bars will normally have ribbed projections (5), so they will not slip when a sufficient length of them is embedded in the ultra-high performance concrete node. Furthermore, the bars can be smooth and with anchoring parts at the end and can even, instead of bars, be profiles or plates with an anchoring system for this purpose.

[0028] Therefore, in the proposed system it is not necessary to weld or bolt it onto the original structure. The connection of all the elements is achieved by altering the modus operandi of the existing nuts, rivets or other reliefs which, thanks to their shape, prevent the metal plates slipping in relation to the concrete. Thus, bolts or rivets, which originally transfer the load between the metal plates they connect, transfer the force from the ultra-high performance concrete to the heads of rivets or bolts and, subsequently, to the node's other metal plates.

[0029] To complete the system, it is necessary to have existing or specially constructed pass-throughs (6) at the nodes of the truss so that there is a sufficient length of force transfer between the reinforcement and the existing structure. These pass-throughs will normally be sealed by the concrete, so that the node, even if it has been necessary to drill through it, will have its strength partially restored as the poured concrete has a strength of the same order of magnitude as that of the original steel, at least in compression.

[0030] Once completed, the system works in such a way that the forces are transferred between the reinforcement element and the reinforced element, both parallel, right at the nodes of the truss, so that the global distribution of stresses that normal trusses have due to their internal isostatism is not altered. Therefore, with this system, used passively, there is no disturbance of the internal forces of the truss, which in other methods results in the need to act on other elements. This does not mean that it is not also possible to use the proposed device actively, by stressing the reinforcement element, so that the parallel reinforced element is unloaded, although at the cost of a redistribution of stresses in the rest of the structure.

[0031] Nowadays, truss bridge structure reinforcement projects are usually resolved by welding steel parts onto the existing structure, meaning that welded or bolted connections have to be made on site. If the original bridge is corroded, it may even be necessary to remove damaged plates and replace them with new ones, either by cutting the plate or by removing rivets or bolts. On other occasions, prestressing is applied to unload the structure, although this solution is limited in truss structures to the extent that the compression added by the stressing must not excessively overload any part, which makes it necessary to reinforce the structure by adding more steel parts on top of the existing structure. With this invention, the reinforcement of the existing structure is achieved just in the elements that require it, but without the unwanted need to dismantle plates or parts beforehand, or the difficulty of supplementing them by welding or bolting on new elements. The linear reinforcement elements (2) are joined together by means of ultra-high performance concrete elements (3), but only in the favourable circumstance that there are reliefs and projections that allow the reinforcement-concrete connection to be linked to the concrete-structure connection. Furthermore, in order for the linear reinforcement element (2) to function correctly in tension or compression, the connection must be made right at the nodes of the truss. The linear reinforcement element must also be able to pass through the other elements of the truss without interruption, and therefore, if not present, the necessary pass-throughs (6) must be opened. Afterwards, these pass-throughs can be sealed by the ultra-high performance concrete, which will restore part of the bearing capacity lost when the pass-through is drilled.

Examples

Embodiment Construction

[0027]As can be seen in the figures referred to, the different components of the reinforcement system described in this invention are distributed over the existing structure which has linear elements with insufficient structural capacity (1). There are one or more linear reinforcement elements (2), generally bars, which are parallel to the elements of the existing structure to be reinforced, which may be the upper or lower chord, the diagonals or the vertical uprights. At the ends of the reinforcements and coinciding with the nodes of the truss, there are ultra-high performance concrete elements (3) that are immobilised in their position thanks to the heads or reliefs (4) of the rivets, bolts or nuts on the existing structure, preventing slippage between the concrete and the steel of the existing structure. These solid blocks are made at the connection points of the elements that make up the truss, and which have insufficient bearing capacity, by pouring an ultra-high performance co...

Claims

1. System for reinforcing existing structures, which, being applicable to truss-type metal structures or structures that at least have linear metal elements with insufficient structural capacity (1) and riveted connections, comprises linear reinforcement elements (2) arranged parallel to the linear elements with insufficient structural capacity (1), including one or more pass-through areas (6) at the nodes of the existing structure which, if closed, obstruct the continuity of the linear reinforcing element (2), characterized in that it also features the following structural elements: • several ultra-high performance concrete elements (3) that transfer the load between the linear reinforcement elements (2) and the existing structure at the truss nodes, • a relief (4), which is specific to the existing structure, formed by rivet heads that allow it to be connected to the ultra-high performance concrete elements (3) at the nodes, • a projection (5) of the linear reinforcement element (2) that allows connection of the linear reinforcement elements (2) with the ultra-high performance concrete elements (3).

2. System for reinforcing existing structures, according to claim 1, characterized in that the relief (4) of the existing structure is formed by bolt heads, projections or other rough elements.

3. System for reinforcing existing structures, according to claim 1, characterized in that the projections (5) of the linear reinforcement element (2) are ribbed elements or anchor plates.

4. System for reinforcing existing structures, according to claim 1, characterized in that the linear reinforcement element (2) is an open or closed profile, a plate, a bar or a pre-stressing tendon.

5. System for reinforcing existing structures, according to claim 1, characterized in that the linear reinforcement element (2) is made of steel, concrete or other resistant material.

6. System for reinforcing existing structures, according to claim 1, characterized in that the linear reinforcement element (2) can act passively or actively.

7. System for reinforcing existing structures, according to claim 1, characterized in that the pass-through areas (6) can previously exist in the existing structure or have to be drilled expressly.

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