Construction methods for prestressed concrete in flat slab floor slabs

Abstract

This invention belongs to the field of prestressed construction technology, specifically disclosing a method for prestressing construction in flat slab floor slabs. The method includes a podium building and several towers forming partial enclosures around the podium. The podium building overlaps with each tower, and prestress is formed at the overlap. The construction method includes the following steps: Prestressing zoning: Dividing the podium building and the overlap between the podium and the towers into several zones along the prestressing direction; Forming several prestressing stresses along each zone, with each zone forming transverse and / or vertical prestressing between the podium and the towers; Prestressing construction: Performing corresponding prestressing tensioning along each zone, using a single tensioning method to reach the design tension value; In the prestressing construction, the construction sequence of the several zones is to first construct the vertical prestressing, then the transverse prestressing. This invention has the effects of reducing project construction costs, improving construction quality, and accelerating project construction progress.

Description

Technical Field

[0001] This invention relates to the technical field of prestressed construction methods in floor slabs, and in particular to prestressed construction methods in flat slabs. Background Technology

[0002] To meet the functional requirements of the building and the need for a large parking space, some podium buildings are designed with a large span and ultra-long prestressed structure in plan dimensions. The floor slabs do not have beams and are supported on the load-bearing columns by column capitals. The prestressed area of ​​the podium building has a construction area of ​​1837m2. While meeting the load-bearing capacity, it can effectively reduce the self-weight of the floor slab. The design adopts the post-tensioned two-way bonded prestressed floor slab structure construction technology. The floor slab is cast in one go. After the concrete is poured and the design strength reaches more than 75%, the steel reinforcement is tensioned. The force transmission path relies on anchorages to prevent the elastic rebound of the steel reinforcement, so that the concrete section receives prestress.

[0003] In existing technologies, the large area of ​​the podium structure that needs to be poured at one time makes the construction procedures and tensioning process of the prestressed floor slabs of the podium and the three towers more complex, making it difficult to control the quality of concrete pouring and resulting in a long construction period. In addition, the following problems also exist: The use of post-cast strips addresses the issues of additional stress caused by uneven settlement between the high-rise main building and the low-rise podium building, as well as concrete shrinkage after tensioning, in the "tower-first" construction deployment. The problem of shrinkage cracks caused by temperature stress in large-area prestressed reinforced concrete floor slabs without beams can be solved by setting construction joints. Summary of the Invention

[0004] The purpose of this invention is to provide a construction method for prestressed concrete slabs without beams. The method employs a "tower first, podium follow" construction deployment, with each tower construction area divided into sequential sections. The prestressing design, while ensuring the structure meets load-bearing requirements, must also fully consider the actual construction area deployment and optimize the prestressing tensioning sequence. This method is of great significance for effectively controlling the pouring quality of large-area flat slabs without beams, enhancing slab elasticity, reducing concrete cracks caused by structural elastic deformation, avoiding large one-time investments in the support system, reducing project construction costs, improving construction quality, and accelerating project progress.

[0005] To achieve the above-mentioned technical effects, the present invention is implemented through the following technical means.

[0006] A construction method for prestressing in flat slab floor slabs includes a podium and several towers forming a partial enclosure around the perimeter of the podium, wherein the podium overlaps with each tower and prestressing is formed at the overlap, and the construction method includes the following steps; Prestressed zoning: The podium building and the junction between the podium building and the tower are divided into several zones along the prestressing direction; Along the area, several prestressing zones are formed, and each area forms transverse prestressing and / or vertical prestressing between the podium and the tower; Prestressed construction: along each of the aforementioned areas, corresponding prestressing tensioning is performed, and the prestressing tensioning adopts a tensioning method of tensioning to the design tension value in one go; In the prestressed construction, the construction sequence for several areas is as follows: first, vertical prestressing is constructed, and then horizontal prestressing is constructed. In the prestressed construction, the tower is constructed first, followed by the podium.

[0007] As a further improvement of the present invention, in the step of prestressed zoning, the construction area is first divided into a tower construction area and a podium construction area according to the tower and the podium, and then the podium construction area is divided according to the principle of equal area. The tower construction area is divided into a boundary area, an area near the steel strands, and an area along the direction of the support plate.

[0008] As a further improvement of the present invention, the tower construction is carried out in the following order: first the boundary area, then the area near the steel strand, and finally the area along the support plate direction.

[0009] (2) Considering that P5 is located in the tower area, based on the structural form of the tower area and the relationship between the main tower and the podium, and considering the influence of the superstructure on the prestressed floor slab, under the premise of the tower construction deployment first, the tower and podium areas are divided by post-cast strips; under the above requirements, the post-cast strips in the P5 area consider the structural relationship of the column caps of W1, W2, and W3, and the original design layout of the transverse prestressing, and the post-cast strip area is designed in a stepped shape, which effectively reduces the changes to the structural form and prestressing design principles.

[0010] As a further improvement of the present invention, in the prestressed zoning step, the zoning between the tower and the podium is determined by the location of the post-cast strip.

[0011] As a further improvement of the present invention, in the prestressed construction, the tensioning end of the prestress is located at the post-cast strip or on the outside of the podium.

[0012] As a further improvement of the present invention, it also includes a design for extending the casting strip, specifically: adding reinforcing bars at the casting strip containing the prestressed tensioning end.

[0013] As a further improvement of the present invention, in some of the prestressed overlaps between adjacent areas in several of the areas, the prestressed overlaps adopt bidirectional prestressed overlaps, and the length of the bidirectional prestressed overlaps is 0.8-1.2m.

[0014] As a further improvement of the present invention, among the several areas, at least one area consisting of towers near the edge of the podium building is included.

[0015] As a further improvement of the present invention, in the prestressed construction process, the prestressed construction of each area includes pouring and tensioning, and each area is poured first and then tensioned, and the construction of the next area is carried out after the tensioning is completed.

[0016] As a further improvement of the present invention, when the length of the steel strand is 10-25m, the initial tension prestress formed by the tensioning of the steel strand is 600-800psi.

[0017] The beneficial effects of this invention are as follows: In this invention, a segmented approach is adopted, and a sequence is added during construction, thereby solving the problem of prestressed slab layout in the "tower first" construction deployment. P5 is poured as a separate block following the tower first.

[0018] In this invention, the large area of ​​the podium building presents complex challenges in pouring concrete, but dividing the space into sections solves the problems of excessively large areas requiring single-pour casting of flat slabs and complex tensioning processes. It also allows for the overlapping of different professional construction methods across different sections, improving worker utilization and overall construction efficiency.

[0019] In this invention, the large initial investment in the support system is avoided, and the use of a block construction method reduces the amount of support and formwork materials used, increases the number of times support and formwork materials can be reused, and reduces construction costs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart illustrating the construction method for prestressed concrete in flat slabs provided by this invention; Figure 2 A diagram showing the distribution of longitudinal prestress in the podium and tower in Embodiment 2 of the present invention; Figure 3 A diagram showing the distribution of transverse prestress in the podium and tower in Embodiment 2 of the present invention; Figure 4 A schematic diagram of the structure with added reinforcing bars provided by the present invention; In the picture: 100, Post-pouring strip; 200, Reinforcing bar; 300, Threaded bar; 400, Steel strand; 500, Floor slab. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0025] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0026] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Example 1 In this embodiment, refer to the appendix. Figure 1-4 The introduction will focus on the principles and effects of this invention.

[0029] First, the principle of this invention is as follows: based on the construction area of ​​the prestressed floor slab, the structural form and boundary characteristics of the tower, and the location characteristics of the post-cast strip and construction joint of the prestressed slab, the overall prestressed flat slab is divided into four blocks, and concrete tensioning and pouring are carried out in sequence.

[0030] Secondly, the beneficial effects of the present invention are as follows: (1) It solved the problem of prestressed slab layout in the "tower first" construction deployment, and the floor slab was poured as a separate block along with the tower. (2) It solved the problem of large-area flat slabs being poured in one go and the tensioning process being complicated. (3) It avoided large one-time investment in the support system, and the use of block construction reduced the amount of support and formwork materials, increased the number of times support and formwork materials could be reused, and reduced construction costs. (4) Different professional construction was carried out in each block, which improved the utilization rate of workers and the overall construction efficiency.

[0031] Furthermore, the differences between this invention and the prior art are as follows: (1) Divide the large-area flat slab into different construction areas by dividing it into sections.

[0032] (2) The prestressing tensioning is divided into plate tensioning by whole tensioning, and the tensioning sequence is optimized.

[0033] (3) Add a post-pouring strip and set the tensioning end at the post-pouring strip to solve the impact of prestressing tension on the floor slab.

[0034] (4) Optimize the pouring sequence to improve pouring quality and construction efficiency.

[0035] The beneficial effects achieved by this invention through the above-mentioned technological innovations are as follows: (1) The problem of additional stress and concrete shrinkage after tensioning caused by uneven settlement between the high-rise main building and the low-rise podium building in the "tower first" construction deployment is solved by setting up post-pouring strips. Since this structure is a large-area integral raft foundation, the former has a relatively small impact, and the latter problem is mainly solved.

[0036] (2) The problem of shrinkage cracks caused by temperature stress in large-area prestressed reinforced concrete floor slabs without beams can be solved by setting construction joints.

[0037] (3) The division of construction blocks solves the problem of excessively large prestressed one-time operation surface, increases the rigidity of prestressed floor slabs, and reduces the occurrence of concrete cracks caused by elastic deformation.

[0038] (4) By optimizing the arrangement of prestress, adjusting the position of corrugated pipe and the installation sequence of steel strand, and optimizing the calculation of prestressing elongation, a concrete prestressing tensioning process that meets the actual engineering technology needs is established.

[0039] (5) During the prestressed construction process, the prestressed design of the area where the tower and the podium are combined (P5, P6) was changed from an overall continuous design to a segmented design, which saves tower construction time, improves tower construction efficiency, and further ensures the construction deployment of "tower first".

[0040] (6) Optimize the concrete mix ratio, adjust the concrete aggregate size, and use expansive concrete in the post-pouring strip to improve the concrete quality during the block pouring process and enhance the overall integrity of the concrete pouring.

[0041] (7) By dividing the construction blocks, we can avoid large one-time investment in the support system, increase the number of times the support and formwork materials are turned over, and reduce construction costs.

[0042] (8) Solve the problems of excessively large pouring surface, excessively long pouring cycle, and difficulty in reasonably arranging the flow distance between each process, which delays the construction progress and is not conducive to improving construction efficiency.

[0043] Example 2 In this embodiment, a detailed description is provided in conjunction with a specific application.

[0044] In this embodiment, the technical features of the invention are applied to the building's functional use and the large space of the garage. Specifically, in this embodiment, to improve the utilization rate of the garage space, the original floor design adopted the post-tensioned, two-way bonded prestressed slab technology without beams. The prestressed floor slab P0 is designed as a whole, and both longitudinal and transverse prestressing designs adopt a continuous arrangement. (Refer to Appendix) Figure 2 As shown, it is a prestressed layout diagram for the podium area.

[0045] In this embodiment, the characteristics of the building and the construction process are as follows: (1) Due to the constraints of on-site construction conditions and the deployment of tower construction first, the podium and tower could not form a complete working surface for simultaneous construction. Furthermore, since the area of ​​each tower and podium is relatively large, based on the construction deployment and while meeting the overall design requirements, the P0 area was optimized and divided into: Tower P5; Podium P6, P7, and P8; a total of 4 construction areas. The main reason for the division of P5 was the "tower first" construction deployment; the main reason for the division of P6, P7, and P8 was the difficulty of one-time pouring and tensioning of large-area flat slabs, which had an adverse impact on the construction progress. (2) Considering that P5 is located in the tower area, based on the structural form of the tower area and the relationship between the main tower and the podium, and considering the influence of the superstructure on the prestressed floor slab, under the premise of the tower construction deployment first, the tower and podium areas are divided by post-cast strips; under the above requirements, the post-cast strips in the P5 area consider the structural relationship of the column caps of W1, W2, and W3, and the original design layout of the transverse prestressing, and the post-cast strip area is designed in a stepped shape, which effectively reduces the changes to the structural form and prestressing design principles.

[0046] In this embodiment, the P5 post-cast strip is divided into three steps. (1) The first step is located at the boundary between the tower and the group building, and the integral support plate connecting W1 and the column is located at the junction of the tower and the group building. Due to the tower's construction deployment first, W1 and its corresponding 2 / 3 area support plate are cast first. (2) The second step considers not dividing the support plate at the top of the W2 wall, satisfying the principle of dividing within 1 / 3 of the span and having a distance of not less than 200mm from the nearest steel strand. (3) The third step is considered the same as the second step. (4) The reason why the second step and the third stage cannot be simplified into one step is that it is impossible to simultaneously satisfy the requirement that the post-cast strip division must be carried out along the support plate direction and within one-third of the span from the support position.

[0047] (3) The prestressing of the podium area is divided into three sections: P6, P7, and P8. The prestressing design adopts an overlapping method, with a bidirectional prestressing overlap length of 1 meter. In the longitudinal prestressing area, the prestressing tendons in P6 are set independently, and the prestressing tendons in P8 are overlapped in the P7 section; in the transverse prestressing area, the prestressing tendons in P7 and P8 are overlapped in the P6 section. Therefore, according to the prestressing overlap sequence, the concrete pouring sequence is P6→P7→P8, and the concrete pouring sequence is irreversible. (4) In the original two-way prestressed floor slab design, the tensioning ends were all located on the outside of the structural floor slab, and the fixed ends were all located on the inside of the structural floor slab; in the optimized prestressed structure, the longitudinal prestressing arrangement is as follows: the tensioning ends of P5 and P7 are all located in the post-pouring strip area, and the tensioning ends of P6 and P8 are located in the outer edge area of ​​the floor slab; the transverse prestressing arrangement is as follows: the tensioning ends of P5, P7, and P8 are all located in the post-pouring strip area, and the tensioning end of P6 is located in the outer edge area of ​​the floor slab.

[0048] In this invention, the arrangement of bidirectional prestressing tendons remains unchanged from the original design. When the floor slab is divided, the magnitude, location, height, and quantity of prestressing tendons remain basically unchanged from the original design. The transverse prestressing tendons are densely arranged at the column caps to support the prestressed beams, while the longitudinal prestressing tendons are evenly arranged.

[0049] (5) The reinforcement arrangement shall be based on the original design reinforcement area and size. The reinforcement shall be disconnected and lapped at the construction joint. Quick-closing mesh shall be used at the construction joint to prevent concrete loss at the junction.

[0050] (6) After each block of concrete is poured and the strength meets 100%, tensioning is required. The tensioning sequence is P6→P7→P8. After each block is poured, tensioning is required first. After tensioning is completed, the next block of concrete pouring is carried out. The pouring and tensioning sequence is: P6 pouring → P6 tensioning → P7 pouring → P7 tensioning → P8 pouring → P8 tensioning → post-pouring strip pouring.

[0051] Specifically, in this invention, the tensioning sequence is as follows: first, horizontal tensioning, then longitudinal tensioning; first, middle tensioning, then symmetrical tensioning on both the top and bottom sides; the reason for tensioning horizontally before longitudinally is that the horizontal prestress is concentrated at the column cap, acting as a prestressed beam; the longitudinal prestress is evenly distributed, similar to the function of distribution reinforcement. The purpose of symmetrical tensioning on both sides is to ensure that the floor slab is subjected to uniform stress.

[0052] (7) Compared with the original design of tensioning the prestressed floor slab step by step, the prestressed length of the optimized concrete floor slab is greatly reduced. The method of tensioning to the design tension value in one step is adjusted, which reduces the prestress loss caused by the inward shrinkage of the steel strands, friction and deformation of the anchorage during the unloading process of tensioning step by step. This is conducive to improving the tensioning accuracy. After the prestressed tendons are tensioned, the ducts should be grouted within 24 hours.

[0053] (8) The initial tension strength of prestressed steel strands is positively correlated with the length of the steel strands. Before the floor slab is divided, the length of the prestressed steel strands is about 50m, which is greater than the design requirement of 30m. The initial tension stress is 1000psi. After the floor slab is divided, the length of the steel strands is 10-25m, which is less than the design requirement of 30m. The initial tension stress is reduced to 700psi. For steel strands of the same material and specifications, according to the formula △L=(P E x L) / (A P XE P ), where P E Let A be the average tension force of the prestressing tendon, L be the length of the prestressing tendon, and A be the average tension force of the prestressing tendon. P E represents the cross-sectional area of ​​the prestressing tendon. P The elastic modulus of the prestressing tendon; the theoretical elongation of the prestressing tendon, ΔL, is also positively correlated with the length of the steel strand. After the floor slab is divided, the theoretical elongation of the steel strand decreases accordingly. According to formula E X =P req / (P req -P0)×L1, where, E X P represents the actual elongation. reqTo achieve 100% tensile stress, P0 is the initial tensile stress, and L1 is the final elongation corresponding to reaching the design tensile stress. After the floor slab is partitioned, the length of the prestressing tendons is significantly reduced, and the initial tensile stress P0 is adjusted from 1000psi to 700psi. Under the same conditions, the L1 value is also less affected by the frictional resistance of the duct and the retraction of the tool anchor steel strand. Therefore, due to the influence of the prestressing length, the actual elongation after the floor slab is partitioned is also relatively reduced compared to before partitioning.

[0054] (9) The prestressing in each construction block adopts the bidirectional tensioning method. Each prestressing tendon is tensioned at one end, with a fixed end and a tensioning end. In the location with a post-pouring strip, the tensioning end is set at the post-pouring strip. In the location without a post-pouring strip, the prestressing tensioning end is set on the outside of the floor slab.

[0055] (10) After the prestressed floor slab is optimized and partitioned, the initial tension force and the amount of tension elongation are reduced accordingly. Compared with the prestressing tensioning method of the whole floor slab, the prestress loss caused by the friction of the duct and elastic compression after the floor slab is partitioned is reduced accordingly, which is more beneficial to the structural bearing capacity.

[0056] (11) The optimized prestressed concrete floor slab, after applying prestress, improves the stiffness of the components, delays or reduces the time of crack appearance, increases the durability of the concrete floor slab, reduces vibration and elastic deformation, significantly improves the elastic strength of the prestressed floor slab structure, and makes the original resistance stronger.

[0057] (12) The reinforcement at the post-cast strip is set along the entire length (the original floor slab reinforcement design remains unchanged). Since the post-cast strip is treated as the tensioning end, the reinforcement at this location is reinforced (adding stress reinforcement). The post-cast strip should be poured 30 days after the concrete on both sides has been poured and the prestressing tensioning has been completed. The formwork is removed after the concrete strength grade of the post-cast strip reaches 100%. The post-cast strip is set here to prevent cracking of the concrete beam and slab due to the expansion of the concrete due to hydration or shrinkage due to drying. At the same time, it facilitates the prestressing tensioning. After the concrete reaches a certain strength, concrete is poured in this area, and finally the concrete beam or slab forms a complete slab.

[0058] In this invention, reinforcing bars are added at the casting strip containing the prestressed tensioning end. The specific installation process is as follows: See attached document Figure 4 As shown, reinforcing bars 200mm in diameter are added within a 1m range on both sides of the 100mm width of the post-cast strip. Five 12mm diameter, 200mm spacing threaded bars are arranged parallel to the post-cast strip direction in two layers, top and bottom. Perpendicular to the post-cast strip direction, 300 diameter, 12mm diameter, 200mm spacing threaded bars are arranged in successive densities on both sides. These bars are bent at the edge of the post-cast strip and lapped before the post-cast strip concrete is poured, meeting the design requirement of a lap length of 52 times the bar diameter.

[0059] In actual construction, the steel strand 400 intersects with the reinforcing bar 200, while the floor slab 500 is set on the side.

[0060] (13) While ensuring that the overall design requirements are met, each construction block area has an independent prestressed construction and tensioning sequence, which does not interfere with each other; at the same time, the location of the construction joints of the blocks is designed separately to ensure that the overall structural system meets the requirements.

[0061] In this invention, the prestressed zoning is based on the construction area of ​​the prestressed floor slab, the structural form and boundary characteristics of the tower, and the location characteristics of the post-cast strips and construction joints of the prestressed slab. The P5 division is characterized as follows: P5 is located in the construction area of ​​Tower 3. According to the principle of "Tower first", P5 needs to be poured first. Therefore, the division of P5 mainly considers the following three points: First, the division is carried out at the boundary between Tower 3 and the podium to ensure the principle of Tower first. Second, the shear walls W1, W2, W3 and the upper support plate of the shear walls in the Tower 3 area have been poured first. The division of the post-pouring strip needs to be carried out along the direction of the support plate and within one-third of the span from the support position. Third, the principle that the distance between the floor slab division position and the nearest steel strand is not less than 200mm is considered to ensure that no weak concrete surface is generated during the tensioning of the steel strand.

[0062] The division characteristics of P6, P7, and P8 are as follows: (1) All three areas are located in the podium area, and the floor slabs are divided according to the principle that the areas are not much different; (2) The post-cast strips are divided along the boundary between the tower and the podium, and along the direction of the main beams in the tower area, without cutting the original structural beams. (3) The construction joint of P6 is divided along the direction of the three post-cast strips of the tower and meets the requirement of being within one-third of the span from the support position. (4) The construction joints of P7 and P8 are divided within one-third of the span in the middle, and meet the requirement that the parallel distance between the construction joint position and the nearest steel strand is not less than 200mm, the length of the steel strand overlap area is not less than 1000mm, without cutting the original column caps, and the areas of P7 and P8 are not much different.

[0063] Application effects and prospects for widespread application of this invention After the implementation of this technology, the difficulties of prestressing tensioning and pouring construction for large-area flat slabs were readily resolved. By using segmented pouring and tensioning, the process not only simplified the challenge of large-volume one-time pouring of prestressed floor slabs, but also reduced the pouring risks to a certain extent. The difficulty of tensioning work was also reduced, providing a certain guarantee for the safe construction of the floor slab structure.

[0064] In terms of construction progress, since segmented pouring is different from the large-area operation of monolithic pouring, the construction work of various trades in the construction team does not need to be coordinated with the long-term arrangement of monolithic pouring operations. The cross-operation of various trades can be carried out, and the idle work caused by improper on-site deployment is conducive to the rational allocation of resources, optimization of construction procedures, improvement of construction efficiency, and reduction of costs, thus achieving good economic benefits.

[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A construction method for prestressed concrete in flat slab floor slabs, characterized in that, It can meet the functional requirements of the building and the large space requirements of the garage, including a podium and several towers forming a partial enclosure around the podium. The podium overlaps with each tower, and the overlap is prestressed. The construction method includes the following steps. Prestressing Zoning: The podium and the junction between the podium and the tower are divided into several zones along the prestressing direction. Each zone forms transverse prestress and / or vertical prestress between the podium and the tower. Prestressing Construction: Prestressing is performed along each zone, and the prestressing is performed using a single tensioning method to the design tension value. In the prestressing construction, the construction sequence of the several zones is to first construct the vertical prestress, and then construct the transverse prestress. The prestressing construction is carried out in the order of tower first, followed by podium. The podium and tower areas are divided into: Tower 3 P5; Podium P6, P7, P8; a total of 4 construction areas. The P5 post-cast strip in the tower area is divided into three steps. (1) The first step is located at the boundary between the tower and the podium, and the integral support plate connecting the shear wall W1 and the column is located at the junction of the tower and the podium. Due to the construction deployment of the tower first, the shear wall W1 and its corresponding 2 / 3 area support plate are poured first. (2) The second step meets the principle of dividing within 1 / 3 of the span and the distance from the nearest steel strand is not less than 200mm. (3) The third step is considered the same as the second step. It also includes adding reinforcing bars at the casting strip containing the prestressed tension end. Specifically, reinforcing bars are added within 1m of the concrete slab on both sides of the width of the casting strip. Five 12mm diameter, 200mm spacing threaded bars are arranged in two layers parallel to the direction of the casting strip. Perpendicular to the direction of the casting strip, threaded bars with a diameter of 12mm and a spacing of 200mm are arranged in succession on both sides. The bars are bent at the edge of the casting strip and overlapped before the concrete of the casting strip is poured. The steel strands and reinforcing bars are intersected and arranged, while the floor slab is set on the side of the load-bearing reinforcement formed by the steel strands and reinforcing bars.

2. The construction method for prestressed concrete in flat slabs according to claim 1, characterized in that, In the prestressed zoning process, the construction area is first divided into a tower construction area and a podium construction area based on the tower and podium. Then, the podium construction area is divided according to the principle of equal area. The tower construction area is further divided into a boundary area, an area near the steel strands, and an area along the support plate direction.

3. The construction method for prestressed concrete in flat slabs according to claim 1, characterized in that, The construction of the tower follows the sequence of first constructing the boundary area, then the area near the steel strands, and finally the area along the support plate direction.

4. The construction method for prestressed concrete in flat slabs according to claim 2, characterized in that, In the prestressed zoning process, the zoning between the tower and the podium is determined by the location of the post-cast strip.

5. The construction method for prestressed concrete in flat slabs according to claim 4, characterized in that, In the prestressed construction, the tensioning end of the prestress is located at the post-cast strip or on the outside of the podium.

6. The construction method for prestressed concrete in flat slabs according to claim 4, characterized in that, It also includes the design of extending the casting strip, specifically: adding reinforcing bars at the casting strip containing the prestressed tensioning end.

7. The construction method for prestressed concrete in flat slabs according to claim 1, characterized in that, In several of the aforementioned areas, if there is a prestressed overlap between some adjacent areas, then the prestressed overlap shall be a bidirectional prestressed overlap, and the length of the bidirectional prestressed overlap shall be 0.8-1.2m.

8. The construction method for prestressed concrete in flat slabs according to claim 1, characterized in that, Among the aforementioned areas, at least one area comprises towers located near the edge of the podium building.

9. The construction method for prestressed concrete in flat slabs according to claim 1, characterized in that, In the prestressed construction process, each area's prestressed construction includes pouring and tensioning. Each area is poured first and then tensioned, and the next area's construction begins only after the tensioning is completed.

10. The construction method for prestressed concrete in a flat slab floor according to claim 9, characterized in that, When the length of the steel strand is 10-25m, the initial tension prestress formed by tensioning the steel strand is 600-800psi.

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