Prestressed concrete composite slab beam edge structure

Abstract

The utility model relates to a kind of prestressed concrete composite slab beam edge structure, recessed groove is set to the end of prefabricated prestressed concrete composite slab inward, the recessed groove is matched with the formwork edge of cast-in-place concrete beam in situ to form the lapping area that can contain installation deviation;Elastic sealing rubber strip is arranged between the recessed groove and cast-in-place concrete beam formwork, so that the height difference between the bottom surface of composite slab and the top surface of beam formwork is elastically absorbed by the sealing rubber strip and sealing is achieved to prevent leakage of mortar.The utility model needs only to align the recessed groove with beam side formwork and press into position lightly during hoisting, so that the adjustable space of recessed groove can be used to quickly complete elevation and flatness correction, the installation time of single slab is shortened by more than 30% on average, and the workload of tower crane occupation and manual fine adjustment is greatly reduced.

Description

Technical Field

[0001] This utility model relates to prefabricated concrete structures, specifically a prestressed concrete composite slab beam edge structure. Background Technology

[0002] In prefabricated concrete structures, PK prestressed concrete composite slabs have been widely used in high-rise building floor systems due to their advantages such as high load-bearing capacity, fast construction speed, and good overall slab integrity. The composite slabs are typically prefabricated in a factory with a 40mm thick prestressed base slab, installed on site, and then share the load with the upper cast-in-place layer. However, the lap joint between the composite slab and the cast-in-place concrete beams (or walls) remains a key and challenging aspect of construction quality control.

[0003] Currently, the conventional construction practice is to directly erect the composite slab base plate on the edge of the side or bottom formwork of the cast-in-place beam, with the joints only covered by subsequent plastering or decorative layers. This joint is highly susceptible to quality defects due to the following reasons:

[0004] Template installation error: During construction, the cast-in-place beam template (usually using 15mm thick wooden template or aluminum template) is affected by human operation, template deformation, positioning deviation, etc., and its edge straightness and elevation error often exceed ±5mm, which makes it impossible for the composite slab to fit accurately.

[0005] The inherent error of the composite slab: During the production, transportation and hoisting process, the precast base slab may also be warped and have dimensional deviations (especially the straightness of the slab edges), which will further aggravate the misalignment of the joints.

[0006] No gaps in joint construction: In existing composite slab standard drawings (such as "15G366-1"), the joint of slab and beam is only simply shown as "slab edge lap beam side formwork", without providing construction measures for adjustable deviations, and without considering the need for sealing and preventing grout leakage.

[0007] The above errors, when added together, lead to the following typical problems:

[0008] Misalignment: A height difference (commonly 3~10mm) is formed between the bottom surface of the composite slab and the surface of the beam side formwork, and obvious "steps" appear at the bottom of the floor slab, affecting the flatness of the ceiling.

[0009] Grout leakage and contamination: The joints are not sealed, and cement grout seeps out from the gaps when the cast-in-place concrete is poured, contaminating the bottom surface of the composite slab and forming "tear-shaped" defects, which need to be manually removed and repaired later.

[0010] High rework costs: According to current acceptance standards (such as GB50204-2015), the flatness deviation of the bottom surface of the floor slab must be ≤4mm. However, the above defects often lead to large-scale rework, increasing the cost of putty, sanding and leveling in the decoration stage (the overall cost increases by about 15~25 yuan / ㎡).

[0011] Existing patents mostly focus on the arrangement of prestressed tendons in the composite slab itself (such as CN110591665A) or the crack resistance of the composite layer (such as CN213697897U), but lack systematic technical solutions for the construction problem of "adjustment of deviation of slab-beam lap joint". Utility Model Content

[0012] The present invention aims to overcome the defects of the prior art and provide a prestressed concrete composite slab beam edge structure to solve the above-mentioned technical problems.

[0013] To solve the above-mentioned technical problems, this utility model is implemented as follows:

[0014] A prestressed concrete composite slab beam edge structure is characterized in that: an inwardly recessed groove is provided at the end of the precast prestressed concrete composite slab, which cooperates with the edge of the formwork of the cast-in-place concrete beam to form an overlap area that can accommodate installation deviations; an elastic sealing strip is provided between the groove and the formwork of the cast-in-place concrete beam, so that the height difference between the bottom surface of the composite slab and the top surface of the beam formwork is elastically absorbed by the sealing strip and a seal is achieved to prevent grout leakage.

[0015] The prestressed concrete composite slab beam edge structure is characterized in that: the groove has a rectangular cross-section, and its width is symmetrically arranged within the thickness range of the composite slab, with a single-sided width of 15–25 mm, a total width of 30–50 mm, and a groove depth of 3–8 mm.

[0016] The prestressed concrete composite slab beam edge structure is characterized in that: the groove has a depth of 5 mm and a width of 20 mm on one side, so as to achieve precise overlap between the composite slab and the cast-in-place beam formwork within an installation deviation range of ±5 mm.

[0017] The prestressed concrete composite slab beam edge structure is characterized in that: the elastic sealing strip is a closed-cell foamed EPDM rubber strip, the original thickness of which is equal to or slightly greater than the groove depth, and the rebound rate after compression is ≥60%, so as to continuously fill the gap between the composite slab and the beam formwork.

[0018] The prestressed concrete composite slab beam edge structure is characterized in that: the thickness of the prestressed concrete composite slab is 40 mm, the thickness of the cast-in-place concrete beam formwork is 15 mm, and the groove is located 5 mm above the bottom surface of the composite slab, so that the bottom surface of the composite slab is flush with the top surface of the beam formwork after installation.

[0019] The prestressed concrete composite slab beam edge structure is characterized in that: the groove is formed by a square groove set at the end of the steel mold during the prefabrication stage of the composite slab, the square groove is fixed by a detachable clamp and cast as a whole with the mold, ensuring that the groove size accuracy is ≤±1 mm.

[0020] The prestressed concrete composite slab beam edge structure is characterized in that: the elastic sealing strip is pre-attached into the groove before the composite slab is hoisted, and the exposed surface of the strip is provided with anti-stick release paper. During on-site installation, the release paper is removed and the groove of the composite slab is directly fastened to the cast-in-place beam formwork.

[0021] The prestressed concrete composite slab beam edge structure is characterized in that: the overlap area, through the combination of groove and sealing strip, controls the misalignment of the joint between the composite slab and the cast-in-place beam to ≤2 mm, and prevents grout leakage during the concrete pouring stage.

[0022] The beneficial effects of this utility model are as follows: As can be seen from the above technical solution, this application provides a prestressed concrete composite slab beam edge structure. During hoisting, it is only necessary to align the groove with the beam side formwork and press it into place. The adjustable space of the groove can be used to quickly complete the elevation and flatness correction. The installation time of a single slab is shortened by an average of more than 30%, which greatly reduces the occupation of tower cranes and the amount of manual fine-tuning work. It also reduces the quality risks of misalignment and grout leakage between the PK prestressed concrete composite slab and the cast-in-place concrete beam, improves the installation quality of the PK prestressed concrete composite slab, and saves costs. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0024] Figure 1 This is a schematic diagram of the structure of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0026] like Figure 1 As shown: A prestressed concrete composite slab beam edge structure, wherein an inwardly recessed groove 2 is provided at the end of the precast prestressed concrete composite slab 1, which cooperates with the edge of the formwork of the cast-in-place concrete beam to form an overlap area that can accommodate installation deviations; an elastic sealing strip 3 is provided between the groove 2 and the cast-in-place concrete beam formwork 4, so that the height difference between the bottom surface of the composite slab and the top surface of the beam formwork is elastically absorbed by the sealing strip and a seal is achieved to prevent grout leakage.

[0027] The groove has a rectangular cross-section and its width is symmetrically arranged within the thickness range of the laminated plate. The width of one side is 15–25 mm, the total width is 30–50 mm, and the groove depth is 3–8 mm.

[0028] The groove is 5 mm deep and 20 mm wide on one side to achieve precise overlap between the composite slab and the cast-in-place beam formwork within an installation deviation range of ±5 mm.

[0029] The elastic sealing strip is a closed-cell foamed EPDM rubber strip with an original thickness equal to or slightly greater than the groove depth and a rebound rate of ≥60% after compression, so as to continuously fill the gap between the composite slab and the beam formwork.

[0030] The thickness of the prestressed concrete composite slab is 40 mm, the thickness of the cast-in-place concrete beam formwork is 15 mm, and the groove is located 5 mm above the bottom surface of the composite slab, so that the bottom surface of the composite slab is flush with the top surface of the beam formwork after installation.

[0031] The groove is formed by a square groove set at the end of the steel mold during the prefabrication stage of the composite plate. The square groove is fixed by a detachable clamp and cast as a whole with the mold to ensure that the dimensional accuracy of the groove is ≤±1 mm.

[0032] The elastic sealing strip is pre-attached into the groove before the composite slab is hoisted. The exposed surface of the strip is covered with anti-stick release paper. During on-site installation, the release paper is removed and the groove of the composite slab is directly fastened to the cast-in-place beam formwork.

[0033] The overlapping area, through the combination of grooves and sealing strips, controls the misalignment of the joint between the composite slab and the cast-in-place beam to ≤2 mm and prevents grout leakage during the concrete pouring stage.

[0034] The construction method for the prestressed concrete composite slab beam edge structure described above includes the following steps:

[0035] a) According to the design drawings, arrange and fix the forming groove strips at both ends of the composite plate steel mold, so that the groove width on each side is ≥20 mm and the depth is 5 mm;

[0036] b) After the steel reinforcement is tied and the prestressing tendons are tensioned in the steel mold, concrete is poured to form a grooved prestressed concrete composite slab.

[0037] c) After the concrete reaches the demolding strength, the formwork is removed, and the composite slab is transported to the construction site;

[0038] d) Before on-site hoisting, continuously apply the elastic sealing strip along the entire length of the groove in the composite plate, with the strip thickness equal to or slightly greater than the groove depth;

[0039] e) Hoist the composite slab above the cast-in-place concrete beam formwork, so that the grooves fit into the top edge of the beam formwork, and use the rubber strips to elastically adjust the elevation of the composite slab until the bottom surface of the composite slab is flush with the top surface of the beam formwork.

[0040] f) Fix temporary supports for composite slabs, and complete the binding of composite slab reinforcement, beam side formwork, and composite layer formwork reinforcement;

[0041] g) Pour the composite layer and beam concrete. Under the lateral pressure of the concrete, the adhesive strip is further compressed and seals the joint, achieving integrated beam and slab construction without misalignment or grout leakage.

[0042] Furthermore,

[0043] Step a) The medium strip is fixed to the end of the steel mold by a detachable magnetic box or bolt clamp to ensure that the groove size accuracy is ≤ ±1 mm.

[0044] In step b), the thickness of the composite slab bottom plate is 40 mm, and the prestressing tendons are tensioned using the pre-tensioning method, with the tensioning stress controlled at 0.70 fptk.

[0045] The elastic sealing strip used in step d) is a closed-cell foamed EPDM rubber strip with an original thickness of 6 mm and a rebound rate of ≥60% after compression.

[0046] Step e) During the hoisting process, a laser level is used to monitor the elevation of the bottom surface of the composite slab in real time to ensure that the height difference between the bottom of the slab and the top surface of the beam formwork is ≤2 mm.

[0047] Step g) Keep the temporary supports of the composite slab in place while pouring concrete until the concrete strength of the composite layer reaches 75% of the design strength before removing the supports.

[0048] By adopting the above technical solution, a 20 mm × 5 mm groove is formed in one step at the end of the composite slab, eliminating the need for repeated shims and mortar leveling processes in traditional methods. During hoisting, the groove only needs to be aligned with the beam side formwork and gently pressed into place. The adjustable space of the groove can then be used to quickly complete the elevation and flatness correction. The installation time of a single slab is reduced by an average of more than 30%, significantly reducing the occupation of tower cranes and the amount of manual fine-tuning work.

[0049] The groove and the elastic sealing strip together form a three-in-one structure of "error tolerance-absorption-sealing": the groove allows for an installation deviation of ±5mm, and the strip rebounds to fill the remaining gap after being compressed, so that the height difference between the bottom surface of the composite slab and the top surface of the beam formwork is controlled within 2mm. This completely solves the visual quality problems such as misalignment, grout leakage, and rust that are common in traditional joints, and the flatness of the floor slab bottom surface can reach 98% in one go.

[0050] By eliminating the costs of extensive grinding, plastering, patching, and secondary ceiling covering in the later stages, calculations from multiple projects show that approximately 15 to 25 yuan can be saved in labor and material costs per square meter of floor space. At the same time, it reduces indirect costs caused by rework and construction delays, resulting in significant overall economic benefits.

[0051] The groove is formed at the end of the steel mold in the factory using a detachable clamp, eliminating the need for additional mold investment; the sealing strip is a universal sealing material that can be applied in batches to PK prestressed composite slabs of varying thicknesses and strengths. This structure is suitable for wooden molds, aluminum molds, and steel mold systems, offering strong compatibility and facilitating rapid deployment on existing production lines.

[0052] The sealing strip is made of closed-cell foamed EPDM rubber, which is alkali-resistant, aging-resistant, and has the same lifespan as the concrete. The groove is located at the edge of the compression zone of the composite slab, and has minimal impact on the cross-sectional bearing capacity. Actual measurements show that after adopting this structure, the joint performance, deflection, and crack control of the composite slab and the cast-in-place beam all meet the design requirements, and the need for subsequent maintenance is almost zero.

[0053] The above are merely embodiments provided in this application and are not intended to limit this application. Although this application has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, 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.

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