A construction method for cast-in-place beams and floor slabs

Abstract

This invention relates to the field of building construction, specifically to a construction method for cast-in-place beams and floor slabs, comprising: binding the beam steel frame: installing and binding reinforcing bars at the pre-set beam body position to form the beam steel frame; cavity laying: laying a bottom formwork along the bottom of the beam steel frame, laying side formwork along both sides of the beam steel frame, and supporting the bottom and side formwork; pre-convex treatment: pre-convexizing the middle part of the beam steel frame; beam edge formwork installation: laying the beam edge formwork horizontally along the length of the beam steel frame, and installing flexible strips on the upper surface of the side of the beam edge formwork closest to the beam steel frame; composite slab laying: hoisting and laying the composite slabs one by one between adjacent beam steel frames, with the two sides of the composite slabs respectively placed on the flexible strips on the beam edge formwork; concrete pouring: pouring concrete into the beam steel frame and composite slabs to integrate them. By implementing this solution, the problem of grout leakage at the junction of the cast-in-place structure and the precast composite slab is solved.

Description

Technical Field

[0001] This invention relates to the field of building construction, and specifically to a construction method for cast-in-place beams and floor slabs. Background Technology

[0002] With the development of the construction industry, prefabricated formwork has been gradually introduced into traditional construction operations to improve construction progress. Prefabricated formwork is prefabricated in factories and only needs to be assembled with the cast-in-place structure on-site, thus saving on-site construction steps and shortening the project construction cycle. Therefore, the introduction of prefabricated formwork (such as composite slabs) has become a standard practice in current construction. However, in actual construction, this new construction method has also brought new technical problems. For example, the construction at the junction of the cast-in-place structure and the prefabricated slab involves many procedures and is quite difficult. One common problem is grout leakage at the junction of the cast-in-place structure and the prefabricated composite slab. Summary of the Invention

[0003] The present invention aims to provide a construction method for cast-in-place beams and floor slabs to reduce the grout leakage rate at the interface between cast-in-place structures and precast composite slabs.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a construction method for cast-in-place beams and floor slabs, comprising the following steps:

[0005] S1. Pre-protrusion treatment: Erect the full-span scaffolding on site and perform pre-protrusion treatment on the middle position of the pre-set beam body;

[0006] S2. Cavity laying: Lay the bottom formwork of the beam and the side formwork of the beam on both sides of the bottom formwork along the preset position of the beam body. The bottom formwork of the beam and the two side formwork of the beam formwork form a cavity for pouring the concrete of the beam body and support the side formwork of the beam.

[0007] S3. Binding the steel frame of the beam: Install steel bars in the cavity and bind them to form the steel frame of the beam;

[0008] S4. Beam side formwork installation: Beam side formwork is laid horizontally on both sides along the length of the beam steel frame. The beam side formwork is located above the beam side formwork, and the beam side formwork is perpendicular to and abuts against the beam side formwork. Flexible strips are installed on the upper surface of the beam side formwork on the side closest to the beam steel frame.

[0009] S5. Laying of composite slabs: The composite slabs are hoisted one by one and laid between the steel frames of two adjacent beams. The two sides of the composite slabs are placed on the flexible strips on the beam side formwork respectively. The truss steel bars on the composite slabs are bound to the steel frame of the beams with steel bars.

[0010] S6. Concrete pouring: Pour concrete into the steel frame of the beam and the composite slab to integrate the two into one.

[0011] The principle and advantages of this scheme are:

[0012] Regarding the issue of grout leakage at the junction of cast-in-place structures and precast composite slabs, this is a new problem arising from a new construction process, and there is no existing experience in the industry to refer to for handling it. The applicant initially analyzed that it might be due to gaps at the junction, which could be caused by various factors, such as unevenness of the composite slab surface or deformation of the formwork in contact with the bottom of the composite slab. Therefore, the applicant imposed strict requirements on the surface flatness of the composite slab manufacturers and inspected the formwork, replacing any deformed formwork promptly. However, the final result was still unsatisfactory. Subsequent analysis revealed that the main reason was that a single construction project involves hundreds of different composite slab specifications and tens of thousands of junction joints. Since the composite slabs are made of cast concrete, achieving a uniform flatness across hundreds of different specifications is extremely difficult. Secondly, regarding the inspection of formwork, firstly, since the number of formwork involved is enormous, reaching tens of thousands, the inspection project is huge, and replacing them all directly would be extremely costly; secondly, it is difficult to judge the deformation of the formwork. Because cement grout is highly fluid, even a small gap at the interface can lead to grout leakage. Therefore, even slight deformation of the formwork can cause gaps and grout leakage, but it is difficult for workers to judge slight deformation of the formwork with the naked eye.

[0013] After several trials and errors, the beam edge formwork was laid horizontally along the length of the beam steel frame. The beam edge formwork was positioned above the beam side formwork, perpendicular to and abutting against it. Flexible strips were installed on the upper surface of the beam edge formwork closest to the beam steel frame. This method of laying the beam edge formwork provided sufficient space for the flexible strips, ensuring their stability. Furthermore, once the flexible strips were stably installed, their deformation compensated for unevenness between the composite slab and the beam edge formwork, effectively preventing gaps between them. This approach not only reduced the production difficulty in ensuring the flatness of the composite slab but also avoided the massive engineering work required to check for formwork deformation or the huge cost of direct replacement in various new construction projects. More significantly, it greatly reduced gaps at the junctions, effectively controlling grout leakage.

[0014] Although the above-mentioned operations effectively controlled grout leakage, large-area localized grout leakage still occurred during later construction. Analysis revealed that during concrete pouring, the load and vibrations caused slight subsidence of the beam structure, resulting in gaps between the beam side formwork and the edge formwork installed on both sides of the beam. Additionally, another reason was the stress generated in and around the contact area when the concrete and beam formwork (beam bottom and side formwork) were pressed together, causing the beam formwork to subside and creating gaps between the side and edge formwork. This allowed cement grout to leak out, resulting in large-area grout leakage along the beam edges. To address this issue, the applicant pre-convexed the middle section of the beam structure.

[0015] Preferably, as an improvement, in the pre-convex treatment step, the pre-convex height of the beam steel frame is 0.1%-0.3% of the span of the beam steel frame. When the pre-convex height of the beam steel frame is less than 0.1% of the span of the beam steel frame, the middle part of the beam will sink below the horizontal line during the concrete pouring process, resulting in the risk of grout leakage. When the pre-convex height of the beam steel frame is greater than 0.3% of the span of the beam steel frame, the main body of the beam will have an upward concavity problem after the main body of the beam is formed.

[0016] Preferably, as an improvement, in the beam side formwork installation step, the beam side formwork abuts against the side wall of the beam steel frame, and one side of the flexible strip is aligned with one side of the beam side formwork. Through the above arrangement, it is ensured that the side wall of the beam side formwork and the flexible strip are on the same vertical plane as the side wall of the beam steel frame, so that the side wall of the main beam is straight and without protrusions after the concrete is poured.

[0017] Preferably, as an improvement, the width of the flexible strip in the beam edge formwork installation step is 1cm-3cm. If the width of the flexible strip is less than 1cm, it is easy to rub off or cause the flexible strip to twist during the laying of the composite slab. If the width of the flexible strip is greater than 3cm, it will lead to increased costs.

[0018] Preferably, as an improvement, the flexible strip is a foam strip. The foam strip is pasted on the beam edge formwork. The foam strip has a certain deformation and a certain support force, and at the same time, it has a good barrier effect on the concrete, further ensuring the sealing of the junction and avoiding grout leakage. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of Embodiment 2 of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of Embodiment 4 of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure of Embodiment 5 of the present invention. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method:

[0023] The reference numerals in the accompanying drawings include: screw 1, top sleeve 2, sleeve 3, support plate 4, baffle 5, connecting plate 6, handle 7, extension plate 8, fastener 9, beam side mold 10, flexible strip 11, mounting cylinder 12, pressing channel 13, conveying channel 14, transverse opening 15, pressing component 16, cap 17, support frame 18, force-applying component 19, and extrusion component 20.

[0024] Example 1

[0025] A construction method for cast-in-place beams and floor slabs includes the following steps:

[0026] S1. Pre-protrusion treatment: The full-span scaffolding is erected on site. Specifically, horizontal bars are set at intervals of 1.5m along the main span of the beam, and vertical bars are set at intervals of 0.9m below the horizontal bars. Pre-protrusion treatment is performed at the middle position along the preset main span of the beam, that is, the scaffolding at the middle position of the preset main span of the beam is higher than the scaffolding at other positions by a certain height. In this embodiment, the pre-protrusion height at the middle of the main span of the beam is 0.2% of the main span of the beam. For example, if the main span of the beam is 20m, the pre-protrusion height is 2cm.

[0027] S2. Cavity Installation: The bottom formwork of the beam body and the side formwork on both sides of the bottom formwork are installed at the preset positions of the beam body. The bottom of the side formwork abuts against the upper surface of the bottom formwork, thus forming a cavity for pouring the concrete of the beam body. The fixing structure for the side formwork is the same on both sides. Taking the fixing structure of one side as an example, a wooden strip (hereinafter referred to as the lower wooden strip) is horizontally fixed to multiple horizontal bars and abuts against the outside of the side formwork. A second wooden strip is placed horizontally above the lower wooden strip, and then a third wooden strip connects the upper and lower wooden strips. This fixes one side of the beam formwork. The fixing structures on both sides clamp and fix the side formwork on both sides of the beam steel frame, ensuring the stability of the subsequent concrete pouring.

[0028] S3. Binding the steel frame of the beam: According to the design drawings, install steel bars in the cavity and bind them to form the steel frame of the beam;

[0029] S4. Beam Side Formwork Installation: Beam side formwork is laid horizontally along both sides of the beam steel frame's length (span). The beam side formwork is positioned above the beam side formwork, perpendicular to and abutting against it. Flexible strips are continuously installed on the upper surface of the beam side formwork closest to the beam steel frame. The width of the flexible strips is preferably 2cm, and their thickness is 0.5cm-2cm. One side of the flexible strip is aligned with one side of the beam side formwork. Flexible strips can be made of deformable flexible materials such as foam strips, sponge strips, or double-sided adhesive sponge. If foam strips or sponge strips are used, they can be adhered to the beam side formwork using double-sided adhesive or other adhesives. In this embodiment, double-sided adhesive sponge is preferred for faster, more convenient, and more efficient construction.

[0030] S5. Laying of composite slabs: The composite slabs are hoisted one by one and laid between adjacent steel beams. The two sides of the composite slabs are placed on double-sided adhesive sponge on the beam edge formwork, which also provides some stability. The truss reinforcement on the composite slabs is then bound to the steel beam frame using reinforcing bars.

[0031] Gap detection: The gaps at the junction of all cast-in-place beams and composite slabs are detected by shining a flashlight on the junction and then observing whether there is light leakage on the back of the junction. If light leakage is found, it indicates that there is a subsidence and gap problem, and the subsided part needs to be corrected.

[0032] S6. Concrete pouring: Pour concrete into the steel frame of the beam and the composite slab to integrate the two into one.

[0033] Grout leakage detection

[0034] Judgment criteria: Whether blocky cement lumps can be seen with the naked eye at the junction of the cast-in-place beam and the composite slab.

[0035] Leakage detection results for areas where this plan was not implemented: A total of 320 points were detected, of which 68 were found to be leaking grout, resulting in a leakage rate of 21.3% and a pass rate of 78.7%.

[0036] The test results after implementing this embodiment are as follows: a total of 320 points were tested, of which 26 points were found to be leaking grout, with a leakage rate of 8.1% and a pass rate of 91.9%, which far exceeds the 80% pass rate required by the acceptance specifications.

[0037] In summary, the leakage rate was effectively controlled by implementing this solution.

[0038] Example 2

[0039] This embodiment uses the same construction method as Embodiment 1, except that after the flexible strip 11 is pasted, it is then fixed to the beam edge formwork 10 by the fastener 9. In actual construction, it was found that the pasted flexible strip 11 was easily rubbed off during the hoisting of the composite slab, leading to partial loose adhesion between the composite slab and the beam edge formwork 10, resulting in grout leakage. Therefore, to solve this problem, the fastener 9 was used to fix the flexible strip 11. Initially, iron nails were used to fix the flexible strip 11 to the beam edge formwork 10. However, it was found that due to the large span area, nailing was labor-intensive and dangerous. Most importantly, the iron nails caused the flexible strip 11 to partially sink, and the thick nail nuts created height differences on the surface of the flexible strip 11, resulting in gaps and minor grout leakage. Furthermore, no suitable fastener 9 or a quick and labor-saving device for installing the fastener 9 was found on the market. Therefore, the applicant independently developed a fastener 9 and a device for installing the fastener 9.

[0040] The fastener 9 is T-shaped and is formed by integrally molding a horizontal part and a vertical part. The bottom end of the vertical part is conical. The fastener 9 is made of metal. In this embodiment, nickel-plated iron is used. The width of the horizontal part is 0.5-2mm and the thickness is 0.3-0.8mm. The length of the vertical part can be designed according to different specifications. For example, in this embodiment, the thickness of the flexible strip 11 is 1.5cm and the thickness of the beam edge mold 10 is 0.3cm, so the length of the vertical part is designed to be 1.7cm.

[0041] like Figure 1 As shown, the device for installing the fixing component includes a feeding section and an installation section. The installation section includes an installation cylinder 12, which has a vertically extending pressing channel 13. A pressing component 16 is vertically slidably connected within the pressing channel 13, with its upper and lower ends located outside and inside the installation cylinder 12, respectively. The feeding section is fixed to the side wall of the installation cylinder 12 and includes a conveying channel 14 for conveying the fixing component 9. The conveying channel 14 is rectangular and communicates with the pressing channel 13. A horizontal opening 15 is provided at the bottom of the conveying channel 14 to accommodate the vertical part of the fixing component 9. A pressing component 20 for pushing the fixing component 9 is slidably connected to the horizontal opening 15. A cap 17 is detachably connected to the end of the conveying channel 14 away from the installation cylinder 12. In this embodiment, the cap 17 is snapped onto the left end of the conveying channel 14, and a compression spring connects the cap 17 and the pressing component 20. The upper opening of the conveying channel 14 is for discharging the fixing component 9. A support frame 18 is fixedly installed at the lower part of the mounting cylinder 12. The support frame 18 supports the device and facilitates downward force applied by construction personnel.

[0042] Installation method of fastener 9: A plate of fasteners 9 is placed horizontally on the conveyor channel 14 (a plate of fasteners 9 means that the manufacturer is required to glue several fasteners 9 side by side into a plate). The vertical part of the fastener 9 protrudes from the horizontal opening 15 and fixes the cap 17. At this time, the fastener 9 moves to the right of the pressing channel 13 under the action of the compression spring. When the rightmost fastener 9 is located in the pressing channel 13 and is pressed against the right side wall of the pressing channel 13, the construction worker presses the pressing piece 16 downwards every 15cm to press it into the flexible strip 11 and the beam edge mold 10, thereby achieving horizontal limiting and fixing of the flexible strip 11 and the beam edge mold 10, reducing the risk of the flexible strip 11 being rubbed off. By implementing this device, the construction worker only needs to perform the pressing operation, which is simple, safe and can effectively improve efficiency. At the same time, the thickness of the horizontal part of the fastener 9 is much smaller than the nut of the nail, so it will not cause the flexible strip 11 to have a height difference and cause grout leakage.

[0043] Grout leakage detection

[0044] Judgment criteria: Same as in Example 1

[0045] Test results: A total of 320 points were tested, of which 12 points were found to be leaking grout, with a leakage rate of 3.7% and a pass rate of 96.3%.

[0046] Example 3

[0047] The difference between this embodiment and Embodiment 2 is that the upper end of the pressing member 16 is horizontally threaded with a force-applying member 19, and the pressing member 16 passes through the force-applying member 19. This arrangement makes the force-applying member 19 adjustable on the pressing member 16. The height of the force-applying member 19 can be adjusted according to the total thickness of the flexible member and the beam edge mold 10, ensuring that the height of the pressing member 16 below the force-applying member 19 is appropriate. Thus, when the force-applying member 19 is pushed against the mounting cylinder 12, the pressing member 16 precisely presses the vertical part of the fixing member 9 completely into the flexible member and the beam edge mold 10. This eliminates the need for construction personnel to control the force and the pressing stroke of the pressing member 16 based on experience, reducing the skill requirements for construction personnel. Furthermore, a return spring connects the force-applying member 19 and the mounting cylinder 12.

[0048] Example 4

[0049] As attached Figure 2As shown, in this embodiment, the tool used in the pre-convex processing step and the gap detection step is an adjustment device, including an adjustment mechanism, a support mechanism, and a connecting mechanism. The adjustment mechanism includes a screw 1 and a top sleeve 2 threadedly connected to the screw 1. The adjustment mechanism also includes a sleeve 3 slidably connected to the screw 1. A horizontal support plate 4 is welded to the end of the sleeve 3 away from the screw 1, and baffles 5 are welded vertically upward on both opposite sides of the support plate 4. The outer diameter of the sleeve 3 is smaller than the outer diameter of the top sleeve 2 but larger than the inner diameter of the top sleeve 2, so the top sleeve 2 provides support for the sleeve 3. The connecting mechanism includes a connecting plate 6 connected to the end of the screw 1 away from the support plate 4, and a connecting hole is provided circumferentially on the connecting plate 6. To facilitate the application of force, handles 7 are welded to the left and right sides of the top sleeve 2, respectively.

[0050] This adjustment device is installed on a vertical pole in the middle of the beam body. By rotating the top sleeve 2, the top sleeve 2 rises, thereby driving the support plate 4 of the support mechanism to rise. The support plate 4 then pushes the beam body upward to the designated position. This solution is easy to operate and can be completed by one person. During use, only the top sleeve needs to be rotated to complete the fine adjustment of the beam body. It has a simple structure and low cost. In addition, after use, this device can be removed from the support column, which facilitates storage and transportation.

[0051] Example 5

[0052] like Figure 3 As shown, the technical difference between this embodiment and embodiment 3 lies in the following: the support plate 4 is hollow inside, and both sides of the support plate 4 have openings. Extension plates 8 are slidably connected to the openings on both sides. The extension plates 8 have vertically threaded holes located away from the support plate 4, and threaded stops are threaded into these holes. In another embodiment, the threaded hole and threaded stop can be replaced by a baffle 5 welded vertically upwards on the side of the extension plate 8 away from the support plate 4. Protrusions are welded to both sides of the upper part of the screw 1, and the sleeve 3 has vertically provided grooves for the protrusions to slide inside. Thus, when the top sleeve 2 rotates and pushes the sleeve 3 upwards, the sleeve 3 only moves vertically, allowing the support plate 4 to more accurately align with the object to be supported. An annular groove is provided on the lower end face of the sleeve 3 or the upper end face of the top sleeve 2, and a ball bearing is rotatably connected within the groove, protruding from the groove surface. Therefore, when the top sleeve 2 rotates and pushes the sleeve 3, the friction between the contact surfaces is reduced, thereby reducing the force required from the operator and reducing wear between the two.

[0053] Since the main beam is initially supported by a grid of steel pipes (horizontal bars) laid horizontally and vertically, the support plate 4 in this device acts on the steel pipes when adjusting the main beam. Since the steel pipes in the support layer are laid in different ways and the number of steel pipes in each group is different, the support length of the support plate 4 can be adjusted by sliding the extension plate 8 for different numbers of steel pipe groups.

[0054] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A construction method for cast-in-place beams and floor slabs, characterized in that: Includes the following steps, S1. Pre-protrusion treatment: Erect the full-span scaffolding on site and perform pre-protrusion treatment on the middle position of the pre-set beam body; S2. Cavity laying: Lay the bottom formwork of the beam and the side formwork of the beam on both sides of the bottom formwork along the preset position of the beam body. The bottom formwork of the beam and the two side formwork of the beam formwork form a cavity for pouring the concrete of the beam body and support the side formwork of the beam. S3. Binding the steel frame of the beam: Install steel bars in the cavity and bind them to form the steel frame of the beam; S4. Beam side formwork installation: Beam side formwork is laid horizontally on both sides along the length of the beam steel frame. The beam side formwork is located above the beam side formwork, and the beam side formwork is perpendicular to and abuts against the beam side formwork. Flexible strips are installed on the upper surface of the beam side formwork on the side closest to the beam steel frame. S5. Laying of composite slabs: The composite slabs are hoisted one by one and laid between the steel frames of two adjacent beams. The two sides of the composite slabs are placed on the flexible strips on the beam side formwork respectively. The truss steel bars on the composite slabs are bound to the steel frame of the beams with steel bars. S6. Concrete pouring: Pour concrete into the steel frame of the beam and the composite slab to integrate the two into one.

2. The construction method for cast-in-place beams and floor slabs according to claim 1, characterized in that: In the pre-convex treatment step, the pre-convex height of the steel beam frame is 0.1%-0.3% of the span of the steel beam frame.

3. The construction method for cast-in-place beams and floor slabs according to claim 2, characterized in that: In the beam side formwork installation step, the beam side formwork abuts against the side wall of the beam steel frame, and one side of the flexible strip is aligned with one side of the beam side formwork.

4. A construction method for cast-in-place beams and floor slabs according to claim 3, characterized in that: In the beam side formwork installation step, the width of the flexible strip is 1cm-3cm.

5. A construction method for cast-in-place beams and floor slabs according to claim 4, characterized in that: The flexible strip is a foam strip, which is then attached to the beam edge formwork.

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