A production method of prestressed composite prefabricated stairs and stairs

Abstract

The invention discloses a production method of a prestressed composite prefabricated staircase and the staircase, the production method comprising the following steps: passing a plurality of prestressed steel bars through a prefabricated base plate mold, tensioning the two ends of the prestressed steel bars to a set tension, and then pouring concrete into the prefabricated base plate mold; curing the concrete in the prefabricated base plate mold, and when the concrete strength reaches the requirement, loosening the prestressed steel bars, demoulding, and obtaining a prefabricated base plate; placing a steel mesh on the prefabricated base plate, placing the prefabricated base plate and the steel mesh into a staircase mold, pouring concrete into the staircase mold, and vibrating; curing the concrete in the staircase mold, and when the concrete strength reaches the requirement, demoulding, and obtaining a prestressed composite prefabricated staircase; the prefabricated base plate of the invention adopts prestressed steel bars, and the use load of the staircase first offsets the existing prestress in the concrete, thereby improving the strength of the prefabricated staircase and reducing the generation of transverse cracks.

Description

Technical Field

[0001] The invention relates to the technical field of prefabricated stair production, and in particular to a production method of a prestressed composite prefabricated staircase and the staircase. Background Art

[0002] As one of the most important components of a building, stairs are an indispensable part of a general multi-story building. They are used as a connecting passage between the upper and lower floors. Generally, there are two ways to achieve this: traditional cast-in-place and prefabricated staircase installation. Traditional cast-in-place means that concrete is poured on the formwork at the construction site, and the cast-in-place stairs are formed after the concrete solidifies. Prefabricated stairs refer to stairs that are prefabricated in a factory, which are hoisted to the installation location, and then the two ends of the prefabricated stairs are connected to the upper and lower floors respectively using a reliable connection method.

[0003] There are usually two methods for producing existing prefabricated stairs. One is to use steel plates to make prefabricated staircase templates, and then pour concrete into the templates after tying the staircase steel cage. After the concrete solidifies, the template is removed. This method is to cast the prefabricated stairs into an integrated structure. Since the prefabricated stairs need to go through steps such as demoulding, transportation and hoisting before they can be placed in the use position, which are steps that traditional cast-in-place stairs do not have, the risk of staircase cracking is increased; in addition, the prefabricated stairs are produced using vertical molds, and the stairs are placed horizontally during the use stage. In most cases, the bending moment generated under the action of their own weight has exceeded the concrete cracking bending moment, coupled with the upper constant load and live load, it is easy to cause the staircase bottom plate to crack and produce transverse cracks, which poses a safety hazard and increases the subsequent maintenance cost; the other is to prefabricate the stairs in parts, such as prefabricating the cast-in-place stair slabs and steps separately, and assembling them on site. Although the prefabricated stairs produced in this way are convenient for transportation, they put forward higher requirements on the connectors and connection methods. In addition, the problem of transverse cracks caused by cracks on the bottom surface of the stairs cannot be avoided.

[0004] There are also methods for producing prestressed stairs in the prior art. The production method of prestressed stairs usually involves first tensioning the prestressed steel bars, and then pouring concrete on the tensioned prestressed steel bars to achieve the production of the prestressed stairs. However, when using this method to produce prestressed stairs, there are problems such as difficulty in implementing prestressing, poor control of prestress loss, and high tensioning costs. In addition, this production method requires tensioning the prestressed steel bars before pouring each staircase, and the production efficiency is low. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a production method and stairs of a prestressed composite prefabricated staircase, which solves the problem that transverse cracks are easily generated on the bottom surface of the existing prefabricated stairs, and can effectively improve the strength of the stairs and reduce the generation of cracks; at the same time, by mass producing prefabricated bottom plates, the production efficiency of the stairs is improved.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a method for producing a prestressed composite prefabricated staircase is provided, comprising the following steps:

[0008] Step 1: Pass multiple prestressed steel bars through the prefabricated base plate mold, tension the two ends of the prestressed steel bars to a set tension, and then pour concrete into the prefabricated base plate mold;

[0009] Step 2: Curing the concrete of the prefabricated bottom plate mold, when the concrete strength reaches the requirement, loosening the prestressed steel bars, demoulding, and obtaining the prefabricated bottom plate;

[0010] Step 3: Place a steel mesh on the prefabricated base plate, place the prefabricated base plate and the steel mesh into a staircase mold, pour concrete into the staircase mold, and vibrate;

[0011] Step 4: Cure the concrete in the stair mold, and when the concrete strength reaches the requirement, demould it to obtain a prestressed composite prefabricated staircase.

[0012] In some embodiments of the present invention, in step one, a plurality of prestressed steel bars are tensioned simultaneously.

[0013] In some embodiments of the present invention, in step 1, a certain length of prestressed steel bars is passed through a plurality of prefabricated floor slab molds, and a certain distance is spaced between two adjacent prefabricated floor slab molds.

[0014] In some embodiments of the present invention, in step 2, after the prestressed steel bars are loosened, the prestressed steel bars between two adjacent molds are cut and demolded to obtain a plurality of prefabricated bottom plates.

[0015] In some embodiments of the present invention, the prestressed steel bars in the prefabricated base plate obtained in step 2 extend 5-90 cm from both ends of the prefabricated base plate, one end of which is arranged parallel to the prefabricated base plate, and the other end is bent and arranged to form a certain angle with the prefabricated base plate.

[0016] In some embodiments of the present invention, the steel mesh is a steel mesh woven with longitudinal steel bars and transverse steel bars, and rectangular steel cages are provided at both ends of the steel mesh.

[0017] In some embodiments of the present invention, when the steel mesh is placed on the prefabricated bottom plate, the prestressed steel bars extending out of the two ends of the prefabricated bottom plate are extended into the rectangular steel cages at the two ends of the steel mesh.

[0018] In some embodiments of the present invention, in step 1, the casting thickness of the prefabricated base plate is 3-15 cm.

[0019] In the second aspect of the present invention, there is provided a prestressed composite prefabricated staircase, which is obtained by the production method described in the first aspect, and includes a cast-in-place stair tread and a prefabricated base plate, wherein the prefabricated base plate is provided with prestressed steel bars, and the cast-in-place stair tread is provided with a steel mesh, and both ends of the prestressed steel bars extend into the steel mesh; the prefabricated base plate is made of cast concrete with tensioned prestressed steel bars, and the cast-in-place stair tread is built into an integrated structure with the prefabricated base plate by pouring concrete.

[0020] In some embodiments of the present invention, the precast base plate is a rectangular concrete slab structure, and the upper surface of the precast base plate is in contact with the bottom surface of the cast-in-place stair slab.

[0021] One or more technical solutions of the present invention have the following beneficial effects:

[0022] (1) The production method of the prestressed composite prefabricated staircase provided by the present invention is to cast the cast-in-place stair tread and the prefabricated base plate separately, first cast the prefabricated base plate, then cast the cast-in-place stair tread, and finally cast the prefabricated base plate and the cast-in-place stair tread into an integrated structure; through this casting method, prestressed steel bars can be laid in the prefabricated base plate, and the prestressed steel bars are first tensioned and then concrete is cast to form the prefabricated base plate. When in use, the use load of the staircase first offsets the existing prestress in the concrete, and then as the load increases, the concrete is tensile and then cracks appear, thereby improving the load-bearing strength of the prefabricated staircase and reducing the generation of transverse cracks.

[0023] (2) In the production method of prestressed composite prefabricated stairs provided by the present invention, when casting the cast-in-place stair treads, the two ends of the prestressed steel bars in the prefabricated bottom plate can extend into the interior of the two ends of the steel mesh, so that the cast-in-place stair treads and the prefabricated bottom plate can be directly cast into an integrated structure. Therefore, compared with the existing split casting and then connected by connecting parts, the prefabricated bottom plate and the cast-in-place stair tread of the present invention do not require other connecting parts to connect them, thereby improving the stability of the connection between the prefabricated bottom plate and the cast-in-place stair tread.

[0024] (3) The production method of prestressed composite prefabricated stairs provided by the present invention has the advantages that the prefabricated bottom plate is cast by using prestressed steel bars, and the cast-in-place stair tread is cast by using ordinary steel bars. Compared with ordinary steel bars, prestressed steel bars have a smaller diameter and higher strength. Compared with the existing method of casting entirely with steel mesh, the use of steel can be reduced.

[0025] (4) The production method of the prestressed composite prefabricated staircase provided by the present invention is to tension the prestressed steel bars before pouring the prefabricated base plate, thereby truly exerting the prestress of the prestressed steel bars and converting the prestress of the steel bars into the crack resistance, strength and shear resistance of the prefabricated staircase, thereby improving the performance of the prefabricated staircase and reducing the occurrence of cracks.

[0026] (5) The present invention provides a method for producing prestressed composite prefabricated stairs. The prefabricated bottom plate is standardized and mass-produced through a prestressed long line platform, which improves the production efficiency of the stairs. Compared with the single prestressing loss value, it can be effectively controlled, and the prestressed steel bars are arranged in a zigzag shape along the inclined section and two straight sections of the stairs, making it technically possible to realize the prestressed staircase process. This method reduces the production cost. The steel bars in the bottom plate and the stair section plate are deeply embedded in the rectangular steel cages at both ends for reliable and effective anchoring, so that the two parts form an integrated structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the production method of the prestressed composite prefabricated staircase of the present invention;

[0028] Figure 2 It is a schematic diagram of the prestressed composite prefabricated staircase of the present invention;

[0029] Figure 3 It is a schematic diagram of the prestressed composite prefabricated staircase after being disassembled according to the present invention.

[0030] In the figure: 1. cast-in-place stair slab; 101. steel mesh; 1011. longitudinal steel bar; 1012. first transverse steel bar; 1013. lower end steel cage; 1014. upper end steel cage; 102. groove; 2. prefabricated bottom plate; 201. prestressed steel bar; 202. second transverse steel bar. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0032] Example 1

[0033] In a typical embodiment of the present invention, a method for producing a prestressed composite prefabricated staircase is provided, comprising the following steps:

[0034] Step 1: Pass multiple prestressed steel bars through the prefabricated base plate mold, tension both ends of the prestressed steel bars to a set tension, and then pour concrete into the prefabricated base plate mold.

[0035] Specifically, the prefabricated base plate mold is a rectangular groove structure, and a plurality of long holes are arranged on two opposite surfaces of the prefabricated base plate mold for passing a plurality of prestressed steel bars. The spacing between adjacent long holes is 2 cm to accommodate the uniform arrangement of different numbers of prestressed steel bars under different loads. When arranging the prestressed steel bars, the distance between two adjacent prestressed steel bars is 5-15 cm. Within this range, it can ensure high strength and reduce the use of prestressed steel bars to a certain extent.

[0036] Furthermore, tensioning is performed on both ends of multiple prestressed steel bars at the same time. By applying tension to the prestressed steel bars in advance, the prestressed steel bars to which prestressing is applied are subjected to tensile stress. After the bars are broken, the shrinkage of the prestressed steel bars will produce compressive stress on the concrete, thereby causing it to produce a certain deformation to cope with the load that the stairs will be subjected to in the later stage. Technical personnel in this field can select the corresponding tension to tension the two ends of the prestressed steel bars as needed.

[0037] Among them, the prestressed steel bars use 1570 grade stress-relieving spiral rib steel wire with a diameter range of 5 to 7 mm.

[0038] Of course, in order to further improve the strength of the prefabricated base plate, multiple prestressed steel bars can be bundled through multiple transverse steel bars. The transverse steel bars are arranged vertically to the prestressed steel bars, and the transverse steel bars are ordinary steel bars. The prestressed steel bars and the transverse steel bars form a steel mesh and are cast in the prefabricated base plate.

[0039] Step 2: Curing the concrete of the prefabricated base plate mold, when the concrete strength reaches the requirement, loosen the prestressed steel bars, demould and obtain the prefabricated base plate.

[0040] During maintenance, normal temperature maintenance or steam maintenance can be adopted according to the season. When steam maintenance is adopted, the maintenance temperature should be controlled between 40-60 degrees. The continuous maintenance time should be no less than 4 hours. When the concrete strength reaches 75% of the design strength, the prestressed steel bars can be released and the steel bars can be cut and demolded.

[0041] In order to improve the production efficiency of the prefabricated base plate, a certain length of prestressed steel bars can be passed through multiple prefabricated base plate molds, and two adjacent prefabricated base plate molds can be separated by a certain distance, specifically, 10-180 cm, to ensure that both ends of the prestressed steel bars can extend out of the end surface of the prefabricated base plate; after loosening the prestressed steel bars, the prestressed steel bars between the two adjacent molds are cut and demoulded to obtain multiple prefabricated base plates.

[0042] The obtained precast base plate is a rectangular concrete slab, and the casting thickness of the precast base plate is 3-15cm. If the thickness of the precast base plate is too thin, the base plate will be too arched, and if it is too thick, it will be difficult to hoist it into the stair mold. By limiting the thickness of the precast base plate within this range, the precast base plate can not only play a prestressing role, but also be easy to hoist. The prestressed steel bars in the precast base plate extend 5-90cm from both ends of the precast base plate, one end of which is arranged parallel to the precast base plate, and the other end is bent to form a certain angle with the precast base plate. The end of the prestressed steel bar parallel to the precast base plate extends into the upper end of the steel mesh, and the end of the prestressed steel bar at a certain angle to the precast base plate extends into the lower end of the steel mesh. In this way, when pouring the cast-in-place stair slab concrete, the precast base plate and the cast-in-place stair slab can be cast into an integrated structure, and no other parts are required for connection, so that a stable connection between the precast base plate and the cast-in-place stair slab can be achieved.

[0043] Step 3: Place a steel mesh on the prefabricated base plate, place the prefabricated base plate and the steel mesh into the stair mold, pour concrete into the stair mold, and vibrate.

[0044] The steel mesh in this step is a steel mesh woven with longitudinal steel bars and transverse steel bars, and both ends of the steel mesh are woven into rectangular steel cages. When the steel mesh is placed on the precast base plate, the prestressed steel bars extending from both ends of the precast base plate are extended into the rectangular steel cages at both ends of the steel mesh. After the precast base plate and the steel mesh are placed in the stair mold, concrete is poured into the stair mold to form a cast-in-place stair slab, so that the precast base plate and the cast-in-place stair slab are cast into an integrated structure.

[0045] Among them, the steel bars in the steel mesh are ordinary steel bars. Here, ordinary steel bars refer to steel bars without prestress. Prestressed steel bars are high-strength steel bars that have been stretched. Pre-designed prestress is applied during the stretching process to make them have higher strength and toughness. Ordinary steel bars do not undergo this treatment, and their strength and toughness are relatively low.

[0046] When vibrating, use a vibrating rod to vibrate the concrete. The vibrating rod should be perpendicular to the concrete surface and inserted quickly and pulled out slowly to vibrate evenly. When there is no obvious collapse on the concrete surface, cement slurry appears, and no bubbles appear, end the vibration of that part to achieve the best density and strength of the concrete. The vibration time is based on the standard that the concrete no longer sinks significantly, no bubbles appear, and floating slurry appears on the surface. If the vibration time is too long, it will cause too much cement slurry in the concrete to be lost, and the surface is prone to sand and water seepage, which will reduce the uniformity and strength of the concrete.

[0047] Step 4: Cure the concrete in the stair mold, and when the concrete strength reaches the requirement, demould it to obtain a prestressed composite prefabricated staircase.

[0048] During curing, normal temperature curing or steam curing can be adopted according to the season. When steam curing is adopted, the curing temperature should be controlled between 40-60 degrees. The continuous curing time should be not less than 4 hours. The concrete strength reaches 75% of the design strength and then demolding is carried out. After demolding, it is placed in the yard for natural curing.

[0049] During the process of pouring the cast-in-place stair treads, installation holes are reserved at both ends of the stairs, and the stairs are installed on the cast-in-place stair beams of the upper and lower layers through the installation holes.

[0050] The production method of the prestressed composite prefabricated staircase provided in the present embodiment is to first cast the prefabricated base plate and then cast the cast-in-place stair tread. The prestressed steel bars are first tensioned and then concrete is cast to form the prefabricated base plate. The prestressed steel bars exposed at both ends of the prefabricated base plate are first extended into both ends of the steel mesh and then the cast-in-place stair tread is cast, so that the cast-in-place stair tread and the prefabricated base plate are cast into an integrated structure. This can effectively solve the problem of horizontal cracks being easily generated on the bottom surface of the existing prefabricated stairs and reduce the generation of cracks by improving the strength of the stairs.

[0051] Example 2

[0052] In a typical embodiment of the present invention, a prestressed composite prefabricated staircase is provided, which is obtained by the production method described in Example 1, such as Figure 2 As shown, it includes a cast-in-place stair slab 1 and a precast base plate 2, wherein the precast base plate 2 is provided with prestressed steel bars 201, and the cast-in-place stair slab 1 is provided with a steel mesh 101, and both ends of the prestressed steel bars 201 extend into the steel mesh 101; the precast base plate 2 is made of concrete poured with the tensioned prestressed steel bars 201, and the cast-in-place stair slab 1 is built into an integrated structure with the precast base plate 2 by pouring concrete.

[0053] The cast-in-place stair tread 1 serves as the main structure of the prefabricated staircase. Steps are arranged on the upper surface of the cast-in-place stair tread. A groove 102 is formed on the bottom surface of the cast-in-place stair tread due to the placement of the prefabricated bottom plate 2 during casting, so that the cast-in-place stair tread 1 wraps the prefabricated bottom plate 2 on three sides.

[0054] The precast base plate 2 is a rectangular concrete slab structure, the upper surface of the precast base plate 2 is in contact with the bottom surface of the cast-in-place ladder plate 1, and multiple prestressed steel bars 201 are arranged in parallel in the width direction of the precast base plate 2, and a certain distance is separated between two adjacent prestressed steel bars 201.

[0055] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for producing a prestressed composite prefabricated staircase, characterized in that: The following steps are involved: Step 1: Pass multiple prestressed steel bars through the prefabricated base plate mold, tension the two ends of the prestressed steel bars to a set tension, and then pour concrete into the prefabricated base plate mold; A certain length of prestressed steel bars are passed through a plurality of prefabricated bottom plate molds, and two adjacent prefabricated bottom plate molds are spaced a certain distance apart. After the prestressed steel bars are loosened, the prestressed steel bars between the two adjacent molds are cut; By applying tension to the prestressed steel bars in advance, the prestressed steel bars are subjected to tensile stress. After the steel bars are broken, the prestressed steel bars shrink and produce compressive stress on the concrete, which in turn causes a certain deformation to cope with the loads on the stairs in the later stage, thereby reducing the occurrence of transverse cracks. Step 2: Curing the concrete of the prefabricated bottom plate mold, when the concrete strength reaches the requirement, loosening the prestressed steel bars, demoulding, and obtaining the prefabricated bottom plate; Step 3: Place a steel mesh on the prefabricated base plate, place the prefabricated base plate and the steel mesh into a staircase mold, pour concrete into the staircase mold, and vibrate; Step 4: Cure the concrete in the stair mold, and when the concrete strength reaches the requirement, demould it to obtain a prestressed composite prefabricated staircase.

2. The method for producing prestressed composite prefabricated stairs according to claim 1, characterized in that: In the step 1, a plurality of prestressed steel bars are tensioned simultaneously.

3. The method for producing prestressed composite prefabricated stairs according to claim 1, characterized in that: The prestressed steel bars in the prefabricated bottom plate obtained in step 2 extend 5-90 cm beyond both ends of the prefabricated bottom plate, one end of which is arranged parallel to the prefabricated bottom plate, and the other end is bent and arranged to form a certain angle with the prefabricated bottom plate.

4. The method for producing prestressed composite prefabricated stairs according to claim 3, characterized in that: The steel mesh is a steel mesh woven from longitudinal steel bars and transverse steel bars, and rectangular steel cages are arranged at both ends of the steel mesh.

5. The method for producing prestressed composite prefabricated stairs according to claim 4, characterized in that: When placing the steel mesh on the precast base plate, the prestressed steel bars extending from both ends of the precast base plate are extended into the rectangular steel cages at both ends of the steel mesh.

6. The method for producing prestressed composite prefabricated stairs according to claim 1, characterized in that: In the step 1, the casting thickness of the prefabricated base plate is 3-15 cm.

7. A prestressed composite prefabricated staircase, obtained by the production method according to any one of claims 1 to 6, characterized in that: It includes a cast-in-place stair slab and a precast base slab, wherein the precast base slab is provided with prestressed steel bars, the cast-in-place stair slab is provided with a steel mesh, and both ends of the prestressed steel bars extend into the steel mesh; the precast base slab is made of poured concrete with tensioned prestressed steel bars, and the cast-in-place stair slab is built into an integrated structure with the precast base slab by pouring concrete.

8. The prestressed composite prefabricated staircase according to claim 7, characterized in that: The prefabricated bottom plate is a rectangular concrete plate structure, and the upper surface of the prefabricated bottom plate is in contact with the bottom surface of the cast-in-place stair slab.

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