Concrete crack prevention structure and construction method

Abstract

To provide a concrete crack prevention structure capable of simply preventing the occurrence of cracks without increasing the thickness of holding concrete, and a construction method thereof.SOLUTION: Provided is a structure 10 for preventing cracks around a joint 20 in a pressing concrete 18 provided on a concrete slab 12 via a heat insulating material 16, in which a crack prevention member 22 is provided continuously across the joint 20 between the heat insulating material 16 directly below the joint 20 and the pressing concrete 18.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a concrete crack prevention structure suitable for use in concrete supporting a roadway insulation material, and a construction method thereof. [Background technology]

[0002] Traditionally, logistics facilities and other buildings are planned to allow large vehicles to drive on the roof. As shown in Figure 4(1), a holding concrete 4 is typically installed on top of the roof slab 1 to protect the waterproofing material 2 and insulation material 3. Because the rigidity of the insulation material 3 is generally low, when the wheels 5 of a heavy vehicle drive over the holding concrete 4, the holding concrete 4 deforms, causing it to sink. In particular, when the vehicle drives over the corners of joints 6, cracks 7 can occur in the holding concrete 4 at a 45° angle in plan view, as shown in Figure 4(2).

[0003] On the other hand, as a conventional technique for preventing sinking and unevenness of concrete floors, for example, a technique in which anti-warping reinforcing bars 9 are provided in joints 6 of a concrete floor 8 as shown in FIG. 5 is known.

[0004] Also, in the field of bridges, a step prevention mechanism is known, as shown in Patent Document 1. This is a mechanism that prevents sinking and steps in concrete floors caused by running vehicles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6832465 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the above-mentioned conventional anti-warping rebars are installed in the joints of rooftop concrete, there are problems such as the risk that they may not be able to keep up with the expansion and contraction of the holding concrete due to temperature changes, and the installation is time-consuming.In addition, the above-mentioned conventional step prevention mechanism is difficult to apply to holding concrete on insulation material.

[0007] Additionally, while thickening the holding concrete can prevent cracks from occurring, this is undesirable as it increases the weight and cost of the building. For this reason, there has been a demand for a technology that can easily prevent cracks from occurring without thickening the holding concrete.

[0008] The present invention has been made in consideration of the above, and aims to provide a concrete crack prevention structure and a construction method thereof that can easily prevent the occurrence of cracks without increasing the thickness of the holding concrete. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the objectives, the concrete crack prevention structure of the present invention is a structure for preventing cracks around joints in holding concrete placed on a concrete slab via insulation, and is characterized by having a crack prevention member that is continuously placed across the joint between the insulation directly below the joint and the holding concrete.

[0010] Another concrete crack prevention structure according to the present invention is characterized in that, in the above-described invention, the crack prevention member is an iron plate that is continuously arranged across the holding concrete divided by the joints, centered on the intersection of the joints in a plan view.

[0011] Another concrete crack prevention structure according to the present invention is characterized in that, in the above-mentioned invention, the dimensions of the steel plate are set based on the contact area of ​​the tires of the vehicle that will be running on the holding concrete.

[0012] In addition, the method of constructing a concrete crack prevention structure according to the present invention is a method of constructing the above-mentioned concrete crack prevention structure, characterized in that after laying insulation material on a concrete slab, a crack prevention member is installed at a predetermined position on top of the insulation material and fixed to the insulation material, and then a holding concrete is installed. [Effects of the Invention]

[0013] The concrete crack prevention structure of the present invention is a structure for preventing cracks around joints in holding concrete placed on a concrete slab via insulation, and is equipped with crack prevention members that are continuously installed across the joint between the insulation directly below the joint and the holding concrete, thereby achieving the effect of easily preventing cracks from occurring without making the holding concrete thicker.

[0014] In addition, according to another concrete crack prevention structure of the present invention, the crack prevention member is a steel plate that is continuously placed across the holding concrete divided by the joints, centered on the intersection of the joints in a plan view, thereby achieving the effect of easily preventing the occurrence of cracks around the intersection of the joints.

[0015] In addition, according to another concrete crack prevention structure of the present invention, the dimensions of the steel plate are set based on the contact area of ​​the tires of the vehicle that will be running on the holding concrete, thereby achieving the effect of effectively preventing cracks from occurring around the intersections of the joints.

[0016] In addition, according to the method for constructing a concrete crack prevention structure of the present invention, which is a method for constructing the above-mentioned concrete crack prevention structure, after laying insulation material on a concrete slab, a crack prevention member is installed at a predetermined position on top of the insulation material and fixed to the insulation material, and then the holding concrete is constructed, thereby achieving the effect of making it possible to easily construct a concrete crack prevention structure without making the holding concrete thicker. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 shows an embodiment of a concrete crack prevention structure and a construction method thereof according to the present invention, where (1) is a plan view and (2) is a side cross-sectional view. [Figure 2] FIG. 2 shows an analytical model for verifying the effects of the present invention, where (1) is an explanatory diagram of the modeling range, (2) is a perspective view of the FEM model, and (3) is a cross-sectional view of the FEM model. [Figure 3] FIG. 3 is a diagram showing the analysis results. [Figure 4] FIG. 4(1) is a side cross-sectional view of a conventional rooftop thermal insulation structure, and (2) is a plan view showing the state of cracks at the corners of the conventional retaining concrete. [Figure 5] FIG. 5 shows a conventional reinforcing bar for preventing warping of concrete floors. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete crack prevention structure and a construction method thereof according to the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0019] As shown in Figure 1, a concrete crack prevention structure 10 according to an embodiment of the present invention is a structure for preventing cracks around joints 20 in a holding concrete 18 that is installed on a roof slab 12 (concrete slab) via a sheet-like waterproofing material 14 and a layer of insulating material 16. This concrete crack prevention structure 10 includes a reinforcing steel plate 22 (crack prevention member) that is installed continuously across the joint 20 between the insulating material 16 and the holding concrete 18 directly below the joint 20.

[0020] The iron plate 22 is a square flat plate made of iron, and is placed continuously across the holding concrete 18 divided by the joints 20, with the intersection 24 (corner) of the joints 20, which intersect like a cross in a plan view, as the center of the plate. Each side of the iron plate 22 is parallel to or perpendicular to the extension direction of the joints 20. The dimensions of the iron plate 22 are desirably set based on the contact area of ​​the tires of a vehicle that will be running on the holding concrete 18; for example, it is preferable to set the dimensions to about twice the contact area of ​​the vehicle's tires.

[0021] In this embodiment, the dimensions of the steel plate 22 are assumed to be approximately 6 mm thick and 400 mm x 400 mm long, but the steel plate of the present invention is not limited to these dimensions. The dimensions and thickness of the steel plate may be changed depending on the load conditions and the physical properties of the holding concrete 18 and the insulation material 16. Furthermore, the arrangement of the steel plate of the present invention is not limited to one in which each side of the steel plate is parallel or perpendicular to the extension direction of the joints, but may also be one in which each side of the steel plate is oblique to the extension direction of the joints. Furthermore, the steel plate of the present invention is not limited to a square plate, but may be a plate of other shapes, such as a circle.

[0022] According to the above configuration, the steel plate 22 is installed between the insulation material 16 and the holding concrete 18 around the intersection 24 of the joint 20, reinforcing the strength of this area. When a wheel load acts around the intersection 24, the effect of the steel plate 22 is to distribute the load on the insulation material 16, reducing deformation of the insulation material 16. As a result, deformation of the holding concrete 18 is also reduced, preventing cracks from occurring. Therefore, according to this embodiment, cracks can be easily prevented from occurring around the intersection 24 of the joint 20 without increasing the thickness of the holding concrete 18.

[0023] When constructing the concrete crack prevention structure 10, for example, waterproofing material 14 and insulating material 16 are laid on top of the roof slab 12, and then the iron plate 22 is placed in a predetermined position on top of the insulating material 16 and secured to the insulating material 16 with tape or the like. In this way, the installation of the iron plate 22 is very easy. After that, the holding concrete 18 is placed on top of these.

[0024] According to the above construction method, the concrete crack prevention structure 10 can be easily constructed without increasing the thickness of the holding concrete 18. In addition, the expansion and contraction of the holding concrete 18 due to temperature changes is not affected.

[0025] In the above embodiment, the crack prevention member is an iron plate, but the present invention is not limited to this. Instead of an iron plate, a plate material such as a stainless steel plate may be used to prevent rust. The dimensions and thickness of the plate material may be changed depending on the load conditions and the physical properties of the concrete and insulation. In this case, the same effects as those described above can be achieved.

[0026] (Verification of the effects of the present invention) Next, an FEM analysis performed to verify the effects of the present invention and the results thereof will be described.

[0027] The joint pitch of the holding concrete was set to 3m, and the modeling range for the FEM analysis was set as shown in Figure 2(1). Figure 2(2) shows a perspective view of the FEM model, and Figure 2(3) shows a cross-sectional view of the FEM model. The holding concrete and insulation material were each modeled using hexahedral solid elements, and the steel plate was modeled using shell elements. The length of one side of each element was set to 25mm or less. The base thickness of the holding concrete was 100mm, and a model with a thickness of 150mm was also created for comparison.

[0028] The constraint conditions were set so that the model end was symmetrical about the X-axis or Y-axis, and the bottom of the insulation was fixed in translation on the Z-axis and in rotation on the X-, Y-, and Z-axes.

[0029] Taking into account the wheel load of a heavy vehicle, the loading conditions were set at two nodes in a 200mm x 200mm area near the center as shown in Figure 2(2), with a total load of 68kN in the downward direction along the Z axis. The material properties are shown in Table 1. In this verification, FEM analysis was performed assuming all properties were linear.

[0030] [Table 1]

[0031] The following three types of analysis cases were used: Analysis Case 1: 100 mm thick holding concrete with steel plate reinforcement; Analysis Case 2: 100 mm thick holding concrete without steel plate reinforcement; Analysis Case 3: 150 mm thick holding concrete without steel plate reinforcement. Therefore, Analysis Case 1 corresponds to the example, and Analysis Cases 2 and 3 correspond to the comparative examples.

[0032] The analysis results are shown in Figure 3. Figure 3 (1) is a diagram of Z-direction deformation for analysis case 1, and (2) is its solid element stress diagram. Figure 3 (3) is a diagram of Z-direction deformation for analysis case 2, and (4) is its solid element stress diagram. Figure 3 (5) is a diagram of Z-direction deformation for analysis case 3, and (6) is its solid element stress diagram. The analysis results are summarized in Table 2.

[0033] [Table 2]

[0034] In analysis case 2, where the thickness of the concrete is 100 mm and there is no steel plate reinforcement, the allowable tensile stress of the concrete is σ = 0.56 × (Fc). 0.5 =2.76N / mm 2If the stress exceeds this limit, cracks may occur. On the other hand, in analysis case 1, where steel plate reinforcement was used, the effect of the reinforcing steel plates was able to reduce both deformation and tensile stress, and they remained within the allowable tensile stress of the concrete. Furthermore, the difference in deformation and tensile stress between analysis case 1 and analysis case 3, where the holding concrete thickness was 150 mm, was small, within 5%, and it was confirmed that steel plate reinforcement had the same effect as increasing the holding concrete thickness by 50 mm.

[0035] In the above analysis, an example was explained in which an iron plate was used, but it is believed that similar results would be obtained if a plate material such as a stainless steel plate were used instead of an iron plate.

[0036] As described above, the concrete crack prevention structure of the present invention is a structure for preventing cracks around joints in holding concrete placed on a concrete slab via insulation, and is equipped with crack prevention members that are continuously installed across the joint between the insulation directly below the joint and the holding concrete, making it possible to easily prevent cracks from occurring without making the holding concrete thicker.

[0037] In addition, according to another concrete crack prevention structure of the present invention, the crack prevention member is a steel plate that is continuously placed across the holding concrete divided by the joints, centered on the intersection of the joints in a plan view, so that cracks can be easily prevented from occurring around the intersection of the joints.

[0038] In addition, according to another concrete crack prevention structure of the present invention, the dimensions of the steel plate are set based on the contact area of ​​the tires of the vehicle that will be running on the holding concrete, thereby effectively preventing cracks from occurring around the intersections of the joints.

[0039] In addition, according to the method for constructing a concrete crack prevention structure of the present invention, which is a method for constructing the above-mentioned concrete crack prevention structure, after laying insulation material on a concrete slab, a crack prevention member is installed at a predetermined position on top of the insulation material and fixed to the insulation material, and then the holding concrete is constructed, so that the concrete crack prevention structure can be easily constructed without making the holding concrete thicker. [Industrial Applicability]

[0040] As described above, the concrete crack prevention structure and construction method of the present invention are useful for roof slabs on which large vehicles run, and are particularly suitable for easily preventing the occurrence of cracks without increasing the thickness of the holding concrete. [Explanation of symbols]

[0041] 10. Concrete crack prevention structure 12 Roof slab (concrete slab) 14 Waterproof material 16. Insulation 18 Reinforced concrete 20 Joint 22 Steel plate (crack prevention material) 24 Intersection

Claims

1. A structure for preventing cracks around joints in a holding concrete installed on a concrete slab via a thermal insulation material, a crack prevention member provided continuously across the joint between the heat insulating material and the holding concrete directly below the joint; A concrete crack prevention structure characterized in that the crack prevention member is a steel plate that is continuously placed across the holding concrete divided by the joints, centered on the intersection of the joints in a plan view.

2. A concrete crack prevention structure as described in Claim 1, characterized in that the dimensions of the steel plate are set based on the contact area of ​​the tires of a vehicle that is scheduled to run on the holding concrete.

3. A method for constructing the concrete crack prevention structure according to claim 1 or 2, A method for constructing a concrete crack prevention structure, characterized by laying the insulation material on top of the concrete slab, installing the crack prevention member at a predetermined position on top of the insulation material and fixing it to the insulation material, and then constructing the holding concrete.

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