Design method of composite wall

Abstract

To provide a design method of a composite wall that enables rational design of a composite wall that is integrated by joining an earth retaining stress material and a reinforced concrete wall with a shear connector.SOLUTION: A design method of a composite wall that is integrated by joining an earth retaining stress material and a reinforced concrete wall with a shear connector comprises: a step S2 of creating a separation model in which beam elements representing each of the earth retaining stress materials and the reinforced concrete wall are connected by spring elements of a plurality of shear connectors arranged at intervals in a vertical direction; steps S3 and S4 of applying loads to the separation model and performing calculations; and a step S5 of checking whether stress of each member such as the shear connectors is within an allowable range based on the calculation results.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a design method for a composite wall in which a retaining stress member and a reinforced concrete wall are integrated by connecting them with shear connectors. [Background technology]

[0002] As disclosed in Patent Document 1, a retaining wall is made by joining a retaining stress material such as an H-shaped steel beam, which serves as the core material of the retaining wall, to a reinforced concrete wall (underground exterior wall) with headed studs to form a composite wall.

[0003] The design of such composite walls is generally based on the Architectural Institute of Japan's "Guidelines and Commentary on Design of Composite Structures" (Non-Patent Document 1, hereinafter referred to as the "Composite Guidelines"), which calculates the number of shear connectors (headed studs) required for a fully composite wall in which a reinforced concrete wall and earth retaining stress material are integrated.

[0004] In detail, the number of headed studs required for a composite wall is determined based on the ultimate strength of the reinforced concrete wall, earth retaining stress members, and headed studs, and as a rule they are evenly spaced. In other words, once the dimensions of the reinforced concrete wall and earth retaining stress members are determined, the number of headed studs required is also determined at the same time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3785351 [Non-patent literature]

[0006] [Non-Patent Document 1] "Design Guidelines and Commentary for Composite Structures 2023," Architectural Institute of Japan, August 2023 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the depth of a composite wall increases and the lateral pressure increases, the required dimensions of the reinforced concrete wall and the earth retaining stress material also increase, so a design method that complies with the composite guidelines may require an excessive number of shear connectors.

[0008] Therefore, the object of the present invention is to provide a method for designing composite walls that enables rational design of composite walls that are integrated by joining earth retaining stress members and reinforced concrete walls with shear connectors. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the design method of the composite wall of the present invention is a design method of a composite wall in which a retaining stress member and a reinforced concrete wall are integrated by joining them with shear connectors, and is characterized by comprising the steps of: creating a separated model in which beam elements representing the retaining stress member and the reinforced concrete wall are connected by a plurality of spring elements of the shear connectors arranged at intervals in the vertical direction; applying a load to the separated model to perform a calculation; and checking whether the stress of the shear connector is within an allowable range based on the results of the calculation.

[0010] Here, the retaining stress member may be a sectional steel, the shear connector may be a headed stud or a deformed steel bar stud, and the spring element may include a tension spring and a shear spring.

[0011] Furthermore, it is preferable to include a step of evaluating the strength and stiffness of the shear connector based on the results of an experiment using a specimen manufactured in accordance with the pouring direction of the concrete of the reinforced concrete wall, and to determine the arrangement of the shear connector taking the evaluation into consideration. The evaluation can be used as a correction coefficient to be multiplied in the calculation formula for the strength or stiffness of the shear connector.

[0012] On the other hand, the tip of the shear connector can be configured to be located closer to the earth retaining stress member than the reinforcing bars arranged in the reinforced concrete wall. [Effects of the Invention]

[0013] In the composite wall design method of the present invention, a separate model is first created in which beam elements representing the earth retaining stress members and the reinforced concrete wall are connected by multiple shear connector spring elements spaced apart in the vertical direction. Then, a load is applied to the separate model and the calculation results are used to check whether the shear connector placement is appropriate.

[0014] This makes it possible to rationally design the required number and placement locations of shear connectors for composite walls, which are formed by joining earth retaining stress members and reinforced concrete walls with shear connectors. [Brief explanation of the drawings]

[0015] [Figure 1] 10 is a flowchart illustrating a method for designing a composite wall according to the present embodiment. [Figure 2] 1 is an explanatory diagram showing the configuration of a composite wall designed by the composite wall design method of this embodiment. FIG. [Figure 3] FIG. 2 is a cross-sectional view illustrating the configuration of a composite wall. [Figure 4] FIG. 10 is an explanatory diagram illustrating a separation model of a composite wall. [Figure 5] These are diagrams explaining the differences in concrete pouring directions, where (a) is an explanatory diagram showing the pouring direction assumed by the composite guideline, and (b) is an explanatory diagram showing the pouring direction of an actual composite wall. [Figure 6] FIG. 10 is an explanatory diagram illustrating an example of the arrangement of headed studs determined from the calculation results using a separation model. [Figure 7] FIG. 1 is an explanatory diagram illustrating the placement of headed studs in an open-top composite wall. [Figure 8]FIG. 10 is an explanatory diagram showing an example of the positional relationship between a headed stud and a reinforcing bar. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a flowchart illustrating a composite wall design method according to the present embodiment, and Fig. 2 is an explanatory diagram showing the configuration of a composite wall designed by the composite wall design method according to the present embodiment.

[0017] The composite wall designed by the composite wall design method of this embodiment is a composite wall in which an earth retaining wall 1 and an underground exterior wall 2, which is a reinforced concrete wall, are integrated, as shown in Figure 2. By integrating the underground exterior wall 2 with the earth retaining wall 1, it is possible to reduce the wall thickness of the reinforced concrete wall, and the amount of rebar and concrete can be reduced. In other words, it is possible to reduce costs and shorten the construction period.

[0018] The earth retaining wall 1 is installed to protect the excavation surface and prevent collapse when excavating the ground G. For example, the earth retaining wall 1 includes a soil cement wall made of soil cement, which is created by injecting and stirring a cement-based solidification material into the ground G, and earth retaining stress members 11 placed at intervals in the soil cement, and a parent pile horizontal sheet pile wall constructed by inserting earth retaining stress members 11 at intervals into the ground G.

[0019] As shown in Figure 2, structural steel such as H-beams, I-beams, and channel steels are used for the earth retaining stress members 11 arranged at intervals across the width of the earth retaining wall 1. The earth retaining stress members 11 have flange surfaces 111 that face the underground exterior wall 2, and shear connectors are attached to these flange surfaces 111.

[0020] On the other hand, the basement exterior wall 2 is an RC wall composed of reinforcing bars 22 arranged in the horizontal and vertical directions and a concrete section 21 poured inside the retaining wall 1. Here, Fig. 2 shows a configuration in which a reinforced concrete floor slab 4 is provided only on the lower end side of the basement exterior wall 2, but as shown in Fig. 6, floor slabs 4 may be provided on the floors above and below the basement exterior wall 2, or as shown in Fig. 7, a floor slab 4 may be provided only on the bottom side of the basement exterior wall 2.

[0021] Shear connectors are components that connect the earth retaining stress members 11 and the underground exterior wall 2 in composite walls, and resist shear deformation and tensile forces at the joint surface. Headed studs 3 as shown in Figures 3 and 4, or deformed steel bar studs made from deformed reinforcing bars, etc. can be used as shear connectors.

[0022] The headed stud 3 is attached to the earth retaining stress member 11 by welding or the like, facing in a direction perpendicular to the flange surface 111. The headed stud 3 joined to the flange surface 111 has a shaft 32 and an expanded head 31. Figure 3 shows a state in which the head 31, which is the tip of the headed stud 3, reaches the reinforcing bars 22 of the underground exterior wall 2 (a state in which the head 31 is placed within the reinforcement). As will be described later with reference to Figure 8, it is also possible to have the head 31 of the headed stud 3A not reach the reinforcing bars 22 of the underground exterior wall 2 (a state in which the head 31 is placed in the unreinforced concrete portion 21).

[0023] Next, each step of the design method for the composite wall of this embodiment will be described with reference to FIG. First, in step S1, the cross sections of the earth retaining stress members 11 set during the temporary design are imported, and the cross sections of the members to be considered when designing the headed studs 3 and the underground exterior wall 2 are set. Here, in the earth retaining wall 1, the soil cement portion other than the earth retaining stress members 11 is not considered as a structural member.

[0024] For the earth retaining stress material 11, the cross-sectional shape of the H-shaped steel or the like, spacing, material constants such as Young's modulus, etc. are set. For the headed studs 3, the cross-sectional area of the shaft 32, length, material constants such as Young's modulus, etc. are set. Furthermore, for the headed studs 3, the number of studs to be placed, placement position (spacing), etc. are set. And for the underground exterior wall 2, the cross-sectional shape as a reinforced concrete wall, wall reinforcement, material constants such as Young's modulus, etc. are set.

[0025] In the next step S2, a separation model is created. Figure 4 is a diagram explaining how to replace the structure of a composite wall with a separation model. First, the earth retaining stress member 11 is modeled as a beam element M1, and the underground exterior wall 2 is also modeled as a beam element M2.

[0026] The cross-sectional performance is set for the beam element M1 that models the earth retaining stress member 11 based on the data set in step S1, such as the member cross section of the earth retaining stress member 11. The cross-sectional performance is also set for the beam element M2 that models the underground exterior wall 2 based on the data set in step S1, such as the member cross section of the underground exterior wall 2.

[0027] On the other hand, the headed studs 3 are modeled as multiple spring elements M3 arranged at intervals in the vertical direction set in step S1. Each spring element M3 is made up of a tension spring M31 and a shear spring M32.

[0028] In the design method for the composite wall of this embodiment, the bearing capacity and rigidity of the headed stud 3 were evaluated by element experiments in order to set the tension spring M31 and shear spring M32 in the separation model.

[0029] The Composite Guidelines (Non-Patent Document 1) provides a formula for calculating the shear strength and tensile strength of a headed stud. This formula is applied to composite beams, so it assumes a situation in which concrete a2 is poured axially (see arrow) to the head of a headed stud a3 connected vertically to an H-shaped steel a1, as shown in Figure 5(a).

[0030] In contrast, in the case of composite walls, when considering the actual construction procedures, the concrete pouring direction is perpendicular to the axis of the headed studs 3 (see arrow), as shown in Figure 5(b). Previous research has reported that if the concrete is poured in the direction shown in Figure 5(b), the shear strength and tensile strength will decrease, but there are few such experimental examples and the current situation is that there is a lack of data.

[0031] Therefore, we decided to conduct element experiments on the headed stud 3 used as a shear connector, and to evaluate the rigidity and strength of the headed stud 3, which are necessary for constructing a separation model and designing the shear connector.

[0032] The element tests were conducted using tension and shear tests. The shear strength formula for headed studs 3 obtained from the test results is shown below. <Shear strength formula> sc q s =β S 0.5 sc a√(F c E c ) where: sc q s is the corrected shear strength, β S is the reduction rate, which is a correction coefficient based on the experimental results, sc a is the cross-sectional area of the shank 32 of the headed stud 3, F c is the design strength of concrete, E c is the Young's modulus of concrete.

[0033] In the above formula, the reduction rate β S The calculation formula without indicates the ultimate shear strength of the composite guideline. In other words, the reduction rate β S By setting the value, the shear strength of the headed stud 3 of the composite wall was evaluated. In the results of this experiment, the reduction rate β S was 0.9.

[0034] On the other hand, the allowable tensile force formula for headed stud 3 obtained from the experimental results is shown below. <Allowable tensile force formula> sc p a =β T min( sc p a1 , sc p a2 ) sc p a1 =φ1 sc σ pa · sc a sc p a2 =φ2 c σ t A c where: sc p a is the corrected allowable tensile force, β T is the reduction rate, which is a correction coefficient based on the experimental results, sc p a1 is the allowable tensile force of the shank 32 of the headed stud 3, sc p a2 are the allowable tensile force due to cone-shaped fracture of the concrete anchored with headed stud 3, φ1 and φ2 reduction coefficients, sc σ pa is the tensile strength of the shaft portion 32, sc a is the cross-sectional area of the shaft portion 32, c σ t is the tensile strength of concrete against cone-shaped fracture, A c is the effective horizontal projection area of the concrete cone-shaped fracture surface.

[0035] In the above formula, the reduction rate β T The calculation formula without indicates the allowable tensile force of the composite guideline. In other words, the reduction rate β T By setting this, the corrected allowable tensile force of the headed stud 3 of the composite wall was evaluated. In the results of this experiment, the reduction rate β T was 0.7.

[0036] In both the shear strength formula and the allowable tensile strength formula, the reduction rate β due to the concrete pouring direction is calculated using the calculation formula based on the composite guidelines.S ,β T By setting this, it was possible to evaluate the strength of headed studs3 of composite walls.

[0037] Next, we will explain the stiffness evaluation formula for the headed stud 3 required to construct the separation model. First, in the tensile stiffness evaluation formula, the tensile stiffness was evaluated by setting the bearing deformation of the concrete directly above the head 31 of the headed stud 3 and the deformation of the shank 32 of the headed stud 3 as a series spring relationship.

[0038] <Tensile stiffness evaluation formula> 1 / k T = 1 / (1.5Fc(A0 / A φ16 )) + 1 / (E s · sc a / sc L) where k T is the tensile stiffness, Fc is the design strength of concrete, A0 is the bearing area of the head 31, A φ16 is the bearing area of the 16 mm diameter shaft 32, E s is the Young's modulus of headed stud 3, sc L is the length of the headed stud 3. The 1.5 in this formula is the correction coefficient α obtained from the test results. T is.

[0039] On the other hand, for shear stiffness, an evaluation formula was established that takes into account the influence of the concrete pouring direction, based on the Shima et al. formula shown in the "Standard Specifications for Composite Structures" of the Japan Society of Civil Engineers. <Shear stiffness evaluation formula> Q = 0.8Q S (1-e -αδ / φ ) 0.4 where Q is the shear force, Q S is the ultimate shear strength of the headed stud 3, α is a correction factor based on the concrete strength, δ is the shear displacement, and φ is the shaft diameter of the shaft portion 32. The 0.8 in this equation is the correction factor obtained from the test results.

[0040] In this way, the tensile stiffness k obtained from the element experiment taking into account the concrete pouring direction wasT The spring element M3 of the separation model is set using the shear stiffness evaluation formula. That is, the tension spring M31 has a tension stiffness k T and the shear spring M32 is set based on the shear stiffness evaluation formula.

[0041] Then, a separation model is created in which two parallel beam elements M1 and M2 are connected by multiple spring elements M3, as shown in Figure 4. Here, multiple spring elements M3 are placed at intervals in the vertical direction according to the placement positions and number of headed studs 3 set in step S1.

[0042] In step S3, the applied loads such as earth pressure and water pressure acting from the rear side of the retaining wall 1 are set for the created separation model of the composite wall. Then, in step S4, a stress analysis of the composite wall is performed using the separation model.

[0043] In the next step S5, the calculation results of the stress analysis are checked to see if the stress of each member of the earth retaining stress member 11, the underground exterior wall 2, and the headed stud 3 is within the allowable range. sc q s and corrected allowable tensile force sc p a By using this, a cross-sectional study will be carried out taking into account the concrete pouring direction. If even one component is outside the allowable range, the process will return to step S1, correct the various settings for the component that needs to be changed, and then redo the calculation.

[0044] On the other hand, if the stress of each component falls within the allowable range, the design is completed by arranging the headed studs 3 (shear connectors) set in step S1. If the shear force and tensile force acting on the spring element M3 can be visualized at each position in the height direction in this way, it becomes possible to economically arrange the shear connectors.

[0045] Figure 6 is an explanatory diagram illustrating the placement of headed studs 3 determined from the results of calculations using a separation model when floor slabs 4 are installed above and below an underground exterior wall 2. As shown in the left diagram of Figure 6, with conventional design methods, the headed studs 3 would be placed evenly along the height of the underground exterior wall 2.

[0046] In contrast, the design method using the separation model shown on the right side of Figure 6 allows for the headed studs 3 to be densely arranged at the bottom and top of the basement exterior wall 2 adjacent to the floor slab 4, with the spacing between the headed studs 3 wider around the center of the height of the basement exterior wall 2. This is an example of a free and rational design that satisfies the structural regulations, such as concentrating the headed studs 3 near the floor slab 4, based on the calculation results of the stress analysis using the separation model, which showed that the shear force acting on the headed studs 3 in the center of the floor height is smaller than near the floor slab 4.

[0047] On the other hand, Figure 7 is an explanatory diagram illustrating the arrangement of headed studs 3 in a composite wall with an open top. For example, this can be a composite wall for a dry area or a seismic isolation pit retaining wall. Even in this case, as shown in the left diagram of Figure 7, with conventional design methods, the headed studs 3 would be arranged evenly along the height of the underground exterior wall 2.

[0048] In contrast, with the design method using the separation model shown in the right diagram of Figure 7, headed studs 3 are densely arranged between the floor slab 4 and the lower part of the basement exterior wall 2 adjacent to the floor slab 4, with the spacing between the headed studs 3 being wider from the center to the top in the height direction of the basement exterior wall 2. In short, a rational design is achieved in which headed studs 3 are concentrated in places where joints with studs 3 are required, and spaced apart in other places.

[0049] Next, the operation of the composite wall design method of this embodiment will be described. In the composite wall design method of this embodiment configured as described above, a separation model is first created in which beam elements M1, M2 representing the earth retaining stress member 11 and the underground exterior wall 2, respectively, are connected by spring elements M3 of headed studs 3 arranged at intervals in the vertical direction. Then, an external load is applied to the separation model, and the feasibility of the placement of the headed studs 3 is checked based on the calculation results.

[0050] This makes it possible to rationally design the required number and placement positions of headed studs 3 for composite walls that are integrated by joining the retaining stress material 11 and the underground exterior wall 2 with headed studs 3.

[0051] Such rational arrangement of the headed studs 3 makes it possible to reduce the number of studs and eliminate the need for welding the headed studs 3 to the earth retaining stress material 11 at high altitudes, which is expected to reduce costs and improve safety and productivity on site.

[0052] Furthermore, the design method of the composite guideline does not take into account the tensile force acting on the shear connector, but if a separate model is created and stress analysis is performed, the tensile force of the headed stud 3 can also be taken into account, which will lead to improved quality.

[0053] Furthermore, since the above-mentioned composite guidelines were based on an evaluation of headed studs 3 for reinforced concrete members, it is assumed that the heads 31 of the headed studs 3 reach the reinforcing bars 22, as in the arrangement shown in Figure 3.

[0054] On the other hand, the element experiments taking into account the concrete pouring direction described above were conducted using unreinforced concrete specimens. In other words, the evaluation formulas for the strength and stiffness of the headed stud 3 described above are evaluations for unreinforced concrete.

[0055] Therefore, as shown in the example of the positional relationship between the headed stud 3A and the reinforcing bar 22 in Figure 8, the position of the head 31 of the headed stud 3A does not have to reach the reinforcing bar 22. In short, even if the headed stud 3A is embedded only in the unreinforced concrete portion 21, the shear strength formula and allowable tensile force formula, as well as the tensile stiffness evaluation formula and shear stiffness evaluation formula for the headed stud 3A described above can be applied.

[0056] In this way, if a composite wall is designed using a design method that does not assume that the headed studs 3, 3A will reach the reinforcing bars 22, there is no need to place additional reinforcing bars when the shear connectors do not reach the wall reinforcing bars, as was done in the past. It is also no longer necessary to lengthen the headed studs 3, 3A just to make them reach the wall reinforcing bars. In short, it is possible to reduce the amount of reinforcing bars and the labor required for reinforcing bars.

[0057] The embodiments of the present invention have been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0058] For example, in the above embodiment, headed studs 3, 3A were mainly used as shear connectors, but this is not limited to this. The composite wall design method of this embodiment can also be applied when deformed steel bar studs, such as deformed reinforcing bars, are used as shear connectors. [Explanation of symbols]

[0059] 1: Retaining wall 11: Earth retaining stress material 2: Basement exterior wall (reinforced concrete wall) 22: Reinforced concrete 3, 3A: Headed stud (shear connector) 31: Head (tip) M1,M2: Beam element M3: Spring element M31: Tension spring M32: Shear spring

Claims

1. A design method for a composite wall in which a retaining stress member and a reinforced concrete wall are joined together by a shear connector, creating a separation model in which beam elements representing the earth retaining stress members and the reinforced concrete wall are connected by a plurality of spring elements of the shear connectors arranged at intervals in the vertical direction; performing a calculation by applying a load to the separation model; and a step of checking whether the stress of the shear connector is within an allowable range based on the result of the calculation.

2. 2. The method for designing a composite wall according to claim 1, wherein the retaining stress members are shaped steel and the shear connectors are headed studs or deformed steel bar studs.

3. 3. The method for designing a composite wall according to claim 1, wherein the spring elements include tension springs and shear springs.

4. A step of evaluating the strength and rigidity of the shear connector based on experimental results using a specimen manufactured in accordance with the pouring direction of the concrete of the reinforced concrete wall, 3. The method for designing a composite wall according to claim 1, wherein the placement of the shear connectors is determined taking into consideration the evaluation.

5. 5. The method for designing a composite wall according to claim 4, wherein the evaluation is a correction coefficient to be multiplied in a calculation formula for the strength or rigidity of the shear connector.

6. 3. A method for designing a composite wall according to claim 1, wherein the tip of the shear connector is located closer to the retaining stress member than the reinforcing bars arranged in the reinforced concrete wall.

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