Method for Designing Synthetic Wall

Abstract

Provided is a design method for a composite wall that can be rationally designed, which is a composite wall integrated by joining a retaining stress member and a reinforced concrete wall with a shear connector. 【Solution means】It is a design method for a composite wall integrated by joining a retaining stress member and a reinforced concrete wall with a shear connector. Then, there are provided a step S2 of creating a separation model in which beam elements representing the retaining stress member and the reinforced concrete wall are connected by spring elements of a plurality of shear connectors arranged at intervals in the vertical direction, steps S3 and S4 of applying a load to the separation model and performing calculations, and a step S5 of checking whether the stress of each member such as the shear connector is within the allowable range based on the calculation results.

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 joined by a shear connector to be integrated.

Background Art

[0002] As disclosed in Patent Document 1, a retaining stress member such as an H-shaped steel serving as a core material of a retaining wall and a reinforced concrete wall (underground outer wall) are joined by headed studs and used as a composite wall.

[0003] The design of such a composite wall is generally carried out based on the "Design Guidelines and Explanation for Various Composite Structures" of the Architectural Institute of Japan (Non-Patent Document 1, hereinafter referred to as the "Composite Guidelines"). In these composite guidelines, the required number of shear connectors (headed studs) required for a complete composite wall in which a reinforced concrete wall and a retaining stress member are integrated is calculated.

[0004] Specifically, the required number of headed studs used in the composite wall is determined from the ultimate strength of the reinforced concrete wall, the retaining stress member, and the headed studs, and is generally arranged evenly as a principle. In short, when the member dimensions of the reinforced concrete wall and the retaining stress member are determined, the required number of headed studs is also determined at the same time.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when the depth of the composite wall increases and the lateral pressure increases, the required member dimensions of the reinforced concrete wall and the retaining stress members also increase. Therefore, in the design method based on the composite guidelines, the required number of shear connectors may become excessive.

[0008] Therefore, an object of the present invention is to provide a design method for a composite wall that enables rational design of a composite wall in which a retaining stress member and a reinforced concrete wall are integrated by being joined by a shear connector.

Means for Solving the Problems

[0009] In order to achieve the above object, a design method for a composite wall according to the present invention is a design method for a composite wall in which a retaining stress member and a reinforced concrete wall are integrated by being joined by a shear connector, and beam elements representing each of the retaining stress member and the reinforced concrete wall are connected by spring elements of the plurality of shear connectors arranged at intervals in the vertical direction. Creating a separation model, applying a load to the separation model and performing calculations, and checking whether the stress of the shear connector is within an allowable range based on the result of the calculation. It is characterized by having.

[0010] Here, the retaining stress member is a shaped steel, and the shear connector can be configured as a headed stud or a deformed bar stud. Further, the spring element can be configured to include a tension spring and a shear spring.

[0011] Furthermore, it includes a step of evaluating the endurance and rigidity of the shear connector based on the experimental results using a specimen manufactured in accordance with the casting direction of the concrete of the reinforced concrete wall, and it is preferable to determine the arrangement of the shear connector in consideration of the evaluation. This evaluation can be a correction coefficient multiplied by the arithmetic formula for the endurance or rigidity of the shear connector.

[0012] On the other hand, the tip of the shear connector can be configured to be located on the side of the landslide stress member rather than the reinforcing bars arranged in the reinforced concrete wall.

Advantages of the Invention

[0013] In the design method of the composite wall of the present invention configured as described above, first, a separation model is created in which beam elements representing the landslide stress member and the reinforced concrete wall are connected by spring elements of a plurality of shear connectors arranged at intervals in the vertical direction. Then, based on the calculation results obtained by applying a load to the separation model and performing calculations, the feasibility of the arrangement of the shear connectors is checked.

[0014] Therefore, regarding the composite wall integrated by joining the landslide stress member and the reinforced concrete wall with a shear connector, it becomes possible to rationally design the required number and arrangement position of the shear connectors.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining the design method of the composite wall of the present embodiment. Further, FIG. 2 is an explanatory diagram showing the configuration of the composite wall designed by the design method of the composite wall of the present embodiment.

[0017] As shown in FIG. 2, the composite wall designed by the design method of the composite wall of the present embodiment is a composite wall in which the retaining wall 1 and the underground outer wall 2 which is a reinforced concrete wall are integrated. By integrating the underground outer wall 2 with the retaining wall 1, it becomes possible to reduce the wall thickness of the reinforced concrete wall, and the amount of reinforcing bars and the amount of concrete can be reduced. That is, it becomes possible to reduce costs and shorten the construction period.

[0018] The retaining wall 1 is provided to protect the excavation surface and prevent collapse when excavating the ground G. For example, a soil cement wall composed of soil cement formed by stirring while injecting a cement-based solidifying material or the like into the ground G and the retaining stress members 11 arranged at intervals in the soil cement, and a parent pile cross-sheet pile wall constructed by inserting the retaining stress members 11 into the ground G at intervals, etc. correspond to the retaining wall 1.

[0019] As shown in FIG. 2, for the retaining stress members 11 arranged at intervals in the width direction of the retaining wall 1, shaped steels such as H-shaped steel, I-shaped steel, and channel steel are used. The retaining stress member 11 is provided with a flange surface 111 facing the underground outer wall 2, and a shear connector is attached to this flange surface 111.

[0020] On one hand, the underground outer wall 2 is an RC wall composed of reinforcing bars 22 arranged in the horizontal and vertical directions and a concrete part 21 cast on the indoor side of the retaining wall 1. Here, Figure 2 shows a configuration in which a reinforced concrete floor slab 4 is provided only on the lower end side of the underground outer wall 2. However, as shown in Figure 6, the floor slab 4 may be provided on the upper and lower floors of the underground outer wall 2, or as shown in Figure 7, the floor slab 4 may be provided only on the bottom side of the underground outer wall 2.

[0021] The shear connector is a member that connects the retaining stress member 11 and the underground outer wall 2 in the composite wall and resists the displacement deformation and tensile force of the joint surface. As the shear connector, a stud 3 with a head as shown in Figures 3 and 4, a deformed bar stud made of deformed reinforcing bars, etc. can be used.

[0022] The stud 3 with a head is attached to the retaining stress member 11 by welding or the like in a direction orthogonal to the flange surface 111. The stud 3 with a head joined to the flange surface 111 includes a shaft portion 32 and a widened head portion 31. Figure 3 shows a state where the head portion 31, which is the tip of the stud 3 with a head, reaches the reinforcing bar 22 of the underground outer wall 2 (a state where the head portion 31 is arranged within the reinforcement). Note that, as will be described later with reference to Figure 8, the head portion 31 of the stud 3A with a head can be in a state where it does not reach the reinforcing bar 22 of the underground outer wall 2 (a state where the head portion 31 is arranged in the non-reinforced concrete part 21).

[0023] Next, each step of the design method of the composite wall of the present embodiment will be described with reference to Figure 1. First, in step S1, the member cross-section etc. of the retaining stress member 11 set at the time of preliminary design are incorporated, and the member cross-sections etc. of each member to be considered when designing the stud 3 with a head, the underground outer wall 2, etc. are set. Here, in the retaining wall 1, soil cement parts other than the retaining stress member 11 are not considered as structural members.

[0024] For the retaining stress member 11, set the cross-sectional shape such as H-shaped steel, the arrangement interval, and material constants such as Young's modulus. For the stud 3 with a head, set the cross-sectional area, length, and material constants such as Young's modulus of the shaft portion 32. Furthermore, for the stud 3 with a head, set the number of arrangements and the arrangement position (arrangement interval). For the underground outer wall 2, set the cross-sectional shape as a reinforced concrete wall, the reinforcement of the wall, and material constants such as Young's modulus.

[0025] In the subsequent step S2, a separation model is created. FIG. 4 is a diagram for explaining a method of replacing the configuration of the composite wall with a separation model. First, the retaining stress member 11 is modeled as a beam element M1, and the underground outer wall 2 is also modeled as a beam element M2.

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

[0027] On the other hand, the stud 3 with a head is modeled as a plurality of spring elements M3 arranged at intervals in the vertical direction set in step S1. Each spring element M3 is composed of a tension spring M31 and a shear spring M32.

[0028] In the design method of the composite wall of the present embodiment, in order to set the tension spring M31 and the shear spring M32 in the separation model, the load-bearing capacity and rigidity of the stud 3 with a head are evaluated by element experiments.

[0029] Here, in the composite guideline (Non-Patent Document 1), calculation formulas for obtaining the shear load-bearing capacity and the tensile load-bearing capacity of the stud with a head are described. Since this calculation formula is applicable to a composite beam, as shown in FIG. 5(a), it assumes a situation where concrete a2 is placed in the axial direction (refer to the arrow) with respect to the head of the stud a3 vertically joined to the H-shaped steel a1.

[0030] In contrast, considering the actual construction procedure, as shown in Fig. 5(b), the concrete pouring direction is perpendicular to the axis of the headed stud 3 (see the arrow). Previous studies have reported that when the concrete pouring direction is as shown in Fig. 5(b), the shear strength and tensile strength decrease. However, such experimental examples are few, and the current situation is that the data is scarce.

[0031] Therefore, an element experiment of the headed stud 3 used as a shear connector was conducted to evaluate the rigidity and strength of the headed stud 3 required for the construction of the separation model and the design of the shear connector.

[0032] Tensile experiments and shear tests were conducted for the element experiment. The shear strength formula of the headed stud 3 obtained from the experimental results is shown below. <Shear strength formula> sc q s =β S 0.5 sc a√(F c E c ) Here, 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 shaft portion 32 of the headed stud 3, F c is the design standard strength of the concrete, E c is the Young's modulus of the concrete.

[0033] In the above formula, the formula without the reduction rate β S indicates the ultimate shear strength of the composite index. In short, by setting the reduction rate β S due to the concrete pouring direction for the formula of the ultimate shear strength of the composite index, it was evaluated as the shear strength of the headed stud 3 of the composite wall. In the experimental results of this time, the reduction rate β S due to the concrete pouring direction was 0.9.

[0034] On the other hand, the allowable tensile force formula of the headed stud 3 obtained from the experimental results is shown below. <Allowable Tensile Force Type> 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 Here, sc p a is the corrected allowable tensile force, β T is the reduction rate, which is a correction coefficient based on experimental results, sc p a1 is the allowable tensile force of the shaft portion 32 of the headed stud 3, sc p a2 is the allowable tensile force due to the conical failure of the concrete in which the headed stud 3 is fixed, φ1, φ2 are 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 the concrete against conical failure, A c is the effective horizontal projected area of the conical failure surface of the concrete.

[0035] In the above formula, the reduction rate β T without it represents the allowable tensile force of the composite index. In short, by setting the reduction rate β T due to the concrete placement direction for the formula of the allowable tensile force of the composite index, it is evaluated as the corrected allowable tensile force of the headed stud 3 of the composite wall. In the experimental results of this time, the reduction rate β T due to the concrete placement direction was 0.7.

[0036] In both the shear resistance formula and the allowable tensile force formula, for the formula based on the composite index, the reduction rate β due to the concrete placement directionS , β T By setting this, it was possible to evaluate the load-bearing capacity of the headed stud 3 of the composite wall.

[0037] Subsequently, the rigidity evaluation formula of the headed stud 3 required for constructing the separation model will be explained. First, in the tensile rigidity evaluation formula, the bearing pressure deformation of the concrete directly above the head 31 of the headed stud 3 and the deformation of the shaft portion 32 of the headed stud 3 were set as a series spring relationship to evaluate the tensile rigidity.

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

[0039] On the other hand, for the shear rigidity, an evaluation formula considering the influence of the concrete placement direction was set based on the formula of Shima et al. shown in the "Standard Specification for Composite Structures" of the Japan Society of Civil Engineers. <Shear Rigidity Evaluation Formula> Q = 0.8Q S (1 - e -αδ / φ ) 0.4 Here, Q is the shear force, Q S is the ultimate shear bearing capacity of the headed stud 3, α is the correction coefficient according to the concrete strength, δ is the shear displacement, and φ is the shaft diameter of the shaft portion 32. The 0.8 in this formula is the correction coefficient obtained from the experimental results of this time.

[0040] In this way, the tensile rigidity k obtained from the element experiment considering the concrete placement directionT And, using the tensile stiffness evaluation formula, the spring element M3 of the separation model is set. That is, the tension spring M31 is set based on the tensile stiffness k T and the shear spring M32 is set based on the shear stiffness evaluation formula.

[0041] Then, as shown in FIG. 4, a separation model is created in which two parallel beam elements M1 and M2 are connected by a plurality of spring elements M3. Here, the spring elements M3 are arranged at intervals in the vertical direction according to the arrangement position and number of the stud 3 with a head set in step S1.

[0042] For the created separation model of the composite wall, in step S3, the setting of the acting loads such as the earth pressure and water pressure received from the back side of the retaining wall 1 is performed. And in step S4, the stress analysis of the composite wall using the separation model is performed.

[0043] In the subsequent step S5, referring to the calculation results of the stress analysis, a cross-sectional design is performed to check whether the stresses of each member of the retaining stress member 11, the underground outer wall 2, and the stud 3 with a head are within the allowable range. At this time, by using the above-described corrected shear strength sc q s and the corrected allowable tensile force sc p a a cross-sectional study considering the placing direction of the concrete is carried out. And if there is any member exceeding the allowable range, return to step S1, correct various settings of the members that need to be changed, and then recalculate.

[0044] On the other hand, if the stresses of each member are within the allowable range, the design is completed with the arrangement of the stud 3 (shear connector) with a head set in step S1. In this way, if the shear force and tensile force acting on the spring element M3 can be visualized at each position in the height direction, an economical arrangement of the shear connector becomes possible.

[0045] FIG. 6 is an explanatory diagram illustrating the arrangement of headed studs 3 determined from the calculation results by the separation model in the case where floor slabs 4 are provided above and below the underground outer wall 2. As shown in the left diagram of FIG. 6, in the conventional design method, the headed studs 3 were to be evenly arranged in the height direction of the underground outer wall 2.

[0046] On the other hand, in the design method based on the separation model shown in the right diagram of FIG. 6, the headed studs 3 are densely arranged at the lower and upper parts of the underground outer wall 2 adjacent to the floor slab 4, and the interval between the headed studs 3 can be widened around the center in the height direction of the underground outer wall 2. This is because, as a result of the stress analysis by the separation model, a calculation result was obtained that the shear force acting on the headed studs 3 is smaller in the central part of the floor height compared to the vicinity of the floor slab 4. This is an example of freely and reasonably designing within the range that satisfies the structural details, such as concentrating the arrangement of the headed studs 3 near the floor slab 4.

[0047] On the other hand, FIG. 7 is an explanatory diagram illustrating the arrangement of the headed studs 3 of the composite wall with an open upper part. For example, composite walls such as dry areas and seismic isolation pit retaining walls can be assumed. Also in this case, as shown in the left diagram of FIG. 7, in the conventional design method, the headed studs 3 were to be evenly arranged in the height direction of the underground outer wall 2.

[0048] On the other hand, in the design method based on the separation model shown in the right diagram of FIG. 7, the headed studs 3 are densely arranged at the lower part of the underground outer wall 2 adjacent to the floor slab 4 and between the floor slab 4, and the interval between the headed studs 3 can be widened from the center to the upper part in the height direction of the underground outer wall 2. In short, a reasonable design has been achieved in which the arrangement is concentrated at the locations where joining by the headed studs 3 is required, and the intervals are widened at other locations.

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

[0050] Therefore, regarding the composite wall integrated by joining the retaining stress member 11 and the underground outer wall 2 with the headed studs 3, it becomes possible to rationally design the required number, arrangement position, etc. of the headed studs 3.

[0051] With such a rational arrangement of the headed studs 3, it becomes possible to reduce the number and reduce operations such as welding the headed studs 3 at high places to the retaining stress member 11, and thus it is possible to expect cost reduction, improvement of safety and productivity at the site.

[0052] Also, in the design method of the composite index, although the tensile force acting on the shear connector is not considered, when creating a separation model and performing stress analysis, the tensile force of the headed studs 3 can also be considered, so that the quality can be improved.

[0053] Further, since the above-described composite index is obtained by evaluating the headed studs 3 for reinforced concrete members, it is premised that the head 31 of the headed studs 3 reaches the reinforcing bar 22, similar to the arrangement shown in FIG. 3.

[0054] On the other hand, the element experiment considering the above-described concrete placing direction is performed using a specimen of non-reinforced concrete. That is, the above-described evaluation formula for the bearing capacity and the evaluation formula for the rigidity of the headed studs 3 are evaluations for non-reinforced concrete.

[0055] Therefore, as in the example of the positional relationship between the headed stud 3A with a head shown in FIG. 8 and the reinforcing bar 22, the position of the head 31 of the headed stud 3A may not reach the reinforcing bar 22. In short, even if the headed stud 3A is embedded only in the non-reinforced concrete portion 21, the shear strength formula, allowable tensile force formula, tensile rigidity evaluation formula, and shear rigidity evaluation formula of the headed stud 3A described above can be applied.

[0056] If the composite wall is designed by a design method that does not assume that the headed studs 3, 3A reach the reinforcing bar 22 in this way, it is not necessary to additionally arrange reinforcing bars as in the conventional case when the shear connectors do not reach the wall reinforcement. Also, it is not necessary to make the length of the headed studs 3, 3A long only to reach the wall reinforcement. In short, the amount of reinforcing bars and the labor of arranging the reinforcement can be reduced.

[0057] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, 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, the headed studs 3, 3A are mainly used as examples of the shear connectors for explanation. However, the present invention is not limited to this, and even when deformed bar steel studs such as deformed reinforcing bars become shear connectors, the design method of the composite wall of the present embodiment can be applied.

Explanation of Reference Numerals

[0059] 1: Retaining wall 11: Retaining stress member 2: Underground outer wall (reinforced concrete wall) 22: Reinforcing bar 3, 3A: Headed stud (shear connector) 31: Head (tip) M1, M2: Beam element M3: Spring element M31: Tensile spring M32: Shear spring

Claims

1. A design method for a composite wall integrated by joining a retaining stress member and a reinforced concrete wall with a shear connector, comprising the steps of creating a separation model in which beam elements representing each of the retaining stress member and the reinforced concrete wall are connected by spring elements of the plurality of shear connectors arranged at intervals in the vertical direction, applying a load to the separation model and performing calculations, and checking whether the stress of the shear connector is within an allowable range based on the result of the calculation, wherein the shear connector is a headed stud or a deformed bar stud, the spring elements include a tension spring and a shear spring, and the modeling of the tension spring and the shear spring is performed using evaluation formulas for tensile stiffness and shear stiffness created based on experimental results using specimens manufactured in accordance with the placing direction of the concrete of the reinforced concrete wall. A design method for a composite wall, characterized in that it is performed.

2. The design method for a composite wall according to claim 1, wherein the retaining stress member is a structural steel shape.

3. The design method for a composite wall according to claim 1 or 2, characterized in that the arrangement of the shear connector is determined based on the result of the calculation.

4. The design method for a composite wall according to claim 1 or 2, characterized in that a correction coefficient based on the experimental results is incorporated into the evaluation formula.

5. The design method for a composite wall according to claim 1 or 2, characterized in that the tip of the shear connector is located on the retaining stress member side with respect to the reinforcing bars arranged in the reinforced concrete wall.

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