Method for designing steel beam with floor slab

Abstract

To provide a method for designing a steel beam with a floor slab capable of suppressing early deterioration of bearing capacity of a steel beam due to lateral buckling caused by a long-term load and exhibiting sufficient bearing capacity and deformation performance in the steel beam with floor slab formed by joining a concrete floor slab and the steel beam through studs.SOLUTION: Both ends of a beam 20 which is a steel beam made of H-shaped steel are rigidly joined to a pair of respective girders, or one end of the beam is rigidly joined and the other end is pin-joined, and a headed stud 30 protruding upward from a beam flange 22 above the beam 20 is buried in a concrete floor slab 10, so that the beam flange 22 and the floor slab 10 are joined to each other. In a design method of the steel beam 50 with floor slab, a rotary spring rigidity per one place of a stud with a head for satisfying an expression (X) of an equation 1 is set as required performance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for designing a steel beam with a floor slab. [Background technology]

[0002] In steel beams with floor slabs, where the floor slab and steel beams made of H-shaped steel are connected by shear connectors such as headed studs, it has been confirmed that the floor slab restrains the horizontal movement outside the structural plane of the top flange (beam flange) of the steel beam and rotation around the material axis, thereby increasing the lateral buckling strength and deformation capacity against long-term loads. Generally, the stiffness and strength against horizontal movement and rotation are examined using a model in which the headed stud joints are replaced with horizontal springs and rotational springs, and then the design of the steel beams with floor slabs (specifically, the diameter and number of headed studs) is carried out.

[0003] Various mechanical models have been proposed to date when examining the required performance of rotational spring stiffness, and among these, the slipout of headed studs and bending deformation of beam flanges are often modeled as series springs, but when this model is used, the design formula tends to be on the safe side, and it can be said that there are currently no generalized mechanical models.Furthermore, when examining the required performance of rotational spring stiffness for the top flange of steel beams, it can also be said that there are currently no generalized, specific evaluation methods.

[0004] When the floor slab is made of highly rigid concrete, its horizontal spring stiffness is sufficiently high, so evaluating its rotational spring stiffness is extremely important for accurately evaluating the lateral buckling strength of the steel beam against long-term loads, and for evaluating and designing the necessary and inherent performance of the steel beam with floor slab. A steel beam with floor slab, which is formed by joining a concrete floor slab and a steel beam with studs, is installed in the building frame in such a way that both ends of a sub-beam, which is a steel beam made of H-shaped steel, are rigidly joined to a pair of main girders that form the frame, or one end of the sub-beam is rigidly joined and the other end is pin-joined, and then headed studs protruding upward from the beam flange above the sub-beam are embedded in the concrete floor slab, thereby joining the beam flange and the floor slab to each other.

[0005] In view of the above, there is a need for a design method for steel beams with floor slabs, which are made by joining a concrete floor slab and a steel beam via studs, that will prevent the steel beams from prematurely losing strength due to lateral buckling caused by long-term loads, and will enable them to exhibit sufficient strength and deformation performance.

[0006] Patent Document 1 proposes a design method for a support structure that can set the elastic lateral buckling strength of an H-section member. This design method is for preventing lateral buckling of an H-section member, which includes an H-section member having a first flange, a second flange, and a web, a plate member supported on the first flange, and a connecting member connecting the first flange and the plate member. The movement and rotation of the first flange are constrained with a given rigidity. In this support structure, when a structure in which the movement and rotation of the first flange are completely constrained is defined as a fully constrained support structure, the elastic lateral buckling strength is set using a reduction factor of the elastic lateral buckling strength of the H-section member of the support structure, which is set based on the horizontal stiffening stiffness coefficient and the rotational stiffening stiffness coefficient, relative to the elastic lateral buckling strength of the H-section member of the fully constrained support structure. Here, a folded-plate roof is given as an example of the plate member supported by the first flange. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2023-97161 Summary of the Invention [Problem to be solved by the invention]

[0008] According to the support structure design method described in Patent Document 1, in a support structure in which the first flange is restrained with any rigidity, it is possible to set the elastic lateral buckling strength Me of the H-section member so that the first flange can be considered to be completely restrained by the plate-like member. This design method is a method for evaluating the elastic lateral buckling strength under various conditions in which the restraint of the top flange (here, the first flange) is incomplete, including when a floor slab is attached, and its purpose is to clarify the conditions under which it can be considered to be completely restrained. Incidentally, in order to enable a so-called rigidly-connected sub-beam, in which both ends of the sub-beam are rigidly connected to a pair of main beams, to exert full plastic strength (to prevent the strength from decreasing prematurely under long-term load), it is not necessarily necessary to completely restrain it. However, at present, the specific required rigidity has not been clarified, and there is no mention of this in Patent Document 1.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a design method for a steel beam with a floor slab, which is formed by joining a concrete floor slab and a steel beam via studs, that can prevent the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and can exhibit sufficient strength and deformation performance. [Means for solving the problem]

[0010] In order to achieve the above object, one aspect of the design method for a steel beam with a floor slab according to the present invention is to: A design method for a steel beam with a floor slab, in which both ends of a sub-beam, which is a steel beam made of H-shaped steel, are rigidly connected to a pair of main girders, or one end of the sub-beam is rigidly connected and the other end is pin-connected, and headed studs protruding upward from the beam flange above the sub-beam are embedded in a concrete floor slab, thereby connecting the beam flange and the floor slab to each other, The required performance is the rotational spring stiffness per headed stud that satisfies the following formula (X).

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[0011] According to this aspect, by designing the rotational spring stiffness per headed stud to satisfy formula (X) as the required performance, it is possible to prevent the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and to design a steel beam with a floor slab that can exhibit sufficient strength and deformation performance.

[0012] Here, formula (X) is based on the results of an elastic-plastic analysis using the finite element method to verify the relationship between the rotational spring stiffness coefficient kr and the strength of a steel beam made of H-shaped steel, where the horizontal movement and rotation of the upper flange are spring-constrained. In this verification, the horizontal spring stiffness was set to a sufficiently high value because the floor slab was made of highly rigid concrete.

[0013] Another aspect of the design method for a steel beam with a floor slab according to the present invention is to A design method for a steel beam with a floor slab, in which both ends of a sub-beam, which is a steel beam made of H-shaped steel, are rigidly connected to a pair of main girders, or one end of the sub-beam is rigidly connected and the other end is pin-connected, and headed studs protruding upward from the beam flange above the sub-beam are embedded in a concrete floor slab, thereby connecting the beam flange and the floor slab to each other, The performance is characterized by the rotational spring rigidity per headed stud, taking into account the interaction between the slippage of the headed stud and the deformation of the beam flange.

[0014] According to this aspect, by taking into account the interaction between the slippage of the headed stud and the deformation of the beam flange and defining the rotational spring stiffness per headed stud as the required performance, the required performance of a steel beam with a floor slab can be determined with high accuracy, preventing the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and allowing the design of a steel beam with a floor slab that can exhibit sufficient strength and deformation performance.

[0015] Another aspect of the design method for a steel beam with a floor slab according to the present invention is to In the case of a single arrangement where the headed stud is installed on the beam flange core, the distance from the beam flange core to the beam flange rotation center is taken as l, and the rotational spring rigidity per headed stud is the smallest value among the values ​​calculated using the formulas Y1 and Y2 in the following cases.

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[0016] According to this embodiment, by designing the rotational spring stiffness per headed stud, which is the smallest value among the values ​​calculated by formulas (Y1) and (Y2), as the required performance, it is possible to determine with high accuracy the required performance of a steel beam with a floor slab in the case of a single arrangement in which the headed stud is installed above the beam flange core, and it is possible to prevent the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and to design a steel beam with a floor slab that can exhibit sufficient strength and deformation performance.

[0017] When the headed studs are double-positioned on the beam flange, the distance from the beam flange center to the beam flange rotation center is defined as l, and the rotational spring rigidity per headed stud is the smallest value among the values ​​calculated using the formulas Z1, Z2, and Z3 in the following cases.

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[0018] According to this embodiment, by designing the rotational spring stiffness per headed stud, which is the smallest value among the values ​​calculated by equations (Z1) to (Z3), as the required performance, it is possible to determine with high accuracy the required performance of a steel beam with a floor slab when the headed studs are double-positioned on the beam flange, thereby preventing the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and to design a steel beam with a floor slab that can exhibit sufficient strength and deformation performance. [Effects of the Invention]

[0019] As can be understood from the above explanation, according to the design method for a steel beam with a floor slab of the present invention, it is possible to design a steel beam with a floor slab that is formed by joining a concrete floor slab and a steel beam via studs, and that can prevent the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and can exhibit sufficient strength and deformation performance. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is an oblique view of an example of a steel beam with a floor slab that is the design target of the design method for a steel beam with a floor slab according to an embodiment, simulating a state in which horizontal displacement and twisting around the material axis occur in the steel beam. [Figure 2] (a) is a diagram illustrating an example of the arrangement of headed studs in a single arrangement, (b) is a diagram illustrating an example of the arrangement of headed studs in a double arrangement (two rows), and (c) is a diagram illustrating an example of the arrangement of headed studs in a double arrangement (staggered). [Figure 3] (a) is a diagram showing the support conditions at the end of the beam flange when the headed studs are single-positioned and the beam flange plate thickness is thick, and (b) is a diagram showing the support conditions at the end of the beam flange when the headed studs are single-positioned and the beam flange plate thickness is thin. [Figure 4](a) is a diagram showing the support conditions at the end of the beam flange when the headed studs are double-positioned and the beam flange plate thickness is thick, (b) is a diagram showing the support conditions at the end of the beam flange when the headed studs are double-positioned and the beam flange plate thickness is medium, and (c) is a diagram showing the support conditions at the end of the beam flange when the headed studs are double-positioned and the beam flange plate thickness is thin. [Figure 5A] FIG. 10 is a diagram illustrating a beam spring model when the headed stud is single-arranged and the beam flange plate thickness is thick. [Figure 5B] FIG. 10 is a diagram illustrating a beam spring model when the headed stud is single-arranged and the beam flange plate thickness is thin. [Figure 6A] FIG. 10 is a diagram illustrating a beam spring model when headed studs are double-arranged and the beam flange plate thickness is thick. [Figure 6B] This is a diagram explaining a beam spring model when the headed studs are double-arranged and the beam flange plate thickness is medium. [Figure 6C] FIG. 10 is a diagram illustrating a beam spring model when headed studs are double-arranged and the beam flange plate thickness is thin. [Figure 7A] FIG. 1 is a diagram showing an example of an entire analytical model for elastic-plastic analysis using the finite element method, which was implemented when formulating required performance in a design method for a steel beam with a floor slab according to an embodiment. [Figure 7B] FIG. 2 is a cross-sectional view of an example of an analytical model, perpendicular to the material axis direction. [Figure 7C] FIG. 10 is a diagram illustrating an example of an external force acting on an example of an analytical model. [Figure 7D] FIG. 10 is a diagram showing the bending moment that occurs under long-term loading when both ends of a sub-beam are rigidly connected to a pair of main beams. [Figure 8] FIG. 10 is a diagram showing the results of an elastic-plastic analysis using the finite element method for steel beams of various cross sections, illustrating the relationship between maximum strength and rotational spring stiffness. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, a method for designing a steel beam with a floor slab according to an embodiment will be described with reference to the accompanying drawings. Note that in this specification and the drawings, substantially identical components will be designated by the same reference numerals, and redundant explanations may be omitted.

[0022] [Design method for steel beams with floor slabs according to the embodiment] <Formulation of performance> First, the formulation of required performance in an example of a design method for a steel beam with a floor slab according to an embodiment will be described with reference to Figures 1 to 6. Here, Figure 1 is a perspective view of an example of a steel beam with a floor slab that is the design target of the design method for a steel beam with a floor slab according to an embodiment, simulating a state in which horizontal displacement and torsion around the material axis occur in the steel beam. Also, Figure 2(a) is a diagram illustrating an example of a single-arranged headed stud arrangement, and Figures 2(b) and 2(c) are diagrams illustrating examples of a double-arranged (two rows) and a staggered (staggered) headed stud arrangement, respectively.

[0023] The steel beam 50 with floor slab to be designed, shown in Figure 1, is formed by embedding headed studs 30 protruding upward from the beam flange 22 (upper flange) of the sub-beam 20, which is a steel beam made of H-shaped steel, into the concrete floor slab 10, thereby joining the beam flange 22 and the floor slab 10 to each other.

[0024] The concrete floor slab 10 is a floor slab made of reinforced concrete (RC (Reinforced Concrete)) that is constructed by pouring concrete on-site, and the reinforced concrete floor slab includes a composite slab made of a deck plate and reinforced concrete.

[0025] The H-shaped steel that forms the sub-beam 20 has a web 21, an upper flange 22 (beam flange), and a lower flange 23, and includes H-shaped steel of various cross-sectional shapes and dimensions, such as medium-width H-shaped steel with a relatively large flange width, and narrow-width H-shaped steel with a relatively small flange width, as exemplified below.

[0026] The example shown in Figure 1 shows an example of a double arrangement in which two headed studs 30 are welded to the left and right of the beam flange core L2 of the beam flange 22 of the steel beam 20, and the pair of headed studs 30 are arranged at a predetermined pitch in the material axis direction (longitudinal direction) of the steel beam 20.

[0027] This double arrangement can be in a two-row arrangement, as shown in Figure 2(b), in which the left and right headed studs 30 are lined up and arranged at a specified pitch in the material axis direction, or in a staggered arrangement, as shown in Figure 2(c), in which the left and right headed studs 30 are offset from each other in the material axis direction and each headed stud 30 is arranged at a specified pitch in the material axis direction.

[0028] Alternatively, the headed studs 30 may be arranged in a single arrangement, as shown in FIG. 2(a), in which the headed studs 30 are arranged at a predetermined pitch on the beam flange core L2.

[0029] The girder 20 may have one end rigidly joined to a pair of main girders (not shown), or one end rigidly joined to one of the pair of main girders and the other end pin-jointed to the other main girder. The main girders (not shown) are also made of H-shaped steel or the like. The ends of the girders are joined to steel columns such as square steel pipes, reinforced concrete columns, or steel-reinforced concrete (SRC) columns, and the framework of the building is formed by these columns, girders, and sub-girders 20.

[0030] As shown in Figure 1, in a steel beam 50 with a floor slab, the floor slab 10 restrains the horizontal movement of the beam flange 22 outside the structural plane (horizontal displacement δh) and the rotation of the steel beam 20 around the material axis L1 (torsion with a torsion angle φ), and this restraint increases the lateral buckling strength and plastic deformation capacity.

[0031] When modeling a steel beam 50 with a floor slab in a computer, in which the horizontal movement and rotation of the beam flange 22 of the steel beam 20 are constrained by a concrete floor slab 10, the constraints on horizontal movement and rotation are simulated by horizontal springs and rotational springs, and an analytical model in which horizontal springs and rotational springs are attached to the beam flange model of the steel beam model is generally applied.

[0032] Since the concrete floor slab 10 has high rigidity, the rigidity of the horizontal spring (horizontal spring rigidity) can be set sufficiently high in the analysis. Therefore, when designing a steel beam with a floor slab that has sufficient strength and deformation performance against lateral buckling due to long-term loads acting on the steel beam, it is extremely important to evaluate the rotational spring rigidity of the concrete floor slab.

[0033] Taking note of this, when establishing a design method for the required performance and inherent performance of steel beams with floor slabs, which are made by joining steel beams to a concrete floor slab via headed studs, the required performance and inherent performance for rotational spring rigidity per headed stud were formulated, and the design method for steel beams with floor slabs was specified based on each of the formulated formulas.

[0034] Next, referring to Figures 2 to 6, when formulating the required performance regarding the rotational spring rigidity per headed stud, we will explain the design formula that defines the required performance, showing the support conditions and beam spring model at the end of the beam flange depending on the arrangement of the headed stud and the thickness of the beam flange.

[0035] Figures 3(a) and 3(b) show the support conditions at the beam flange end for cases where the headed studs are single-positioned and the beam flange is thick and thin, respectively. Figures 4(a), 4(b), and 4(c) show the support conditions at the beam flange end for cases where the headed studs are double-positioned and the beam flange is thick, medium, and thin, respectively. Furthermore, Figures 5A and 5B explain the beam spring model for cases where the headed studs are single-positioned and the beam flange is thick and thin, respectively. Figures 6A, 6B, and 6C explain the beam spring model for cases where the headed studs are double-positioned and the beam flange is thick, medium, and thin, respectively.

[0036] As shown in Figure 2(a), when the headed stud 30 is in a single configuration and the beam flange 22 is thick (for example, when the thickness is 25 mm or more), the support condition for the beam flange end in the rotation direction of the beam flange of a steel beam that rotates (pivots) relative to the floor slab can be considered to be a pin support, as shown in Figure 3(a).This is because the beam flange is thick, so the beam flange does not become plastic due to bending deformation within the range of the beam flange width (the length from the beam flange center to the beam flange end), and does not form a rigid support due to plasticity.

[0037] When a steel beam rotates, the web rotates in addition to the beam flange, so each rotates at an angle θ scf and angle θ w In Figure 3(a), the axial stiffness of the vertical spring due to the axial elongation of the headed stud and the deformation of the concrete is expressed as K sc It is simulated by.

[0038] Considering the support conditions at the beam flange end shown in Figure 3(a), a beam spring model can be simulated for a case where the headed studs are arranged in a single configuration and the beam flange plate thickness is thick, as shown in Figure 5A.

[0039] On the other hand, when the headed stud 30 is in a single arrangement and the plate thickness of the beam flange 22 is thin (for example, when the thickness is less than 22 mm), the support condition of the beam flange end in the rotation direction of the beam flange of the steel beam that rotates (pivots) relative to the floor slab can be considered to be a rigid support, as shown in Figure 3(b). This is because the beam flange plate thickness is thin, and the beam flange becomes plastic due to bending deformation within the range of the beam flange width (the length from the beam flange center to the beam flange end), forming a rigid support.

[0040] Taking into account the support conditions at the beam flange end shown in Figure 3(b), the beam spring model for a case where the headed stud is arranged in a single configuration and the beam flange plate thickness is thin can be modeled as shown in Figure 5B.

[0041] In this way, in the case of a single arrangement where the headed stud is installed on the beam flange core, taking into account the two conditions shown in Figures 5A and 5B, when formulating the rotational spring stiffness per headed stud as the inherent performance, the distance from the beam flange core to the beam flange rotation center is taken as l, and the rotational spring stiffness per headed stud, which is the smallest value among the values ​​calculated using equations (Y1) and (Y2) for each of the following cases, is taken as the inherent performance.

[0042]

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[0043] In the case of a double arrangement of headed studs 30 in two rows as shown in Figure 2(b), or a double arrangement of headed studs 30 in a staggered pattern as shown in Figure 2(c), and the thickness of the beam flange 22 is thick (for example, 25 mm or more), the support condition for the beam flange end in the rotation direction of the beam flange of a steel beam that rotates (pivots) relative to the floor slab can be considered to be a pin support, as shown in Figure 4(a). This is because the beam flange is thick, so the beam flange does not become plastic due to bending deformation within the range of its width (the length from the beam flange center to the beam flange end), and does not form a rigid support due to plasticity.

[0044] Taking into account the support conditions at the beam flange end shown in Figure 4(a), a beam spring model can be simulated for a case where the headed studs are double-arranged and the beam flange plate thickness is thick, as shown in Figure 6A.

[0045] On the other hand, when the headed studs 30 are double-positioned and the plate thickness of the beam flange 22 is medium (for example, when the thickness is 22 mm or more and less than 25 mm), as shown in Figure 4(b), the support condition of the beam flange end in the rotation direction of the beam flange of a steel beam that rotates (pivots) relative to the floor slab can be considered to be a rigid support in the range from the position of the headed stud in the rotation direction to the end of the beam flange. This is because the plate thickness of the beam flange is medium, and the beam flange becomes plastic due to bending deformation within the range outside the headed stud in the rotation direction, forming a rigid support.

[0046] Taking into account the support conditions at the beam flange end shown in Figure 4(b), a beam spring model can be simulated for a case where the headed studs are arranged in a single configuration and the beam flange plate thickness is thin, as shown in Figure 6B.

[0047] On the other hand, when the headed studs 30 are double-positioned and the beam flange 22 is thin (for example, when the thickness is less than 22 mm), as shown in Figure 4(c), the support condition of the beam flange end in the rotation direction of the beam flange of a steel beam that rotates (pivots) relative to the floor slab can be considered to be a rigid support in the range from the center of the beam flange to the position of the headed stud in the rotation direction. This is because the beam flange is thin, so the beam flange plasticizes due to bending deformation within the range inside the headed stud in the rotation direction, forming a rigid support.

[0048] Taking into account the support conditions at the beam flange end shown in Figure 4(c), the beam spring model for a case where the headed studs are arranged in a single configuration and the beam flange plate thickness is thin can be modeled as shown in Figure 6C.

[0049] In this way, when headed studs are double-positioned, taking into account the three conditions shown in Figures 6A to 6C, when formulating the rotational spring stiffness per headed stud as the required performance, the distance from the beam flange center to the beam flange rotation center is defined as l, and the minimum value of the rotational spring stiffness per headed stud calculated using equations (Z1), (Z2), and (Z3) for each of the following cases is taken as the required performance.

[0050]

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[0051] As described above, by designing the rotational spring stiffness per headed stud, which is the smallest value among the values ​​calculated by formulas (Y1) and (Y2), as the required performance, it is possible to determine with high accuracy the required performance of a steel beam with a floor slab in the case of a single arrangement in which the headed stud is installed above the beam flange core, and it is possible to prevent the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and to design a steel beam with a floor slab that can exhibit sufficient strength and deformation performance.

[0052] Furthermore, by designing the rotational spring stiffness per headed stud, which is the smallest value among the values ​​calculated by equations (Z1) to (Z3), as the required performance, it is possible to determine with high accuracy the required performance of a steel beam with a floor slab when the headed studs are double-positioned on the beam flange, thereby preventing the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and allowing the design of a steel beam with a floor slab that can exhibit sufficient strength and deformation performance.

[0053] Furthermore, as shown in the beam spring model in Figures 5 and 6, by deriving the deformation of the beam flange by assuming that the headed stud slipout is supported by a vertical spring, it is possible to take into account the interaction between the headed stud slipout and the deformation of the beam flange.

[0054] <Formulation of required performance> Next, with reference to Figs. 7 and 8, the formulation of required performance will be described in an example of a design method for a steel beam with a floor slab according to the embodiment.

[0055] Here, Fig. 7A is a diagram showing the entire example of an analytical model in an elastic-plastic analysis using the finite element method (FEM) performed when formulating the required performance in a design method for a steel beam with a floor slab according to an embodiment, Fig. 7B is a cross-sectional view of the example analytical model perpendicular to the material axis direction, Fig. 7C is a diagram showing an example of an external force acting on the example analytical model, and Fig. 7D is a diagram showing the bending moment that occurs under long-term load when both ends of a sub-beam are rigidly connected to a pair of main beams. Also, Fig. 8 is a diagram showing the analysis results of an elastic-plastic analysis using the finite element method for steel beams of various cross sections, and shows the analysis results regarding the relationship between maximum strength and rotational spring stiffness.

[0056] When formulating the required and available performance regarding rotational spring stiffness per headed stud, the inventors performed an elastic-plastic analysis using the finite element method and verified the relationship between the rotational spring stiffness coefficient kr and the strength of a steel beam made of H-shaped steel, in which the horizontal movement and rotation of the beam flange are spring-constrained.

[0057] The steel beams shown in Figures 7A and 7B are steel beams with seven cross sections as shown in Table 1 below, with three cross sections being standard medium-width cross sections and four cross sections being narrow-width cross sections prone to lateral buckling.

[0058] For the narrow cross section, a thin web cross section that is prone to lateral buckling was selected based on the manufacturing range of rolled H-section steel. The member length L was uniformly set to 20 times the beam depth H. The longer the beam length, the more likely lateral buckling will occur, and the larger the required rotational spring stiffness coefficient kr. In practice, it is thought that L / H will be at most around 20, so here we set L / H=20 as a conservative consideration.

[0059] The analysis model was constructed using four-node shell elements, with the left and right ends of the material pin-supported and fixed against torsional deformation, while boundary conditions were given for free bending and warping deformation around the weak axis.In addition, as a restraint effect of the floor slab on the beam flange (upper flange), movement in the Z direction was restrained by horizontal springs at 200mm intervals at the nodes at the center of the cross section of the beam flange, and rotation around the X axis (material axis) was restrained by rotational springs.

[0060] Since it is well known that the horizontal spring stiffness is sufficiently high when restraint by the floor slab is expected, the horizontal spring stiffness coefficient kh was set to a uniform value of 1000, and the rotational spring stiffness coefficient kr was given as a variable between 0.1 and 500 (0.1, 0.5, 1, 5, 10, 50, 100, 500).

[0061] The horizontal spring stiffness coefficient kh and the rotational spring stiffness coefficient kr are given by the following formula (U) based on the horizontal spring stiffness kh per location of the horizontal spring and the rotational spring stiffness kr per location of the rotational spring.

[0062]

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[0063] As shown in Figure 7C, a bending moment M was applied at the end of the member and a uniformly distributed load p was applied at the center of the cross section of the beam flange in the middle of the member, in order to reproduce the bending moment distribution that occurs when a rigidly connected sub-beam (both ends of the sub-beam are rigidly connected to a pair of main beams) is subjected to long-term loading, as shown in Figure 7D.

[0064] The analysis results for the relationship between maximum strength and rotational spring stiffness are shown in Fig. 8. In Fig. 8, the vertical axis represents the maximum strength as the ratio of the member end moment to the full plastic moment.

[0065] [Table 1]

[0066] In this analysis, it was determined that for H-shaped steel of any cross section, the maximum strength increases as the rotational spring stiffness coefficient kr increases, and that once kr reaches a certain size, there is no change in the load-deformation relationship even if kr increases further.

[0067] From Figure 8, it can be seen that a full plastic moment is exerted in H-shaped steel of all cross sections by setting kr ≥ 5. Based on these analysis results, it was decided that the required performance was the rotational spring rigidity per headed stud that satisfied the following formula (X).

[0068]

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[0069] By designing the rotational spring stiffness per headed stud to satisfy formula (X) as the required performance, it is possible to prevent the steel beam from prematurely losing strength due to lateral buckling caused by long-term loads, and to design a steel beam with a floor slab that can exhibit sufficient strength and deformation performance.

[0070] It should be noted that the present invention is not limited to the configurations shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, the present invention can be modified within the scope of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0071] 10: Floor slab (concrete floor slab) 12M: Horizontal spring model 14M: Rotational spring model 20: Small beam (steel beam, H-beam) 20M: Steel beam model 21:Web 21M:Web Model 22: Beam flange (upper flange) 22M: Beam flange model (top flange model) 23: Lower flange 23M: Lower flange model 30: Headed stud 50: Steel beam with floor slab L1: Material shaft L2: Beam flange center

Claims

1. A design method for a steel beam with a floor slab, in which both ends of a sub-beam, which is a steel beam made of H-shaped steel, are rigidly connected to a pair of main girders, or one end of the sub-beam is rigidly connected and the other end is pin-connected, and headed studs protruding upward from the beam flange above the sub-beam are embedded in a concrete floor slab, thereby connecting the beam flange and the floor slab to each other, A design method for a steel beam with a floor slab, characterized in that the required performance is a rotational spring stiffness per headed stud that satisfies the following formula (X): [Equation 1]

2. A design method for a steel beam with a floor slab, in which both ends of a sub-beam, which is a steel beam made of H-shaped steel, are rigidly connected to a pair of main girders, or one end of the sub-beam is rigidly connected and the other end is pin-connected, and headed studs protruding upward from the beam flange above the sub-beam are embedded in a concrete floor slab, thereby connecting the beam flange and the floor slab to each other, A design method for a steel beam with a floor slab, characterized in that the rotational spring rigidity per headed stud is set as the required performance, taking into account the interaction between the slipout of the headed stud and the deformation of the beam flange.

3. A design method for a steel beam with a floor slab as described in claim 2, characterized in that in the case of a single arrangement in which the headed stud is installed on the beam flange core, the distance from the beam flange core to the beam flange rotation center is l, and the rotational spring rigidity per headed stud, which is the smallest value among the values ​​calculated using equations Y1 and Y2 in the following cases, is taken as the retained performance. [Equation 2]

4. A design method for a steel beam with a floor slab as described in claim 2, characterized in that, when the headed studs are double-positioned on the beam flange, the distance from the beam flange center to the beam flange rotation center is l, and the rotational spring rigidity per headed stud, which is the smallest value among the values ​​calculated using the following formulas Z1, Z2, and Z3 for each case, is taken as the required performance. [Equation 3]

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