Building structural design methods

Abstract

By enabling easy and reliable brace selection without repeated design work, design efficiency can be improved, and the time required for design can be reduced. [Solution] The method includes: a target yield deformation angle setting step of setting a target yield deformation angle γ, which is a desired yield deformation angle in the building frame; a brace specification setting step of calculating the shear strength Q of the frame based on the target yield deformation angle γ and setting the brace specifications based on the shear strength Q; and a brace input amount determination step of determining the number of braces and the amount to be used based on the brace specifications and the strength of the braces.

Description

Technical Field

[0001] The present invention relates to a method for designing the structure of a building.

Background Art

[0002] Conventionally, in order to absorb and attenuate the vibration energy acting on a building due to disturbances such as earthquakes and strong winds and impart vibration damping performance to the building, measures such as installing braces in the building structure have been frequently used (for example, see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional design method of braces provided in the building structure, it is common to use a design method for determining the required strength in view of the sharing ratio between the shear strength required for the building and the strength borne by the braces. In such a design method, when the stress received by the braces during an earthquake exceeds the allowable stress level, although the cross-section of the braces is increased to increase the required strength, increasing the cross-section of the braces to increase the rigidity will increase the sharing ratio of the braces. That is, since the force concentrates on the braces, more strength is required and repeated examinations are necessary. Therefore, the working time required for designing braces with the required strength increases, and the working efficiency decreases. Thus, there is a demand for improving the efficiency of the design, and there is room for improvement in this regard.

[0005] This invention has been made in view of the above-mentioned problems, and aims to provide a structural design method for buildings that can improve design efficiency and reduce the time required for design by making it easy and reliable to select braces without having to perform repeated designs. [Means for solving the problem]

[0006] (1) Embodiment 1 of the building structural design method according to the present invention is a building structural design method equipped with a brace structure, characterized by comprising: a target yield deformation angle setting step of setting a target yield deformation angle which is a desired yield deformation angle in the frame of the building; a brace specification setting step of calculating the shear strength of the frame based on the target yield deformation angle and setting the specifications of the brace based on the shear strength; and a brace input amount determination step of determining the number of braces and the amount to be used which can be obtained from the strength of the brace based on the specifications of the brace.

[0007] This invention allows for the calculation of the shear strength of the building frame based on the target yield deformation angle obtained in the target yield deformation angle setting step, the setting of brace specifications, and the determination of the brace quantity based on the brace specifications in the brace quantity determination step. In other words, this structural design method allows for the design of braces that are suitable from the viewpoint of the target yield deformation angle of the building frame, and prevents the concentration of force on the braces alone. Therefore, it eliminates the need for repeated design work, improves design efficiency by making brace selection easy and reliable, and reduces the time required for design.

[0008] (2) In aspect 2 of the present invention, in the building structural design method of aspect 1, the target yield deformation angle is preferably a yield deformation angle that corresponds to the allowable value of the inter-story drift angle of the frame during an earthquake.

[0009] This invention allows for the selection of brace core material based on the inter-story drift angle in the structural plane of the frame, and the calculation of the shear strength of the frame to determine the brace specifications. Therefore, it eliminates the need for repeated design work and allows for more accurate brace determination, thereby significantly reducing the time required for design.

[0010] (3) A third aspect of the present invention is a building structural design method according to aspect 2, wherein in the step of determining the amount of brace to be used, the amount of brace to be used is determined, and the ratio of the frame and the brace to satisfy the calculated shear strength of the frame is determined.

[0011] In this case, by determining the amount of bracing to be used, it is possible to design the building to meet the design value for shear strength, and the ratio of load sharing between the bracing and the frame can be determined. Therefore, it becomes unnecessary to repeatedly redesign the structure until the optimal bracing is found, as the cross-sectional area of ​​the bracing becomes too large and the force concentrates too much on the bracing, resulting in an efficient design.

[0012] (4) Aspect 4 of the present invention is a building structural design method in any one of aspects 1 to 3, wherein the brace is a buckling-restrained brace comprising a long core material whose ends are connected to the frame and a restraining member that suppresses buckling of the core material, and the core material preferably has a plastic portion.

[0013] In this case, since the restraining member suppresses buckling, a buckling-restrained brace with a core material that is prone to buckling under compression (low compressive stiffness) can be used, thereby expanding the range in which the yield deformation angle can be selected. In other words, with a buckling-restrained brace, even if the core material is made thinner, the problem of buckling due to compression is less likely to occur, and the cross-sectional area can be reduced by using a material with high yield strength for the core material. Therefore, it is possible to design buildings with a large yield deformation angle while maintaining the same axial load-bearing capacity (cross-sectional area × yield strength), thereby improving the design flexibility of the building.

[0014] (5) Aspect 5 of the present invention may be characterized in that, in the building structural design method of aspect 4, in the brace specification setting step, the material strength of the plastic portion of the buckling-restrained brace is set as the specification.

[0015] In this case, since it is possible to select from multiple buckling-restrained braces with different material strengths in the plastic deformation portion of the core material, the options for determining the brace specifications increase, and the range of selectable options can be broadened.

[0016] (6) Aspect 6 of the present invention may be a building structural design method according to aspect 4 or aspect 5, characterized in that in the brace specification setting step, the length of the plastic portion of the buckling-restrained brace is set as the specification.

[0017] In this case, since it is possible to select from multiple buckling-restrained braces with different lengths of plastic deformation in the core material, the options for determining the brace specifications increase, and the range of selections can be broadened. [Effects of the Invention]

[0018] According to the structural design method for buildings of the present invention, design efficiency can be improved and the time required for design can be reduced by easily and reliably selecting braces without having to perform repeated designs. [Brief explanation of the drawing]

[0019] [Figure 1] A side view showing a buckling-restrained brace according to an embodiment of the present invention installed in the frame of a building. [Figure 2] Figure 1 shows a perspective view of a partially fractured buckling-restrained brace. [Figure 3] This is a perspective view of the core material of a buckling-restrained brace. [Figure 4] This is a perspective view of the restraint member of a buckling-restrained brace. [Figure 5]A diagram showing the stiffness adjustment of a buckling restraint brace, where (a) is a diagram showing the change in stiffness in a high-stiffness state, and (b) is a diagram showing the change in stiffness in a low-stiffness state. [Figure 6] A diagram for explaining a method of calculating the yield displacement of a buckling restraint brace. [Figure 7] A diagram showing the characteristics of a buckling restraint brace, which is a diagram showing the relationship between the yield deformation angle γ and the shear resistance Q of each brace. [Figure 8] A diagram for explaining a structural design method of a brace structure of a building. [Figure 9] In FIG. 7, it is a diagram showing a method of selecting a buckling restraint brace from a buckling restraint brace set in a building with a small number of bracing planes where the braces are arranged. [Figure 10] In FIG. 7, it is a diagram showing a method of selecting a buckling restraint brace from a buckling restraint brace set in a building where a pile is arranged directly below the brace. [Figure 11] In FIG. 7, it is a diagram showing a method of selecting a buckling restraint brace from a buckling restraint brace set for wind load response or great earthquake response. [Figure 12] In FIG. 7, it is a diagram showing a method of selecting a buckling restraint brace from a buckling restraint brace set for energy absorption corresponding to small amplitudes.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a structural design method of a building according to an embodiment of the present invention will be described based on the drawings.

[0021] (Buckling restraint brace) As shown in FIGS. 1 and 2, the buckling restraint brace 1 according to the present embodiment is applied to a brace that can be used for the frame 2A of the building 2 as a seismic element of the building, absorb and attenuate vibration energy during an earthquake, and more reliably and preferably suppress the sway of the building 2. The frame 2A is composed of columns 25 and beams 26.

[0022] The buckling-restrained brace 1 of this embodiment comprises a long core material 10 whose ends are connected to the frame 2A of the building 2, and restraining members 20 that suppress buckling of the core material 10. The buckling-restrained brace 1 absorbs external forces (vibration energy such as earthquake energy) acting in the axial direction of the brace by plastic deformation of the core material 10. Furthermore, the restraining members 20 prevent buckling of the core material 10 and allow the core material 10 to undergo plastic deformation efficiently. As a result, it exhibits excellent vibration damping performance and effectively improves the vibration resistance performance of the building 2. Here, the direction along the central axis of the buckling-restrained brace 1 will be defined as the axial direction X, and the explanation will follow.

[0023] Figure 3 is a perspective view of the core material 10 of the buckling-restrained brace 1. As shown in Figure 3, the core material 10 is made of steel and absorbs and dampens vibration energy (earthquake energy, etc.) acting on the building 2 through plastic deformation. The core material 10 has a plastic deformation section 11 with a uniform shape in the cross-sectional area perpendicular to the axis, and a pair of widening sections 12 (12A, 12B) (ends) located at both ends of the plastic deformation section 11 in the axial direction X, the area of ​​the cross-sectional area perpendicular to the axis being larger than the area of ​​the cross-sectional area perpendicular to the axis of the plastic deformation section 11. The core material 10 is integrally provided with the plastic deformation section 11 and both widening sections 12A, 12B.

[0024] The plastic deformation portion 11 extends along the axial direction X of the buckling-restrained brace 1. As shown in the illustrated example, the plastic deformation portion 11 may be formed in a cross shape, with a pair of strip-shaped steel plates of a certain width dimension perpendicular to each other in cross-section. The plastic deformation portion 11 plastically deforms when vibration energy is applied to it and absorbs this vibration energy. Here, the length of the plastic deformation portion 11 in the axial direction X is denoted as the plastic deformation portion length L1.

[0025] A pair of widening sections 12A and 12B are integrally provided on both ends of the plastic deformation section 11. These widening sections 12A and 12B extend continuously outward in the axial direction X from the plastic deformation section 11 and are formed to be wider than the plastic deformation section 11. The widening sections 12A and 12B have a restraining section 121 that is restrained by a restraining member 20 and a connecting end 122 that protrudes outward in the axial direction X from the restraining member 20. The restraining section 121 is embedded in the mortar (filling section 22) of the restraining member 20.

[0026] The connecting end 122 has a larger width dimension and a larger area of ​​the cross-sectional area perpendicular to the axis than the restraining part 121. Multiple bolt holes 122a are formed in the connecting end 122, and it is bolted to a gusset plate 27 (see Figure 1) attached to the frame 2A by welding or the like. In this way, it is integrally joined to both ends of the core material 10. Thus, the pair of widening parts 12A and 12B also serve as connecting parts that connect to the seismic-resistant object (frame 2A). Furthermore, if the buckling-restrained brace 1 is erected by welding instead of bolting the connecting end 122 to the frame 2A of the building 2, the bolt holes 122a may be omitted.

[0027] Figure 4 is a perspective view of the restraint member 20 of the buckling-restrained brace 1. As shown in Figure 4, the restraining member 20 prevents buckling of the core material 10. The restraining member 20 is provided so as to cover the plastic deformation portion 11 of the core material 10 from all sides, extends in the axial direction X, and restrains out-of-plane deformation of the core material 10. The restraining member 20 has a restraining cylinder portion 21 made of a cylindrical steel pipe and a filling portion 22 made of mortar that fills the entire inside of the restraining cylinder portion 21.

[0028] The restraining cylinder portion 21 is positioned to cover the restraining portions 121 of the plastic deformation portion 11 and the widening portion 12. That is, the core material 10 is coaxially inserted inside the restraining cylinder portion 21, and the connecting ends 122 at both ends protrude from the restraining cylinder portion 21. The axial length X of the restraining member 20 is set to be approximately equal to the combined length of the plastic deformation portion 11 of the core material 10 and the lengths of the restraining portions 121 of both widening portions 12A and 12B.

[0029] As shown in Figure 2, caps 23 are provided at both ends of the restraining cylinder portion 21 in the axial direction X, closing the opening of the restraining cylinder portion 21. The caps 23 prevent the mortar constituting the filling portion 22 (filling material) from flowing out when manufacturing the filling portion 22 (filling material) inside the restraining cylinder portion 21, and also restrict the movement of the filling portion 22 in the axial direction X when the buckling restraining brace 1 is in use.

[0030] The filling portion 22 is formed from mortar that has hardened after being filled into the restraining cylinder portion 21 together with the core material 10. A portion of the core material 10 is embedded in the filling portion 22. The restraining member 20 is provided with an unbonded material (not shown) that is interposed between the core material 10 and the filling portion 22 and allows relative movement between the core material 10 and the filling portion 22 by elastically deforming in accordance with the deformation of the core material 10. Examples of unbonded materials include sheet-like, elastically deformable rubber members. In each of the multiple buckling-restrained braces 1, the filling portion 22 is in close contact with the entire circumference of the unbonded material without any gaps in a cross section perpendicular to the longitudinal direction of the core material 10. The unbonded material elastically deforms when the core material 10 expands or contracts. In this case, since there is no gap between the core material 10 and the filling portion 22, it is possible to adjust the material strength of the core material 10 and the length of the plastic deformation portion 11 based on the target yield deformation angle.

[0031] Furthermore, the core material 10 is set based on the material strength of the plasticized portion 11, or the target yield deformation angle γ of the frame 2A on which the plasticized portion L1 is installed.

[0032] Figure 5 shows the adjustment of the stiffness of the buckling-restrained brace 1, where (a) shows the change in stiffness when the stiffness is increased, and (b) shows the change in stiffness when the stiffness is decreased. In Figures 5(a) and (b), the horizontal axis represents the inter-story deformation δ of the buckling-restrained brace 1, and the vertical axis represents the shear force P applied to the inter-story load of the structural plane on which the buckling-restrained brace 1 is installed. In Figure 5, the slope of the line passing through the origin represents the magnitude of the equivalent stiffness (equivalent tensile stiffness) of the buckling-restrained brace 1. A larger slope (a steeper line) indicates higher equivalent stiffness, and a smaller slope (a flatter line) indicates lower equivalent stiffness. In the buckling-restrained brace 1 of this embodiment described above, the stiffness of the brace (and the shear strength of the buckling-restrained brace 1, described later, based on the stiffness of the brace) can be adjusted to match the magnitude of the target yield deformation angle (i.e., the target yield deformation angle γ).

[0033] As shown in Figure 5(a), the buckling-restrained brace 1 is designed so that the equivalent stiffness can be adjusted by changing the length in the axial direction X (plastic deformation length L1) of the plastic deformation portion 11 of the core material 10. For example, as shown in Figure 5(a), the equivalent stiffness (slope of the line) shown by the dashed-dotted line is higher than that shown by the solid line. Here, in the case of the dashed-dotted line, the plastic deformation length L1 is longer than in the case of the solid line. Note that even when the plastic deformation length L1 is lengthened, the overall length of the core material 10 does not change (it cannot be geometrically changed in relation to the structural plane), so in this case, the length of the widened portion 12 (i.e., the portion with a larger cross-sectional area and stiffness than the plastic deformation portion 11) becomes shorter. By lengthening the plastic deformation length L1 in this way, the stiffness can be increased so that it is at the position of the dashed-dotted line rather than the solid line. When the cross-sectional shape of the core material 10 is flat, the equivalent stiffness is, for example, 1.2 to 1.7 times that of a typical brace. Furthermore, when the cross-sectional shape of the core material 10 is cross-shaped, the equivalent stiffness is, for example, 1.1 to 1.5 times that of a typical brace.

[0034] Furthermore, as shown in Figure 5(b), the equivalent stiffness (slope of the line) shown by the dashed-dotted line is lower than that shown by the solid line. Here, in the case of the dashed-dotted line, a high-strength material is used for the core material 10 compared to the case of the solid line. In this way, the buckling-restrained brace 1 is designed so that the equivalent stiffness can be adjusted by changing the material of the core material 10. That is, by adopting a high-strength material for the core material 10 and increasing the material strength, the stiffness can be reduced. Note that when a high-strength material is adopted, if the axial load-bearing capacity (yield axial force) is to be the same as when a high-strength material is not adopted, the cross-sectional area can be reduced. Reducing the cross-sectional area in this way reduces the equivalent stiffness. For example, by changing the core material 10 from an earthquake-resistant type steel material such as SN490 to a vibration-damping type steel material such as BTHT385, the stiffness can be reduced to 0.84 times. Furthermore, by changing the core material 10 from, for example, SN490 seismic-resistant steel to BTHT440 vibration-damping steel, the rigidity can be reduced to 0.74 times.

[0035] Figure 6 is a diagram illustrating the method for calculating the yield displacement δ of the buckling-restrained brace 1. As shown in Figure 6, the yield displacement δ of the buckling-restrained brace 1 is a fixed value that can be geometrically determined from the length H of the column 25 and the length D of the beam 26 using equation (1). In equation (1), σ is the material strength of the core material 10 of the buckling-restrained brace 1, L is the diagonal length of the frame 2A, and E is Young's modulus. In other words, the yield displacement δ of the buckling-restrained brace 1 can be determined if the brace shape (angle, equivalent stiffness, etc.) and strength are determined.

[0036]

number

[0037] Furthermore, the target yield deformation angle γ of building 2 can be determined by formula (2). For example, in the case of a moderate earthquake (magnitude 5 or higher), the target yield deformation angle γ of building 2 is 1 / 200 (1 / 120) or less. The yield deformation angle γ of a normal brace is approximately 1 / 500. In contrast, the yield deformation angle γ of buckling-restrained brace 1 is 1 / 600 to 1 / 200. That is, with buckling-restrained brace 1, the yield deformation angle γ can be adjusted within the range of 1 / 600 to 1 / 200.

[0038]

number

[0039] (Buckling Restraint Brace Set) In this embodiment, when designing the brace structure in the frame 2A to be installed, a buckling-restrained brace set S consisting of multiple buckling-restrained braces 1 (1Aa, 1Ab, 1Ba, 1Bb, 1Ca, 1Cb, 1Da, 1Db) with different material strengths or axial lengths L of the plastic deformation portion 11 is provided in advance. The buckling-restrained brace set S is provided so that the buckling-restrained brace 1 connected to the frame 2A to be installed can be selected from multiple buckling-restrained braces 1Aa, 1Ab, 1Ba, 1Bb, 1Ca, 1Cb, 1Da, 1Db.

[0040] In this embodiment, the buckling-restrained brace set S consists of four types of steel, and for each type, there are two patterns: a standard member and a member with the maximum equivalent stiffness, for a total of eight buckling-restrained braces 1 (four types of steel × two patterns). The member with the maximum equivalent stiffness for each type of steel is a member that maximizes equivalent stiffness by making the plastic deformation portion 11 as short as possible and the widening portion 12 as long as possible without changing the cross-sectional shape of the plastic deformation portion 11. On the other hand, the standard member for each type of steel is a member that maximizes the achievable inter-story drift angle by making the plastic deformation portion 11 as long as possible and the widening portion 12 as short as possible without changing the cross-sectional shape of the plastic deformation portion 11. The eight braces included in the buckling-restrained brace set S are designated as the 1st brace 1A to the 4th brace 1D for each type of steel. The 1st brace 1A is SN400B, with the standard member indicated by the symbol 1Aa and the member with the maximum equivalent stiffness indicated by the symbol 1Ab. The second brace 1B is made of SN490B, with the standard member indicated by the symbol 1Ba and the member with the highest equivalent stiffness indicated by the symbol 1Bb. The third brace 1C is made of BTHT385B, with the standard member indicated by the symbol 1Ca and the member with the highest equivalent stiffness indicated by the symbol 1Cb. The fourth brace 1D is made of BTHT440B, with the standard member indicated by the symbol 1Da and the member with the highest equivalent stiffness indicated by the symbol 1Db.

[0041] As shown in Figure 6, the material strength or length L1 of the plastic deformation portion 11 of each of the multiple buckling-restrained braces 1 included in the buckling-restrained brace set S may be set based on the target yield deformation angle γ of the frame 2A to which it is installed (corresponding to the inter-story deformation angle γ at yield described later).

[0042] Figure 7 is a diagram illustrating the characteristics of the buckling-restrained brace 1, showing the relationship between the inter-story drift angle γ and the shear force Q for each brace. In Figure 7, the horizontal axis represents the inter-story drift angle γ, and the vertical axis represents the shear force Q. Here, the shear force Q is the shear force input to the structural plane where the buckling-restrained brace 1 is placed. In this graph, the shear force Q is the shear force that the buckling-restrained brace 1 can withstand at the inter-story drift angle γ, and can also be said to represent the shear strength of the buckling-restrained brace 1. Figure 7 shows the standard members (thick lines) and the case where the equivalent stiffness is maximum (thin lines) for each steel material of the buckling-restrained brace S included in the buckling-restrained brace set S.

[0043] Furthermore, Figure 7 also shows a conventional brace (thick solid line), although it is not included in the buckling-restrained brace set S. The conventional brace has only a core material 10 and does not have a restraining member 20. Such a conventional brace avoids buckling under compressive load by increasing its stiffness in order to ensure axial strength, that is, by increasing the second moment of area. As a result, its tensile stiffness (equivalent stiffness) is greater than that of the buckling-restrained brace 1 included in the buckling-restrained brace set S. In contrast, the buckling-restrained brace 1 included in the buckling-restrained brace set S can suppress buckling of the core material 10 when compressed by the restraining member 20. Therefore, the axial strength against compressive load can be increased without changing the cross-sectional shape, such as by making the core material 10 thicker, to increase stiffness. Thus, there is no need to increase the tensile load to prevent buckling, and for example, the length can be adjusted while keeping the cross-sectional area of ​​the plastic deformation portion 11 the same, and the necessary axial strength can be obtained for both compressive and tensile loads.

[0044] Here, the buckling-restrained brace 1 to be installed on the frame 2A is selected from the buckling-restrained brace set S described above to be appropriate for the design. That is, for example, based on the yield deformation angle (target yield deformation angle γ) corresponding to the allowable inter-story drift angle of building 2 during an earthquake and the yield-time inter-story drift angle of the buckling-restrained brace 1, a brace is selected that has the performance to make the yield-time inter-story drift angle of the buckling-restrained brace 1 greater than the earthquake-time inter-story drift angle (target yield deformation angle γ) of building 2.

[0045] (Structural design method for Building 2) Next, we will explain the specific structural design method for the brace structure of Building 2 by selecting buckling-restrained brace 1. Figure 8 is a diagram illustrating the structural design method for the brace structure of Building 2. The structural design method includes a target yield deformation angle setting step S1 (hereinafter also referred to as step S1), a brace specification setting step (hereinafter also referred to as step S2), and a brace insertion amount determination step (hereinafter also referred to as step S3).

[0046] In the target yield deformation angle setting step (step S1), the target yield deformation angle γ, which is the desired yield deformation angle in the frame 2A of building 2, is set. The target yield deformation angle γ is the target yield deformation angle in building 2 and is set based on conditions such as the shape of building 2, floor height, number of stories, size of frame 2A, and magnitude of earthquakes. The target yield deformation angle γ at this time is the yield deformation angle corresponding to the allowable inter-story drift angle of frame 2A during an earthquake.

[0047] Next, in the brace specification setting step (step S2), the shear strength of frame 2A is calculated based on the target yield deformation angle γ of building 2, and the brace specifications are set based on the calculated shear strength. The symbol 2A shown in Figure 8 is a graph showing the relationship between the yield deformation angle γ and the shear force Q in frame 2A. In this graph, the shear force Q is the shear force that frame 2A can withstand at the inter-story drift angle γ, and can be said to represent the shear strength of frame 2A. Step S2 can be said to be the process of obtaining this graph.

[0048] Subsequently, the specifications for the buckling-restrained brace 1 are set based on the shear strength of the frame 2A. Specifically, the material for the core material 10 of the buckling-restrained brace 1 provided in the brace structure is selected. Here, a buckling-restrained brace 1 that does not yield at the target yield deformation angle γ of 1 / 300 in the primary design is selected from the buckling-restrained brace set S. That is, in the buckling-restrained brace set S shown in Figure 7, the third brace 1Ca, the fourth brace 1Da, and 1Db, which have a yield deformation angle greater than 1 / 300, are the candidates for selection, and among them, for example, the third brace 1Ca, a standard member of the steel grade BTHT385B with the greatest equivalent stiffness, is selected. Note that the first brace 1Aa, 1Ab, the second brace 1Ba, 1Bb, and the third brace 1Cb are excluded from selection because they yield at 1 / 300. Furthermore, each of the braces 1A to 1D in the buckling-restrained brace set S differs in the material strength of the core material 10 and the length L1 of the plastic deformation portion 11 of the buckling-restrained brace 1.

[0049] Next, in the brace input amount determination step (step S3), the input amount is determined based on the specifications of the buckling-restrained brace 1 obtained in step S2, which is calculated from the number of buckling-restrained braces 1 and the load-bearing capacity of each buckling-restrained brace 1. Here, the input amount corresponds to the total load-bearing capacity of building 2, which is calculated by multiplying the number of buckling-restrained braces 1 by the load-bearing capacity of each buckling-restrained brace.

[0050] As a result, the shear strength of buckling-restrained brace 1 (the third brace 1Ca selected in step S2) is determined such that the sum of the contribution ratio V1 of frame 2A and the contribution ratio V2 of the third brace 1Cb (V1+V2) equals the design value (here, the primary design shear strength Qt1) of building 2, which is set from the target yield deformation angle γ of building 2. In other words, the specifications of buckling-restrained brace 1 are set (modified) based on the shear strength required for this buckling-restrained brace 1. More specifically, the shear force distribution ratio is set for both frame 2A and buckling-restrained brace 1. In addition, a design value representing the shear strength of building 2 is set corresponding to the target yield deformation angle γ of building 2. In the following, as shown in Figure 8, the shear strength of building 2 during the initial design phase (target yield deformation angle γ = 1 / 300) will be denoted as Qt1. Here, the specifications for buckling-restrained brace 1 are determined such that the sum of the shear force V1 that frame 2A can bear, which is determined based on the shear strength and load-sharing ratio of frame 2A during the initial design phase (target yield deformation angle γ = 1 / 300), and the shear force V2 that the third brace 1Cb can bear, which is determined based on the shear strength and load-sharing ratio of the third brace 1Cb, (V1 + V2) equals the design value (here, the shear strength Qt1 in the initial design phase) which is the shear strength of building 2 set from the target yield deformation angle γ of building 2. In other words, in steps S3 and S4, the specifications of the buckling-restrained brace 1 can be determined based on the shear strength Q of the frame 2A. The specifications of this buckling-restrained brace 1 include, for example, the cross-sectional area of ​​the plastic deformation section 11, the number of structural surfaces (number of arrangements in the entire building (cumulative of frame 2A with and without braces)), the material strength of the core material 10, and the length of the plastic deformation section L1. By changing the specifications of the buckling-restrained brace 1, the relationship between the target yield deformation angle γ and the shear force Q is changed, as shown by the dashed graph line in Figure 8. As a result, for example, the shear strength Qt1 of the primary design of building 2 changes.

[0051] Furthermore, in the case of the shear strength Qt2 of building 2 in the secondary design, the shear strength Q of buckling-restrained brace 1 (the third brace 1Cb selected in step S2) is determined from the sum of the contribution ratio V1 of frame 2A and the contribution ratio V2 of the third brace 1Cb (V1 + V2), just as in the primary design. This allows for the determination of the appropriate amount of buckling-restrained brace 1 for building 2, and enables the design of the brace structure.

[0052] Here, in the case where there are multiple buckling-restrained braces 1, such as in the buckling-restrained brace set S, <1> Like the fourth brace 1Da, a buckling-restrained brace 1 has high axial strength that can accommodate large inter-story drift angles, <2> The advantages of the first brace 1Ab, which has high equivalent stiffness, and the buckling-restrained brace 1 are summarized below. first, <1> The advantages of buckling-restrained braces 1, such as the fourth brace 1Da, which have high axial strength, include (1) easier placement in small quantities, (2) easier to cope with pile pull-out forces, and (3) easier to cope with wind loads and maximum earthquakes.

[0053] Figure 9 shows a method for selecting a buckling-restrained brace 1 from a buckling-restrained brace set S in a building with a small number of structural planes where braces are placed, as shown in Figure 7. If the number of structural elements (structural planes) in building 2 is small and the number of buckling-restrained braces 1 to be placed is small, for example, the target yield deformation angle γ in the primary design can be set to 1 / 250 (the region indicated by symbol R1 in Figure 9), and the buckling-restrained brace 1 of the 4th brace 1Da made of high-strength material BTHT440B steel can be selected. In this way, by using the 4th brace 1Da made of high-strength material, a small number of braces can be placed. In other words, if the target yield deformation angle γ is set to 1 / 250 and high-strength material is not used, the number of braces will increase. Furthermore, a case where the number of buckling-restrained braces 1 is small can be applied, for example, when the number of bracing surfaces is small.

[0054] Figure 10 shows the method for selecting a buckling-restrained brace 1 from a buckling-restrained brace set S in building 2, where a pile is placed directly below the brace, as shown in Figure 7. In building 2, where piles are placed directly beneath the braces, and the amount of buckling-restrained braces 1 to be used in the secondary design is determined, a buckling-restrained brace 1 with a small shear strength Q can be selected from the buckling-restrained brace set S when the target yield deformation angle γ in the primary design is 1 / 300. Here, the second brace 1Ba, the third brace 1Ca, 1Cb, and the fourth brace 1Da, 1Db are the candidates for selection. Of these, the fourth brace 1Da, a standard member of steel type BTHT440B with a small shear strength Q, is selected instead of the second brace 1Ba, which has the highest equivalent stiffness. This makes it possible to reduce the stress generated when an inter-story deformation of 1 / 300, which is the inter-story deformation angle in the primary design, is input from the region indicated by R2 in Figure 10 to the region indicated by R3, thereby reducing the stress input to the buckling-restrained brace 1. Therefore, the pile uplift, which increases in conjunction with the stress on the buckling-restrained brace 1 generated in the primary design, can be reduced.

[0055] Figure 11 shows the method for selecting buckling-restrained brace 1 from buckling-restrained brace set S in Figure 7 for wind load resistance and maximum earthquake resistance. When setting the target yield deformation angle γ of frame 2A to be larger than the inter-story drift angle γ1 required to cope with wind loads, as shown in Figure 11, a buckling-restrained brace 1 can be selected from the buckling-restrained brace set S so that the yield deformation angle is greater than the inter-story displacement and does not become plastic (the region indicated by symbol R4 in Figure 11). Furthermore, in the case of responding to maximum earthquakes, as shown in Figure 11 for wind loads, a buckling-restrained brace 1 can be selected from a buckling-restrained brace set S with a wider elastic range that does not undergo plastic deformation.

[0056] next, <2> One advantage of a buckling-restrained brace 1 with high equivalent stiffness, such as the first brace 1Ab, is that it makes it easier to absorb energy from small amplitudes. Figure 12 shows the method for selecting the buckling-restrained brace 1 from the buckling-restrained brace set S in response to energy absorption from small amplitudes, as shown in Figure 7. In this figure, the energy absorbed by each brace when an inter-story drift angle is input is represented by the size of the area between the graph line corresponding to each brace and the X-axis. For example, when an earthquake with an inter-story displacement angle of 1 / 300 (e.g., a rare earthquake) is input, if a brace with high equivalent stiffness, such as the first brace 1Ab, is selected, energy will be absorbed even after the brace has yielded, equivalent to the area of ​​the region labeled R5 in Figure 12. Therefore, it can be said that a buckling-restrained brace 1 with high equivalent stiffness, such as the first brace 1Ab, is more efficient at absorbing energy from small amplitudes. Thus, when setting the target yield deformation angle γ of the frame 2A within a small range to absorb energy from small amplitudes, as shown in Figure 12, a buckling-restrained brace 1 can be selected from the buckling-restrained brace set S to create a vibration-damping structure, such that it falls within the energy absorption range (the region indicated by symbol R5 in Figure 12) at the set target yield deformation angle γ. This approach is particularly effective when designing using the so-called energy method (seismic design calculation method based on energy balance). The energy method is a method stipulated in Ministry of Land, Infrastructure, Transport and Tourism Notification No. 631 of 2005.

[0057] Next, the function of the building's structural design method described above will be explained in detail based on the drawings. According to the structural design method for building 2 of this embodiment, based on the target yield deformation angle γ of the frame 2A of building 2 obtained in the target yield deformation angle setting step (step S1), the shear strength Q of the frame 2A is calculated in the brace specification setting step (steps S2 and S3), the specifications of the buckling-restrained brace 1 are set, and further, in the brace input amount determination step (step S4), the amount of buckling-restrained brace 1 to be used is determined based on the specifications of the buckling-restrained brace 1. In other words, with this structural design method, a buckling-restrained brace 1 suitable from the viewpoint of the target yield deformation angle γ of the frame 2A of building 2 can be designed, and the force borne solely by the buckling-restrained brace 1 is not concentrated. Therefore, it is not necessary to perform repeated designs, and the selection of the buckling-restrained brace 1 can be performed easily and reliably, improving design efficiency and reducing the time required for design.

[0058] Furthermore, in this embodiment, the target yield deformation angle γ is the yield deformation angle corresponding to the allowable inter-story drift angle of frame 2A during an earthquake. This allows for the selection of the core material 10 of the buckling-restrained brace 1 based on the inter-story drift angle in the structural plane of frame 2A, and the calculation of the shear strength of frame 2A to determine the specifications of the buckling-restrained brace 1. Therefore, it eliminates the need for iterative design and allows for more accurate determination of the brace, thereby significantly reducing the time required for design.

[0059] Furthermore, in this embodiment, in the brace specification setting step, the amount of buckling-restrained brace 1 is determined in the brace input amount determination step (step S4), thereby determining the ratio of the frame 2A and the buckling-restrained brace 1 that satisfy the calculated shear strength of the frame 2A. This allows for the design of the building 2 to meet the design value for shear strength by determining the amount of buckling-restrained brace 1 to be used, and the ratio of load sharing between buckling-restrained brace 1 and frame 2A can be determined. As a result, repeated design work is not required until the optimal brace is determined, due to the cross-sectional area of ​​buckling-restrained brace 1 becoming too large and causing excessive force concentration on buckling-restrained brace 1, thus enabling efficient design.

[0060] In this embodiment, the buckling-restrained brace 1 comprises a long core material 10 whose ends are connected to the frame 2A, and a restraining member 20 that suppresses buckling of the core material 10. The core material 10 has a plastic deformation portion 11. In this case, since the restraining member 20 suppresses buckling, a buckling-restrained brace 1 having a core material 10 that is prone to buckling during compression (low compressive stiffness) can be used, thereby expanding the range in which the yield deformation angle can be selected. In other words, in the case of a buckling-restrained brace 1, even if the core material 10 is made thinner, the problem of buckling due to compression is less likely to occur, and the cross-sectional area can be reduced by using a material with high yield strength for the core material 10. Therefore, a building 2 with a large yield deformation angle can be designed while maintaining the same axial load-bearing capacity (cross-sectional area × yield strength), thereby improving the design flexibility of the building 2.

[0061] Furthermore, in this embodiment, in the brace specification setting step, the material strength of the plastic deformation portion 11 of the buckling-restrained brace 1 is set as a specification. This allows selection from multiple buckling-restrained braces 1 with different material strengths in the plastic deformation portion 11 of the core material 10, thereby increasing the options for determining the brace specifications and broadening the range of selections.

[0062] Furthermore, in this embodiment, in the brace specification setting step, the length L1 of the plastic deformation portion 11 in the core material 10 of the buckling-restrained brace 1 is set as a specification. This allows selection from multiple buckling-restrained braces 1 with different lengths L1 of the plastic deformation portion 11 in the core material 10, thereby increasing the options for determining the brace specifications and broadening the range of selections.

[0063] In the building structural design method according to the embodiment described above, design efficiency can be improved and the time required for design can be reduced by easily and reliably selecting braces without having to perform iterative design.

[0064] Although embodiments of the building structural design method according to the present invention have been described above, the present invention is not limited to the above embodiments, and it is possible to replace the components in the above embodiments with well-known components as appropriate without departing from the spirit of the invention.

[0065] For example, in the embodiment described above, the buckling-restrained brace 1 is the target of the brace structure design, but it is not limited to the buckling-restrained brace 1, and conventional braces can also be used as the target.

[0066] Furthermore, in this embodiment, the method for determining the buckling-restrained brace 1 in the brace specification setting step of the building structural design method is to use a buckling-restrained brace set S. However, the design method using a buckling-restrained brace set S is just one example, and the method is not limited to using such a buckling-restrained brace set S. [Explanation of Symbols]

[0067] 1. Buckling-restrained brace 2 buildings 2A Frame 10 Core material 11 Plasticization part 12 Widening section (end) 13 Buckling restraint material 20 Restraining member 21 Restraint cylinder part 22 Filling section (filling material) 23 Lid material S Buckling Restraint Brace Set γ Target yield deformation angle of the building δ Interlayer deformation (brace yield displacement) σ Core material strength P: Shear force Length of H column D Length of the beam L-shaped diagonal length of the frame L1 Length of the plasticized portion E Young's modulus Q Shear strength Qt1 Primary design shear strength Shear strength of Qt2 secondary design V1 Frame share V2 brace distribution X-axis direction

Claims

1. A structural design method for a building equipped with a bracing structure, A target yield deformation angle setting step, which sets a target yield deformation angle, which is a desired yield deformation angle in the frame of the building, A brace specification setting step involves calculating the shear strength of the frame based on the target yield deformation angle and setting the brace specifications based on the shear strength, A brace input amount determination step, which determines the number of braces and the amount to be input based on the brace specifications and the brace load capacity, A structural design method for buildings having [specific characteristics / features].

2. The structural design method for a building according to claim 1, wherein the target yield deformation angle is the yield deformation angle corresponding to the allowable value of the inter-story drift angle of the frame during an earthquake.

3. The structural design method for a building according to claim 1 or 2, wherein in the step of determining the amount of brace to be used, the amount of brace to be used is determined, thereby determining the ratio of the frame and the brace that satisfies the calculated shear strength of the frame.

4. The brace is a buckling-restrained brace comprising a long core material whose ends are connected to the frame, and a restraining member that suppresses buckling of the core material. The structural design method for a building according to claim 1 or 2, wherein the core material has a plasticized portion.

5. The building structural design method according to claim 4, wherein in the brace specification setting step, the material strength of the plastic portion of the buckling-restrained brace is set as the specification.

6. The building structural design method according to claim 4, wherein in the brace specification setting step, the length of the plastic portion of the buckling-restrained brace is set as the specification.

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