Design device for steel beams, design method for steel beams, design program for steel beams, and steel beams

Abstract

This invention provides a design device for steel beams that ensures the energy from seismic forces acting on the steel beams is reliably absorbed by the end beams. [Solution] The steel beam design device 50 comprises a central beam and end beams joined to the central beam at at least one end in the axial direction of the central beam and also joined to a column, and includes a cross-sectional area design unit 51a that designs the steel beam to satisfy a mathematical formula, and a plastic deformation design unit 51b that designs the end beam to have a plastic deformation region due to bending moment when an external seismic force acts on the steel beam.

Description

Technical Field

[0001] The present invention relates to a steel frame beam design device, a steel frame beam design method, a steel frame beam design program, and a steel frame beam.

Background Art

[0002] Conventionally, as a form of joining a steel frame beam composed of H-shaped steel to a column, a bracket form can be cited (for example, see Patent Document 1). The bracket form is a form in which the end of the steel frame beam (hereinafter referred to as the end beam) is joined to the column by welding or the like. In the case of this bracket form, cost reduction of the steel frame beam has been attempted by reducing the plate thickness of the central part of the steel frame beam (hereinafter referred to as the central beam), where the acting external force is relatively small.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the cross-sectional area of the central beam is made smaller than that of the end beam, the yield strength of the central beam decreases as the cross-sectional shape of the steel frame beam changes. Therefore, unexpected shear yielding or bending yielding due to seismic external forces may occur in the central beam.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a steel frame beam design device, a steel frame beam design method, a steel frame beam design program, and a steel frame beam designed by these, which can surely absorb the energy due to seismic external forces by the end beam when seismic external forces act on the steel frame beam.

Means for Solving the Problems

[0006] To solve the above problems, the present invention proposes the following means. (1) Aspect 1 of the present invention is a design device for a steel beam comprising a central beam and an end beam joined to the central beam at at least one end in the material axis direction of the central beam and joined to a column, the design device for a steel beam comprising: a cross-sectional area design unit that designs the steel beam so as to satisfy formula (1); and a plasticization design unit that designs the end beam so as to have a plasticization region due to a bending moment when seismic external force acts on the steel beam. Here, A1 is the cross-sectional area of the end beam, and A2 is the cross-sectional area of the central beam.

[0007] [Number]

[0008] (2) Aspect 2 of the present invention is a design method for a steel beam comprising a central beam and an end beam joined to the central beam at at least one end in the material axis direction of the central beam and joined to a column, the design method for a steel beam comprising: a cross-sectional area design step of designing the steel beam so as to satisfy formula (2); and a plasticization design step of designing the end beam so as to have a plasticization region due to a bending moment when seismic external force acts on the steel beam. Here, A1 is the cross-sectional area of the end beam, and A2 is the cross-sectional area of the central beam.

[0009] [Number]

[0010] (3) Aspect 3 of the present invention is a design program for a design device for designing a steel beam comprising a central beam and an end beam joined to the central beam at at least one end in the material axis direction of the central beam and joined to a column, the design program causing the design device to function as: a cross-sectional area design unit that designs the steel beam so as to satisfy formula (3); and a plasticization design unit that designs the end beam so as to have a plasticization region due to a bending moment when seismic external force acts on the steel beam. However, A1 is the cross-sectional area of ​​the end beam, and A2 is the cross-sectional area of ​​the central beam.

[0011]

number

[0012] Note that equation (1) is identical to equations (2) and (3). In these inventions, a steel beam comprising a central beam and end beams is configured such that the end beams are connected to columns. The cross-sectional area design department (in the cross-sectional area design process) designs the steel beam such that equation (1) is satisfied, where the cross-sectional area A1 of the end beams is greater than the cross-sectional area A2 of the central beam. The plastic deformation design department (in the plastic deformation design process) designs the steel beam such that when seismic forces act on it, the end beams have a region of plastic deformation due to bending moment. Therefore, even if the cross-sectional configuration is designed to satisfy equation (1), when seismic forces act on the steel beam, the plastic deformation region of the end beam absorbs the energy caused by the seismic forces. For this reason, the energy caused by seismic forces can be reliably absorbed by the end beam.

[0013] (4) Embodiment 4 of the present invention may be the steel beam design apparatus described in (1), which includes a central bending elastic design unit that designs the steel beam to satisfy equations (11) and (12) and the central beam to remain within the elastic range with respect to bending moment. However, A f1 The total cross-sectional area of ​​the pair of flanges of the end beam, A f2 b2 is the total cross-sectional area of ​​the pair of flanges of the central beam, b2 is half the width of the flanges of the central beam, and t f2 F is the plate thickness of the flange of the central beam. f2 This is the reference strength of the material strength of the flange of the central beam.

[0014]

number

[0015] (5)Aspect 5 of the present invention may be a design method for a steel beam as described in (2), comprising a central bending elasticity design step of designing such that the steel beam satisfies equations (13) and (14) and the central beam remains within the elastic range with respect to the bending moment. However, A f1 is the total cross-sectional area of the pair of flanges of the end beam, A f2 is the total cross-sectional area of the pair of flanges of the central beam, b2 is half the length of the width of the flange of the central beam, t f2 is the plate thickness of the flange of the central beam, F f2 is the reference strength of the material strength of the flange of the central beam.

[0016]

Number

[0017] (6)Aspect 6 of the present invention may be a design program for a steel beam as described in (3), which causes the design device to function as a central bending elasticity design unit that designs such that the steel beam satisfies equations (15) and (16) and the central beam remains within the elastic range with respect to the bending moment. However, A f1 is the total cross-sectional area of the pair of flanges of the end beam, A f2 is the total cross-sectional area of the pair of flanges of the central beam, b2 is half the length of the width of the flange of the central beam, t f2 is the plate thickness of the flange of the central beam, F f2 is the reference strength of the material strength of the flange of the central beam.

[0018]

Number

[0019] Note that equation (11) is the same as equations (13) and (15), and equation (12) is the same as equations (14) and (16). In these inventions, the central bending elasticity design unit (in the central bending elasticity design step), in the steel beam, the total cross-sectional area A of the pair of flanges of the end beam f1The total cross-sectional area A of the pair of flanges of the central beam f2 Design to satisfy equation (11), which states that the width-to-thickness ratio of the flange of the central beam is greater than the value specified for the flange of type FB of "beams / H-shaped steel" in Article 3 of Public Notice No. 1792 of 1980 (hereinafter referred to as the Public Notice). Furthermore, design so that the central beam remains within the elastic range with respect to bending moment. Therefore, even if the cross-sectional configuration is designed to satisfy equation (11) and the flange width-to-thickness ratio is designed to satisfy equation (12), the central beam remains within the elastic range with respect to bending moments. This prevents the central beam from bending and yielding under bending moments.

[0020] (7) Embodiment 7 of the present invention may be a steel beam design device according to (1) or (4), comprising a central shear elastic design unit that designs the steel beam to satisfy equations (21) and (22) and the central beam to remain within the elastic range with respect to shear force. However, A w1 A is the cross-sectional area of ​​the web of the end beam. w2 d2 is the cross-sectional area of ​​the web of the central beam, d2 is the height of the web of the central beam, and t w2 F is the thickness of the web of the central beam. w2 This is the reference strength of the material strength of the web of the central beam.

[0021]

number

[0022] (8) Embodiment 8 of the present invention may be the steel beam design method according to (2) or (5), comprising a central shear elastic design step of designing the steel beam so that it satisfies equations (23) and (24) and the central beam remains within the elastic range with respect to shear force. However, A w1 A is the cross-sectional area of ​​the web of the end beam. w2 d2 is the cross-sectional area of ​​the web of the central beam, d2 is the height of the web of the central beam, and t w2F is the thickness of the web of the central beam. w2 This is the reference strength of the material strength of the web of the central beam.

[0023]

number

[0024] (9) Embodiment 9 of the present invention may be a design program for a steel beam as described in (3) or (6), wherein the design device functions as a central shear elastic design unit that designs the steel beam to satisfy equations (25) and (26) and the central beam to remain within the elastic range with respect to shear force. However, A w1 A is the cross-sectional area of ​​the web of the end beam. w2 d2 is the cross-sectional area of ​​the web of the central beam, d2 is the height of the web of the central beam, and t w2 F is the thickness of the web of the central beam. w2 This is the reference strength of the material strength of the web of the central beam.

[0025]

number

[0026] Note that equation (21) is identical to equations (23) and (25), and equation (22) is identical to equations (24) and (26). In these inventions, the central shear elastic design unit (in the central shear elastic design process) determines the cross-sectional area A of the web of the end beam in a steel beam. w1 The cross-sectional area A of the web of the central beam w2 Design to satisfy equation (21), which states that it is greater than [the specified value]. Design the web of the central beam to satisfy equation (22), which states that the width-to-thickness ratio is greater than the value specified in the notification for the web of type FB, "beam / H-shaped steel". Furthermore, design the central beam so that it remains within the elastic range against shear force. Therefore, even if the cross-sectional configuration is designed to satisfy equation (21) and the web width-to-thickness ratio is designed to satisfy equation (22), the central beam remains within the elastic range against shear forces. This prevents the central beam from shear yielding under shear forces.

[0027] (10) Embodiment 10 of the present invention may be a steel beam designed by a steel beam design device described in any one of (1), (4), and (7). (11) Embodiment 11 of the present invention may be a steel beam designed by the steel beam design method described in any one of (2), (5), and (8). (12) Embodiment 12 of the present invention may be a steel beam designed by the steel beam design program described in any one of (3), (6), and (9).

[0028] In these inventions, when seismic forces act on a steel beam, the plastic deformation of the steel beam due to the seismic forces is limited to the end beams, thereby enabling economical design by reducing the cross-sectional area of ​​the central beam while reliably absorbing seismic energy. [Effects of the Invention]

[0029] The present invention relates to a steel beam design apparatus, a steel beam design method, a steel beam design program, and a steel beam in which, when an earthquake force acts on the steel beam, the energy due to the earthquake force can be reliably absorbed by the end beams. [Brief explanation of the drawing]

[0030] [Figure 1] This is a side view of a column-beam joint structure using a steel beam according to one embodiment of the present invention. [Figure 2] This diagram models the conditions under which a steel beam is subjected to inversely symmetrical bending. [Figure 3] This figure shows the results of the study to determine whether or not the central beam will bend and yield. [Figure 4] This figure shows the results of the study to determine whether or not the central beam will shear yield. [Figure 5]This figure shows an overview of an example of a steel beam design apparatus according to this embodiment. [Figure 6] This flowchart shows an example of a design method for steel beams in this embodiment. [Figure 7] This flowchart shows an example of a specific steel beam design method. [Modes for carrying out the invention]

[0031] Hereinafter, a design apparatus for steel beams, a design method for steel beams, a design program for steel beams, and an embodiment of a steel beam according to the present invention will be described with reference to Figures 1 to 7.

[0032] [1. Structure of steel beams] As shown in Figure 1, the steel beam 10 of this embodiment is used in the column-beam joint structure 1. The column-beam joint structure 1 comprises a pair of columns 5 and a steel beam 10. The composition of column 5 is not limited. For example, column 5 is made of reinforced concrete (RC). Column 5 extends in the vertical direction. A pair of columns 5 are arranged spaced apart from each other along the horizontal plane. Furthermore, the material used to form column 5 is not limited to reinforced concrete; it may also be square steel pipe, welded box section, H-beam, reinforced steel concrete (SRC), etc.

[0033] The steel beam 10 extends along the horizontal plane. In this embodiment, the steel beam 10 includes a central beam 11, a pair of end beams 21, and beam connecting members 31. The central beam 11 and the end beams 21 are made of steel and are formed from H-shaped steel. For example, the central beam 11 and the pair of end beams 21 are formed from rolled H-shaped steel. The central beam 11 has a pair of central flanges 12 and 13 and a central web 14.

[0034] The central flanges 12, 13 and the central web 14 are formed in a flat plate shape. The central flanges 12 and 13 are positioned opposite each other in the vertical direction. The central flange 12 is positioned above the central flange 13. The central web 14 is positioned between the central flange 12 and the central flange 13. The central web 14 is joined to the intermediate portion in the width direction of the central flange 12 and the intermediate portion in the width direction of the central flange 13, respectively.

[0035] The end beam 21 has a pair of end flanges 22, 23 and an end web 24. The end flanges 22, 23 and the end web 24 are formed in a flat plate shape. The end flanges 22 and 23 are arranged to face each other in the vertical direction. End flange 22 is positioned above end flange 23. The end web 24 is positioned between the end flange 22 and the end flange 23. The end web 24 is joined to the intermediate portion in the width direction of the end flange 22 and the intermediate portion in the width direction of the end flange 23, respectively.

[0036] The pair of end beams 21 are positioned to sandwich the central beam 11 in the direction of the material axis Z. For example, the beam connecting member 31, although not shown in the figure, includes a joint plate, high-strength bolts, etc. The pair of end beams 21 are joined to the central beam 11 at both ends in the material axis direction Z of the central beam 11 by the beam connecting members 31. The material axis direction Z is also the material axis direction of the entire steel beam 10. The pair of end beams 21 are joined to the column 5 by a column connecting member (not shown) having a joint plate, high-strength bolts, etc. The pair of end beams 21 constitute a bracket.

[0037] Here, the thickness direction of the webs 14 and 24 in the steel beam 10 is defined as the width direction X. In the steel beam 10, the direction in which the central flanges 12 and 13 face each other, and the direction in which the end flanges 22 and 23 face each other, are defined as the height direction Y. Alternatively, the steel beam 10 may not have one end beam 21, and the central beam 11 may be extended in the direction Z of the material axis where the one end beam 21 was located, with the extended portion of the central beam 11 not being connected to the column 5. In this case, the column-beam connection structure 1 has only one column 5, and for example, at the end of the extended central beam 11, only the central web 14 is pin-connected to a beam (not shown).

[0038] Here, the specifications of the steel beam 10 are defined. Regarding the central beam 11, the plate thickness of the central flanges 12 and 13 is t f2 (mm) is specified. The length of half the width (length in the width direction X) of each of the central flanges 12 and 13 is specified as b2 (mm). Length b2 is half the width of each of the central flanges 12 and 13. The thickness of the central web 14 is t w2 The height of the central web 14 (length in the height direction Y) is defined as d2 (mm). The cross-sectional area of ​​the central beam 11, defined by the plane perpendicular to the material axis Z, is A2 (mm²). 2 ) is stipulated. The total cross-sectional area of ​​the central flanges 12 and 13, defined by the plane perpendicular to the material axis Z, is A f2 (mm 2 ) is defined as follows: The cross-sectional area of ​​the central web 14 by a plane perpendicular to the material axis Z is A w2 (mm 2 ) is defined as follows. The cross-sectional area A2 is (A f2 +A w2 It is equal to ). The standard strength of the material strength of the central flanges 12 and 13 is F f2 (N / mm) is specified. The standard strength of the material strength of the central web 14 is F w2 It is specified as (N / mm).

[0039] The cross-sectional area of ​​the end beam 21, defined by the plane perpendicular to the material axis Z, is A1 (mm²). 2 ) is defined as follows. For the end beam 21, the total cross-sectional area of ​​the end flanges 22 and 23 formed by planes perpendicular to the material axis Z is defined as A f1 (mm 2) is defined as follows: The cross-sectional area of ​​the end web 24 by a plane perpendicular to the material axis Z is A w1 (mm 2 ) is defined as follows. The cross-sectional area A1 is (A f1 +A w1 It is equal to ). The length Z in the axial direction of the steel beam 10 is L(mm) 2 ) is stipulated.

[0040] Generally, steel beams 10 are designed to satisfy equation (31). Furthermore, it is preferable that the steel beam 10 be designed to satisfy at least one of equations (32) and (33).

[0041]

number

[0042] Thus, the cross-sectional shape of the central beam 11 and the cross-sectional shape of the end beams 21 are different. The central beam and the pair of end beams may be formed from welded H-shaped steel. In this case, the central web of the central beam and the end webs of the pair of end beams may be integrally formed from a single steel plate, and the steel beam may be constructed by welding the pair of central flanges and the pair of end flanges to this steel plate.

[0043] [2. Examination of energy absorption by steel beams] The following describes the results of our study on the energy absorption of the steel beam 10. In the central beam 11, (A) a comparison was made between cases where bending yield occurred and cases where it did not, and (B) a comparison was made between cases where shear yield occurred and cases where it did not.

[0044] In the following analysis, we performed the analysis under the conditions (1) to (3) below. (1) Elastoplastic analysis was performed using FEM (Finite Element Method). (2) As shown in Figure 2, the conditions under which the steel beam 10 undergoes inverse symmetric bending when seismic external forces (external forces due to earthquakes) act on it were modeled. Specifically, boundary conditions were given to both ends of the steel beam 10 in the material axis direction Z, namely the fixed end (hereinafter also referred to as the end on the column 5A side) and the fixed roller end (hereinafter also referred to as the end on the column 5B side). That is, at both ends of the steel beam 10 in the material axis direction Z, movement in the width direction X and height direction Y, and rotation around the width direction X and height direction Y were constrained relative to the column 5. Furthermore, movement in the material axis direction Z was constrained at only one end, leaving the other end free, while rotation around the material axis direction Z was constrained at both ends. Loading was performed by applying a forced downward displacement to the fixed roller end side as described above. When a forced displacement of δ (mm) is applied downward to the end of the steel beam 10 on the column 5B side, the end of the steel beam 10 on the column 5A side is displaced by member angle θ (rad). The member angle θ is the value of (δ / L).

[0045] (3) The stress-strain relationship of the steel beam 10 is that of 490N class steel commonly used for beams (standard strength F of allowable stress is 325 N / mm²). 2 ) was applied. (4) The cross-sectional shapes and lengths of the end beams 21 and the central beam 11 were adjusted so that the presence or absence of bending yield and shear yield of the central beam 11 could be compared.

[0046] [2.1.(A) Examination of whether the central beam will bend and yield] The cross-sectional shape of the end beams 21 was H-900×300×16×19 and the cross-sectional shape of the central beam 11 was H-900×250×12×14 when the central beam 11 underwent bending yield. The length L of the steel beam 10 was set to 8000 mm. The lengths of the central beam 11 and the end beams 21 were adjusted so that bending yield would occur in the central beam 11. On the other hand, when the central beam 11 does not yield in bending, the cross-sectional shape of the end beams 21 is H-900×275×16×16, and the cross-sectional shape of the central beam 11 is H-900×275×12×14. The length L of the steel beam 10 is 8000 mm. In this case, the steel beam 10 satisfies equations (31), (32), and (36).

[0047]

number

[0048] (36) is a condition specified in the notification for the flange type to be FC or FD. The length of the central beam 11 and the length of the end beams 21 were adjusted to prevent bending yield from occurring in the central beam 11. The results of the study are shown in Figure 3. In Figure 3, the horizontal axis represents (θ / θp) and the vertical axis represents (M / Mp). Here, M represents the bending moment (N·mm) at the end of the steel beam 10 in the material axis direction Z. Mp represents the full plastic moment (N·mm) at the end of the steel beam 10 in the material axis direction Z. θp represents the elastic member angle (rad) calculated for the full plastic moment Mp based on the cross-sectional shape and length of the steel beam 10.

[0049] When the central beam 11 yielded by bending, its length was 6000 mm, and the length of each end beam 21 was 1000 mm. When the central beam 11 did not yield by bending, its length was 4000 mm, and the length of each end beam 21 was 2000 mm.

[0050] If the central beam 11 yields in bending, no plastic deformation occurs in the end beams 21, which are expected to absorb energy through plastic deformation. Furthermore, plastic deformation of the steel beam 10 proceeds with a considerably low load-bearing capacity. On the other hand, if the central beam 11 does not yield in bending, energy absorption due to plastic deformation in the end beams 21 has been confirmed. As a result, the cross-section of the central beam 11 can be made lighter while still exhibiting stable performance against seismic forces.

[0051] [2.2.(B) Examination of whether the central beam will yield under shear] The cross-sectional shape of the end beams 21 was H-900×300×16×32 when the central beam 11 underwent shear yielding, and the cross-sectional shape of the central beam 11 was H-900×300×12×32. The length L of the steel beam 10 was set to 4000 mm. The lengths of the central beam 11 and the end beams 21 were adjusted so that shear yielding would occur in the central beam 11. On the other hand, when the central beam 11 does not shear yield, the cross-sectional shape of the end beams 21 is H-900×250×16×19, and the cross-sectional shape of the central beam 11 is H-900×250×12×19. The length L of the steel beam 10 is 4000 mm. In this case, the steel beam 10 satisfies equations (31), (33), and (37).

[0052]

number

[0053] Formula (37) is a condition specified in the notification for the web type to be FC or FD. The length of the central beam 11 and the length of the end beams 21 were adjusted so that shear yielding would not occur in the central beam 11. The results of the study are shown in Figure 4. In Figure 4, the horizontal axis represents (θ / θp) and the vertical axis represents (M / Mp). In both cases, whether the central beam 11 underwent shear yielding or not, the length of the central beam 11 was 2000 mm, and the length of each end beam 21 was 1000 mm.

[0054] When the central beam 11 undergoes shear yielding, plastic deformation does not occur in the end beams 21, which are expected to absorb energy through plasticity. Furthermore, the load-bearing capacity of the steel beam 10 decreases as a result of the shear yielding of the central beam 11. On the other hand, if the central beam 11 does not shear yield, energy absorption due to plastic deformation in the end beams 21 has been confirmed. As a result, the cross-section of the central beam 11 can be made lighter while still exhibiting stable performance against seismic forces.

[0055] [3. Design device for steel beams] Figure 5 shows an example of a steel beam design device (hereinafter simply referred to as the design device) 50 of this embodiment. The design device 50 is a computer and comprises a CPU (Central Processing Unit) 51, a main memory 55, an auxiliary memory 60, an input / output interface (IO / I / F) 65, and a recording / playback device 70. The CPU 51, main memory 55, auxiliary memory 60, input / output interface 65, and recording / playback device 70 are connected to each other by a bus 75.

[0056] The main memory 55 is RAM (Random Access Memory) or the like, which serves as the work area for the CPU 51. The input / output interface 65 is connected to an input device 66 such as a keyboard or mouse, and a display device 67. The recording and playback device 70 records and plays back data to and from a recording medium 71 such as a USB (Universal Serial Bus) memory.

[0057] The auxiliary storage device 60 is an SSD (Solid State Drive) or the like, which stores various data and programs. The auxiliary storage device 60 stores the steel beam design program (hereinafter simply referred to as the design program) 61 for making the computer function as a design device 50, as well as various other programs such as the OS program. The design program 61 and other programs are imported from the recording medium 71 to the auxiliary storage device 60 via the recording and playback device 70. The design program 61 and the like are stored on the recording medium 71. These programs may also be imported into the auxiliary storage device 60 from an external device via a disc-type recording medium such as a CD or DVD, or via a communication device (not shown).

[0058] The CPU 51 performs various calculation processes. Functionally, the CPU 51 has a cross-sectional area design unit 51a, a plastic deformation design unit 51b, a central bending elasticity design unit 51c, and a central shear elasticity design unit 51d. The cross-sectional area design section 51a designs the steel beam 10 so that it satisfies equation (31). The plastic deformation design unit 51b designs the end beam 21 such that when an external seismic force acts on the steel beam 10, the end beam 21 has a plastic deformation region due to the bending moment generated by the external seismic force. The plastic deformation region referred to here means the region in which the material has undergone plastic deformation. The central bending elastic design section 51c designs the steel beam 10 to satisfy equations (32) and (36), and the central beam 11 to remain within the elastic range with respect to the bending moment generated by seismic external forces. Remaining within the elastic range here means not undergoing plastic deformation. The central shear elastic design unit 51d designs the steel beam 10 to satisfy equations (33) and (37), and the central beam 11 to remain within the elastic range against shear forces generated by seismic forces.

[0059] The functional components of the CPU 51, namely the cross-sectional area design unit 51a, the plastic deformation design unit 51b, the central bending elasticity design unit 51c, and the central shear elasticity design unit 51d, function when the CPU 51 executes a design program 61 and the like stored in the auxiliary storage device 60. The design program 61 is a program for the design device 50 that designs the steel beam 10. The design program 61 causes the design device 50 to function as the cross-sectional area design unit 51a, the plastic deformation design unit 51b, the central bending elasticity design unit 51c, and the central shear elasticity design unit 51d.

[0060] [4. Design Methods for Steel Beams] As shown in Figure 6, the steel beam design method (hereinafter simply referred to as the design method) S1 of this embodiment comprises a cross-sectional area design step S5, a plastic deformation design step S6, a central bending elasticity design step S7, and a central shear elasticity design step S8. The cross-sectional area design process S5 is to design the steel beam 10 so that it satisfies equation (31). The plastic deformation design process S6 is designed so that when an external seismic force acts on the steel beam 10, the end beam 21 has a plastic deformation region due to the bending moment generated by the external seismic force. The central bending elastic design process S7 is designed so that the steel beam 10 satisfies equations (32) and (36), and the central beam 11 remains within the elastic range against bending moments caused by seismic forces. The central shear elastic design process S8 is designed so that the steel beam 10 satisfies equations (33) and (37), and the central beam 11 remains within the elastic range against shear forces generated by seismic forces.

[0061] By performing the above steps, all steps of design method S1 are completed, and the steel beam 10 is designed.

[0062] [5. Steel Beams] The steel beam 10 in this embodiment is designed by the design device 50. Alternatively, the steel beam 10 in this embodiment may be designed by the design method S1. The steel beam 10 in this embodiment may also be designed by the design program 61.

[0063] [6. Specific examples of steel beam design methods] The following describes a specific example of the design method of this embodiment. For example, when a building has multiple floors and multiple steel beams, the following design method is performed in parallel for each steel beam. In the following explanation, we will assume that one of the multiple steel beams is steel beam 10. For example, seismic forces are determined based on "Commentary on Technical Standards for Structural Structures of Buildings, 2020 Edition," edited by the Japan Building Administration Information Center and the Japan Building Disaster Prevention Association, published by the National Official Gazette Sales Cooperative Association.

[0064] As shown in Figure 7, first, in step S10, the cross-sectional shape of the central beam 11, the cross-sectional shape of the end beams 21, the type of steel used for the steel beams 10, and the length L of the steel beams 10 are determined. Once step S10 is completed, the process proceeds to step S11. Next, in step S11, the full plastic bending strength and full plastic shear strength of the central beam 11 and the end beams 21 are calculated. Note that the full plastic bending strength is equal to the full plastic moment Mp. The full plastic shear strength is equal to (the total cross-sectional area A of the web). w It is calculated as ) × (standard strength F of the web material strength ÷ √3). Once step S11 is completed, the process moves on to step S12.

[0065] Here, in step S10, when determining the length L of the steel beam 10, if both ends of the steel beam are connected to columns, for example, using the length L of the steel beam calculated by dividing twice the full plastic moment of the end beam by the full plastic shear strength of the central beam, and multiplying this by the strength increase rate from the full plastic moment of the end beam assumed in the design (for example, 1.2), can reduce the need for rework in step 15 described later. Furthermore, if only one end of the steel beam is connected to the column, the same calculation can be performed by considering twice the full plastic moment as 1.

[0066] Next, in step S12, the seismic external force acting on the steel beam 10 is determined. Once step S12 is completed, the process proceeds to step S13. Next, in step S13, it is determined whether the end beam 21 has a region of plastic deformation due to bending moment when the steel beam 10 undergoes plastic deformation due to seismic external force. If the result in step S13 is YES, the process proceeds to step S14; if the result is NO, the process proceeds to step S10. When moving from step S13 to step S10, for example, the cross-sectional area A of the end flanges 22 and 23 f1 It is preferable to reduce this value. Even if the end beam 21 has a plastic deformation region due to shear force, this state is unstable and therefore not considered in step S13.

[0067] Next, in step S14, it is determined whether the central beam 11 maintains elasticity against the bending moment. If the result in step S14 is YES, the process proceeds to step S15; if the result is NO, the process proceeds to step S10. When moving from step S14 to step S10, for example, the cross-sectional area A of the central flanges 12 and 13 f2 It is preferable to increase the size.

[0068] Next, in step S15, it is determined whether the central beam 11 maintains elasticity against shear force. If the result in step S15 is YES, all steps of design method S2 are completed and the steel beam 10 is designed. On the other hand, if the result in step S15 is NO, the process proceeds to step S10. When transitioning from step S15 to step S10, for example, the cross-sectional area A of the central web 14 w2 It is preferable to increase the size.

[0069] In step S13, known simulation software can be used to determine whether or not a plastic deformation region exists, and in steps S14 and S15, known simulation software can be used to determine whether or not elasticity is maintained. The design method S2 is repeated until multiple steel beams are designed, at which point the building is designed.

[0070] [7. Effects of this embodiment] As described above, in the design apparatus 50, design method S1, and design program 61 of this embodiment, in a steel beam 10 comprising a central beam 11 and end beams 21, the end beams 21 are connected to the columns 5. The cross-sectional area design unit 51a (in the cross-sectional area design process S5) designs the steel beam 10 such that equation (31) is satisfied, where the cross-sectional area A1 of the end beam 21 is greater than the cross-sectional area A2 of the central beam 11. The plastic deformation design unit 51b (in the plastic deformation design process S6) designs the steel beam 10 such that when an external seismic force acts on it, the end beams 21 have a plastic deformation region due to the bending moment. Therefore, even if the cross-sectional configuration is designed to satisfy equation (31), when an earthquake force acts on the steel beam 10, the plastic deformation region of the end beam 21 absorbs the energy caused by the earthquake force. For this reason, the energy caused by the earthquake force can be reliably absorbed by the end beam 21.

[0071] The steel beam 10 satisfies equations (32) and (36), and the design device 50 includes a central bending elastic design unit 51c (design method S1 includes a central bending elastic design step S7). Therefore, the central bending elastic design section 51c (in the central bending elastic design process S7) determines the total cross-sectional area A of the end flanges 22 and 23 in the steel beam 10. f1 The total cross-sectional area A of the central flanges 12 and 13 f2 Design to satisfy equation (32), which states that the width-to-thickness ratio of the central flanges 12 and 13 is greater than the value specified in the notification for flanges of type FB, "beams / H-shaped steel". Then, design the central beam 11 to remain within the elastic range with respect to bending moment. Therefore, even if the cross-sectional configuration is designed to satisfy equation (32) and the width-to-thickness ratio of the central flanges 12 and 13 is designed to satisfy equation (36), the central beam 11 remains within the elastic range with respect to bending moments. This prevents the central beam 11 from bending and yielding under bending moments.

[0072] The steel beam satisfies equations (33) and (37), and the design device 50 includes a central shear elastic design unit 51d (design method S1 includes a central shear elastic design step S8). As a result, the central shear elastic design unit 51d (in the central shear elastic design process S8) determines the cross-sectional area A of the end web 24 in the steel beam 10. w1 The cross-sectional area A of the central web 14 w2 The design satisfies equation (33), which states that the width-to-thickness ratio of the central web 14 is greater than the value specified in the notification for the central web 14 of type FB, "beam / H-shaped steel". The design also satisfies equation (37), which states that the width-to-thickness ratio of the central web 14 is greater than the value specified in the notification. Furthermore, the design ensures that the central beam 11 remains within the elastic range against shear force. Therefore, even if the cross-sectional configuration is designed to satisfy equation (33) and the width-to-thickness ratio of the central web 14 is designed to satisfy equation (37), the central beam 11 remains within the elastic range against shear force. This prevents the central beam 11 from shear yielding under shear force.

[0073] Furthermore, in the steel beam 10 of this embodiment, when an external seismic force acts on the steel beam 10, the energy due to the external seismic force can be reliably absorbed by the end beam 21.

[0074] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications, combinations, deletions, etc., of the configuration are also included without departing from the spirit of the present invention. For example, in the above embodiment, the steel beam 10 may not satisfy at least one of equations (32) and (36), or the design device 50 may not include a central bending elastic design unit 51c (design method S1 may not include a central bending elastic design step S7). The steel beam may not satisfy at least one of equations (33) and (37), or the design device 50 may not include a central shear elastic design unit 51d (the design method S1 may not include a central shear elastic design step S8). [Explanation of Symbols]

[0075] 5 pillars 10 Steel beams 11 Central beam 12,13 Center flange (flange) 14. Central Web (Web) 21 End beam 22,23 End flange (flange) 24 End web (web) 50 Design equipment (design equipment for steel beams) 51a Cross-sectional area design department 51b Plasticity Design Department 51c Central bending elasticity design section 51d Central Shear Elastic Design Department 61 Design Program (Steel Beam Design Program) S1 Design Method (Design Method for Steel Beams) S5 Cross-sectional area design process S6 Plasticization design process S7 Central Bending Elasticity Design Process S8 Central Shear Elastic Design Process Z Material axis direction

Claims

1. A design device for a steel beam comprising a central beam and an end beam joined to the central beam at at least one end in the axial direction of the central beam and also joined to a column, A cross-sectional area design unit that designs the steel beam to satisfy equation (1), A plastic deformation design unit designs the end beams so that they have a plastic deformation region due to bending moment when seismic external forces act on the steel beams, A design device for steel beams, equipped with the following features. However, A １ A is the cross-sectional area of ​​the end beam, ２ This is the cross-sectional area of ​​the central beam. [Math 1]

2. The steel beam design apparatus according to claim 1, comprising a central bending elastic design unit that designs the steel beam to satisfy equations (2) and (3) and the central beam to remain within the elastic range with respect to bending moment. However, A ｆ１ The total cross-sectional area of ​​the pair of flanges of the end beam, A ｆ２ b is the total cross-sectional area of ​​the pair of flanges of the central beam, ２ The length of the central beam is half the width of the flange, t ｆ２ F is the plate thickness of the flange of the central beam. ｆ２ This is the reference strength of the material strength of the flange of the central beam. [Math 2]

3. The steel beam design apparatus according to claim 1 or 2, comprising a central shear elastic design unit that designs the steel beam to satisfy equations (4) and (5) and the central beam to remain within the elastic range with respect to shear force. However, A ｗ１ is the cross-sectional area of the web of the end beam, A ｗ２ is the cross-sectional area of the web of the central beam, d ２ is the height of the web of the central beam, t ｗ２ is the plate thickness of the web of the central beam, F ｗ２ is the reference strength of the material strength of the web of the central beam. [Math 3]

4. A steel beam designed by the steel beam design apparatus described in claim 1.

5. A steel beam designed by the steel beam design device described in claim 2.

6. A steel beam designed by the steel beam design device described in claim 3.

7. A method for designing a steel beam comprising a central beam and an end beam joined to the central beam at at least one end in the axial direction of the central beam and also joined to a column, A cross-sectional area design process for designing the steel beam such that it satisfies equation (11), A plastic deformation design process is performed to design the end beam so that it has a plastic deformation region due to bending moment when an external seismic force acts on the steel beam. A design method for steel beams that includes the following features. However, A １ A is the cross-sectional area of ​​the end beam, ２ This is the cross-sectional area of ​​the central beam. [Math 4]

8. The method for designing a steel beam according to claim 7, further comprising a central bending elastic design step of designing the steel beam to satisfy equations (12) and (13) and the central beam to remain within the elastic range with respect to bending moment. However, A ｆ１ The total cross-sectional area of ​​the pair of flanges of the end beam, A ｆ２ b is the total cross-sectional area of ​​the pair of flanges of the central beam, ２ The length of the central beam is half the width of the flange, t ｆ２ F is the plate thickness of the flange of the central beam. ｆ２ This is the reference strength of the material strength of the flange of the central beam. [Math 5]

9. A method for designing a steel beam according to claim 7 or 8, comprising a central shear elastic design step of designing the steel beam to satisfy equations (14) and (15) and the central beam to remain within the elastic range with respect to shear force. However, A ｗ１ A is the cross-sectional area of ​​the web of the end beam. ｗ２ d is the cross-sectional area of ​​the web of the central beam, ２ The height of the web of the central beam, t ｗ２ F is the thickness of the web of the central beam. ｗ２ This is the reference strength of the material strength of the web of the central beam. [Math 6]

10. A steel beam designed by the steel beam design method described in claim 7.

11. A steel beam designed by the steel beam design method described in claim 8.

12. A steel beam designed by the steel beam design method described in claim 9.

13. A design program for a design device that designs a steel beam comprising a central beam and an end beam joined to the central beam at at least one end of the central beam in the direction of the material axis and also joined to a column, The aforementioned design device, A cross-sectional area design unit that designs the steel beam to satisfy equation (21), A plastic deformation design unit designs the end beams so that they have a plastic deformation region due to bending moment when seismic external forces act on the steel beams, A design program for steel beams that makes them function. However, A １ A is the cross-sectional area of ​​the end beam, ２ This is the cross-sectional area of ​​the central beam. [Number 7]

14. The aforementioned design device, The steel beam design program according to claim 13, wherein the steel beam satisfies equations (22) and (23), and functions as a central bending elastic design unit that designs the central beam to remain within the elastic range with respect to bending moment. However, A ｆ１ The total cross-sectional area of ​​the pair of flanges of the end beam, A ｆ２ b is the total cross-sectional area of ​​the pair of flanges of the central beam, ２ The length of the central beam is half the width of the flange, t ｆ２ F is the plate thickness of the flange of the central beam. ｆ２ This is the reference strength of the material strength of the flange of the central beam. [Number 8]

15. The aforementioned design device, A steel beam design program according to claim 13 or 14, wherein the steel beam satisfies equations (24) and (25), and the central beam is designed to remain within the elastic range against shear force, functioning as a central shear elastic design unit. However, A ｗ１ A is the cross-sectional area of ​​the web of the end beam. ｗ２ d is the cross-sectional area of ​​the web of the central beam, ２ The height of the web of the central beam, t ｗ２ F is the thickness of the web of the central beam. ｗ２ This is the reference strength of the material strength of the web of the central beam. [Number 9]

16. A steel beam designed by the steel beam design program described in claim 13.

17. A steel beam designed by the steel beam design program described in claim 14.

18. A steel beam designed by the steel beam design program described in claim 15.

Images