Design method for steel frame structure

Abstract

To provide a method for determining the member type of a beam member, which can be used to determine the member type for evaluating deformation performance of a beam member by clarifying the relationship between bearing force applied to a joint and a bracket of a friction joint with a high strength bolt and plastic deformation capacity of a central material.SOLUTION: There is provided a method for determining the member type of a beam member in which a joint of friction joining by a high strength bolt connecting a central member and a bracket is arranged at an end of the member. The method comprises the steps of: setting a width-to-thickness ratio type of the central material; determining performance of the joint and the bracket on the basis of a joint coefficient; and determining the member type of the beam member on the basis of the width-to-thickness ratio type and the joint coefficient.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for determining the member type of a beam member provided with a friction joint by a high-strength bolt connecting a central member and a bracket to the end of the member, and a steel frame column-beam joint structure.

Background Art

[0002] In steel frame structures, as disclosed in Patent Documents 1 and 2, a method is known in which a through diaphragm at a column-beam joint is expanded planarly to form a bracket. In the joint at the end of the beam member described in these documents, the bolt hole position of the high-strength bolt joint farthest from the column (hereinafter referred to as the "first bolt position") is designed to be the starting point of the plasticized region. That is, only the central member side of the beam member is plasticized during an earthquake load.

[0003] By the way, when the secondary design of the structural design of the steel frame structure of Patent Documents 1 and 2 is based on the seismic design of Route 3 ("Explanation of Technical Standards for Building Structural Relationships, 2020 Edition", Editorial Committee for Explanation of Technical Standards for Building Structural Relationships, 2020.10), similar to the structural design of a steel frame structure using a conventional steel beam, the required holding horizontal load-carrying capacity is obtained by the structural characteristic coefficient Ds corresponding to the type of member group (hereinafter referred to as the "member type"). The structural characteristic coefficient Ds is determined according to the member type corresponding to the plastic deformation capacity of the member.

[0004] The member type of a steel beam member is given types FA, FB, FC, and FD according to the width-thickness ratio of the beam member, as shown in Notification No. 1792, No. 3, Second Paragraph, issued by the Ministry of Construction in 1980. In structural design, the member type (hereinafter referred to as the "width-thickness ratio type") is determined by the width-thickness ratio of the flange and web of the beam member to be designed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in the steel frame structures of Patent Documents 1 and 2, since the high-strength bolt friction joints are located at the member ends where the bending moment increases when horizontal forces such as seismic forces act, if slippage occurs in the joints relatively early, there is a possibility that the plastic deformation capacity of the central member (steel beam) of the beam member cannot be fully exerted.

[0007] In short, if the relationship between the bearing capacity given to the joints and brackets and the plastic deformation capacity of the central member is not clear, it is impossible to accurately evaluate the deformation performance of the entire beam member, but such disclosure is not found in Patent Documents 1 and 2.

[0008] Therefore, an object of the present invention is to provide a method for determining the member type of a beam member that can determine the member type for evaluating the deformation performance of the beam member by clarifying the relationship between the bearing capacity given to the joints and brackets by high-strength bolts and the plastic deformation capacity of the central member. [Means for Solving the Problems]

[0009] In order to achieve the above object, the method for determining the member type of a beam member of the present invention is a method for determining the member type of a beam member provided with a high-strength bolt friction joint connecting a central member and a bracket at a member end, comprising: a step of setting a width-thickness ratio type of the central member; a step of determining the performance of the joint and the bracket based on a joint coefficient; and a step of determining the member type of the beam member based on the width-thickness ratio type and the joint coefficient.

[0010] Here, the joint coefficient is determined by the stress increase rate due to strain hardening after the central member reaches full plasticity and the statistical values of the yield strength and shear strength of the steel materials used for the joint and the bracket, and the stress increase rate can also be set for each member type of the beam member.

[0011] And, the joint part may be configured to include a bracket protruding from the steel column, a gusset plate in which the side of the steel column is widened and the side of the central member is formed to the width of the central member, and a plurality of high-strength bolts for joining the end of the gusset plate on the steel column side to the bracket and joining the end of the gusset plate on the central member side to the central member.

[0012] It is preferable to arrange at least the second row and above of the high-strength bolts on the central member side in parallel. For example, when arranging the high-strength bolts on the central member side of the joint in a staggered pattern, the arrangement of the high-strength bolts at the first bolt position and the second bolt position is preferably arranged in parallel.

[0013] The invention of the steel column-beam joint structure is a steel column-beam joint structure for connecting a beam member narrower in width than the column width to a steel column, including a bracket protruding from the steel column, a gusset plate in which the side of the steel column is widened and the side of the central member of the beam member is formed to the width of the central member, and a plurality of high-strength bolts for joining the end of the gusset plate on the steel column side to the bracket and joining the end of the gusset plate on the central member side to the central member of the beam member, characterized in that at least the second row and above of the high-strength bolts on the central member side are arranged in parallel.

Advantages of the Invention

[0014] In the method for determining the member type of the beam member of the present invention configured as described above, the member type of the beam member is determined based on the width-thickness ratio type representing the plastic deformation ability of the central member and the joint coefficient representing the performance of the joint and the bracket.

[0015] Thus, if we want to clarify the relationship between the bearing strength applied to the friction joint and bracket using high-strength bolts and the plastic deformation capacity of the central member, we can determine the member type for evaluating the deformation performance of the beam member according to the design concept such as fully exerting the plastic deformation capacity of the central member.

[0016] Also, in the invention of the steel column-beam joint structure, for example, even when the arrangement of high-strength bolts for the friction joint between the central member and the gusset plate is in a staggered arrangement, by arranging the high-strength bolts in the first bolt position (the first row on the central member side) and the second bolt position (the second row on the central member side) in a parallel arrangement, excessive reduction in the tension of the high-strength bolts after the second bolt position due to the plasticization of the flange of the central member can be suppressed.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a method for determining the member type of the beam member in this embodiment. Further, FIG. 2 is a perspective view showing the configuration of the steel column-beam joint structure 1 in this embodiment. Furthermore, FIGS. 3 and 4 are an explanatory diagram and a side view showing the configuration of the material end portion of the beam connected to the steel column 2 of the steel column-beam joint structure 1 and the plasticized region.

[0019] As shown in FIG. 2, the steel column-beam joint structure 1 used in the description of this embodiment is provided at the intersection where a central member 3 narrower than the column width is connected to the steel column 2 which is a column member. Here, the beam 11 serving as a beam member is mainly composed of a joint 12 connecting a bracket 13 protruding from the steel column 2 and the central member 3, and the central member 3 extending from the joint 12 toward the other column or the like. In FIGS. 3 and 4, for simplicity of explanation, only the beam 11 in one direction of FIG. 2 and the steel column 2 are extracted and shown.

[0020] For the steel column 2, steel structures such as a rectangular steel pipe including a substantially square shape in plan view, a circular steel pipe, and a welded fabricated box-shaped cross section can be used. Also, a concrete-filled steel tube column (CFT: Concrete Filled Tube) in which the inside of the steel tube is filled with concrete can be used as the steel column 2.

[0021] At the intersection with the beam 11, the inside of the steel column 2 is closed by a continuous diaphragm 4 formed of a steel plate. The continuous diaphragm 4 is arranged at intervals above and below the intersection. The intersection of the steel column 2 provided with the continuous diaphragm 4 may use a ready-made product or can also be assembled by welding.

[0022] The continuous diaphragm 4 is formed by a through portion 41 that penetrates the inside of the steel column 2 and a bracket flange 42 that projects outward, with a single integral steel plate. For example, in the continuous diaphragm 4 formed by a steel plate that is approximately octagonal in plan view, an annular portion that projects to the side of the steel column 2 with an inner edge that is approximately square and an outer edge that is approximately octagonal serves as the bracket flange 42.

[0023] Between the bracket flanges 42 of the continuous diaphragm 4 that project from above and below the intersection of the steel columns 2, they are connected by a bracket web 43 formed by a steel plate that is approximately rectangular in side view (see Figures 2 and 4).

[0024] The bracket web 43 has the same amount of projection from the side of the steel column 2 as the bracket flange 42 and is arranged on each side of the steel column 2. And the bracket web 43 is joined to the side of the steel column 2, the lower surface of the upper bracket flange 42, and the upper surface of the lower bracket flange 42 by fillet welding. A plurality of bolt holes for passing high-strength bolts or ultra-high-strength bolts are drilled in the bracket flange 42 and the bracket web 43. The number and position of the bolt holes can be set arbitrarily.

[0025] The bracket flange 42 and the bracket web 43 are provided in accordance with the positions of each part of the center member 3 of the beam 11 to be connected. The center member 3 is a beam body (steel beam) formed of a steel structure such as an H-shaped steel, and includes an upper flange 31, a lower flange 32, and a web 33 that connects them. Here, the thickness of the bracket flange 42 is made equal to or greater than the thickness of the flanges (31, 32) of the center member 3, and the thickness of the bracket web 43 is made equal to or greater than the thickness of the web 33 of the center member 3.

[0026] The bracket flange 42 of the upper continuous diaphragm 4 is provided at a position that abuts against the upper flange 31 of the center member 3, and the bracket flange 42 of the lower continuous diaphragm 4 is provided at a position that abuts against the lower flange 32 of the center member 3. And the bracket web 43 is provided at a position that abuts against the web 33 of the center member 3.

[0027] That is, the continuous diaphragm 4 of the present embodiment has a general "function as a continuous diaphragm" in the prior art and a "function as a beam bracket" for connecting the central member 3. Therefore, the bracket flange 42 and the bracket web 43 are collectively referred to as the bracket 13.

[0028] A plurality of bolt holes for passing high-strength bolts or ultra-high-strength bolts are drilled in the upper flange 31, the lower flange 32, and the web 33 at the axial end of the central member 3. The number and position of the bolt holes can be arbitrarily set.

[0029] The bracket flange 42 and the central member 3 thus butted are frictionally joined by high-strength bolts 6 including ultra-high-strength bolts via the gusset plate 5. In short, the end of the gusset plate 5 on the steel column side is joined to the bracket flange 42 of the continuous diaphragm 4, and the end of the gusset plate 5 on the central member side is joined to the end of the central member 3.

[0030] Further, the gusset plate 5 is formed of a steel plate such that the side on the steel column side is widened and the side on the central member side has the width of the central member. That is, the gusset plate 5 spanned between the upper surface of the bracket flange 42 of the upper continuous diaphragm 4 and the upper flange 31 of the central member 3 is formed in a substantially trapezoidal shape in plan view with the width of the edge adjacent to the steel column 2 being wider than the width of the central member and the edge on the central member side having the width of the central member. The gusset plate 5 spanned between the lower surface of the bracket flange 42 of the lower continuous diaphragm 4 and the lower flange 32 of the central member 3 is also formed in a similar substantially trapezoidal shape in plan view.

[0031] On the other hand, the opposing gusset plate 51 (see FIG. 4) that faces the gusset plate 5 with the upper flange 31 or the lower flange 32 interposed therebetween is formed to have a width of half or less of the width of the gusset plate 5 so that it can be disposed on both sides of the web 33 of the central member 3. The opposing gusset plate 51 does not have to have the same thickness as the gusset plate 5 and can be set to an arbitrary thickness.

[0032] Also, the web side gusset plates 52 respectively spanned between the side surfaces of both the bracket web 43 and the web 33 of the central member 3 are formed of steel plates into substantially rectangular shapes in side view with a height lower than that of the web 33 of the central member 3.

[0033] A plurality of bolt holes for passing high-strength bolts or ultra-high-strength bolts are drilled in the gusset plate 5, the opposing side gusset plate 51, and the web side gusset plate 52. The number and position of the bolt holes are made to coincide with those of the bolt holes in the upper flange 31, the lower flange 32, the web 33, the bracket flange 42, and the bracket web 43 of the central member 3.

[0034] Subsequently, the focused cross-section of the beam 11 of the steel frame column-beam joint structure 1 will be described with reference to FIGS. 3 and 4. The beam 11 of the steel frame column-beam joint structure 1 is designed to yield at the first bolt position (the bolt hole position of the high-strength bolt joint by the high-strength bolt 6 farthest from the steel frame column 2 in the A cross-section position) of the central member 3. Then, a plasticized region is formed toward the center of the span in the portion of the central member 3 adjacent to the first bolt position (the first row on the central member side).

[0035] Here, when the high-strength bolts 6 arranged on the upper flange 31 and the lower flange 32 are stagger-arranged, in order to suppress an excessive decrease in the tension of the high-strength bolts 6 after the second bolt position (the second row on the central member side) due to plasticization of the flanges (31, 32) of the central member 3, it is preferable that the arrangement of the high-strength bolts 6 at the first bolt position and the second bolt position be arranged in parallel as shown in FIGS. 2 and 3. Also, the arrangement of the high-strength bolts 6 for the friction joint between the bracket flange 42 and the gusset plate 5 may be arranged in parallel.

[0036] Further, with respect to the A cross-section at the first bolt position of the central member 3, among the high-strength bolts 6 that join the flanges (31, 32) of the central member 3 and the gusset plate 5, the cross-section at the bolt position closest to the end of the central member 3 is defined as the B cross-section. Further, among the high-strength bolts 6 that join the bracket flange 42 and the gusset plate 5, the cross-section at the bolt position of the joint 12 closest to the end of the central member 3 is defined as the D cross-section, and the cross-section at the midpoint between the B cross-section and the D cross-section is defined as the C cross-section. And the cross-section at the bolt position of the high-strength bolt 6 closest to the steel column 2 is defined as the E cross-section.

[0037] Next, a method for determining the member type of the beam member in the present embodiment will be described. In the present embodiment, taking the beam 11 having the joint 12 of the steel column-beam joint structure 1 described above as an example, a method for determining the member type for evaluating the deformation performance of the beam 11 will be described.

[0038] As described in the background art, the structural characteristic coefficient Ds in the seismic design of Route 3 of the steel structure is given for each member type of FA - FD defined in "Ministry of Construction Notification No. 1792, No. 3, Second Item, 1980". Therefore, even when the steel column-beam joint structure 1 provided with the beam 11 having the joint 12 of the present embodiment described above is seismically designed by Route 3, it is necessary to determine the member type of the beam 11 in the same manner as the conventional steel beam member.

[0039] Therefore, in the present embodiment, the classification of the member type of the beam 11 is defined as equivalent to FA, equivalent to FB, equivalent to FC, and equivalent to FD. The beam 11 classified into the member types equivalent to FA - FD is defined to be able to exhibit plastic deformation capacity equivalent to that of the conventional steel beam members classified into FA - FD in "Ministry of Construction Notification No. 1792, No. 3, Second Item, 1980".

[0040] Figs. 5 and 6 schematically show the method for determining the member type of the beam 11. In the beam 11, after the central member 3 reaches full plasticity at the A cross-section position, the bending moment increases due to the stress increase caused by the strain hardening of the central member 3 in the same manner as the conventional construction method. And based on the experimental results conducted by the inventor of the present application, the following two types of subsequent behaviors are considered.

[0041] First, considering the case where the width-to-thickness ratio type of the central member 3 is FA, when the yield bending strength of the joint 12 and the bracket 13, and the shear strength of the joint 12 exceed the "strength at the maximum deformation assumed for the central member 3 of FA", as shown in Fig. 5(a), the beam 11 can exhibit a plastic deformation capacity equivalent to FA.

[0042] On the other hand, when the yield bending strength of the joint 12 and the bracket 13, and the shear strength of the joint 12 are lower than the "strength at the maximum deformation assumed for the central member 3 of FA", as shown in Fig. 5(b), Fig. 6(a), and Fig. 6(b), the plastic deformation capacity of the entire beam 11 does not meet the value expected for the central member 3 of FA. That is, even if the width-to-thickness ratio type of the central member 3 is FA, depending on the yield bending strength of the joint 12, the yield bending strength of the bracket 13, and the shear strength of the joint 12, the member type of the entire beam 11 may become equivalent to FB, FC, or FD.

[0043] Specifically, as shown in Fig. 5(b), when the joint 12 yields, the bracket 13 yields, or the joint 12 slips after the plastic deformation capacity assumed for FB is exerted, the member type of the beam 11 becomes equivalent to FB. On the other hand, as shown in Fig. 6(a), when the joint 12 yields, the bracket 13 yields, or the joint 12 slips after the plastic deformation capacity assumed for FC is exerted, the member type of the beam 11 becomes equivalent to FC. And as shown in Fig. 6(b), when the central member 3 reaches full plasticity and then the joint 12 yields, the bracket 13 yields, or the joint 12 slips, the member type of the beam 11 becomes equivalent to FD.

[0044] In short, for the member type of the beam 11 to be equivalent to FA - FD, it means that until the central member 3 exerts a plastic deformation capacity equivalent to FA - FD, the yield of the joint 12, the slip of the friction joint of the high-strength bolt 6, and the yield of the bracket 13 do not occur.

[0045] And the "strength at the maximum deformation assumed" for each member type (equivalent to FA - FD) of the beam 11 is, as shown in Figs. 5 and 6, the full plastic moment M pIt is determined by multiplying by the joint coefficient α. That is, the member type of the beam 11 will be determined by the joint coefficient α.

[0046] FIG. 1 is an explanatory diagram showing an outline of a method for determining the member type of the beam member according to the present embodiment summarized above. As shown in this figure, it schematically shows that "even if the width-to-thickness ratio type of the central member 3 is FA, the member type of the beam 11 may be equivalent to FB, FC, or FD depending on the yield bending strength of the joint 12, the yield bending strength of the bracket 13, and the shear strength of the joint 12."

[0047] In short, it can be said that the member type of the beam 11 is determined by the joint coefficient α selected by the designer when designing the joint 12 and the bracket 13. This concept is unprecedented and cannot be found not only in Patent Documents 1 and 2 but also in the academic guidelines summarizing the design method of beam joints.

[0048] Subsequently, a method for setting the joint coefficient α in the method for determining the member type of the beam member according to the present embodiment will be described. The joint coefficient α is determined by "the stress increase due to strain hardening of the central member 3" and "the difference between the yield strength of the central member 3, the gussets (5, 51, 52) and the bracket 13, and the nominal value and the actual value of the shear strength of the friction joint of the high-strength bolt 6".

[0049] FIG. 7 is an explanatory diagram schematically showing the relationship between the bending moment acting on each part of the beam 11 when the maximum endurance assumed by the central member 3 is reached, the yield bending strength and shear strength of the joint 12, and the yield bending strength of the bracket 13. In the figure, A M p is the full plastic moment of the central member 3. If the stress increase rate due to strain hardening after the central member 3 reaches the full plastic moment is represented by ξ, the bending moment acting on the first bolt position (A-section position) at the assumed maximum deformation is A M max = ξ × A M p and can be expressed as follows.

[0050] When the central member 3 reaches the full plastic moment at the first bolt position (A-section position), the bending moments acting on each section (B-section, D-section, E-section) of the joint 12 and the bracket 13 are A M p , B M du , D M du , E M du Assuming that, at the maximum deformation assumed, the bending moments acting on each section are, as in the A-section, B M max = ξ × B M du , D M max = ξ × D M du , E M max = ξ × E M du they can be expressed as follows.

[0051] Since the joint 12 and the bracket 13 remain within the elastic range until the central member 3 exhibits a predetermined plastic deformation capacity, the "yield bending resistance of each section of the joint 12 ( JB M y , JD M y ), the yield bending resistance of the bracket 13 ( JE M y ), and the slip resistance of the friction joint of the high-strength bolt 6 ( br M slip , bc M slip )" in the schematic diagram of Fig. 7 and the bending moments acting on each section ( JB M y , JD M y , JE M y ) are expressed in equations as follows.

[0052] <Yield bending resistance of the gusset plates (5, 51, 52) JB M fy > JB M fy ≧ ξ × B M du JD M fy ≥ ξ × D M du <Yield bending strength of Bracket 13 JE M fy > JE M fy ≥ ξ × E M du

[0053] <Shearing strength of Joint 12 bc M slip ≥ ξ × B M du (On the side of the central member) br M slip ≥ ξ × E M du (On the side of the bracket)

[0054] The above formula is to ensure that when the actual value of the yield strength of the steel material is equal to the nominal value, each of the "yield bending strength of Joint 12, yield bending strength of Bracket 13, and shearing strength of Joint 12" has a strength equal to or greater than the "bending moment obtained by multiplying the stress increase rate ξ by the bending moment of each cross-section when the central member 3 reaches the full plastic moment at the A cross-section position". However, generally, there are differences between the design values and the actual values of the yield bending strength and shearing strength of Joint 12 and the yield bending strength of Bracket 13.

[0055] Therefore, refer to the "Design Guidelines for Steel Structure Joints" (Architectural Institute of Japan, 2021.2) (hereinafter referred to as the "Joint Guidelines"). For the yield strength of the steel materials used for the gusset plates (5, 51, 52) of Joint 12 and Bracket 13, and the shearing strength of Joint 12, correction factors considering the variation of the actual value with respect to the nominal value are β 1 , β 2 , β 3 respectively. Then, the above formula can be expressed in a form considering the variation of the actual value with respect to the nominal value of the material strength.

[0056] <Yield bending strength of the gusset plates (5, 51, 52) JB Mfy > JB M fy ≥ ξ·β 1 · B M du JD M fy ≥ ξ·β 1 · D M du <Yield bending strength of bracket 13 JE M fy > JE M fy ≥ ξ·β 2 · E M du

[0057] <Sliding resistance of joint 12 bc M slip ≥ ξ·β 3 · B M du (On the center member side) br M slip ≥ ξ·β 3 · E M du (On the bracket side)

[0058] Furthermore, using the joint coefficient α s , α br , α slip to organize, it becomes as follows: <Yield bending strength of gusset plate (5, 51, 52) JB M fy > JB M fy ≥ α s · B M du (Equation 1) JD M fy ≥ α s · D M du (Equation 2) <Yield bending strength of bracket 13 JE M fy > JE Mfy ≧ α br · E M du (Formula 3)

[0059] <Shearing strength of joint 12 bc M slip ≧ α slip · B M du (On the center member side) (Formula 4) br M slip ≧ α slip · E M du (On the bracket side) (Formula 5)

[0060] In short, "keeping the joint 12 and the bracket 13 within the elastic range until the center member 3 exhibits a predetermined plastic deformation capacity" corresponds to the act of confirming that, as shown in the above formula, "the yield bending strength or the shearing strength of each part exceeds the value obtained by multiplying the bending moment acting on each cross-section at the time of full plasticity at the A cross-section position by the joint coefficient".

[0061] As described above, the joint coefficient (α s , α br , α slip ) is obtained by multiplying "the stress increase rate ξ due to strain hardening of the center member 3" by "the correction coefficient (β 1 , β 2 , β 3 )" considering the variation of the actual values with respect to the nominal values of the yield strength and the shearing strength of the steel materials used for the joint 12 and the bracket 13.

[0062] Here, β 1 is the correction coefficient determined from the average value and the standard deviation of the yield strengths of the center member 3 and the gusset plates (5, 51, 52), β 2 is the correction coefficient determined from the average value and the standard deviation of the yield strengths of the center member 3 and the bracket 13, and β 3 is the correction coefficient determined from the average value and the standard deviation of the yield strength of the center member 3 and the shearing strength of the friction joint of the high-strength bolt 6.

[0063] And, in order to determine the member type of the beam 11 according to the strength of the joint 12, it is necessary to know the "stress increase rate ξ due to strain hardening of the central member 3" when the plastic deformation ability required for each member type is exhibited.

[0064] Therefore, a method for setting the stress increase rate ξ due to strain hardening will be described. Here, referring to the "Joint Guidelines" again, the relationship between the plastic deformation ability θ max / θ p of the beam and the stress increase rate ξ is shown by the following equation.

Equation

[0065] Therefore, substituting the plastic deformation ability θ max / θ p required for the steel beam members of each member type into the above equation, the stress increase rate ξ due to strain hardening of the central member 3 in each member type of the beam 11 can be obtained.

[0066] Regarding the equivalent of FA, when not based on individual consideration in the "Joint Guidelines", the stress increase rate ξ is 1.20 by applying the value. Regarding the equivalent of FD, since almost no plastic deformation ability of the central member 3 can be expected, by applying the value of the "Joint Guidelines", the stress increase rate ξ is 1.05.

[0067] And, regarding the equivalents of FB and FC, the stress increase rate ξ is determined based on the following idea. According to the "Technical Standards Explanation Book on the Structural Relationship of Buildings 2020 Edition" (Editorial Committee for the Technical Standards Explanation Book on the Structural Relationship of Buildings, 2020.10), the plastic deformation abilities required for the beams of the member types FA, FB, and FC are 4.0, 2.0, and 0.0, respectively, as the lower limit values of the plastic deformation magnification. The plastic deformation magnification is the plastic ratio (θ max / θ pSince it is obtained by subtracting 1 from , the lower limit values of the plastic ratios required for the beams FA, FB, and FC are 5.0, 3.0, and 1.0, respectively. Therefore, the ranges of the plastic ratios required for the beams FA, FB, and FC are FA is 5.0 or more, FB is 3.0 - 5.0, and FC is 1.0 - 3.0.

[0068] Regarding the ranges of the plastic ratios of the beams required for each member type, in the method for determining the member type of the beam member of the present embodiment, the plastic ratio (θ max / θ p ) for obtaining the stress increase rates ξ equivalent to FB and FC is set to the "median value" of each plastic ratio range. FIG. 8 is an explanatory diagram of setting the stress increase rate with respect to the median value of the plastic ratio required for the beams of each member type. And FIG. 9 shows the stress increase rate (ξ) calculated by substituting the plastic ratio (θ max / θ p ) for each member type into the formula (Equation 1) of the stress increase rate ξ of the above-mentioned "joint guideline".

[0069] That is, the plastic ratio for obtaining the stress increase rate ξ is set to θ max / θ p = 4.0 for the equivalent of FB, and θ max / θ p = 2.0 for the equivalent of FC. As shown in FIG. 8, if the stress increase rate ξ is set with respect to the median value of the plastic ratio required for the beams of each member type, the beam 11 is guaranteed to always exhibit the lower limit value of the plastic ratio required for the beams of each member type, so it is a safe-side evaluation.

[0070] Thus, according to the method for determining the member type of the beam member of the present embodiment, the member type (deformation performance) of the entire beam 11 with the joint 12 can be determined using the joint coefficients (α s , α br , α slip ).

[0071] And the correction coefficients (β s , β br , β slip ) used when obtaining the joint coefficients (α 1 , β 2 , β 3) is a coefficient determined from the statistical values of the yield strength and shear strength of the steel material, and can be obtained from the above "joint guidelines" and each statistical value. Specifically, β 1 is the ratio β bc of the actual value to the nominal value of the yield strength of the central member 3, and the correction coefficient based on the material strength determined from "the ratio β s of the actual value to the nominal value of the yield strength of the gusset plates (5, 51, 52)". Also, β 2 is the ratio β bc of the actual value to the nominal value of the yield strength of the central member 3, and the correction coefficient based on the material strength determined from "the ratio β br of the actual value to the nominal value of the yield strength of the bracket 13". And β 3 is the ratio β bc of the actual value to the nominal value of the yield strength of the central member 3, and the correction coefficient based on the material strength determined from "the ratio β slip of the actual value to the nominal value of the shear strength".

[0072] In FIG. 10, the joint coefficients (α s , α br , α slip ) for each member type are illustrated. Thus, in the method for determining the member type of the beam member of the present embodiment, by designing the joint 12 and the bracket 13 using the joint coefficients (α s , α br , α slip ), the member type of the entire beam 11 can be easily determined.

[0073] Furthermore, according to the experimental results conducted by the inventor of the present application, the history characteristics of the beam 11 can also be controlled. Specifically, in the beam 11, even if the full plastic resistance of the central member 3 is the same, different history characteristics can be obtained depending on the resistance given to the joint 12 and the bracket 13.

[0074] For example, if the joint 12 and the bracket 13 do not yield until reaching the maximum strength of the central member 3 and no slip occurs in the joint 12, the load-deformation relationship of the beam 11 can maintain a spindle-shaped history property until the main slip occurs. In short, if the joint 12 and the bracket 13 remain within the elastic range until the central member 3 exhibits a predetermined plastic deformation capacity, a spindle-shaped history property characteristic of a steel member can be achieved.

[0075] On the other hand, when slip occurs in the joint 12, a rapid decrease in strength occurs due to the influence of the main slip, and the load-deformation relationship becomes a saw-tooth-shaped history property due to repeated slips. Thus, by clarifying the relationship between the strength imparted to the joint 12 and the bracket 13 and the plastic deformation capacity of the central member 3, the performance of the beam 11 having the joint 12 and the bracket 13 can be easily determined.

[0076] Next, a method for determining the member type of the beam member and the action of the steel column-beam connection structure according to the present embodiment will be described. In the method for determining the member type of the beam member according to the present embodiment configured as described above, after setting the relationship between the width-thickness ratio type representing the plastic deformation capacity of the central member 3 and the performance of the joint 12 and the bracket 13, the performance of the joint 12 and the bracket 13 is determined based on the joint coefficient (α s , α br , α slip ). Then, as shown in FIGS. 1 and 10, based on the width-thickness ratio type of the central member 3 and the joint coefficient (α s , α br , α slip ), the member type of the beam 11 is determined.

[0077] Thus, if the relationship between the strength imparted to the joint 12 and the bracket 13 by the friction joint using the high-strength bolt 6 and the plastic deformation capacity of the central member 3 is to be clarified, according to the design concept such as wanting to fully exhibit the plastic deformation capacity of the central member 3, the member type for evaluating the deformation performance of the beam 11 can be easily determined.

[0078] For example, in the design of a conventional beam joint, if it suffices to confirm that the joint does not break with respect to the bending moment at the joint position when the material end of the beam reaches the "maximum bending strength", yielding or slipping of the joint may occur before the beam exhibits a predetermined plastic deformation capacity. However, if major slipping occurs in the joint shortly after the central member reaches full plasticity, the strength will show a property of a sharp decline.

[0079] Therefore, in this embodiment, by clarifying the relationship between the strength imparted to the joint 12 and the bracket 13 and the plastic deformation capacity of the central member 3, the following deformation performance can be imparted to the beam 11.

[0080] That is, by designing the joint 12 and the bracket 13 according to the joint coefficient corresponding to the plastic deformation capacity expected for the central member 3, deformation performance such as "deformation performance in which strength reduction due to major slipping occurs shortly after the central member 3 reaches full plasticity", "deformation performance in which strength reduction due to major slipping occurs after the central member 3 reaches full plasticity and exhibits a certain plastic deformation capacity", and "deformation performance in which no major slipping occurs until the end of loading" can be determined for the beam 11.

[0081] Therefore, in the method for determining the member type of the beam member of this embodiment, the joint 12 and the bracket 13 are designed based on the above (Equation 1)-(Equation 5) with respect to the bending moment acting on the beam 11. Here, for the stress increase rate ξ for obtaining the joint coefficient, in the case of equivalent to FB and equivalent to FC, as shown in FIG. 8, it is calculated with respect to the median value of the plastic ratios obtained for the steel beam members of each member type. The joint coefficients (α s 、α br 、α slip ) are as shown in FIG. 10.

[0082] If the details of the joint 12 and the bracket 13 can be determined according to the performance of the beam 11 required by the designer in this way, it becomes possible to optimize the construction cost according to the design result by the joint coefficient without changing the cross section of the central member 3.

[0083] Also, in the steel column-beam joint structure 1 of the present embodiment, even when the arrangement of the high-strength bolts 6 for the friction joint between the central member 3 and the gusset plate 5 is staggered, by arranging the high-strength bolts 6 at the first bolt position (A-section position) and the second bolt position (adjacent to the first bolt position) in parallel, it becomes possible to suppress an excessive decrease in the tension of the high-strength bolts 6 after the second bolt position due to the plasticization of the flanges (31, 32) of the central member 3.

[0084] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes within the scope not departing from the gist of the present invention are included in the present invention.

[0085] For example, in the above embodiment, the method for determining the member type of the beam 11 in the steel column-beam joint structure 1 in which the central member 3 is connected to the bracket 13 protruding from the four sides of the steel column 2 via the joint 12 has been described, but it is not limited thereto. The deformation performance of a beam member having a friction joint by high-strength bolts in a form different from the joint 12 described above can also be easily evaluated by the present invention.

Explanation of reference numerals

[0086] 11: Beam (beam member) 12: Joint 13: Bracket 2: Steel column (column) 3: Central member 5: Gusset plate 6: High-strength bolt

Claims

1. A design method for a steel frame structure having a beam member provided with a friction joint by a high-strength bolt that connects a central member and a bracket at the end of a member, comprising: a step of setting a width-thickness ratio type of the central member; a step of comparing a first strength, which is the yield bending strength and slip strength of the joint and the yield bending strength of the bracket, with a second strength, which is the strength at the maximum deformation assumed for the central member of the set width-thickness ratio type; a step of determining, as the member type of the beam member, the category of the set width-thickness ratio type when any of the first strengths exceeds the second strength, and determining, as the member type of the beam member, the corresponding category lower than the set width-thickness ratio type when at least one of the first strengths is lower than the second strength; a step of designing the joint and the bracket of the beam member so that the determined member type of the beam member becomes a category that exhibits an expected plastic deformation capacity; the second strength is determined as a value obtained by multiplying a joint coefficient by the bending moment acting on the position of the joint or the bracket at the full plasticity of the central member; the joint coefficient is determined by the product of the stress increase rate due to strain hardening after the central member reaches full plasticity and a correction coefficient determined from the ratio of the actual value to the nominal value of the yield strength and slip strength of the steel used for the joint and the bracket; the stress increase rate is set for each member type of the beam member. A design method for a steel frame structure characterized by this.

2. the bracket projecting from the steel column; a gusset plate in which the steel column side is widened and the central member side is formed to the width of the central member; a plurality of high-strength bolts that join the end of the gusset plate on the steel column side to the bracket and join the end of the gusset plate on the central member side to the central member; The design method for a steel frame structure according to claim 1, characterized in that the joint has the gusset plate.

3. The design method for a steel frame structure according to claim 2, characterized in that at least the second row of the high-strength bolts on the central member side is arranged in parallel.

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