Steel frame column-beam connection structure

Abstract

To provide a steel column-beam joint structure capable of preventing excessive reduction in tension of high strength bolts due to plasticisation of a flange of a central material.SOLUTION: A steel column-beam joint structure that connects a beam 11 with a narrower width than a column width to a steel column 2 is provided. It comprises a bracket flange 42 overhanging from the steel column, a bracing plate 5, which is widened on its steel column side to form a central material side of the beam with a central material width, and a plurality of high strength bolts 6, which connect a steel column side end of the bracing plate to the bracket flange, and connect a central material side end of the bracing plate to the central material 3 of the beam. At least up to the second row of high strength bolts on the central material side are arranged in parallel.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a steel column-beam connection structure that connects a beam member narrower than the column width to a steel column. [Background technology]

[0002] In steel frame structures, as disclosed in Patent Documents 1 and 2, a construction method is known in which the through diaphragm of the column-beam joint is expanded planarly to form a bracket. In the joints at the end of beam members described in these documents, the bolt hole position of the high-strength bolt joint furthest from the column (hereinafter referred to as the "first bolt position") is designed to be the starting point of the plastic deformation region. In other words, under seismic load, only the central member side of the beam member is plastically deformed.

[0003] By the way, when the secondary design of the structural design of steel frame structures described in Patent Documents 1 and 2 is to be seismically designed according to Route 3 ("Commentary on Technical Standards Related to the Structure of Buildings, 2020 Edition," Editorial Committee for Commentary on Technical Standards Related to the Structure of Buildings, 2020.10), the required horizontal load-bearing capacity will be determined by the structural characteristic coefficient Ds corresponding to the type of member group (hereinafter referred to as "member type"), similar to the structural design of steel frame structures using conventional steel beams. The value of the structural characteristic coefficient Ds is determined according to the member type corresponding to the plastic deformation capacity of the member.

[0004] As indicated in the Ministry of Construction Notification No. 1792 of 1980, the member types of steel beam members are assigned as FA, FB, FC, and FD according to the width-to-thickness ratio of the beam member. In structural design, the member type (hereinafter referred to as "width-to-thickness ratio type") is determined by the width-to-thickness ratio of the flange and web of the beam member being designed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4770096 [Patent Document 2] Japanese Patent Publication No. 2020-94344 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in the steel frame structures described in Patent Documents 1 and 2, the joints of high-strength bolt friction connections are located at the ends of the members where the bending moment becomes large when horizontal forces such as seismic forces are applied. Therefore, if slippage occurs in the joints relatively early, there is a risk that the plastic deformation capacity of the central member (steel beam) of the beam member may not be fully utilized.

[0007] On the other hand, if all the high-strength bolts that frictionally join the central member and the bracket are arranged in a staggered pattern, the tension of the high-strength bolts may decrease excessively due to plastic deformation of the flange of the central member.

[0008] Therefore, the present invention aims to provide a steel column-beam joint structure that can suppress an excessive decrease in the tension of high-strength bolts due to the plastic deformation of the flange of the central member. [Means for solving the problem]

[0009] To achieve the above objective, the steel column-beam joint structure of the present invention is a steel column-beam joint structure for connecting a beam member narrower than the column width to a steel column, comprising: a bracket extending from the steel column; a splice plate whose steel column side is widened so that the central member side of the beam member is formed to the width of the central member; and a plurality of high-strength bolts which connect the end of the splice plate on the steel column side to the bracket and the end of the splice plate on the central member side to the central member of the beam member, wherein at least two rows of the high-strength bolts on the central member side are arranged in parallel. [Effects of the Invention]

[0010] In the steel column-beam joint structure of the present invention configured in this way, even when the arrangement of high-strength bolts for the friction joint between the central member and the splice plate is staggered, by arranging the high-strength bolts at the first bolt position (first row on the central member side) and the second bolt position (second row on the central member side) in parallel, it is possible to suppress an excessive decrease in the tension of the high-strength bolts from the second bolt position onward due to plastic deformation of the flange of the central member. [Brief explanation of the drawing]

[0011] [Figure 1] This is an explanatory diagram illustrating the general method for determining the type of member in a beam. [Figure 2] This is a perspective view showing the configuration of the steel column-beam joint structure of this embodiment. [Figure 3] This is an explanatory diagram showing the structure of the end portion of a beam connected to a steel column and the plastic deformation region. [Figure 4] This is a side view showing the configuration of the end portion of a beam connected to a steel column. [Figure 5] These diagrams illustrate the types of members used in a beam, with (a) being an explanatory diagram corresponding to FA and (b) being an explanatory diagram corresponding to FB. [Figure 6] These are diagrams illustrating the types of members set for a beam, where (a) is an explanatory diagram corresponding to FC and (b) is an explanatory diagram corresponding to FD. [Figure 7] This is a schematic diagram illustrating the relationship between the bending moment acting on each part of the beam when the central member reaches its maximum load-bearing capacity, and the yield bending strength and sliding strength of the joints. [Figure 8] This diagram illustrates how to set the stress increase rate relative to the median plasticity ratio required for beams of each member type. [Figure 9] This is an explanatory diagram showing the relationship between the plasticity ratio and the stress increase rate for each type of component. [Figure 10] This is an explanatory diagram illustrating the joint coefficients for each type of component. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is an explanatory diagram illustrating the general method for determining the member type of the beam member. Figure 2 is a perspective view showing the configuration of the steel column-beam joint structure 1 of this embodiment. Furthermore, Figures 3 and 4 are explanatory diagrams and side views showing the configuration of the member end and the plastic deformation region of the beam connected to the steel column 2 of the steel column-beam joint structure 1.

[0013] The steel column-beam joint structure 1 used in the description of this embodiment is provided at the intersection where a central member 3, which is narrower than the column width, is connected to a steel column 2, which is a column member, as shown in Figure 2. Here, the beam 11, which is a beam member, is mainly composed of a joint 12 that connects a bracket 13 extending from the steel column 2 to the central member 3, and a central member 3 that extends from the joint 12 toward the other column or the like. In Figures 3 and 4, for the sake of simplicity, only the beam 11 and steel column 2 in one direction from Figure 2 are shown.

[0014] Steel columns 2 can be made of various types of steel, including rectangular steel pipes (including roughly square shapes in plan view), circular steel pipes, and welded box-section steel pipes. Alternatively, concrete-filled tube (CFT) steel pipes, in which concrete is filled inside the steel pipe, can also be used as steel column 2.

[0015] At the intersection with beam 11, the interior of the steel column 2 is sealed by a through diaphragm 4 made of steel plate. The through diaphragm 4 is positioned at intervals above and below the intersection. The intersection of the steel column 2, where the through diaphragm 4 is installed, may use a pre-fabricated product or it may be assembled by welding.

[0016] The through diaphragm 4 is formed from a single, integrated steel plate, with a penetration portion 41 that goes through the inside of the steel column 2 and a bracket flange 42 that protrudes outwards. For example, in a through diaphragm 4 formed from a steel plate that is roughly octagonal in plan view, the annular portion that protrudes to the side of the steel column 2, which has a roughly square inner edge and a roughly octagonal outer edge, becomes the bracket flange 42.

[0017] The bracket flanges 42 of the through diaphragm 4, which protrudes from above and below the intersection of the steel column 2, are connected by a bracket web 43 formed by a steel plate that is roughly rectangular in side view (see Figures 2 and 4).

[0018] The bracket web 43 is positioned on each side of the steel column 2, with the same overhang from the side of the steel column 2 as the bracket flange 42. The bracket web 43 is then 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. Multiple bolt holes are drilled in the bracket flange 42 and bracket web 43 for passing high-strength bolts or ultra-high-strength bolts. The number and position of the bolt holes can be set arbitrarily.

[0019] The bracket flange 42 and bracket web 43 are provided in accordance with the positions of each part of the central member 3 of the beam 11 to be connected. The central member 3 is a beam body (steel beam) formed of steel such as an H-shaped steel, and comprises an upper flange 31, a lower flange 32, and a web 33 connecting them. Here, the thickness of the bracket flange 42 is equal to or greater than the thickness of the flanges (31, 32) of the central member 3, and the thickness of the bracket web 43 is equal to or greater than the thickness of the web 33 of the central member 3.

[0020] The bracket flange 42 of the upper through diaphragm 4 is positioned to abut against the upper flange 31 of the central member 3, and the bracket flange 42 of the lower through diaphragm 4 is positioned to abut against the lower flange 32 of the central member 3. The bracket web 43 is positioned to abut against the web 33 of the central member 3.

[0021] In other words, the through diaphragm 4 of this embodiment has both the function of a "through diaphragm" as is common in conventional technology, and the function of 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.

[0022] Multiple bolt holes are drilled in the upper flange 31, lower flange 32, and web 33 at the axial ends of the central member 3 for passing high-strength bolts or ultra-high-strength bolts. The number and position of the bolt holes can be set arbitrarily.

[0023] The bracket flange 42 and the central member 3, which are butted together in this manner, are friction-joined via the splice plate 5 by high-strength bolts 6, including ultra-high-strength bolts. In short, the end of the splice plate 5 on the steel column side is joined to the bracket flange 42 of the through diaphragm 4, and the end of the splice plate 5 on the central member side is joined to the end of the central member 3.

[0024] Furthermore, the splice plate 5 is formed from a steel plate such that the side facing the steel column is widened and the side facing the central member is the width of the central member. That is, the splice plate 5 that spans between the upper surface of the bracket flange 42 of the upper through diaphragm 4 and the upper flange 31 of the central member 3 is formed in a roughly 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 being the width of the central member. The splice plate 5 that spans between the lower surface of the bracket flange 42 of the lower through diaphragm 4 and the lower flange 32 of the central member 3 is also formed in a similar roughly trapezoidal shape in plan view.

[0025] In contrast, the opposing side splice plate 51 (see Figure 4), which is positioned opposite the splice plate 5 with the upper flange 31 or lower flange 32 in between, is formed to be less than half the width of the splice plate 5 so that it can be positioned on both sides of the web 33 of the central member 3. The opposing side splice plate 51 does not have to be the same thickness as the splice plate 5, and can be set to any thickness.

[0026] Furthermore, the web side splice plates 52, which are spanned between the sides of the bracket web 43 and the web 33 of the central member 3, are formed from steel plates in a roughly rectangular shape when viewed from the side, and are lower in height than the web 33 of the central member 3.

[0027] Multiple bolt holes are drilled in the splice plate 5, the opposing splice plate 51, and the web splice plate 52 for passing high-strength bolts or ultra-high-strength bolts. The number and position of the bolt holes are to match those of the upper flange 31, lower flange 32, web 33, bracket flange 42, and bracket web 43 of the central member 3.

[0028] Next, we will explain the cross-section of beam 11 of the steel column-beam joint structure 1, referring to Figures 3 and 4. The beam 11 of the steel column-beam joint structure 1 is designed to yield at the first bolt position of the central member 3 (section A position (bolt hole position of the high-strength bolt joint by the high-strength bolt 6 furthest from the steel column 2)). Then, a plastic deformation region is formed in the portion of the central member 3 adjacent to the first bolt position (first row on the central member side), toward the center of the span.

[0029] Here, when the high-strength bolts 6 placed on the upper flange 31 and the lower flange 32 are arranged in a staggered pattern, it is preferable to arrange the high-strength bolts 6 at the first bolt position and the second bolt position in parallel, as shown in Figures 2 and 3, in order to suppress an excessive decrease in the tension of the high-strength bolts 6 from the second bolt position (second row on the central member side) onward due to the plastic deformation of the flanges (31, 32) of the central member 3. Furthermore, the arrangement of the high-strength bolts 6 for the friction joint between the bracket flange 42 and the splice plate 5 may also be in parallel.

[0030] Furthermore, with respect to section A of the first bolt position of the central member 3, the section of the high-strength bolt 6 that connects the flange (31, 32) of the central member 3 to the splice plate 5 is defined as section B, at the bolt position closest to the end of the central member 3. In addition, among the high-strength bolts 6 that connect the bracket flange 42 to the splice plate 5, the section of the joint 12 that is closest to the end of the central member 3 is defined as section D, and the section midway between sections B and D is defined as section C. Finally, the section of the high-strength bolt 6 that is closest to the steel column 2 is defined as section E.

[0031] Next, we will explain how to determine the type of member for a beam. In this embodiment, a method for determining the type of member to evaluate the deformation performance of a beam 11 will be described, using a beam 11 having a joint 12 of the steel column-beam joint structure 1 described above as an example.

[0032] As described in the background technology section, the structural characteristic coefficient Ds in the seismic design of steel structures under Route 3 is given for each member type of FA-FD as defined in "Ministry of Construction Notification No. 1792 of 1980, Article 3, Paragraph 2". Therefore, when seismically designing the steel column-beam joint structure 1, which is provided with the beam 11 having the joint 12 of this embodiment described above, under Route 3, it is necessary to define the member type of the beam 11 in the same way as conventional steel beam members.

[0033] Therefore, in this embodiment, the classification of member types for beam 11 is defined as equivalent to FA, equivalent to FB, equivalent to FC, and equivalent to FD. Beams 11 classified as equivalent to FA-FD are defined as being able to exhibit plastic deformation capacity equivalent to conventional steel beam members classified as FA-FD in "Ministry of Construction Notification No. 1792 of 1980, Article 3, Paragraph 2".

[0034] Figures 5 and 6 schematically illustrate the method for determining the member type of beam 11. In beam 11, after the central member 3 reaches full plasticity at section A, the bending moment increases due to stress increase caused by strain hardening of the central member 3, similar to conventional construction methods. Based on experimental results conducted by the inventors of this application, the following two types of behavior are possible thereafter.

[0035] First, considering the case where the width-to-thickness ratio of the central member 3 is of type FA, if the yield bending strength of the joint 12 and bracket 13, as well as the sliding strength of the joint 12, exceeds the "maximum deformation strength assumed for the central member 3 of type FA", then the beam 11 can exhibit plastic deformation capacity equivalent to that of FA, as shown in Figure 5(a).

[0036] On the other hand, if the yield bending strength of the joint 12 and bracket 13, and the sliding strength of the joint 12 are lower than the "maximum deformation strength assumed for the central member 3 of FA," then, as shown in Figures 5(b), 6(a), and 6(b), the overall plastic deformation capacity of the beam 11 will not meet the expected value for the central member 3 of FA. In other words, even if the width-to-thickness ratio type of the central member 3 is FA, the member type of the beam 11 as a whole 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 sliding strength of the joint 12.

[0037] More specifically, as shown in Figure 5(b), if the joint 12 yields, the bracket 13 yields, or the joint 12 slips after the plastic deformation capacity assumed for FB is achieved, the member type of the beam 11 becomes equivalent to FB. On the other hand, as shown in Figure 6(a), if the joint 12 yields, the bracket 13 yields, or the joint 12 slips after the plastic deformation capacity assumed for FC is achieved, the member type of the beam 11 becomes equivalent to FC. Then, as shown in Figure 6(b), if the joint 12 yields, the bracket 13 yields, or the joint 12 slips after the central member 3 has reached full plasticity, the member type of the beam 11 becomes equivalent to FD.

[0038] In short, the member type of beam 11 being equivalent to FA-FD means that yielding of the joint 12, slippage of the friction joint of the high-strength bolt 6, and yielding of the bracket 13 will not occur until the central member 3 exhibits plastic deformation capacity equivalent to FA-FD.

[0039] Furthermore, the "assumed maximum deformation load-bearing capacity" for each member type of beam 11 (equivalent to FA-FD) is as shown in Figures 5 and 6, with respect to the full plastic moment M. p This is determined by multiplying by the joint coefficient α. In other words, the member type of beam 11 is determined by the joint coefficient α.

[0040] FIG. 1 is an explanatory diagram showing an outline of a method for determining the member type of the beam member summarized above. As shown in this figure, it schematically shows that "even if the width-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."

[0041] 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 not conventional 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.

[0042] Subsequently, the method for setting the joint coefficient α in the method for determining the member type of the beam member 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 gusset plates (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."

[0043] FIG. 7 is an explanatory diagram schematically showing the relationship between the bending moment acting on each part of the beam 11 when the central member 3 reaches the assumed maximum bearing capacity, 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 such.

[0044] When the central member 3 reaches the full plastic moment A M pWhen it reaches this point, the bending moment acting on each cross section (B section, D section, E section) of the joint 12 and bracket 13 is B M du , D M du , E M du Therefore, the bending moment acting on each cross-section at the assumed maximum deformation is, similar to cross-section A, B M max =ξ× B M du , D M max =ξ× D M du , E M max =ξ× E M du It can be expressed as follows.

[0045] The joint 12 and bracket 13 remain within the elastic range until the central member 3 exhibits a predetermined plastic deformation capacity, and therefore, in the schematic diagram of Figure 7, the yield bending strength of each cross-section of the joint 12 is... JB M y , JD M y ), the yield bending strength of bracket 13 ( JE M y ) and the sliding strength of the friction joint of the high-strength bolt 6 ( br M slip , bc M slip ) and the bending moment acting on each cross-section ( JB M y , JD M y , JE M y The relationship between ( ) and can be expressed as an equation as follows:

[0046] <Yield bending strength of splice plates (5, 51, 52) JB M fy > JB M fy ≧ ξ× B M du JD M fy ≧ ξ× D Mdu <Yield bending strength of bracket 13 JE M fy > JE M fy ≧ ξ× E M du

[0047] <Slip resistance of joint 12> bc M slip ≧ ξ× B M du (center material side) br M slip ≧ ξ× E M du (Bracket side)

[0048] The above formula attempts to ensure that the yield bending strength of the joint 12, the yield bending strength of the bracket 13, and the sliding strength of the joint 12 are all greater than the bending moment obtained by multiplying the bending moment of each section when the central member 3 reaches the full plastic moment at section A by the stress increase rate ξ, assuming that the actual yield strength of the steel material is equal to the nominal value. However, it is common for there to be a difference between the design value and the actual value of the yield bending strength and sliding strength of the joint 12 and the yield bending strength of the bracket 13.

[0049] Therefore, we will refer to the "Design Guidelines for Steel Structure Joints" (Architectural Institute of Japan, 2021.2) (hereinafter referred to as the "Joint Guidelines"). If we set the yield strength of the steel material used in the splice plates (5, 51, 52) of joint 12 and the bracket 13, and the sliding strength of joint 12, as correction coefficients β1, β2, and β3, respectively, that take into account the variation in actual values ​​relative to the nominal values, then the above equation can be written in a form that takes into account the variation in actual values ​​relative to the nominal values ​​of material strength.

[0050] <Yield bending strength of splice plates (5, 51, 52) JB M fy > JB M fy ≧ ξ·β1· B M du JD M fy ≧ ξ·β1· D M du <Yield bending strength of bracket 13 JE M fy > JE M fy ≧ ξ·β2· E M du

[0051] <Sliding resistance of joint 12 bc M slip ≧ ξ·β3· B M du (Center member side) br M slip ≧ ξ·β3· E M du (Bracket side)

[0052] Furthermore, the joint coefficient α s ,α br ,α slip When sorted using, 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 M fy ≧ α br · E M du (Equation 3)

[0053] <Sliding resistance of joint 12 bc M slip≥ α slip · B M du (Central material side) (Formula 4) br M slip ≥ α slip · E M du (Bracket side) (Formula 5)

[0054] In short, "keeping the joint 12 and bracket 13 within the elastic range until the central member 3 exhibits a predetermined plastic deformation capacity" is equivalent to confirming, as shown in the above equation, that "the yield bending strength or sliding strength of each part exceeds the value obtained by multiplying the bending moment acting on each cross section at the A cross section position during full plastic deformation by the joint coefficient."

[0055] As mentioned above, the joint coefficient (α s ,α br ,α slip The stress rate is calculated by multiplying the "stress increase rate ξ due to strain hardening of the central member 3" by "correction coefficients (β1, β2, β3) that take into account the variation in actual values ​​relative to the nominal values ​​of the yield strength and sliding resistance of the steel used in the joint 12 and bracket 13".

[0056] Here, β1 is a correction factor determined from the mean and standard deviation of the yield strength of the central member 3 and the splice plates (5, 51, 52), β2 is a correction factor determined from the mean and standard deviation of the yield strength of the central member 3 and the bracket 13, and β3 is a correction factor determined from the yield strength of the central member 3 and the mean and standard deviation of the sliding resistance of the friction joint of the high-strength bolt 6.

[0057] Furthermore, in order to determine the member type of the beam 11 according to the load-bearing capacity applied to 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 capacity required for each member type is exerted.

[0058] Therefore, we will now explain how to set the stress increase rate ξ due to strain hardening. Here again, referring to the "Guidelines for Joints," the plastic deformation capacity θ of the beam is... max / θ pThe relationship between the stress increase rate ξ and the stress increase rate is shown in the following equation.

number

[0059] Therefore, the plastic deformation capacity θ required for each type of steel beam member is calculated using the above formula. max / θ p By substituting these values, the stress increase rate ξ due to strain hardening of the central member 3 in each type of member of the beam 11 can be determined.

[0060] For the FA equivalent, the stress increase rate ξ is 1.20, using the value from the "Joint Guidelines" for cases where individual considerations are not taken. For the FD equivalent, since the plastic deformation capacity of the central member 3 is almost negligible, the stress increase rate ξ is 1.05, using the value from the "Joint Guidelines".

[0061] Furthermore, for FB equivalent and FC equivalent, the stress increase rate ξ is determined using the following approach. According to the "2020 Edition Commentary on Technical Standards for the Structure of Buildings" (Edited by the Editorial Committee for the Commentary on Technical Standards for the Structure of Buildings, October 2020), the required plastic deformation capacity for beams of member types FA, FB, and FC is 4.0, 2.0, and 0.0, respectively, with a lower limit of the plastic deformation ratio. The plastic deformation ratio is calculated using the plasticity ratio (θ). max / θ p Since it can be obtained by subtracting 1 from ), the lower limits of the plasticity ratio required for FA, FB, and FC beams are 5.0, 3.0, and 1.0, respectively. Therefore, the range of plasticity ratios required for FA, FB, and FC beams is 5.0 or higher for FA, 3.0-5.0 for FB, and 1.0-3.0 for FC.

[0062] For the range of plasticity ratios required for each type of beam, the method for determining the type of beam member involves determining the plasticity ratio (θ) for calculating the stress increase rate ξ equivalent to FB and FC. max / θ pThe value of ) is set to the "median" of the range of plasticity ratios for each member type. Figure 8 is an explanatory diagram of setting the stress increase rate for the median of the plasticity ratio required for beams of each member type. Figure 9 is an example of setting the plasticity ratio (θ) for each member type in the formula (Equation 1) for the stress increase rate ξ of the "Joint Guidelines" mentioned above. max / θ p This shows the stress increase rate (ξ) calculated by substituting ).

[0063] In other words, the plasticity ratio used to determine the stress increase rate ξ is θ, which corresponds to FB. max / θ p Let = 4.0, and the FC equivalent is θ max / θ p Let = 2.0. As shown in Figure 8, if the stress increase rate ξ is set to the median value of the plasticity ratio required for beams of each member type, beam 11 is guaranteed to exhibit the lower limit of the plasticity ratio required for beams of each member type, thus resulting in a conservative evaluation.

[0064] With this method of determining the member type of beam member, the joint coefficient (α s , α br , α slip The type of member (deformation performance) of the entire beam 11 with the joint 12 can be determined using this method.

[0065] And the joint coefficient (α s , α br , α slip The correction coefficients (β1, β2, β3) used when determining the yield strength and sliding resistance of the steel material are coefficients determined from the statistical values ​​of the yield strength and sliding resistance of the steel material, and can be determined from the above "Joint Guidelines" and each statistical value. Specifically, β1 is the ratio of the actual value to the nominal value of the yield strength of the central member 3 β bc " and "the ratio of the actual value to the nominal value in the yield strength of the splice plates (5, 51, 52) β s This is a correction coefficient based on the material strength determined from ". Also, β2 is the ratio of the actual value to the nominal value in the yield strength of the central material 3 β bc " and "the ratio of the actual value to the nominal value in the yield strength of bracket 13 β brThis is a correction coefficient based on the material strength determined from ". And β3 is the ratio of the actual value to the nominal value in the yield strength of the central material 3 β bc " and "β, the ratio of the actual value to the nominal value in sliding resistance slip This is a correction factor based on the material strength determined by "[ ]".

[0066] Figure 10 shows the joint coefficient (α) for each type of member. s , α br , α slip ) was given as an example. Thus, in the method for determining the member type of beam member, the joint coefficient (α s , α br , α slip By designing the joint 12 and bracket 13 using ), the type of member for the entire beam 11 can be easily determined.

[0067] Furthermore, according to experimental results conducted by the present inventor, the hysteretic properties of the beam 11 can also be controlled. Specifically, in the beam 11, even if the total plastic load-bearing capacity of the central member 3 is the same, different hysteretic properties can be obtained depending on the load-bearing capacity applied to the joint 12 and the bracket 13.

[0068] For example, if the joints 12 and brackets 13 are designed not to yield until the central member 3 reaches its maximum load-bearing capacity, and no slippage occurs in the joints 12, then the load-deformation relationship of the beam 11 can maintain a spindle-shaped hysteretic behavior until the main slippage occurs. In short, as long as the joints 12 and brackets 13 remain within the elastic range until the central member 3 exhibits a predetermined plastic deformation capacity, the spindle-shaped hysteretic behavior characteristic of steel members can be achieved.

[0069] On the other hand, if slippage occurs in the joint 12, the load-bearing capacity will rapidly decrease due to the effect of the main slippage, and repeated slippage will cause the load-deformation relationship to take on a sawtooth hysteretic pattern. In this way, by clarifying the relationship between the load-bearing capacity applied to the joint 12 and bracket 13 and the plastic deformation capacity of the central member 3, the performance of the beam 11 having the joint 12 and bracket 13 can be easily determined.

[0070] Next, the operation of the steel column-beam joint structure of this embodiment will be described. In the method for determining the member type of the beam member, the relationship between the width-to-thickness ratio type, which represents the plastic deformation capacity of the central member 3, and the performance of the joints 12 and brackets 13 is set, and the performance of the joints 12 and brackets 13 is determined by the joint coefficient (α s , α br , α slip It is determined based on the width-to-thickness ratio type of the central member 3 and the joint coefficient (α) as shown in Figures 1 and 10. s , α br , α slip The type of member for beam 11 is determined based on the above.

[0071] Thus, by clarifying the relationship between the load-bearing capacity applied to the friction joints 12 and brackets 13 by the high-strength bolts 6 and the plastic deformation capacity of the central member 3, it becomes easy to determine the type of member for evaluating the deformation performance of the beam 11, according to the design philosophy, such as wanting to fully utilize the plastic deformation capacity of the central member 3.

[0072] For example, if, as in the design of conventional beam joints, it is sufficient to confirm that the joint does not break under the bending moment at the joint position when the beam end reaches its "maximum bending strength," then yielding or slippage of the joint may occur before the beam can exert its predetermined plastic deformation capacity. However, if the main slippage occurs in the joint soon after the central member has reached full plasticity, the load-bearing capacity will decrease rapidly.

[0073] Therefore, in this embodiment, by clarifying the relationship between the load-bearing capacity applied to the joint 12 and bracket 13 and the plastic deformation capacity of the central member 3, the following deformation performance can be provided to the beam 11.

[0074] In other words, by designing the joint 12 and bracket 13 using a joint coefficient corresponding to the plastic deformation capacity expected of the central member 3, it becomes possible to determine the deformation performance of the beam 11, such as "deformation performance in which a decrease in load-bearing capacity due to main slip occurs soon after the central member 3 reaches full plasticity," "deformation performance in which a decrease in load-bearing capacity due to main slip occurs after the central member 3 has reached full plasticity and has exhibited a certain degree of plastic deformation capacity," and "deformation performance in which no main slip occurs until the end of loading."

[0075] Therefore, in determining the member type of the beam member, the joint 12 and bracket 13 are designed based on the bending moment acting on the beam 11, according to the above-mentioned (Equation 1)-(Equation 5). Here, the stress rise rate ξ for determining the joint coefficient is calculated for the median value of the plasticity ratio required for the steel beam member of each member type, as shown in Figure 8, in the case of FB equivalent and FC equivalent. The joint coefficient (α) is shown in relation to the member type of the beam 11 (FA equivalent - FD equivalent) and the width-to-thickness ratio type of the central member 3. s , α br , α slip The result is shown in Figure 10.

[0076] If the details of the joints 12 and brackets 13 can be determined according to the performance of the beam 11 required by the designer, then it becomes possible to optimize the structural costs according to the design results based on the joint coefficient without changing the cross-section of the central member 3.

[0077] In the steel column-beam joint structure 1 of this embodiment, even when the high-strength bolts 6 for the friction joint between the central member 3 and the splice plate 5 are arranged in a staggered pattern, by arranging the high-strength bolts 6 at the first bolt position (section A position) and the second bolt position (adjacent to the first bolt position) in parallel, it is possible to suppress an excessive decrease in the tension of the high-strength bolts 6 from the second bolt position onward due to plastic deformation of the flanges (31, 32) of the central member 3.

[0078] While embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and any design modifications that do not depart from the spirit of the present invention are included in the present invention.

[0079] For example, the above embodiment described a method for determining the member type of a beam 11 in a steel column-beam joint structure 1 in which a central member 3 is connected to brackets 13 extending outwards on all four sides of a steel column 2 via joints 12, but it is not limited to this. It can also be applied to beam members having friction joints using high-strength bolts of a different form than the joints 12 described above. [Explanation of Symbols]

[0080] 11: Beam (beam member) 12: Fittings 13: Bracket 2: Steel column (column) 3: Central material 5: Plate 6: High-strength bolts

Claims

1. A steel column-beam connection structure in which a beam member narrower than the column width is connected to a steel column, A bracket extending from the aforementioned steel column, A splice plate is formed on the steel column side so that the central member side of the beam member is widened to the width of the central member, The splice plate is joined to the bracket at the end of the steel column side, and the splice plate is joined to the central member at the end of the central member side, and a plurality of high-strength bolts are provided to join the central member of the beam member, At least two rows of the high-strength bolts on the central member side are arranged in parallel. A steel column-beam joint structure characterized in that the high-strength bolts used to join the central member and the splice plate, other than those arranged in parallel, are arranged in a staggered pattern.

2. The steel beam and column joint structure according to claim 1, characterized in that the high-strength bolts used to join the splice plate and the bracket are arranged in parallel.

3. The steel beam-column joint structure according to claim 1 or 2, characterized in that the friction joint using high-strength bolts is designed to have deformation performance such that a reduction in load-bearing capacity due to main sliding occurs after the central member has reached full plasticity and exhibited plastic deformation capacity.

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