JP2024092476A - Beam-column joint part and method for designing the same - Google Patents

Abstract

To make a collapse form of the whole building into a whole collapse having a large energy absorbing amount by making the collapse form of a column-beam joint part not into a column collapse form but into a column-beam joint part collapse form in the column-beam joint part of a welded assembly box-shaped cross-section column and a steel beam.SOLUTION: A column beam joint part of a welded assembly box-shaped cross-section column and a steel beam is constituted by mutually joining four skin plates by corner welding, wherein the corner welding is one or both of under-match welding and partial penetration welding, a total value Σb Mp* of bending moments of material ends when the steel beam attached to a joint part panel of the beam-column joint part is in a fully plastic state, a total value Σc Mp* of fully plastic moments of material ends of the welded assembly box-shaped cross-section column attached to the joint part panel, a total plastic momentpMp1* of the joined part panel and a total plastic moment pMp2* of the joint part panel when it is assumed that the corner welding is overmatch welding and complete penetration welding are made to satisfy a prescribed relation.SELECTED DRAWING: Figure 1

Description

The present invention relates to a column-beam joint between a welded box section member consisting of four skin plates joined together by corner welding and a steel beam, and a design method for the joint.

Square steel pipes such as cold roll-formed square steel pipes, cold press-formed square steel pipes, and welded assembled box section members are often used for column members in buildings. Relatively inexpensive cold roll-formed square steel pipes and cold press-formed square steel pipes are often used for column members in low- to mid-rise buildings and high-rise buildings. In contrast, for column members in super-high-rise buildings, because the required rigidity and strength are very high, welded assembled box section members that can be made larger in cross section, thicker, and stronger are often used.

The manufacturing cost of welded box sections is higher than that of cold roll-formed square steel pipes and cold press-formed square steel pipes. This is due to the fact that the steel plates that make up the skin plates of welded box sections are expensive as the strength of the components increases, and that welding construction management during the manufacturing of welded box sections requires a lot of labor and time.

In particular, when the wall thickness of the welded box section member is very thick, the welding depth is large when the skin plates of the welded box section member are joined to each other by corner welding. Corner welding of the welded box section member is often performed by _CO2 welding or submerged arc welding, but in either case, when the welding depth of the corner welding is large, the corner welding cannot be performed in one pass and the number of welding passes increases. Therefore, the corner welding becomes multi-layered, which increases the manufacturing cost of the welded box section member and extends the manufacturing period.

In addition, in the case of multi-layer submerged arc welding, as disclosed in, for example, Non-Patent Documents 1 and 2, thermal management of the interpass temperature and its holding time, as well as the post-heat temperature and its holding time, is required to prevent the weld metal from prematurely breaking at a low level and falling below the base metal specification strength.

In submerged arc welding, the maximum weld depth that can be achieved in one pass is about 60 mm. Therefore, when manufacturing welded box section components with a wall thickness of 60 mm or more using submerged arc welding, the corner welds become multi-layer submerged arc welding. This requires heat management as described above, which drastically lengthens the manufacturing period for welded box section components.

In response to such problems, a method can be considered in which the thickness of the skin plate constituting the welded box section member is reduced, and the strength of the skin plate is increased to compensate for the reduction in the strength of the entire welded box section member caused by the reduction in the thickness. In this way, corner welding of the welded box section member can be performed by one pass of _CO2 welding or submerged arc welding. However, since the welding material for corner welding needs to be made stronger in accordance with the increase in strength of the skin plate constituting the welded box section member, the workability of corner welding may be reduced.

For example, Patent Document 1 proposes a method for manufacturing a box column in which the corners of a welded box section member are fillet welded from the inside. However, welding work on the inside of a welded box section member places a high workload on the welder and may be dangerous work. Therefore, as disclosed in Non-Patent Document 3, for example, it has been considered to use partial penetration welding for corner welding of welded box section members.

Furthermore, in recent years, with the increase in the size of high-rise buildings and the lengthening of column spans, it is necessary to increase the size and strength of the cross-section of steel beams. That is, depending on the type of building, the cross-section of the beam is determined mainly to prevent the deflection of the beam from exceeding the deflection limit as the column span increases, and it may be necessary to make the steel beam larger in cross-section and stronger. In this way, when a large cross-section and high-strength steel beam is attached to a column-beam joint, the total value of the full plastic strength of the ends of one or more beam members attached around the column-beam joint panel tends to be large. And if the total value of the full plastic strength of the ends of the beam members exceeds the total value of the full plastic strength of the ends of the column members attached above and below the column-beam joint panel, when a large bending moment acts on the column-beam joint, damage may be concentrated at the ends of the column members, and the collapse type of the column-beam joint may become a column collapse type.

If the collapse pattern of the column-beam joint is a column collapse pattern, there is a high risk that the collapse pattern of the entire building will be a partial collapse pattern, which absorbs less energy, rather than a total collapse pattern, which absorbs more energy. This means that a story of the building may collapse with a relatively small input energy of the earthquake.

Japanese Patent No. 5157556

Makoto Yuda and 3 others, "Study on multi-layer submerged arc welding for extra-thick box corner joints (SA440) Part 1 Test overview and preliminary test results", Proceedings of the Architectural Institute of Japan Annual Meeting (Kinki), Architectural Institute of Japan, September 2014, pp. 1045-1046 Takao Fukumoto and 3 others, "Study on multi-layer submerged arc welding for extra-thick box corner joints (SA440) Part 2: Consideration of pre-test and actual test results", Proceedings of the Architectural Institute of Japan Annual Meeting (Kinki), Architectural Institute of Japan, September 2014, pp. 1047-1048 Suetomi Inoue and two others, "Study on the load-bearing capacity of box columns assembled by partial penetration welding (Part 1. Experimental plan and partial penetration welding shear experiment)", Proceedings of the Architectural Institute of Japan Annual Meeting (Kyushu), Architectural Institute of Japan, October 1989, pp. 1253-1254 Architectural Institute of Japan, "Guidelines for Plastic Design of Steel Structures, 3rd Edition," Architectural Institute of Japan, February 2017, pp. 150-155 Architectural Institute of Japan, "Guidelines for Design of Steel Structure Joints, Third Edition," Architectural Institute of Japan, March 2012, pp. 225-226 Maito Kurita and 3 others, "Study on the structural performance of ultra-high strength steel CFT members assembled by undermatching welding, Part 14: Hysteretic behavior and strength evaluation of CFT joint panel with width-thickness ratio of 16.7", Proceedings of the Architectural Institute of Japan Annual Meeting (Tohoku), Architectural Institute of Japan, September 2018, pp. 1425-1426

In order to prevent the collapse type of a column-beam joint from becoming the column collapse type under conditions where the cross section of the beam member has been determined, it is necessary to make the full plastic strength of the column-beam joint panel smaller than the total value of the full plastic strength of the column member ends to make the column-beam joint panel collapse type. However, because an internal diaphragm type is often used for column-beam joints between welded box section columns and steel beams, it is difficult to reduce the full plastic strength of the column-beam joint panel by making the column thickness smaller at the column-beam joint panel than at other parts. Thus, in column-beam joints between welded box section columns and steel beams, it is difficult to make the full plastic strength of the column-beam joint panel smaller than the total value of the column's full plastic strength.

In view of the above problems, the present invention aims to change the collapse pattern of a column-beam joint between a welded box section column and a steel beam from a column-beam joint to a column-beam joint panel collapse pattern rather than a column collapse pattern, thereby enabling the collapse pattern of the entire building to be an overall collapse pattern with a large amount of energy absorption.

To solve the above problems, the present invention has the following features:

[1] A column-beam joint between a welded box section column formed by four skin plates joined together by corner welds and a steel beam, wherein the corner welds are one or both of undermatch welds and partial penetration welds, and the total bending moment _ΣbMp ^* of the material ends when the steel beams attached to the joint panel of the column-beam joint are in a fully plastic state, the total plastic moment _ΣcMp ^* of the material ends of the welded box section columns attached to _the joint panel, the total plastic moment _pMp1 ^* of the joint panel, _{and the} total plastic moment _pMp2 ^* of the joint panel when it is assumed that the corner welds are _overmatch welds and full penetration welds satisfy the relationships in the following equations (1) and (2).

Σ _c M _p ^* < _p M _{p 2} ^* ... (1)
_p M _p1 ^* < Σ _c M _p ^* < Σ _b M _p ^* ... (2)
Here, when the steel beam has a uniform cross section in the axial direction and no widening portion such as a haunch or reinforcing material is provided at the end of the steel beam, the steel beam is in a fully plastic state at the end. In this case, the bending moment at the end of the steel beam when the steel beam is in a fully plastic state is equal to the fully plastic moment of the steel beam. In addition, when the steel beam has a widening portion such as a haunch or reinforcing material at the end, the steel beam may be in a fully plastic state at the boundary between the portion where the widening portion or reinforcing material is provided and the portion where it is not provided. In this case, the bending moment at the end of the steel beam when the steel beam is in a fully plastic state is larger than the fully plastic moment of the steel beam at the boundary, etc., depending on the bending moment distribution in the axial direction of the steel beam. Therefore, when an enlarged portion or reinforcing material such as a haunch is provided at the end of a steel beam, the bending moment at the end of the steel beam when it is in a fully plastic state is calculated, taking into account that the bending strength of the steel beam changes in the axial direction due to the provision of the enlarged portion or reinforcing material.

[2] The column-beam joint according to [1], wherein the skin plate has a tensile strength of 780 N/ ^mm2 or more.

[3] A column-beam joint as described in [1] or [2], in which the groove depth of the corner weld is 60 mm or less.

[4] A beam-column joint as described in [1] or [2], in which the interior of the welded box section member is filled with concrete.

[5] The column-beam joint described in [3], in which the interior of the welded box section member is filled with concrete.

[6] A method for designing a column-beam joint, in which the corner welds are one or both of undermatch welds and partial penetration welds, and the thickness and standard strength of the skin plate, the cross-sectional shape and standard strength of the steel beam, and the weld depth and standard strength of the weld metal of the corner welds are set so that the following values calculated from the thickness and standard strength of the skin plate, the cross-sectional shape and standard strength of the steel beam, and the weld depth and standard strength of the corner _welds satisfy the relationships in the following equations ( ₁₎ and ₍ ^{2 )} : the sum of the bending moments _ΣbMp ^* of the material ends of the welded-assembled box section columns attached to the joint panel when the steel beams are attached to _the joint panel of _the column-beam joint are in a fully plastic state, the sum of the full plastic moments _ΣcMp ^* of the material ends of the welded-assembled box section columns attached to the joint panel, the full plastic moment pMp1* of the joint panel, and the full plastic moment _pMp2 * of the joint panel when it is assumed that the corner welds are overmatch welds and full penetration welds.

Σ _c M _p ^* < _p M _{p 2} ^* ... (1)
_p M _p1 ^* < Σ _c M _p ^* < Σ _b M _p ^* ... (2)
Here, when the steel beam has a uniform cross section in the axial direction and no widening portion such as a haunch or reinforcing material is provided at the end of the steel beam, the steel beam is in a fully plastic state at the end. In this case, the bending moment at the end of the steel beam when the steel beam is in a fully plastic state is equal to the fully plastic moment of the steel beam. In addition, when the steel beam has a widening portion such as a haunch or reinforcing material at the end, the steel beam may be in a fully plastic state at the boundary between the portion where the widening portion or reinforcing material is provided and the portion where it is not provided. In this case, the bending moment at the end of the steel beam when the steel beam is in a fully plastic state is larger than the fully plastic moment of the steel beam at the boundary, etc., depending on the bending moment distribution in the axial direction of the steel beam. Therefore, when an enlarged portion or reinforcing material such as a haunch is provided at the end of a steel beam, the bending moment at the end of the steel beam when it is in a fully plastic state is calculated, taking into account that the bending strength of the steel beam changes in the axial direction due to the provision of the enlarged portion or reinforcing material.

[7] The method for designing a beam-column joint according to [6], wherein the tensile strength of the skin plate is 780 N/ ^mm2 or more.

[8] A method for designing a beam-column joint as described in [6] or [7], in which the groove depth of the corner weld is 60 mm or less.

[9] A method for designing a beam-column joint as described in [6] or [7], in which the interior of the welded box section member is filled with concrete.

[10] A method for designing a beam-column joint as described in [8], in which the interior of the welded box section member is filled with concrete.

According to the beam-column joint and its design method of the present invention, the corner welds of the welded box section column are either or both of undermatch welding and partial penetration welding, so that the full plastic strength of the joint panel of the beam-column joint can be made smaller than the total full plastic strength of the ends of the steel beams attached to the joint panel. And by making the full plastic strength of the joint panel of the beam-column joint smaller than the total full plastic strength of the ends of the column members attached above and below the beam-column joint panel, the collapse type of the beam-column joint can be the beam-column joint panel collapse type. As a result, even if the steel beam has a large cross section or high strength and the total value of the full plastic strength of the ends of the beam members attached to the beam-column joint panel is large, the collapse type of the beam-column joint can be the beam-column joint panel collapse type instead of the column collapse type, and the collapse type of the entire building can be the overall collapse type with a large energy absorption capacity.

In addition, since the corner welds of welded box section columns are either or both of undermatch welding and partial penetration welding, the workability of corner welding of welded box section columns can be significantly improved, and the manufacturing costs and manufacturing time can be significantly reduced.

Fig. 1(a) is a perspective view showing an example of a beam-column joint of the present invention, and Fig. 1(b) is a cross-sectional view of a welded box section member. Figures 2(a) and 2(b) are a cross-sectional view and a side view of a welded box section member, Figures 2(c) and 2(d) are a cross-sectional view and a side view of a mechanical model of the welded box section member, and Figures 2(e) and 2(f) are a cross-sectional view and a side view of a mechanical model when a shear force acts on the welded box section member from the 0° direction. 3(a) to 3(c) are side views showing the shear deformation region and the bending deformation region that occur when a shear force acts on a welded box section member from the 0° direction. FIG. 4 is a graph showing the strength of a panel portion of a beam-to-column joint when a shear force acts on a welded box section member from the 0° direction. 5(a) and 5(b) are diagrams showing test specimens in a load test carried out to verify the effects of the beam-column joint and its design method of the present invention.

Below, we will explain in detail the embodiment of the column-beam joint and its design method of the present invention with reference to the drawings.

Figure 1(a) shows a column-beam joint 1 of this embodiment. Figure 1(b) shows a cross-sectional view of a welded box section column 10 that constitutes the column-beam joint panel portion of the column-beam joint 1.

As shown in Figures 1(a) and 1(b), the column-beam joint 1 of this embodiment is a column-beam joint between a welded box section column 10, which is constructed by joining four skin plates 11, 12 together with corner welds 13, and a steel beam 20. In this embodiment, the steel beam 20 is constructed from an H-shaped steel, but the steel beam in the present invention is not limited to this.

In addition, FIG. 1(a) shows an example of a column-beam joint of the present invention in which welded box section columns 10 are attached to the top and bottom of the column-beam joint panel, and steel beams 20 are attached to the left and right of the column-beam joint panel. The present invention is not limited to this, and can also be applied to cases in which a welded box section column 10 is attached only to the bottom of the column-beam joint panel, or to cases in which one or three or more steel beams 20 are attached around the column-beam joint panel.

As shown in FIG. 1(b), in the column-beam joint 1 of this embodiment, the corner welds 13 that join the four skin plates 11, 12 are partial penetration welds. The corner welds in the present invention are not limited to this, and the corner welds may be full penetration undermatch welds or partial penetration and undermatch welds.

Furthermore, the skin plates 11, 12 and corner welds 13 of the welded box section column 10 constituting the beam-column joint 1 of this embodiment, and the shape and material strength of the steel beam 20 are set to satisfy the relationship of the following formulas (1) and (2). That is, the plate thickness t and yield strength σ _y of the skin plates 11, 12 of the welded box section column 10, the weld depth t _w and weld metal strength σ _yw of the corner weld 13, and the cross-sectional size and yield strength of the steel beam 20 are set to satisfy the relationship of the above formulas (1) and (2).

Σ _c M _p ^* < _p M _{p 2} ^* ... (1)
_p M _p1 ^* < Σ _c M _p ^* < Σ _b M _p ^* ... (2)
In addition, the design method for a column-beam joint in this embodiment sets the plate thickness t and standard strength σ _y of the skin plates 11, 12, the weld depth t _w and weld metal strength σ _yw of the corner weld 13, and the cross-sectional size and standard strength of the steel beam 20 so as to satisfy the relationship between the above equations (1) and (2).

In the above formulas ( ₁ ) and (2), _ΣbMp ^* is the total bending moment of the ends of the steel beams 20 attached to the joint panel of the beam-to-column joint 1 when they are in a fully plastic state, and _ΣcMp ^* is the total plastic moment of the ends of the welded box section columns 10 attached to the joint panel. Also, _pMp1 ^* is the total plastic moment of _the joint panel, _{and pMp2 *} ^is _the total plastic moment of the joint panel when it is assumed that the corner welds 13 are overmatch welds and full penetration welds.

The bending moment _bMp ^* at the end of the steel beam 20 when it is in _a fully plastic state, the fully plastic moment _cMp ^* at the end of the welded box section column 10, and the fully plastic moment _pMp2 ^* of the joint panel when the corner weld 13 is assumed to be _an overmatch weld _and full penetration weld can be calculated, for example, by the method described in non-patent document 4.

In addition, the total plastic moment _p M _p1 ^* of the joint panel taking into consideration the reduction in yield strength due to the corner welds 13 being either or both of an undermatch weld and a partial penetration weld was examined as follows.

First, as shown in Figures 2(a) to 2(d), in a welded box section column 10, it was assumed that the plate thickness t of the skin plate and the weld depth t _w of the corner welds are sufficiently small compared to the plate widths of the skin plates 11, 12, and that the skin plates 11, 12 are concentrated at the center of the plate thickness, and a mechanical model was set up that ignores the shear stress generated in the plate thickness direction of the skin plates 11, 12.

It was assumed that when a shear force acts on the welded box column 10, shear deformation and bending deformation occur at each part of the welded box column 10 as follows:

First, as shown in Fig. 2(e) and Fig. 2(f), when the direction of the shear force acting on the welded box column 10 is parallel to the width direction of one of the pair of opposing skin plates 11 and the other pair of opposing skin plates 12 (hereinafter referred to as "when a force is applied in the 0° direction"), the following assumptions were made. That is, it was assumed that the pair of skin plates 11 parallel to the shear force undergo shear deformation in an area of width ( _dc -X) mm at the center in the width direction, and bending deformation occurs at the upper and lower ends of the panel part of the column-beam joint part in an area of width (X/2) mm at both ends in the width direction. Here, _dc is the distance between the plate thickness centers of the skin plates 11 and 12 of the welded box column 10, and has a relationship of _dc = D-t with respect to the width D of the welded box column 10, and X is in the range of 0≦X≦ _dc /2. Furthermore, it was assumed that shear deformation occurs in all corner welds 13.

In the mechanical model described above, the shear strength of the beam-column joint panel of the welded box column 10 was calculated while changing the value of X within the range of 0≦X≦d _c /2. The minimum value among these shear strengths was determined as the shear strength of the beam-column joint panel of the welded box column 10. Specifically, the calculation was performed with reference to the calculation methods described in Non-Patent Documents 4 and 5. The shear strength _p M _pa of the beam-column joint panel of the welded box column 10 was calculated in this manner, and the results were as shown in the following formulas (3) to (5).

When applying force in the 0° direction,
(1) When 1≦(t _w ·σ _yw )/(t ·σ _y ) (see FIG. 3A ),

(2) When 1-√3( _dc / _db )≦( _tw · _σyw )/(t· _σy )≦1 (see FIG. 3B),

(3) When (t _w σ _yw )/(t σ _y )≦1−√3(d _c /d _b ) (see FIG. 3(c)),

In the above formulas (4) to (5), d _b is the height of the panel part of the column-beam joint. Also, the " _p M _p0 guideline" in the above formulas (3) to (5) is a value calculated according to the following formula (6).

Here, the " _pMp0 guideline" shown in the above formula (6) is _a formula for evaluating the strength of a column-beam joint panel portion described in Non-Patent Document 5, and is the value of the bending moment acting on the column-beam joint panel portion when the entire column-beam joint panel portion shears and reaches its full _{plastic strength. The "pMp0 guideline} " is currently the most widely used formula for evaluating the strength of a column-beam joint panel portion of a welded box section member constructed so that the corner welds 13 are full penetration welds and overmatch welds in which the strength of the weld metal of the corner welds exceeds the strength of the base material.

The shear strength _{p Mpa} of the beam-column joint panel of the welded box section column 10 obtained by the above formulas (3) to (5) varies depending on the ratio (t _w · σ _yw )/(t · σ _y ) of the yield strength of the weld metal of the corner weld (t _w · σ _yw ) to the base metal yield strength (t · σ _y ) and the aspect ratio d b / d c of the beam-column joint panel, as will be explained below.

Figure 4 shows a graph showing the change in the ratio _pMpa /(pMp0 _guideline ) of the shear strength pMpa of the column-beam joint panel part when a force is applied in the 0° direction, calculated using the above equations (3) to (5), to the " _pMp0 guideline" when the ratio of the strength of the corner weld ₁₃ to the base metal strength _{( tw} · _σyw )/( _{t ·} σy) is changed in the range of _{0.0 to} 1.2, for aspect ratios _db / _dc of the column-beam joint panel part of 1.0, 1.5, and 2.0.

4, the smaller the ratio (t _w · σ _yw )/(t · σ _y ) of the yield strength of the weld metal (t _w · σ _yw ) of the corner weld 13 to the base metal yield strength (t · σ _y ), the smaller the yield strength of the beam-column joint panel portion, and the larger the aspect ratio d _b /d _c of the beam-column joint panel portion, the greater the decrease in yield strength of the beam-column joint panel portion. In other words, by using either or both of undermatch welding and partial penetration welding for the corner welds 13 in at least the joint panel portion of the beam-column joint 1, the full plastic yield strength _p M _p1 ^* of the joint panel of the beam-column joint 1 can be reduced. The full plastic yield strength _p M _p1 ^* of the joint panel, taking into account the reduction in yield strength due to the corner weld 13 being one or both of an undermatch weld and a partial penetration weld, can be understood based on the ratio (t _w · σ _yw ) / (t · σ _y ) of the yield strength of the weld metal of the corner weld 13 (t _w · σ _yw ) to the base metal yield strength (t · σ _y ), as shown in Figure 4.

In addition, in the beam-column joint 1 and the design method thereof according to the present embodiment, the tensile strength of the skin plates 11, 12 constituting the welded box section column 10 can be 780 N/ ^mm2 or more. Currently, the strength of steel plates generally used as skin plates of welded box section columns is about 780 N/ ^mm2 at maximum. Steel plates of ⁷⁸⁰ N/mm2 or more tend to have smaller fracture elongation than steel materials with lower strength than this, and when used as skin plates of welded box section columns, it is common to design the skin plates to be used within their elastic range without expecting any deformation capacity. However, as described in Non-Patent Document 6, it has been reported that even steel materials of 780 N/ ^mm2 class exhibit large deformation capacity within the panel of the beam-column joint. As a result, even if 780 N/mm class ² steel plates are used for the skin plates 11, 12, the collapse type of the column-beam joint 1 between the welded-assembled box section column 10 and the steel beam 20 is a column joint panel collapse type, and the deformation capacity of the column-beam joint 1 can be sufficiently secured.

In addition, in the beam-column joint 1 and its design method of this embodiment, it is preferable to set the groove depth of the corner weld 13 to 60 mm or less. As described above, in submerged arc welding, the maximum welding depth that can be performed in one pass is about 60 mm. Therefore, when manufacturing a welded box section member with a thickness of 60 mm or more using submerged arc welding with overmatch welding and full penetration welding, the corner weld 13 becomes a multi-layer submerged arc weld, which requires post-heat management, and the manufacturing period of the welded box section member is significantly extended.

In contrast, in the beam-column joint 1 of the present embodiment, the weld depth t _w of the corner weld 13 of the welded box column 10 is reduced to a partial penetration weld, and the groove depth of the corner weld 13 is set to 60 mm or less, so that the corner weld 13 can be welded in one pass even when the plate thickness t of the skin plates 11, 12 of the welded box column 10 is large. Therefore, since there is no need for post-heat management as in the case of performing full penetration multi-layer submerged arc welding on a welded box member having a wall thickness of 60 mm or more, the weldability of the corner weld 13 is significantly improved, and the manufacturing cost and manufacturing period of the welded box column 10 can be significantly reduced. When the plate thickness t of the skin plates 11, 12 of the welded box column 10 is about 65 mm or less, the above-mentioned effect can be obtained by performing the corner weld 13 as a partial penetration weld, even if the groove depth of the corner weld 13 is not set to 60 mm or less.

By forming the corner welds 13 as undermatch welds or partial penetration welds, the component strength of the welded box column 10 is significantly affected mainly by the joint panel portion. However, in order to ensure that the welded box column 10 can transmit shear force even in portions other than the joint panel portion, it is preferable that the ratio of the strength of the weld metal of the corner welds 13 of the welded box column 10 to the base metal strength (t _w ·σ _yw )/(t·σ _y ) is 0.3 or more.

The beam-column joint 1 of this embodiment and its design method can also be applied to a welded box section column 10 in which the inside is filled with concrete (not shown).

To verify the effectiveness of the beam-column joint and its design method of the present invention, the collapse shape of the beam-column joint was confirmed through numerical analysis, which is explained below.

In this numerical analysis, a planar cross frame analysis model shown in Figure 5 was used to perform a numerical analysis under conditions in which an axial force was applied to the welded box section column 10 while shear forces were applied in an anti-symmetrical manner to both ends of the steel beam 20, and the collapse mode of the beam-column joint 1 was confirmed.

Specifically, the yield strength _σy of the skin plates 11 and 12 constituting the welded box section column 10 of the planar cross frame was set to 630 N/ ^mm2 , the column width was 800 mm, the plate thickness t was 80 mm, and the column height was 12000 mm. In addition, two types of corner welds 13 were set, namely, corner weld A (invention example) and corner weld B (comparison example). For the corner weld A, the analysis model was set assuming that the weld metal yield strength _σyw was 630 N/ ^mm2 , the groove depth _tw was 80 mm, and the weld was constructed so as to be an even-match weld by multi-pass submerged arc welding. For the corner weld B, the analysis model was set assuming that the weld metal yield strength _σyw was 325 N/ ^mm2 , the groove depth _tw was 50 mm, and the weld was constructed so as to be an undermatch weld by one pass submerged arc welding.

In addition, for the steel beam 20, in order to reproduce the case where the bending moment at the end of the steel beam 20 is large when the steel beam 20 reaches a fully plastic state, the yield strength was set to 440 N/ ^mm2 , the beam width to 600 mm, the beam depth to 1,600 mm, the beam flange thickness to 80 mm, the beam web thickness to 40 mm, and the beam length to 24,000 mm.

The upper end of the welded box column 10 in the axial direction was supported by pin rollers, and the lower end of the welded box column 10 was supported by pins, and an axial force with an axial force ratio of 0.4 (0.4N _y , where N _y is the yield axial force of the welded box column 10) was applied. As shown in Fig. 5, when a shear force Q acts on the end of the steel beam 20 in the axial direction in the opposite directions, the total bending moment Σ _b M _p ^* of the end of the steel beam 20 attached to the joint panel when the steel beam 20 is in a fully plastic state, the total plastic moment Σ _c M _p ^* of the end of the welded box column 10 attached to the joint panel, and the full plastic moment _p M _p1 ^* or _p M _p2 ^* of the joint panel were calculated. Table 1 shows the results of this numerical analysis.

As shown in Table 1, in the comparative example where the corner weld 13 is corner weld B, among the total bending moment _ΣbMp ^* of the material end when the steel beam 20 is in a fully plastic state, the total plastic moment _{ΣcMp *} of the material end of the welded box section column 10, and _{the total plastic moment pMp2 *} ^of the joint panel, _ΣcMp ^* _is the smallest. In other words, it _can be ^seen that damage is concentrated at the material end of the welded box section column 10 adjacent to the joint panel of the column-beam joint 1, and there is a high possibility that the collapse type of the column-beam joint 1 will be the column collapse type.

In contrast, in the example of the present invention in which the corner weld 13 is corner weld A, _among the total value _ΣbMp ^* of the bending moment at the end of the steel beam 20 when the steel beam 20 is in a fully plastic state, the total value _ΣcMp ^* of _the ^{full plastic moment at the end of the welded box section column 10, and the total plastic moment pMp1* of the joint panel, pMp1*} _{is the smallest .} ^In other words, the collapse mode of the beam-column joint 1 can be the collapse mode of the joint panel. In addition, the ratio _pMp ^* / _ΣcMp ^* of the total plastic moment _pMp1 ^{* of the joint panel to the total plastic moment ΣcMp*} _{of the} ^end of the welded box section column 10 is 0.77, and when the joint panel collapses, the strength of the end of _the welded box section column 10 has a reserve strength _of about 20 _to 30 percent.

From the above, it has been confirmed that the column-beam joint and its design method of the present invention can make the collapse type of the column-beam joint a column-beam joint panel collapse type rather than a column collapse type, even when the steel beam has a large cross section and high strength, and the total value of the full plastic strength of the ends of the beam members attached to the column-beam joint panel is large.

1 Beam-to-column joint 10 Welded box section column 11, 12 Skin plate 13 Corner weld 20 Steel beam t Skin plate thickness t _w Weld depth of corner weld σ _y Yield strength of skin plate σ _yw Yield strength of weld metal of corner weld

Claims (10)

A column-beam joint between a welded box section column and a steel beam, the column-beam joint being constituted by four skin plates joined together by corner welding,
The corner weld is one or both of an undermatch weld and a partial penetration weld;
A column-beam joint in which the total bending moment _ΣbMp ^* of the ends of the steel beams attached to the joint panel of the column-beam joint when _{they are} in a fully plastic state, the total plastic moment _ΣcMp ^* of the ends of the welded box section columns attached to the joint panel, the total plastic moment _pMp1 ^* of the joint panel, and _the total plastic moment _pMp2 ^* of the joint panel when _it is assumed that the corner welds are overmatch welds and full penetration welds satisfy the relationships in the following equations (1) and (2).
Σ _c M _p ^* < _p M _{p 2} ^* ... (1)
_p M _p1 ^* < Σ _c M _p ^* < Σ _b M _p ^* ... (2) The beam-column joint according to claim 1 , wherein the skin plate has a tensile strength of 780 N/mm ² or more. The beam-column joint according to claim 1 or 2, in which the groove depth of the corner weld is 60 mm or less. The beam-column joint according to claim 1 or 2, in which the inside of the welded box section member is filled with concrete. The beam-column joint according to claim 3, wherein the interior of the welded box section member is filled with concrete. A method for designing a column-beam joint between a welded box section column formed by joining four skin plates together by corner welding and a steel beam, comprising:
The corner weld is one or both of an undermatch weld and a partial penetration weld;
A design method for a column-beam joint, in which the thickness and standard strength of the skin plate, the cross-sectional shape and standard strength of the steel beam, and the weld depth and standard strength of the weld metal of the corner weld are set _so that the total bending moment _ΣbMp ^* of the material end when the steel beam attached to the joint panel of the column _- beam joint is in a fully plastic state, _the total plastic moment _ΣcMp ^* of the material end of the welded assembled box section column attached to the joint panel, the total plastic moment _pMp1 ^* of the joint panel, and the total plastic moment _pMp2 ^* of the joint panel when the corner weld is assumed to be _an overmatch weld and full penetration weld, satisfy the relationships in the following equations (1) and (2).
Σ _c M _p ^* < _p M _{p 2} ^* ... (1)
_p M _p1 ^* < Σ _c M _p ^* < Σ _b M _p ^* ... (2) The method for designing a beam-column joint according to claim 6, wherein the tensile strength of the skin plate is 780 N/ ^mm2 or more. The method for designing a beam-column joint according to claim 6 or 7, in which the groove depth of the corner weld is 60 mm or less. The method for designing a beam-column joint according to claim 6 or 7, in which the interior of the welded box section member is filled with concrete. The method for designing a beam-column joint according to claim 8, wherein the interior of the welded box section member is filled with concrete.

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