JP2013204306A - Column-beam joining structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To alleviate stress concentration locally generated at a corner in a sudden cross-sectional change position adjoining an enlarged cross-sectional area portion in a column-beam joining structure to rigidly join a steel beam, with an end section thereof provided with the enlarged cross-sectional area portion where a cross-sectional area is increased by horizontal haunches, to a column.SOLUTION: In a column-beam joining structure where a column and a steel beam are rigidly joined, the steel beam has: a standard cross-sectional portion with a standard cross-sectional shape of the steel beam; and an enlarged cross-sectional area portion which is positioned closer to an end side than the standard cross-sectional portion and has an enlarged cross-sectional area with a beam width expanded wider in a beam width direction than the standard cross-sectional portion. Through-holes are made, in the enlarged cross-sectional area portion, at a section projected in the beam width direction lateral to the standard cross-sectional portion.

Description

  The present invention relates to a column beam connection structure in which a column and a steel beam are rigidly bonded.

  Conventionally, in the column beam frame 1 as shown in the schematic side view of FIG. 1, the column 10 and the steel beam 20 are rigidly joined by welding or the like. For example, in the example of FIG. 1, the upper and lower flanges 20f and 20f of H-shaped steel forming the main body of the beam 20 are welded to the diaphragms 12 and 12 of the column 10, and the web 20w is connected via the gusset plate 31 and the like. The column 10 is friction bonded.

  Then, when an external force such as seismic force or wind load is input to the column beam frame 1 in the horizontal direction, the bending moment caused thereby is the span direction of the beam 20 (of the beam 20 as shown in FIG. 1). Since it is larger on the end side (hereinafter also referred to as the beam end side) than the center side in the longitudinal direction, the stress becomes maximum at the beam end 20ee, and as a result, the entire cross section first yields and is damaged at the beam end 20ee. To do. That is, in this case, the cross-sectional position that determines the overall strength of the beam 20 is the beam end 20ee. In the following, the cross-sectional position where the overall cross-section yields first to determine the overall strength of the beam 20 is also referred to as “dangerous cross-section position”.

  And when the above-mentioned welding part exists in this dangerous cross-section position, since the said welding part tends to brittle fracture, there exists a possibility of the column beam frame 1 collapsing instantaneously.

  As an example of a method for preventing such brittle fracture at the beam end 20ee, as shown in the perspective view of FIG. 2A, a horizontal hunch 25 is provided at the end of the H-shaped steel forming the main body of the beam 20, and the end of the beam 20 is Increasing the cross-sectional area of the portion 20e is mentioned (Patent Document 1). And according to this method, since the stress acting on the cross section of the end portion 20e is reduced based on the cross sectional area increasing action by the horizontal haunch 25, as shown in the top view of FIG. It changes from the beam end 20ee where the weld exists to a position closer to the center side in the span direction of the beam 20. That is, the dangerous cross-sectional position moves to the position of the center end 25ee of the horizontal haunch 25. And since there is almost no weld in the same position, the instantaneous collapse of the column beam frame 1 resulting from a brittle fracture can be prevented effectively.

JP 2000-309980 A

  By the way, in the beam 20 having the horizontal haunch 25 as described above, the cross-sectional shape of the beam 20 changes suddenly at the position of the end 25ee on the horizontal side in the span direction of the horizontal haunch 25. That is, the dimension in the beam width direction is expanded from the same position as a starting point, and the cross-sectional area of the cross section rapidly increases. Hereinafter, the position where the cross-sectional shape suddenly changes is referred to as a “cross-sectional sudden change position”. However, since the rigidity changes suddenly at this cross-sectional sudden change position, the portion A in FIG. 2A and FIG. Stress can be locally concentrated at the corner A of the sudden change position of the cross section, and a large plastic strain can be concentrated at the corner A (see the FEM analysis result in FIG. 7A). Then, cracks may be generated and propagated intensively at the corner portion A, and as a result, the overall strength of the beam 20 may be reduced. That is, the beam 20 may be damaged by a bending moment smaller than the planned bending moment designed on the assumption that stress is applied uniformly in the beam width direction.

  The present invention has been made in view of the conventional problems as described above, and its purpose is to provide a steel beam and a column having a cross-sectional area increasing portion with an increased cross-sectional area provided with a horizontal hunch or the like at an end. In the column beam connection structure that rigidly joins, the stress concentration locally generated in the corner portion of the sudden change position of the cross section adjacent to the cross sectional area increasing portion is reduced.

In order to achieve this object, the invention shown in claim 1
In a column beam connection structure in which a column and a steel beam are rigidly connected,
The steel beam is widened in the beam width direction from the reference cross section while being positioned closer to the end of the steel beam than the reference cross section, and a reference cross section having a reference cross section of the steel beam A cross-sectional area increasing portion having an increased cross-sectional area,
A through-hole is formed in a portion of the cross-sectional area increasing portion that protrudes outward in the beam width direction from the reference cross-sectional portion.

  According to the first aspect of the present invention, since the through hole is formed in the cross-sectional area increasing portion that protrudes outward in the beam width direction, the gap between the reference cross-sectional area and the cross-sectional area increasing portion is formed. The stiffness difference is reduced. Therefore, it is possible to reduce the stress concentration at the corner portion at the boundary position between the reference cross-sectional portion and the cross-sectional area increasing portion, that is, the cross-sectional sudden change position.

The invention shown in claim 2 is the beam-column joint structure according to claim 1,
At least a part of the joint between the column and the steel beam is a weld,
Bending moment at the beam end when the entire cross-section yields at the boundary position between the reference cross-sectional portion and the cross-sectional area increasing portion, rather than the magnitude of the bending moment at the beam end when the joint yields the entire cross-section The cross-sectional design is such that the bending moment at the beam end when the section where the through-hole is formed in the cross-sectional area increasing portion yields the entire cross-section is smaller. It is characterized by.

  According to the second aspect of the present invention, the entire cross-section yields at the boundary position between the reference cross-section and the cross-sectional area increasing portion, before the junction between the column and the steel beam yields the entire cross-section. Alternatively, before the joint portion between the column and the steel beam yields the entire cross section, the portion where the through hole is formed in the cross sectional area increasing portion yields the entire cross section. Therefore, brittle fracture due to the welded portion of the joint between the column and the steel beam is effectively avoided.

The invention shown in claim 3 is the column beam connection structure according to claim 2,
The through hole is a circular hole,
The boundary portion has a corner portion in a shape where two straight lines intersect,
Bending moment at the beam end when the section where the through hole is formed in the cross-sectional area increasing portion is larger than the magnitude of the bending moment at the beam end when the boundary yields in the entire cross section The cross-sectional design is such that the size of is smaller.

  According to the invention described in claim 3 above, stress is locally concentrated in the portion where the through-hole is formed in the cross-sectional area increasing portion due to the through-hole, but since this through-hole is a circular hole, The degree of concentration of the stress is lighter than the corner portion at the boundary portion between the reference cross section and the cross sectional area increasing portion. Therefore, it is less likely that cracks occur due to stress concentration at the through hole formation portion than at the corner portion. And if the magnitude relationship of a bending moment is set as mentioned above, the formation part of the through-hole in which this crack is hard to generate | occur | produce will come to a full cross-section yield before a boundary part. Therefore, it is possible to effectively avoid a situation in which the beam is rapidly damaged due to a crack in the process of yielding the entire cross section for the first time, and the safety of the column beam connection structure can be improved.

The invention shown in claim 4 is the column beam connection structure according to any one of claims 1 to 3,
The steel beam has H-shaped steel as its main body,
The reference cross section is the H-section steel,
The cross-sectional area increasing portion is formed by welding a horizontal hunch to each edge in the beam width direction of the flange of the H-shaped steel,
The through hole is formed in the horizontal haunch.

According to the fourth aspect of the present invention, since the horizontal haunch is a separate member from the H-shaped steel, it is possible to process through holes in the horizontal haunch before welding to the H-shaped steel. Therefore, the through hole can be formed easily and accurately.
Moreover, since the through hole is formed in the horizontal haunch, that is, it is not formed across the welded portion of the flange of the H-shaped steel and the horizontal haunch, it is possible to prevent stress concentration at the welded portion due to the through hole in advance. As a result, brittle fracture due to cracking in the weld is effectively prevented.

The invention shown in claim 5 is the column beam connection structure according to any one of claims 1 to 4,
A plurality of circular holes as the through holes are provided side by side in the longitudinal direction of the steel beam,
The diameter of the circular hole is smaller as it approaches the end on the column side in the longitudinal direction.

  According to the fifth aspect of the present invention, the diameters of the circular holes arranged in the longitudinal direction become smaller as approaching the end of the steel beam in the longitudinal direction on the column side. Therefore, corresponding to the fact that the magnitude of the bending moment acting on the steel beam during an earthquake increases gradually toward the end of the beam, the stress is applied to the formation part of the circular hole located closer to the end of the beam. It can be designed so that the cross-sectional area that can be borne is large, and it is thereby possible to yield the cross-sections of the portions where these circular holes are formed almost simultaneously. That is, the formation timing of the plastic hinge can be substantially aligned between the portions where the plurality of circular holes are formed. As a result, it becomes a column beam connection structure with excellent vibration energy absorption performance at the time of earthquake.

The invention shown in claim 6 is the column beam connection structure according to any one of claims 1 to 5,
Nothing is inserted into the through hole.

  According to the sixth aspect of the present invention, since nothing is inserted into the through hole, the difference in rigidity between the reference cross section and the cross sectional area increasing portion can be reliably reduced.

  According to the present invention, a cross-section adjacent to a cross-sectional area increasing portion in a beam-to-column connection structure in which a steel beam and a column having a cross-sectional area increasing portion having an increased cross-sectional area by providing a horizontal haunch or the like and a column are rigidly connected. It is possible to reduce the stress concentration locally generated at the corner of the sudden change position.

It is a schematic side view of the column beam structure 1 which also wrote the bending moment figure. FIG. 2A is a perspective view of a conventional beam-column joint structure, and FIG. 2B is a top view thereof. FIG. 3A is an external perspective view of a column beam joint structure according to the present embodiment, and FIG. 3B is a schematic top view thereof. It is a schematic perspective view of the cross-sectional area increase part 20e formed with the single member. It is a column beam connection structure model used for FEM analysis. FIG. 6A is an explanatory diagram of a non-porous rectangular haunch case of the first comparative example, and FIG. 6B is an explanatory diagram of the non-porous trapezoidal haunch case of the second comparative example. FIG. 6C is an explanatory diagram of a perforated rectangular hunch case according to the present embodiment. It is an analysis result (for relative comparison) of a non-hole rectangular haunch case. It is an analysis result (for relative comparison) of a non-hole trapezoidal haunch case. It is an analysis result (for relative comparison) of a perforated rectangular hunch case. It is an analysis result (for absolute evaluation) of a non-hole rectangular haunch case. It is an analysis result (for absolute evaluation) of a non-hole trapezoidal haunch case. It is an analysis result (for absolute evaluation) of a perforated rectangular hunch case. 4 is a graph showing a bending strength line of the beam 20 and a distribution of bending moment generated in the beam 20 when a horizontal external force such as an earthquake force or a wind load acts on the column beam frame 1. 4 is a graph showing a bending strength line of the beam 20 and a distribution of bending moment generated in the beam 20 when a horizontal external force such as an earthquake force or a wind load acts on the column beam frame 1. It is a schematic top view of the modification of this embodiment.

=== This Embodiment ===
FIG. 3A is an external perspective view of a column beam joint structure according to the present embodiment, and FIG. 3B is a schematic top view thereof.

  As shown in FIG. 3A, the column 10 has, for example, a steel square pipe having a rectangular cross section as a main body, and the beam 20 is a steel beam. In this example, the H section steel having a H cross section has a main body. To do. The columns 10 and the beams 20 are rigidly joined to each other. That is, the column 10 has a pair of upper and lower through diaphragms 12, 12. The upper flange 20 f and the lower flange 20 f of the beam 20 are connected to the corresponding through diaphragms 12, 12 by welding, and the web of the beam 20 is also connected. 20w is overlapped with a gusset plate 31 integrally welded to the outer peripheral surface 10s of the column 10 and is friction-joined by bolt fastening, whereby the column 10 and the beam 20 are rigidly joined.

  The “rigid connection” is a connection mode capable of transmitting a moment. In the example of FIG. 3A, the diaphragm 12 is used through the rigid joint. However, the diaphragm 12 is not limited to this, and the outer diaphragm may be used, or the column without using the diaphragm. The flange 20f may be directly connected to the outer peripheral surface 10s of the steel plate 10 by welding, or may be friction bonded by bolt fastening instead of welding. Also, the column 10 is not limited to the above-described square pipe, and a column having a different cross-sectional shape or a column having another structure can be applied as long as the beam 20 can be rigidly joined. For example, a steel round pipe having a circular cross section may be used, a CFT (concrete-filled steel pipe) may be used, or an RC or SRC column may be used.

  The beam 20 has horizontal hunches 25, 25... In the vicinity 20e of the joint with the column 10, that is, in the end 20e in the span direction. As described above, the horizontal hunches 25, 25... Increase the cross section of the end portion 20e of the beam 20 to prevent damage to the joint portion of the beam end 20ee. That is, when the portion of only the H-shaped steel located on the center side in the span direction with respect to the end portion 20e in the beam 20 is defined as the reference cross-sectional portion 20b having the standard cross-sectional shape of the beam 20, this reference cross-sectional portion 20b In order to increase the cross-sectional area of the end 20e of the beam 20, the end 20e is integrally provided as a part of the end 20e in order to widen the end 20e in the beam width direction. It is.

  The horizontal haunch 25 is, for example, a rectangular steel plate in plan view, and is horizontally provided on both sides of the upper flange 20f and the lower flange 20f in the beam width direction. Specifically, each horizontal hunch 25, 25 for the upper flange 20f is abutted against both side surfaces (corresponding to end edges) in the beam width direction of the upper flange 20f and joined together by welding, and the lower flange 20f Each horizontal hunch 25, 25 is abutted against both side surfaces (corresponding to end edges) of the lower flange 20f in the beam width direction and joined together by welding, and is further joined integrally by welding. The horizontal hunches 25, 25 ... for 20f are integrally joined to the through diaphragms 12, 12 of the column 10 by welding on the side surface on the column 10 side.

  Incidentally, as shown in FIG. 3B, the end portion 20e of the beam 20 including the horizontal hunches 25, 25... The horizontal hunch 25 corresponds to “a cross-sectional area increasing portion 20e that is widened in the beam width direction and the cross-sectional area is increased”, and the horizontal haunch 25 is “outside of the cross-sectional area increasing portion 20e in the beam width direction from the reference cross-sectional portion 20b”. This corresponds to the protruding portion 25 ". Furthermore, since the cross-sectional area of the beam 20 is increased from the position of the end 25ee of the center side in the span direction of the beam 20 in the horizontal haunch 25, in this example, the position of the end 25ee is the “section sudden change position”. The section sudden change position corresponds to the “boundary position” according to the claims, that is, “the boundary position between the reference sectional portion 20b and the sectional area increasing portion 20e”.

  Here, in this embodiment, as shown in FIGS. 3A and 3B, each horizontal hunch 25 is formed with a circular hole 25h (corresponding to a through hole) penetrating in the plate thickness direction (vertical direction). As a result, the rigidity difference between the reference cross-section portion 20b and the cross-sectional area increasing portion 20e is reduced, and the portion A in FIG. 2A and FIG. The stress is prevented from concentrating locally on the corner portion A of the.

  More specifically, first, when the circular hole 25h is not formed in the horizontal haunch 25 as in the comparative example of FIG. 2B, as described above, the corner portion A of the sudden change position of the cross section is the sudden change position of the cross section. There is a tendency that a larger plastic strain than that of the portion other than the corner portion A is concentrated (see the FEM analysis result of FIG. 7A). As a result, cracks are generated and propagated particularly in the corner portion A in the sudden change position of the cross section, and as a result, the overall strength of the beam 20 may be reduced. That is, the beam 20 may be damaged by a bending moment smaller than the planned bending moment designed on the assumption that stress is applied uniformly in the beam width direction.

  As a cause of such stress concentration, there is a large difference in rigidity between the reference cross-sectional portion 20b and the cross-sectional area increasing portion 20e. Therefore, in this embodiment, the horizontal haunch 25 of the cross-sectional area increasing portion 20e By forming the circular holes 25h in the plate thickness direction, the difference in rigidity between the reference cross-sectional portion 20b and the cross-sectional area increasing portion 20e is reduced, and the stress concentration in the corner portion A is reduced.

  In this example, the opening shape of the circular hole 25h is a perfect circle. However, the shape is not limited to this, and it may be an ellipse or an ellipse, or a circle formed by combining a plurality of arcs having different curvatures. However, if the curvature of the arc is large, there is a risk that a large stress concentration occurs in the portion of the circular hole 25h where the curvature is large. From the viewpoint of avoiding this stress concentration, the curvature of the circular hole 25h is the entire circumference. The smaller one is preferable.

  The hole diameter of the circular hole 25h is selected from a range of 10 mm to 100 mm, for example, although it depends on the size of the horizontal haunch 25 and the cross-sectional size of the H-shaped steel.

  Further, the circular hole 25 h is formed so as not to protrude from the horizontal haunch 25, that is, to be accommodated in the horizontal haunch 25, whereby the circular hole 25 h is welded to weld the horizontal haunch 25 to the flange 20 f of the beam 20. It does not straddle the department. Therefore, it is possible to prevent stress concentration at the welded portion caused by the circular hole 25h, and as a result, brittle fracture due to cracking at the welded portion is effectively prevented.

  In this embodiment, the horizontal haunch 25 and the H-shaped steel of the beam 20 are separate members, and the horizontal haunch 25 is welded to the H-shaped steel of the beam 20 to form the cross-sectional area increasing portion 20e. However, the present invention is not limited to this, and the cross-sectional area increasing portion 20e may be formed of a single member. For example, as shown in the schematic perspective view of FIG. 4, the flange 20f of the center side portion in the beam width direction is narrower so that the flange width of the center side portion is narrower than the end portion 20e of the beam 20 in the span direction. If a part of both ends are cut out and reduced in width, a cross-sectional area increasing portion 20e made of a single member is formed at the end of the H-shaped steel. However, in that case, when the circular hole 25h is formed in the horizontal haunch 25, the entire beam 20 must be handled, and it becomes difficult to perform the work of forming the circular hole 25h. Therefore, from the viewpoint of ease of drilling, it is preferable that the horizontal hunch 25 and the H-shaped steel of the beam 20 are separate members as in this embodiment of FIG. 3A. That is, in this case, since the horizontal hunch 25 can be welded to the H-shaped steel flange 20f after the circular hole 25h is formed in the horizontal haunch 25, the work of forming the circular hole 25h in the horizontal haunch 25 is facilitated. In addition, the processing accuracy of the circular hole 25h is improved.

  Desirably, the formation position of the circular hole 25h in the span direction should be closer to the position where the cross section suddenly changes than the joint between the beam 20 and the column 10 set at the beam end 20ee, as shown in FIG. 3B. In this way, the effect of reducing the stress concentration on the corner A can be further enhanced.

  Since the effect of reducing the stress concentration in the corner portion A by the circular hole 25h is examined by FEM (finite element method) analysis, this will be described below.

  FIG. 5 shows a beam-column joint structure model used for the FEM analysis. In this analysis, the vicinity of the joint between the column 10 and the beam 20 is measured in the vertical direction, the span direction of the beam 20, and the beam width direction. Only half of each of the three directions is extracted and divided into rectangular elements for modeling. Further, in order to simulate the action state of horizontal external force such as seismic force or wind load, an upward load P is applied to the center position in the span direction of the beam 20 to change the deformation angle R (= δ / L), The change of equivalent plastic strain at that time was analyzed. Note that δ and L related to the deformation angle R are the upper displacement δ of the center position and the distance L from the center position to the core of the column 10, respectively. Various specifications such as dimensions of the column 10, the beam 20, the horizontal hunch 25, and the circular hole 25h used for the analysis are also shown in FIGS. 5 and 6A to 6C.

  Incidentally, in this analysis, since the direction of the horizontal external force such as seismic force is opposite to that of FIG. 1 described above, the upper vertical load P is at the approximate center position in the span direction of the beam 20 in FIG. Thus, the direction of the bending moment acting on the beam 20 is opposite to that in FIG. 1 described above, but these are the inflection point positions of the bending moment (substantially the center position in the span direction). Are different in terms of point symmetry and are substantially the same. However, when such an upward vertical load P is applied, a larger load is applied to the lower flange 20f and the lower horizontal haunch 25 than to the upper flange 20f and the upper horizontal haunch 25. The flange 20f and the lower horizontal hunch 25 have a greater plastic strain. Therefore, the following description will be made focusing on the plastic strain of the lower flange 20f and the lower horizontal hunch 25.

  Although examination cases are shown in FIGS. 6A to 6C, three cases were examined. That is, as a first comparative example, the horizontal haunch 25 has a rectangular shape in plan view and has no circular hole 25h as shown in FIG. 6A, and as a second comparative example, the horizontal haunch 25 has a flat surface as shown in FIG. 6B. A “non-perforated trapezoidal haunch case” that has a circular shape and has a circular hole 25h as shown in FIG. 6C as a case simulating the above-described embodiment. Three cases, “rectangular hunch case” were examined. 6A and the horizontal hunch 25 of the perforated rectangular hunch case in FIG. 6C have the same external dimensions. Further, the horizontal haunch 25 of the non-perforated trapezoidal haunch case of FIG. 6B is tapered from the horizontal haunch 25 of the non-perforated rectangular haunch case of FIG. It is a notch.

  7A to 7C show analysis results when the deformation angle R = 0.02 (= 2%). In each figure, the magnitude (%) of the equivalent plastic strain is shown by shading. That is, it shows that a large equivalent plastic strain is generated in the dark portion, and a small equivalent plastic strain is generated in the thin portion. 7A shows the analysis result of the non-perforated rectangular hunch case, FIG. 7B shows the analysis result of the non-perforated trapezoidal hunch case, and FIG. 7C shows the analysis result of the perforated rectangular hunch case. In FIGS. 7A to 7C, for the purpose of facilitating the relative comparison of the three cases, the density scales (correspondence between the density and the magnitude (%) of plastic strain) on the right side of each figure are aligned with each other. Yes.

  On the other hand, FIGS. 8A to 8C show the scales of the gray scale individually adjusted so that the same analysis results as in FIGS. 7A to 7C can be evaluated for each case. 8A is an analysis result of the non-perforated rectangular haunch case, FIG. 8B is an analysis result of the non-perforated trapezoidal haunch case, and FIG. 8C is an analysis result of the perforated rectangular haunch case.

Referring to FIGS. 7A to 7C, the perforated rectangular hunch case of FIG. 7C is more plastic than the non-porous rectangular haunch case of FIG. 7A and the non-perforated trapezoidal haunch case of FIG. 7B. The strain is relaxed. For example, in FIGS. 7A and 7B, the maximum value of the equivalent plastic strain is 3.28%, whereas in FIG. 7C, it is 2.99%, which is a decrease of about 10%. 8C shows that plastic strain is distributed over a wide range around the circular hole 25h in the perforated rectangular hunch case.
Therefore, if the circular hole 25h is formed in the horizontal haunch 25, it is possible to disperse the plastic strain over a wide range by applying a stress to a portion other than the corner portion A in a wide range. It was confirmed that the concentration of plastic strain in part A was reduced.

  By the way, as described above, the joint portion between the column 10 and the beam 20 located at the beam end 20ee includes a large welded portion (a welded portion between the through diaphragm 12, the flange 20f, and the horizontal haunch 25). When the joint yields in the entire cross section within the beam 20 relatively early, the column beam frame 1 may collapse instantaneously due to brittle fracture of the weld. Therefore, it is desirable to set the joint portion of the beam end 20ee so as to yield the entire cross section at a relatively late timing in the beam 20. In this embodiment, the portion of the cross section sudden change position and the circular hole 25h are desirable. After both of the formed portions yield a full cross section, the joint of the beam end 20ee is set to yield a full cross section.

  Here, a method of setting in this way will be described. FIG. 9 shows the bending strength line of the beam 20 (the bending strength of the cross section at each position in the span direction converted to a moment by the plastic section modulus) and horizontal external forces such as seismic force and wind load on the column beam frame 1. It is a graph which shows distribution of the bending moment which arises in the beam 20 when it acts. The vertical axis represents the magnitude of the bending strength line and the magnitude of the bending moment, and the horizontal axis represents the distance in the span direction of the beam 20 from the beam end 20ee. In the lower part of FIG. 9, the position of the beam 20 is specifically shown in correspondence with the distance in the span direction of the horizontal axis.

  As shown in FIG. 9, since the width of the horizontal haunch 25 is constant from the beam end 20ee to the sudden change position of the cross-section, which is the position of the central end 25ee of the horizontal haunch 25, the portion where the circular hole 25h is formed is excluded. The value of the bending strength line is a constant first predetermined value. And since the cross section of the formation part of the circular hole 25h becomes small by the part of the circular hole 25h, the value of a bending strength line is smaller than the said 1st predetermined value. Further, since there is no horizontal haunch 25 on the center side of the sudden change position of the cross section, the value of the bending strength line is constant at a second predetermined value smaller than the first predetermined value.

  On the other hand, the bending moment acting on the beam 20 is maximum at the beam end 20ee as described above, and decreases with a predetermined inclination in proportion to the distance from the beam end 20ee toward the center in the span direction (for example, See bending moment (I)). If the vertical load P acting on the center position of the beam 20 in the span direction is increased, the bending moment is also increased as I → II → III → IV in FIG. 9 by changing the magnitude of the inclination. However, when the value of the bending moment exceeds the bending strength line in the course of the increase, the portion at the position exceeding the bending yield line sequentially yields in the entire cross section in the order in which it exceeded.

  For example, in the case of FIG. 9, since the bending strength line is first exceeded at the sudden change position of the cross section (see bending moment (II)), first, the entire cross section yields at the position of the sudden change position of the cross section, and then the circular hole 25h Since the bending strength line is exceeded at the position of the forming portion (see bending moment (III)), the yielding of the entire cross section is then yielded at the forming portion of the circular hole 25h, and finally the bending strength line is applied at the position of the joint of the beam end 20ee. (See the bending moment (IV)), and finally the entire cross section yields at the joint of the beam end 20ee.

Therefore, if the bending strength lines are set in advance in the relationship as shown in FIG. 9, the joint portion of the beam end 20ee is yielded in the entire cross section at both the portion where the cross section suddenly changes and the portion where the circular hole 25h is formed. Later, the entire cross-section yields, and as a result, brittle fracture due to the welded portion included in the joint of the beam end 20ee is effectively suppressed.
The relationship between the bending strength lines can be expressed as follows by paying attention to the magnitude of the bending moment acting on the beam end 20ee as the position of the joint.

  That is, “the beam end 20ee when the section at the sudden change position of the cross section yields the entire cross section yields more than the bending moment magnitude Mf (the state of IV) at the beam end 20ee when the joint of the beam end 20ee yields the entire cross section. The bending moment magnitude Mp (II state) at the beam end and the bending moment magnitude Ma (III state) at the beam end 20ee when the formation of the circular hole 25h yields the entire cross-section is smaller. In addition, the cross-sectional dimension of the beam 20, the hole diameter of the circular hole 25h, the hole position in the span direction, and the like are designed ".

  As for the front-rear relationship of the yield timing of the entire cross section between the portion where the cross section suddenly changes and the portion where the circular hole 25h is formed, it is desirable that the portion where the circular hole 25h is formed first yields the entire cross section. The reason for this is as follows.

  As shown in FIG. 9, the shape of the corner portion A at the sudden change position of the cross section is a shape in which two straight lines intersect, but the sharp corner portion A tends to have a large stress concentration. On the other hand, although stress is concentrated on the portion where the circular hole 25h is formed, since the shape is a gentle shape called an arc, the degree of stress concentration is much lighter than that of the corner portion A described above. For this reason, it is preferable to first yield the entire cross section of the formation portion of the circular hole 25h to delay the brittle fracture later, which is preferable for the safety of the column beam frame 1. For this reason, the circular hole It is better to first yield the entire cross section of the formation portion of 25h.

  FIG. 10 is a graph of the bending strength line adjusted to such a context. In the case of the graph, when the bending moment is increased as I → II → III → IV, the bending strength line is exceeded at the position where the circular hole 25h is first formed in the process of the increase. (Refer to bending moment (II)) First, the entire section yields at the part where the circular hole 25h is formed, and then exceeds the bending strength line at the position where the section suddenly changes (see bending moment (III)). Yield the entire section at the position, and finally exceed the bending strength at the position of the joint of the beam end 20ee (see bending moment (IV)), and finally yield the entire section at the joint of the beam end 20ee become.

  Further, the bending strength line that yields the entire cross section of the portion where the circular hole 25h is formed in this way is expressed as follows by paying attention to the magnitude of the bending moment acting on the beam end 20ee. be able to.

  That is, “the beam end 20ee when the formation portion of the circular hole 25h yields the entire cross section rather than the magnitude of the bending moment Mp at the beam end 20ee when the section at the sudden change position of the cross section yields the entire cross section (state III)”. The cross-sectional dimension of the beam 20, the diameter of the circular hole 25h, the position of the hole in the span direction, etc. are designed so that the magnitude of the bending moment Ma at II (state II) becomes smaller. it can.

  FIG. 11 is a schematic top view of a modification of the present embodiment. In the above-described embodiment, one circular hole 25h is formed through each horizontal hunch 25. However, in this modification, two circular holes 25ha and 25hb are provided in the span direction as a plurality of examples for each horizontal hunch 25. The difference is that they are formed side by side, and the other points are the same. Therefore, in the following description, the same code | symbol is attached | subjected about the same structure and the description is abbreviate | omitted.

  As shown in FIG. 11, the horizontal haunch 25 is formed with a large-diameter circular hole 25ha and a circular hole 25hb having a diameter smaller than that of the large-diameter circular hole 25ha arranged in the span direction. The large diameter circular hole 25ha is located on the center side in the span direction, and the small diameter circular hole 25hb is located on the end side in the span direction (beam end 20ee side). Is as follows. As described above, the magnitude of the bending moment acting on the beam 20 gradually increases toward the beam end 20ee. Correspondingly, the diameter of the circular hole 25h located closer to the beam end 20ee is set smaller. By doing so, the cross-sectional area that can bear the stress in the portion where the circular hole 25h is formed can be made larger as the circular hole 25h is located closer to the beam end 20ee, and this can be offset with the above-described gradual increase of the bending moment. As a result, it is possible to yield the cross sections of the circular holes 25ha and 25hb at almost the same timing, that is, plastic hinges are formed at the same timing at the two portions. As a result, the beam-to-column connection structure is excellent in vibration energy absorption performance during an earthquake.

=== Other Embodiments ===
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, The deformation | transformation as shown below is possible in the range which does not deviate from the summary.

  In the above-described embodiment, the H-shaped steel is used as the main body of the steel beam 20, but the present invention is not limited to this. For example, C-shaped cross-section grooved steel may be used as the main body of the beam 20, or a rectangular cross-section steel square pipe may be used as the main body. In this case, only the groove steel and the square pipe are the “reference cross section”, and the horizontal haunch 25 is welded to the end in the span direction of the groove steel and the square pipe. The same end portion can be formed in a “cross-sectional area increasing portion” having a cross-sectional area larger than that of the reference cross-sectional portion.

  In the above-described embodiment, the horizontal hunch 25 having a rectangular shape in plan view is illustrated as the horizontal hunch 25 formed so as to penetrate the circular hole 25h. However, the planar shape is not limited to this. For example, the circular hole 25h may be formed through the horizontal haunch 25 having a trapezoidal shape as illustrated in FIG. 6B, or other planar shapes may be used.

  In the above-described embodiment, whether or not a bolt or the like is inserted into the circular hole 25h of the horizontal haunch 25 is not described, but the circular hole 25h is not a bolt hole or the like, that is, an insert is inserted in the circular hole 25h. Is not inserted at all. As a result, there is almost no constraint on the peripheral portion of the circular hole 25h by the insert, and the stress is widely dispersed in the peripheral portion of the circular hole 25h. As a result, the reference cross-sectional portion 20b and the cross-sectional area increasing portion The rigidity difference from 20e can be reliably reduced.

1 column beam frame, 10 columns, 10s outer peripheral surface, 12 through diaphragm,
20 beams (steel beams), 20b reference cross-section, 20e end (cross-sectional area increasing portion),
20ee Beam end, 20f flange, 20w web,
25 horizontal haunch (part protruding outward in the beam width direction),
25c corner, 25ee end,
25h circular hole (through hole), 25ha circular hole (through hole), 25hb circular hole (through hole),
31 gusset plates,
A corner (point A),

Claims (6)

In a column beam connection structure in which a column and a steel beam are rigidly connected,
The steel beam is widened in the beam width direction from the reference cross section while being positioned closer to the end of the steel beam than the reference cross section, and a reference cross section having a reference cross section of the steel beam A cross-sectional area increasing portion having an increased cross-sectional area,
A column-beam joint structure, wherein a through-hole is formed in a portion of the cross-sectional area increasing portion that protrudes outward in the beam width direction from the reference cross-sectional portion. The beam-column joint structure according to claim 1,
At least a part of the joint between the column and the steel beam is a weld,
The magnitude of the bending moment at the beam end when the boundary portion between the reference cross section and the cross-sectional area increasing portion yields the entire cross section rather than the magnitude of the bending moment at the beam end when the joint yields the entire cross section. And the cross-sectional design is such that the portion of the cross-sectional area increasing portion where the through hole is formed yields a smaller bending moment at the beam end when the entire cross-section yields. Column beam connection structure. The beam-column joint structure according to claim 2,
The through hole is a circular hole,
The boundary portion has a corner portion in a shape where two straight lines intersect,
Bending moment at the beam end when the section where the through hole is formed in the cross-sectional area increasing portion is larger than the magnitude of the bending moment at the beam end when the boundary yields in the entire cross section Column beam connection structure, characterized in that the cross section is designed so that the size of is smaller. The beam-column joint structure according to any one of claims 1 to 3,
The steel beam has H-shaped steel as its main body,
The reference cross section is the H-section steel,
The cross-sectional area increasing portion is formed by welding a horizontal hunch to each edge in the beam width direction of the flange of the H-shaped steel,
The beam-column joining structure, wherein the through hole is formed in the horizontal haunch. The beam-column joint structure according to claim 1,
A plurality of circular holes as the through holes are provided side by side in the longitudinal direction of the steel beam,
The beam-to-column connection structure characterized in that the diameter of the circular hole is smaller toward the end on the column side in the longitudinal direction. The beam-column joint structure according to any one of claims 1 to 5,
A beam-column joint structure in which nothing is inserted into the through hole.