JP2006328688A - Buckling restraining-type axial force bearing member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a buckling restraining-type axial force bearing member which is composed of a steel core having a cruciform cross section and four restraining members each formed of an angle steel, wherein the axial force bearing member can sufficiently exert a restraining effect against partial buckling without additionally providing special members, and makes the 100% use of the energy absorbing ability of the core. <P>SOLUTION: The buckling restraining-type axial force bearing member 1 is formed by arranging a yielding portion 2A at an axial intermediate portion of the core steel plate 2 having the cruciform cross section, attaching mounting portions 2B to both ends of the same, for mounting the axial force bearing member on a structure, attaching the four restraining members 3 each formed of the angle steel to the yielding portion 2A having the cruciform cross section so as to exhibit a cruciform cross section, and connecting each pair of the restraining members 3 pinching each piece of the core steel plate 2 by means of spacers 4, bolts 5, and nuts 6. Herein the thickness Ta of the restraining member 3 is set to satisfy the relationship of Ta≥0.4×Tc, and the pitch p of the bolts assembling the restraining members 3 is set to satisfy the relationship of p≤50×Tc (Tc: plate thickness of the core). Thus when the core is expandably and contractibly deformed due to an external force such as an earthquake, the axial bearing member is subjected to yield deformation without being buckled at the time of contraction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a buckling-restrained axial force bearing member that is incorporated in a structure and controls damage to the structure or absorbs vibration energy by yield deformation of a core material.

  The buckling-restrained axial force bearing member is used to limit the yielding portion and control damage in the structure. Also, energy input to the structure is absorbed by yield deformation. For example, it is used as a brace in a building to absorb the vibration energy of the building due to an earthquake.

  Such a buckling-restraining type axial force bearing member constrains the core material with a restraining material so that the portion that assumes yield can sufficiently yield and deform during tension and compression. The material is prevented from buckling.

  Various types of buckling-restrained axial force bearing members of this type have been developed in the past.For example, a steel pipe is arranged around the core and concrete is filled in the steel pipe. In order to reduce weight and weight, various shape steels are used as a buckling restraining material, and a steel core material is buckled and restrained only by a steel material. The latter, which uses a steel core and a steel buckling restraint, has a cross-shaped cross section for the steel core, and a chevron shaped steel (hereinafter simply referred to as an angle steel) from the four sides of the core. Axial force bearing members that are assembled and joined with angle irons with bolts have been commercialized.

As prior art documents related to the present invention, there are, for example, Patent Documents 1 and 2. The invention of Patent Document 1 is a buckling stiffening member used for vibration control braces, etc., and inserts a flat steel of ultra mild steel as an axial force material into the stiffening pipe of a square steel pipe along the diagonal line of the square steel pipe, A joint plate and two stiffeners are connected to both ends of this flat steel so as to have a cross-shaped cross section. The invention of Patent Document 2 is a buckling-restrained brace, in which a thickened portion is formed by overlapping reinforcing steel plates on both ends in the axial direction of a core made of a flat steel plate, and a cross section assembled by fillet welding using the flat steel plate The core material is covered with a rectangular buckling restraint material, and a sheet-like cushioning material is disposed between the buckling restraint material and the core material.
JP 2000-144930 A JP 2000-27293 A

In order to determine the dimensions and the like of each part of a buckling-restrained type axial force bearing member using a steel cross-shaped core material and four angle-shaped steel buckling restraining materials, the following 2 It is necessary to consider points. That is,
(A) The buckling is restricted so as not to cause the overall buckling shown in FIG. 3 (a), or (b) the plate element is restricted so as not to cause the local buckling shown in FIG. 3 (b). Is it?

  The overall buckling can be designed using an Euler buckling type or a buckling line. As for local buckling, there are many unclear parts, and there is a problem that it is impossible to design with a general design formula.

  The present invention is intended to solve the above-described problems, and in a buckling-restrained axial force bearing member using a steel cross-shaped core material and four angle steel restraints, A buckling-restrained axial force bearing member that can exert a sufficient restraining effect on local buckling without adding a special member and can greatly improve the energy absorption capacity of the core material. It is to provide.

  A buckling-restrained axial force bearing member according to claim 1 of the present invention sandwiches each piece of a steel cross-shaped core material bearing an axial force with a steel-made chevron-shaped restraint material (an angle steel). In the buckling restraint type axial force bearing member that restrains the buckling of the core material by joining the restraint materials with bolts and assembling the restraint material to the core material, the thickness of the core material is Tc (mm). When the restraint material thickness Ta (mm) satisfies the formula (1), and the pitch p (mm) of the bolt for assembling the restraint material is configured to satisfy the formula (2). is there.

Ta ≧ 0.4 × Tc (1)
p ≦ 50 × Tc (2)
In the present invention, for example, as shown in FIG. 1, a yielding portion is provided in an intermediate portion in the axial direction of a core steel plate having a cross-shaped cross section, and attachment portions to structures are provided at both end portions. In a buckling-restrained axial load bearing member in which four angle steel restraints are assembled in a cross-shaped cross section and a pair of angle steels sandwiching each piece of the core steel plate are joined together with a spacer, bolts and nuts The parameters (dimensions, etc.) of the constraining material that does not cause local buckling of the core material have been found. In the present invention, the “angle steel” includes rolled angle steel, steel plate made into a chevron shape by a welding set, steel plate made into a chevron shape by press molding, and other cross-sectional angle steel materials.

  The thickness Ta of the angle steel restraint is made larger than the lower limit of the right side of equation (1) (including the lower limit), and the assembly bolt pitch p of the angle iron restraint is set to the upper limit of the right side of equation (2) By making it smaller (including the upper limit value), when the core material expands and contracts due to an external force such as an earthquake, it yields and deforms without buckling during compression, and the energy absorption capacity of the core material can be used 100%. (See FIG. 2, Table 1 below). When setting the restraint material in consideration of sufficient safety, the plate thickness Ta is made sufficiently larger than the lower limit value of the equation (1), and the bolt pitch p is made larger than the upper limit value of the equation (2). However, if the plate thickness Ta is extremely increased and the bolt pitch p is decreased, it is very uneconomical due to an increase in material and processing.

The buckling constrained axial force bearing member according to claim 2 of the present invention is the buckling constrained axial force bearing member according to claim 1, wherein the yield point or proof stress of the core material is 80 N / mm ² or more and 445 N / mm. ² or less, and the yield point or proof stress of the constraining material is 235 N / mm ² or more.

That is, it is preferable to use a low yield point steel material for building structures (LY steel) or a hot rolled steel material for building structures (SN steel) for the core steel plate (see Table 1 described later). The lower limit of the yield point specified by the standard is 80 N / mm ² for LY100 and 325 N / mm ² for SN490B. LY100 to SN490B or higher can be used. It is preferable to use a general structural rolled steel (SS steel) as the angle steel restraining material. The lower limit of the yield point specified by the standard is 235 N / mm ² in SS400. SS400 or higher is used.

  (1) In a buckling-restrained axial force bearing member made of steel and using a cross-shaped core material and four angle-shaped steel restraint materials, the thickness Ta of the restraint material is Ta ≧ 0.4 × Tc. In addition, by setting the pitch p of the bolt for assembling the restraint material to p ≦ 50 × Tc (Tc: thickness of the core material), when the core material expands and contracts due to an external force such as an earthquake, it does not buckle during compression. The buckling-restraining type axial force bearing member which yields and deforms and can use the energy absorption capacity of the core material 100% and has high energy absorption efficiency and excellent safety can be obtained.

  (2) Since it is only necessary to set the plate thickness and bolt pitch of the constraining material without adding a special member, a buckling-restrained axial force bearing member with high energy absorption efficiency and excellent safety can be manufactured at low cost. Can be produced.

  Hereinafter, the present invention will be described based on the illustrated embodiments. FIG. 1 is a cross-sectional view, an exploded perspective view, and an assembled perspective view showing an embodiment of a buckling-restrained axial force bearing member of the present invention.

  In FIG. 1, a buckling-restrained axial force bearing member 1 of the present invention restrains a core material 2 having a cross-shaped cross section made of steel that bears an axial force and a core material 2 that yields and deforms due to the axial force. The four restraint members 3 made of steel and having a cross-sectional chevron shape to prevent buckling of the steel plate, the bolt 5 and the nut 6 that join the pair of restraint members 3 sandwiching the core member 2 with the spacer 4 therebetween, It is comprised from the buffer material 7 arrange | positioned between the restraint materials 3. FIG.

  The core material 2 is a steel plate of a predetermined length, and is assembled into a cross-shaped cross section by joining the steel plates vertically by welding or the like to the center of both surfaces of one steel plate, and the outer diameter of the central portion in the material axis direction is set. By reducing the length over a predetermined length, a yield portion 2A that yields and deforms by an axial force is formed, and attachment portions 2B to structural members such as column beams are formed at both ends.

  The constraining material 3 is made of angle steel and is arranged at the four corners of the cross-shaped core material 2 and assembled in a cross-shaped cross shape so as to sandwich the four pieces of the core material 2 respectively. The yield portion 2A of the core material 2 that yields and deforms during tension and compression is restrained, and buckling of the yield portion 2A of the core material 2 is prevented during compression.

  The restraining material 3 is of a length that covers the entire yielding portion 2A and a part of the mounting portion 2B, and a gap between the narrow yielding portion 2A is filled with a spacer 4 such as a flat bar, and a pair of adjacent restraining materials 3 Then, the spacer 4 and the mounting portion 2B are sandwiched and fixed with bolts 5 and nuts 6 arranged at a predetermined pitch p in the material axis direction. A bolt hole 8 through which the bolt 5 is inserted is provided in the restraining material 3, the spacer 4, and the attachment portion 2 </ b> B. The bolt hole 8 at the position of the attachment portion 2 </ b> B at one end of the restraint material 3 is a long hole 8 a that is long in the material axis direction, so that it can cope with expansion and contraction of the core material 2.

  The cushioning material 7 is made of rubber or the like and is disposed in the yielding portion 2A. This buffer material 7 reduces the transmission of the load from the core material 2 to the restraint material 3 by making use of the fact that the steel materials do not directly contact each other and is easily deformed. Not limited to this, a sliding plate made of a material having a small friction coefficient may be used to reduce friction to facilitate sliding, or a viscoelastic body such as a polymer system may be used. The vibration energy can be absorbed by the deformation of.

  When the buckling-restrained axial force bearing member 1 having the above-described configuration is incorporated in a column beam structure of a structure and an external force is applied due to an earthquake or the like, the yielding portion 2A of the core material 2 attaches the four restraining materials 3 to each other. As a guide, it stretches in the direction of the material axis when pulled, and shrinks in the direction of the material axis when compressed. During compression, the core material 2 is constrained by the four constraining materials 3, and buckling of the core material 2 is prevented.

  Table 1 shows the results of a fatigue test performed on the buckling-restrained axial force bearing member 1. Since the main purpose is to use it as an energy absorbing member, a fatigue test was carried out. In order to use 100% of the energy absorbing ability of the core material, the fracture mode of the specimen was not buckled and the core was not buckled. It is necessary that the material breaks.

Based on the above test results, the constraining material that does not satisfy the following formula (1) or (2) is buckled in the core material, and the constraining material that satisfies the formulas (1) and (2) at the same time should be used. Thus, it can be confirmed that the core material can be stably restrained.
Ta ≧ 0.4 × Tc (1)
p ≦ 50 × Tc (2)
Ta: board thickness of restraint material p: pitch of bolt for assembling restraint material Tc: board thickness of core material The steel material used at this time is 80 N at the lower limit of the yield point specified by the standard. / Mm ² (LY100) to 325 N / mm ² (SN490B). About a restraint material, it is 235 N / mm < ² > (SS400) by the lower limit of the yield point prescribed | regulated by specification.

In addition, in the case of setting a restraint material in consideration of sufficient safety,
Ta ≧ 0.6 × Tc (3)
p ≦ 40 × Tc (4)
It is desirable to set the degree.

  Regardless of the present invention, when Ta is made thick (Ta> 2 × Tc) or when p is made small (P <5 × Tc), although it is safe, the increase in material and processing is increased. This is a very uneconomic result.

  FIG. 2 is a graph showing the test results of Table 1. In FIG. 2, those satisfying both the conditions of the expressions (1) and (2) of the restraint material thickness Ta and the bolt pitch p are indicated by white circles. This is consistent with the one having good destructive properties in the test (one in which the fatigue test was terminated by breaking the core material). Further, a material that does not satisfy the condition of the plate thickness Ta of the restraining material is indicated by a black triangle mark. In this test body, the core material is buckled during the test. A black square mark indicates that the bolt pitch p is not satisfied. This specimen also buckled the core material during the test.

  In comparison with the boundary line of the condition in FIG. 2, in the “Relationship between Tc and Ta” in FIG. 2 (a), attention should be paid to the white circle mark and the black triangle mark (the black square mark indicates the bolt pitch condition). In the “Relationship between Tc and p” in FIG. 2B, attention should be paid to the white circle mark and the black square mark (the black triangle mark is the plate of the restraint material). It can be excluded because it does not meet the thickness requirement and buckles.)

  If the conditions that the constraint material satisfies are considered in the range on the graph of FIG. 2, the “relationship between Tc and Ta” in FIG. 2A is above the boundary line (solid line), and FIG. It can be said that the “relationship between Tc and p” in b) needs to be lower than the boundary line (solid line). Moreover, in each graph, the boundary line when sufficient safety | security is considered is described with the broken line.

BRIEF DESCRIPTION OF THE DRAWINGS It is one Embodiment of the buckling restraint type axial force bearing member based on this invention, (a) is sectional drawing, (b) is a disassembled perspective view, (c) is an assembly perspective view. It is a result of the fatigue test of the buckling restraint type axial force bearing member which concerns on this invention, (a) is a graph which shows the relationship between Tc and Ta, (b) is a graph which shows the relationship between Tc and p. It is a figure which shows the buckling of the core material in a buckling restraining type axial force bearing member, (a) is whole buckling, (b) is local buckling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Buckling restraint type axial force bearing member 2 ... Core material 2A ... Yield part 2B ... Attachment part 3 ... Restraint material (angle-shaped steel)
4 ... Spacer 5 ... Bolt 6 ... Nut 7 ... Buffer material 8 ... Bolt hole 8a ... Long hole

Claims (2)

The core material is made by sandwiching each piece of a steel cross-shaped core material bearing the axial force with a steel steel cross-shaped chevron-shaped restraint material, joining the restraint materials together with bolts, and assembling the restraint material to the core material. In a buckling-restrained axial force bearing member that restrains buckling of
When the thickness of the core material is Tc, the thickness Ta of the restraining material is Ta ≧ 0.4 × Tc
And the pitch p of the bolt for assembling the restraint material is p ≦ 50 × Tc
A buckling-restrained axial force bearing member, wherein: In buckling constrained axial force bearing member according to claim 1, yield point or proof stress of the core material is at 80 N / mm ² or more 445N / mm ² or less, the yield point or proof stress of restraint material 235N / mm ² or more A buckling-restrained axial force bearing member, wherein:

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