JP2002088910A - Buckling-restrained brace material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly rigid buckling-restrained brace material and early yielding. SOLUTION: A high-strength bolt 5A and a frictional connection cross-shaped gusset plate 3 are welded to both ends of an axial force pipe 1 through end plates 4 to make an axial force member 7, and in the brace material 8b for restraining the buckling of the axial force member 7 by inserting the axial force pipe in a stiffening pipe 2, the axial force pipe is constituted of the brace material 8a having a steel pipe connecting structure constituted of a first steel pipe 1a having a specific YS and a second steel pipe 1b having a sectional area larger than the first steel pipe connected in series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buckling restrained brace material used as a structural element for resisting horizontal force such as seismic force in a building or other structures.

[0002]

2. Description of the Related Art For the purpose of plastically deforming even after compression yielding and exhibiting a stable hysteresis characteristic even under repeated compression and tension loads, a steel pipe transmitting an axial force is restrained from buckling of the entire steel pipe. A steel pipe type structural member in which a steel pipe is inserted or extrapolated is described in JP-A-04-149345. Japanese Patent Application Laid-Open No. 08-068109 describes a structural member in which an end portion of the double-tube type structural member is a cross-shaped joint for high-strength bolt friction joining. These double steel tubular structural members are referred to as buckling restrained braces or simply braces.

FIG. 3 is an axial sectional view showing an example of a conventional brace material. Note that the axial sectional view refers to a sectional view including two points included in the central axis of the illustrated target member. As shown in the drawing, a conventional brace material 8a is formed by a high-strength bolt friction joining bolt at both ends of an axial force tube 1 made of a single steel tube 1c having a predetermined YS (yield strength) via an end plate 4. Weld the cruciform gusset plate 3 having the hole 5B to form the axial force member 7.
Further, the buckling of the axial force tube 1 is restrained by the shaft rigid member 2 (the stiffening tube 2 in FIG. 3). That is, the axial force tube 1
The whole is inserted into the stiffening tube 2 to restrain the buckling of the axial force tube 1. The AA cross section and the BB cross section of FIG. 3 are shown in FIGS. 5 and 6, respectively.

[0004] The brace material 8a is mounted on a frame composed of columns 9 and beams 10 in a form as shown in FIG. When installing, the gusset plate 11
High-strength bolts on the cross-shaped gusset plate 3 of brace material
5A and the attachment plate 6 are friction-welded and fixed.

[0005]

In the above-mentioned conventional brace material, the cross-sectional area of the steel pipe transmitting the axial force is determined by the proof strength required in the structural design. , And is uniquely determined by its cross-sectional area. However, this brace material is used as a structural element for resisting horizontal force such as seismic force in a building or other structures, and is a material having a YS (yield stress) of such a degree as to reach a yield stress at an early stage of deformation. With its stable elasto-plastic hysteresis characteristics, it absorbs the energy input to the building during an earthquake as plastic strain energy and reduces the deformation of the building. And yields earlier. In this case, there is a problem that the conventional brace material cannot cope with the problem.

[0006] In view of this problem, an object of the present invention is to provide a buckling restrained brace material having high rigidity and capable of yielding at an early stage.

[0007]

The above object has been achieved by the present invention as described below. (1) A brace in which cruciform gusset plates for high-strength bolt friction welding are welded to both ends of an axial force tube via end plates to form an axial force member, and buckling of the axial force tube is restrained by a stiffening member. Buckling restraint, wherein the axial force pipe comprises a first steel pipe having a predetermined YS, and a second steel pipe connected to the first steel pipe and having a larger cross-sectional area than the first steel pipe. Brace materials.

[0008] (2) The second steel pipe is one section at the center of the three sections of the axial force pipe, or two sections at both ends, or one of the two sections. The buckling restrained brace material described.

[0009]

1 and 2 are axial sectional views showing an example of a brace material of the present invention. As shown in the figure, the brace material 8b of the present invention has a predetermined Y, for example, as shown in FIG.
In place of the conventional bracing material 8a in which the single steel pipe 1c having S is used as the axial force pipe 1, the axial force pipe 1 is not a single steel pipe, but a part of the length is a steel pipe having a larger cross-sectional area than the other parts. The other portion of the axial force tube 1 other than the second steel tube is a predetermined YS, that is, a low YS steel tube appropriately selected so as to reach the yield stress in the early stage of deformation. (Referred to as a first steel pipe). The first steel pipe 1a and the second steel pipe 1b are connected in series by welding.

In the example of FIG. 1, the central section of the axial pipe is divided into three sections and the second section is used as the second steel pipe. The example of FIG. 2 is divided into two sections. One of the wards is second
It is a steel pipe. 5 and 6 correspond to the cross-sectional views taken along the lines AA and BB in FIGS.
Fig. 3 is a sectional view taken along the line CC in Figs. 1 and 2. The method of mounting the brace material of the present invention on the skeleton is the same as the conventional method, and the mounting form is the same as that shown in FIG.

Next, the operation and effect of the present invention will be described with reference to FIG. FIG. 8 is an explanatory diagram showing a relationship between an axial load and an axial deformation in the present invention and a conventional brace member axial force tube portion. In the vertical axis of FIG. 8, the positive side represents a compressive load, and the negative side represents a tensile load. With a conventional brace material (conventional material), when a compressive load is applied, the axial force tube is buckled and restrained by the stiffening tube, so it does not buckle and shrinks and deforms in the axial direction with a predetermined axial rigidity Ka. When the internal compressive stress reaches the YS of a single steel pipe, it yields. Thereafter, even when a tensile load is applied, the axial force tube expands and deforms in the axial direction with the same axial rigidity Ka as in the case of compression, and yields when the internal tensile stress reaches YS of a single steel tube. When a repeated load of compression and tension is applied, this behavior is repeated, whereby a stable hysteresis characteristic (dotted line in FIG. 8) is presented.

On the other hand, in the brace material of the present invention (material of the present invention), a part of the axial force pipe is a second steel pipe having a larger sectional area than the other part (that is, the first steel pipe). As shown in FIG. 8, the rigidity Kb is higher than the axial rigidity Ka of the axial force tube formed of the first steel pipe alone. Therefore, in the material of the present invention, when the same compressive load as that of the conventional material is applied, the material is shrunk and deformed in the axial direction with a larger axial rigidity Kb, and when the internal compressive stress reaches the YS of the first steel tube, the material is removed from the first steel tube. Will surrender. Thereafter, even when a tensile load is applied, the axial force tube expands and deforms in the axial direction with the same axial rigidity Kb as in the case of compression, and when the internal tensile stress reaches YS of the first steel tube, the portion formed of the first steel tube Surrenders.

In the material of the present invention, since Kb> Ka, the elastic deformation amount for the same load is smaller than that of the conventional material, that is, YS is reached with the elastic deformation amount smaller than that of the conventional material. Surrender early. When a repeated load of compression and tension is applied, the above behavior is repeated, so that a stable hysteresis characteristic (solid line in FIG. 8) is exhibited as in the conventional material.

The fact that Kb> Ka is proved as follows using mathematical formulas. First, the axial rigidity Ka of the conventional material
Is given by the following equation. Ka = EAa / Lt (1) E: Young's modulus Aa: Cross-sectional area of first steel pipe Lt: Length of axial force pipe On the other hand, the axial rigidity Kb of the material of the present invention in which the conventional material is replaced is represented by the following equation. Given. The Young's modulus E was the same for the first steel pipe and the second steel pipe.

Kb = E / (La / Aa + (Lt-La) / Ab) (2) La: length of the first steel pipe (the total length if divided into two or more) Ab: second steel pipe Here, assuming that La / Lt = α and Ab / Aa = β, the following equation is established from equations (1) and (2). Kb / Ka = β / (αβ−α + 1) (3) However, in the material of the present invention, since 0 <α <1 and β> 1, the inequality: β-1> α (β-1) Holds, and if the inequality is transformed, the fractional expression on the right side of the equation (3): β / (αβ−α + 1)
Is greater than one. Therefore, Kb> Ka.

For example, if α = 1/2 and β = 3, the axial rigidity of the material of the present invention is 1.
5 times. The magnification Kb / Ka can be arbitrarily set by changing one or both of α and β in Expression (3). In the present invention, since the first steel pipe mainly plays the role of absorbing the energy input to the building during the earthquake as plastic strain energy, the second steel pipe must be a low YS steel pipe in which plastic deformation occurs early. Is not particularly
It may be a high YS steel pipe. In order to surely cause the plastic deformation of the first steel pipe before the second steel pipe reaches the yield stress, it is preferable to select the second steel pipe whose YS is larger than that of the first steel pipe.

[0017]

As described above, according to the present invention, a buckling restraint having characteristics useful as a vibration-damping brace material, in which the axial stiffness is high and yielding occurs early, while maintaining the stability of load-deformation history characteristics. Since the brace material can be easily realized,
It has an excellent effect of being able to quickly respond to various requirements of seismic design of buildings and other structures.

[Brief description of the drawings]

FIG. 1 is an axial cross-sectional view showing one example of a brace material of the present invention (an example in which one central section of three sections is a second steel pipe).

FIG. 2 is an axial sectional view showing one example of a brace material of the present invention (an example in which one of the two sections is a second steel pipe).

FIG. 3 is an axial sectional view showing an example of a conventional brace material.

FIG. 4 is a front view showing an example of a mode of attaching a brace material to a skeleton.

FIG. 5 is an AA sectional view of FIGS.

FIG. 6 is a sectional view taken along the line BB of FIGS. 1 to 3;

FIG. 7 is a sectional view taken along the line CC in FIGS. 1 and 2;

FIG. 8 is an explanatory view showing a relationship between an axial load and an axial deformation in the present invention and a conventional brace member axial force tube portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Axial force pipe 1a 1st steel pipe 1b 2nd steel pipe 2 Stiffening pipe (stiffening member) 3 Cross shaped gusset plate 4 End plate 5A High strength bolt 5B Bolt hole 6 Base plate 7 Axial force member 8a Brace material (conventional) 8b Brace material (the present invention) 9 beams 10 columns 11 gusset plates

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takanori Shimizu 2-3-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo F-term in Kawasaki Steel Corporation (reference) 2E002 EB12 FA02 FA07 FA08 FB15 LB09 LB13 LC01 MA12 2E125 AA33 AB03 AB17 AC16 AG03 AG12 AG31 AG41 AG43 AG45 AG57 BB08 CA05 CA14 2E163 FA12 FB01 FB09 FB21 FF01

Claims (2)

[Claims] 1. A cross-shaped gusset plate for high-strength bolt friction welding is welded to both ends of an axial force tube via end plates to form an axial force member, and stiffening members restrain buckling of the axial force tube. In the brace material, the axial force tube has a predetermined Y
A first steel pipe having an S and a first steel pipe connected to the first steel pipe;
A buckling-restrained brace material having a second steel pipe having a larger sectional area than a steel pipe. 2. The second steel pipe is one of a central section of the axial pipe divided into three sections, or two sections of both ends, or one of two sections. The buckling restrained brace material described.