JP2000220212A - Steel structure of earthquake-resistant design - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve vibration proofness of a steel structure by providing a brace with an expansible mechanism for generating resistance force proportional to the speed of axial displacement of the brace and expanding and contracting in the axial direction of the brace. SOLUTION: A support rack 1 as a steel structure is formed by steels such as a longitudinal beam 3, a cross beam 4, a vertical material 5, a cross groove 6, a brace 7 and the like. At this time, the brace 7 is provided with a damper 8 adapted to generate resisting force proportional to the axial displacement speed of the brace 7 and expand and contract in the axial direction of the brace 7. The damper 8 generates large resisting force to a sudden horizontal force due to vibration of an earthquake to restrain bending of the support rack 1, and absorbs displacement stress with small resisting force to the low speed displacement due to the ground deformation to prevent damage of the support rack 1. Thus, the support rack 1 can be prevented from being deformed and damaged by vibration of an earthquake and the ground deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel structure having a reinforcing brace, and more particularly to a technique for withstanding a ground deformation caused by an earthquake or the like.

[0002]

2. Description of the Related Art A steel structure such as a pipe support rack or a bridge for supporting a pipeline at a fuel base of petroleum or the like is provided with a brace for reinforcing the steel structure against external force, particularly, horizontal force. Often. Braces are installed diagonally with respect to the frame of the steel structure to reinforce the steel structure, and the steel structure with the brace has a large resistance to horizontal force due to earthquake or wind. Become. FIG. 3 is a model diagram showing a state in which a brace 31 is obliquely attached to a steel structure constituted by a steel frame 30. In such a steel structure, the brace 31 described above with respect to ground vibration (earthquake motion). It is effective and shows resistance. However, these structures
The ground may be deformed significantly due to ground deformation (lateral movement) due to liquefaction or the like during an earthquake. That is, when the foundation portion 32 moves from T1 to T2 due to ground deformation, displacement stress is generated in the axial direction of the brace 31, and the brace 31 is broken (F portion), and the steel structure in which the horizontal resistance is lost. May be greatly deformed and damaged. Therefore, in the conventional steel structure, as a measure against the ground deformation, a foundation pile is driven into a hard ground layer with a small flow so as not to move the base part 32 largely.

[0003]

However, in the conventional steel structure as described above, in order to drive the foundation pile into a hard ground layer with little flow, a very long foundation pile must be driven deep into the ground. In addition, the operation cost becomes large along with the material cost. Further, in recent years, it has become necessary to design a structure assuming a larger earthquake acceleration than before, and the number of braces provided on the structure tends to increase. Structures with increased braces are more resistant to sudden horizontal forces due to seismic motion, but are less flexible and have less tolerance for ground deformation. For this reason, there is a problem that a much larger amount of foundation pile is driven than before, and the cost required for driving the foundation pile is enormous.

[0004] The present invention has been made in view of such problems, and has an earthquake-resistant design capable of effectively withstanding earthquake vibrations and ground deformation and reducing the cost of countermeasures against earthquakes. An object of the present invention is to provide a steel structure.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a steel structure having a reinforcing brace, wherein the brace generates a resistance in proportion to a displacement speed of the brace in the axial direction. In addition, a technology is employed that has a telescopic mechanism that expands and contracts in the axial direction of the brace. In this seismic design steel structure, the brace has a telescopic mechanism,
Even if the base of the structure flows to generate displacement stress in the brace in the axial direction, the expansion and contraction mechanism absorbs the displacement stress, so that the structure can be held without breaking the brace. In addition, the telescopic mechanism generates a resisting force in proportion to the displacement speed in the axial direction. The extension and contraction mechanism absorbs the displacement stress in the axial direction of the brace with a relatively small resistance against displacement at low speed due to ground deformation, thereby preventing damage to the steel structure.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing a configuration of a steel structure according to the present invention. In the present embodiment, the steel structure is a support rack 1 of a fuel transport pipe P. The fuel transported here is, for example, natural gas, propane gas, or petroleum (crude oil). The pipes P are arranged at a predetermined height that is efficient for transportation, and are fixed to the support rack 1 by the support members 2.

[0007] The support rack 1 is a structure formed of a steel frame, and various steel materials such as H steel, I steel, and square pipe are used for the steel frame. This support rack 1 has vertical girder 3, horizontal girder 4,
A steel frame such as a vertical member 5 is configured to mainly resist a bending moment, and a steel frame such as an anti-tilt structure 6 and a diagonal member (brace) 7 is configured to resist a horizontal force. Such a structure 1
, A horizontal force such as a wind load, an earthquake load, and other lateral loads acts thereon. Therefore, the brace 7 is appropriately disposed so that the entire structure 1 is not bent by the horizontal force. In addition to the configuration shown in FIG. 1, an anti-tilt structure 6 and a brace 7 are additionally provided for reinforcement. Further, at the joints such as the nodes B1 and B2, the respective steel frames are joined in a deformable state such as a pin joint. The support rack 1 has a basic structure in which the steel frames are combined in a triangular shape.

The support rack 1 is provided with a base plate 9
Is fixed to the ground by being hit on the base portion 11 by the anchor bolt 10. And the base part 11 is appropriately set according to the state of the underground ground layer. As described later, the steel structure according to the present embodiment is configured so that the structure is not damaged even if the ground flows to some extent, and the foundation pile is driven deep into the hard ground layer in the base portion 11. It is not always necessary to do such things. Further, even when such foundation piles are driven, the number of the foundation piles can be suppressed to a necessary minimum number.

The brace 7 is provided with a telescopic mechanism 8 that can expand and contract in the axial direction of the brace 7. Here, the extension mechanism 8 is a cylindrical damper 8, and each brace 7 supports the support rack 1 via the damper 8. Since only the axial force (axial force: tension and compression) acts on the brace 7, the damper 8 can be arranged at any position between the nodes where the brace 7 is joined. Although the dampers 8 are attached to all the braces 7 in FIG. 1, the number of the braces 7 to which the dampers 8 are attached is determined to be an efficient number from the calculation of the strength of the entire support rack 1 and the manufacturing cost. .

The damper 8 generates a resistance force in proportion to the displacement speed of the brace 7 in the axial direction. That is, the damper 8 suppresses the bending of the support rack 1 by generating a large resistance force against a sudden horizontal force due to, for example, vibration (earthquake motion) at the time of the occurrence of an earthquake. For the displacement (deformation) at a speed of a certain level or less, the supporting rack 1 absorbs the displacement stress with a relatively small resistance and changes the distance between the nodes B3-B4 and B3-B5 between the nodes of the brace 7. To prevent damage. Here, a high-viscosity damper 8 filled with a high-viscosity fluid is used as the damper 8 having a resistance force proportional to the displacement speed. In this damper 8, the resistance of the damper 8 to each displacement speed is designed based on the displacement speed between the nodes B3-B4 and B3-B5 between the nodes at the assumed earthquake acceleration and the desired rigidity of the support rack 1. The maximum expansion and contraction distance of the damper 8 is obtained from the relative displacement of each foundation 11 in the assumed ground deformation.

Next, the operation of the steel structure having the above-described structure when the ground is deformed will be described with reference to FIG. FIG. 2 is a model diagram of a portion of the support rack 1 where the brace 7 is attached. First, in the state shown by the solid line, the support rack 1 is in a stable state. For example, even if a sudden horizontal force due to seismic motion is applied, the damper 8 generates a large resistance force and suppresses the bending of the support rack 1. I do. Next, one of the foundations 11a is
When the support rack 1 moves from 1 to S2, the support rack 1 is deformed, for example, as indicated by imaginary lines in the figure. That is, in this case, a large tensile stress acts in the axial direction of the brace 7a, and the damper 8a attached to the brace 7a extends in the axial direction. At this time, the displacement speed at the time of ground deformation is, for example, several tens of millimeters per 10 minutes, which is not large, so that the resistance of the damper 8a is a relatively small value, and
a gradually expands according to the displacement speed. Node B1
The joints such as and the joint B2 are joined in a state where they are easily deformed in advance. With these, the support rack 1 after the deformation
Is a stable state in which the damper 8a is extended by a certain amount,
In addition, since the joints such as the nodes B1 and B2 are in a plastically deformed state, the stress inside the support rack 1 is relieved to some extent. In the structure in this state,
For example, even if a sudden horizontal force is applied by the seismic motion, the damper 8 generates a large resistance force to suppress the bending of the support rack 1 and to suppress a large deformation such as damage.

The deformed state of the support rack 1 shown by imaginary lines is an example, and various deformed states may be considered according to the strength of each steel frame. For example, the damper 8a may contract and the damper 8b may extend. However, since the displacement stress at the time of deformation is absorbed by the expansion and contraction of the dampers 8a and 8b, the structure of the support rack 1 is maintained in any state after deformation.

As described above, in the support rack 1 shown in this embodiment, since the brace 7 is provided with the damper 8,
The damper 8 generates a large resistance against a sudden horizontal force due to seismic motion or the like and suppresses the bending of the support rack 1, and the displacement of the base 11 at a low speed due to ground deformation or the like. The displacement stress is absorbed by the expansion and contraction of the damper 8, thereby avoiding damage. As described above, the steel structure according to the present embodiment can effectively cope with ground movement caused by an earthquake by utilizing the characteristic of the damper 8 that generates a resistance in proportion to the displacement speed.

Here, a cylindrical damper 8 using a highly viscous fluid as a telescopic mechanism attached to the brace 7 is used.
Although various methods can be applied according to the installation conditions and the assumed axial stress. For example, a friction damper using a frictional force, a viscoelastic damper using a polymer material or a rubber-based material, or a mechanism showing an arbitrary resistance using electric or magnetism may be used.

The damper 8 may be attached to the end of the brace 7 or the like. Further, a damper having characteristics different from those of the damper 8 attached to the brace 7 may be attached to the anti-tilt structure 6, and the support rack 1 may be mounted. May be adapted to the displacement in the width direction.

Further, the steel structure according to the present invention can be applied to various steel structures by simply attaching a damper to a portion to which stress is applied in the axial direction, and is applicable to various steel structures. Needless to say, it is not limited to this.

[0017]

As described above, in the steel structure of the seismic design according to the present invention, since the brace is provided with the expansion and contraction mechanism, the base of the structure flows to generate the axial displacement stress on the brace. Also, since the expansion and contraction mechanism absorbs the displacement stress, the structure can be held without breaking the brace. Also, in this steel structure, the telescopic mechanism generates a resistance in proportion to the displacement speed in the axial direction, so the telescopic mechanism generates a large resistance against sudden horizontal forces due to the earthquake. Since the bending mechanism of the steel structure is suppressed, and the expansion and contraction mechanism shows a small resistance to the ground deformation and absorbs the displacement stress, it is possible to prevent the steel structure from being greatly deformed and damaged. . In addition, by adopting this steel structure, it is possible to reduce the need to drive the foundation pile deep into a hard ground layer with low flow, thereby reducing the material cost and working cost required for driving the foundation pile. The cost of the countermeasures for can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a steel structure according to the present invention.

FIG. 2 is a model diagram of a portion where the brace of FIG. 1 is attached.

FIG. 3 is a model diagram showing a conventional steel structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support rack (steel structure) 7 Brace 8 Damper (expansion mechanism)

Claims (1)

[Claims] 1. A steel structure having a reinforcing brace (7), wherein the brace (7) generates a resistance force in proportion to a displacement speed of the brace (7) in an axial direction, and the brace (7). (7) A steel structure having an earthquake-resistant design, comprising: a telescopic mechanism (8) that expands and contracts in the axial direction.