JP2008297720A - Non-damaged self-restoring seismic isolation and control mechanism for steel bridges - Google Patents

Abstract

To provide a seismic isolation / seismic control mechanism that keeps a structure body intact in response to a maximum earthquake and satisfies the operability after the earthquake.
Both ends of the beam are installed at the top of the column, and the column is fastened to the beam and the foundation by introducing prestress into a PC steel rod arranged in the axial direction of the column.
[Selection] Figure 4

Description

  The present invention relates to an undamaged self-restoring type seismic isolation / damping mechanism for steel bridges.

  In steel gate-type frame structures used for bridge piers and the like, it is common to use earthquake-resistant structures with excellent energy absorption capability, but in recent years, the buckling of Non-Patent Document 1 has been carried out to prevent damage to the main body structure as much as possible. Application of seismic control structures using economical hysteretic dampers such as restrained braces and shear panels is being studied (Fig. 1). In such a structure, although the damage to the main body structure is reduced, there is a possibility that an increase in the reaction force of the column base due to an increase in the shear rigidity of the portal frame and a residual displacement due to plasticization of the hysteresis damper. There is also the problem of occupying the free space of the portal ramen.

In order to suppress the increase in bending moment at the time of an earthquake at the column-to-base and column-to-beam joints in a rigid frame structure, the so-called Non-Patent Document 2 in which the degree of fixation of the column at the anchor and corners is reduced It is conceivable to provide seismic isolation by adopting a semi-rigid connection (Fig. 2). However, in such a structure, damage to the column can be reduced, but there is a possibility of concentration of damage to the joint and an increase in residual displacement after the earthquake. To address this problem, so-called PTED joints (Post-Tensioned Energy Dissipating Connection) (Fig. 3) with self-centering function are used for the joints between beams and columns in multi-story multi-span frames of buildings. This is proposed in Non-Patent Document 3. In PTED joining, a beam and a column are joined by introducing a compressive axial force with a PC steel rod arranged in the axial direction of the beam, and an axial yield type metal damper is placed horizontally at the top and bottom of the beam at the joint. And a pillar. However, when this structure is applied as it is to a portal frame with many examples of application as a ramen pier, the PTED joint has only two corners, and the column base is rigidly connected. There is a problem that energy absorption at the joint cannot be effectively performed due to the small relative rotation at. Furthermore, unlike a building frame, a large dead load of the superstructure acts on the beam, so a support structure that reliably transmits a large beam reaction force to the column while allowing relative rotation as a PTED joint is applied to the inner flange surface of the column. It is not easy to install.

Seismic response characteristics and seismic design method of frames with hysteretic dampers, Japan Steel Structure Association, 1998. Yoshiaki Goto, May in Suzuki, Kiyoshi Matsuura: A Study on the Stability of Semi-rigid Rectangular Frames with Inelastic Properties at the Joint between Beam and Column, Proceedings of JSCE, No. 416, 329-338, 1990. Constantin Christpouluos, Andre Filiatrault, Chia-Ming Uang, Bryan Folz: Posttensioned Energy Dissipating Connections for Moment-Resisting Steel Frames, Journal of structural engineering, pp. 1111-1120, 2002.

The conventional seismic isolation / seismic control mechanism has the following problems a) to e).
a) Residual displacement after an earthquake may occur in damping structures such as buckling-restrained braces and shear panels.
b) Damping structures such as buckling-restrained braces and shear panels occupy free space under the girders.
c) In the so-called semi-rigid structure where the anchorage at the anchors and corners is reduced, there is a possibility that the damage to the joints will be concentrated and the residual displacement after the earthquake will increase.
d) When the PTED joint with self-restoration function proposed for multi-story multi-span frames of architecture is applied to the ramen pier, the column base is rigidly connected, so the relative rotation at the corner is small, Energy absorption at the joint cannot be performed effectively.
e) Unlike a framework, a large dead load of the superstructure acts on the beam on the ramen pier, so a support structure that reliably transmits a large beam reaction force to the column while allowing relative rotation as a PTED joint is provided inside the column. It is not easy to install on the flange surface.

  This invention makes it the subject which should be solved to provide the seismic isolation and damping mechanism which solved the said conventional problem.

The seismic isolation / damping mechanism of the present invention is
a) Prevent the residual deformation of the damper after the earthquake by the self-weight of the superstructure together with the initial tension introduced into the PC steel rod arranged in the axial direction of the column, and make the residual deformation of the whole structure almost zero,
b) A support structure that supports the beam at the top of the column and reliably transmits a large beam reaction force to the column.
c) Absorb energy with a hysteretic damper placed in the axial direction of the column at the junction between the column and the beam, and limit the damage to this replaceable damper part;
It is characterized by.

  Therefore, according to the seismic isolation / seismic control mechanism of the present invention, it is possible to suppress damage to a structure under a maximum earthquake more easily and more economically than before and to prepare for early restoration.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

FIG. 4 shows an example in which the seismic isolation / seismic control mechanism of the present invention is applied to a portal ramen pier.
As shown in this figure
1) Both ends of the beam are installed at the top of the column, and the column is fastened to the beam and foundation by introducing prestress into the PC steel rods arranged in the axial direction of the column.
2) Install a shaft-yield type metal damper to control the amount of relative rotation at the joint where relative rotation occurs and to absorb kinetic energy during an earthquake. The dampers are arranged vertically in two locations near the upper and lower flanges of the columns of each joint so as to resist the bending moment, and connect the columns and beams or the columns and foundations. This damper is plasticized by a tensile force due to Level 2 earthquake motion, but is re-yielded by the compressive force due to the prestress of the PC steel rod and disappears.
With these,
By the above 1), it becomes a semi-rigid seismic isolation structure in which relative rotation occurs at the joint between the column and beam and the column and foundation with respect to horizontal ground motion, and a self-restoring structure,
Plasticization concentrates only on the metal damper described in 2) above, thereby achieving energy absorption,
Moreover, the restoration work can be easily performed by replacing the plasticized damper after the earthquake.
The following effects can be obtained.
a) In addition to the column-to-beam PTED bonding introduced in the vertical direction, the PED bonding at the column base increases relative rotation at each bonding portion, and more effective because four PTED bondings are arranged. Expected to have a seismic isolation and energy absorption function.
b) Since the metal damper is arranged in the vertical direction of the column base, it can function as a rocking-type seismic isolation / damping structure even when the aspect ratio is large and negative reaction force is generated.
c) When plastic elongation occurs in the metal damper, the dead load of the superstructure works positively on the self-restoration function together with the prestress of the PC steel rod, so the prestress on the column is less than when placed horizontally. It's small.
d) Since the beam is supported on the top surface of the column, no complicated support structure is required.
e) No stress concentration or strain concentration at the corners leading to crack initiation.
FIG. 5 shows an example in which the seismic isolation / seismic control mechanism of the present invention is applied to an upper steel arch bridge, and FIG. 6 shows the seismic isolation of the present invention.・ This is an example in which the seismic control mechanism is applied to a single-column pier.

  The seismic isolation / seismic control mechanism of the present invention can be used for structures such as piers.

It is a figure which shows the example which used the conventional axial yield type damper for the portal ramen pier. It is explanatory drawing of the junction part of the semi-rigid joint frame which is one of the conventional seismic isolation structures. It is explanatory drawing of the PTED joining proposed for the building structure. This is an example in which the seismic isolation / seismic control mechanism of the present invention is applied to a portal ramen pier. It is a figure which shows the example which applied the seismic isolation and damping mechanism of this invention to the upper-path type steel arch bridge. It is a figure which shows the example which applied the seismic isolation / seismic control mechanism of this invention to the single column type pier.

Claims (1)

a) Prevent the residual deformation of the damper after the earthquake by the self-weight of the superstructure together with the initial tension introduced into the PC steel rod arranged in the axial direction of the column, and make the residual deformation of the whole structure almost zero,
b) A support structure that supports the beam at the top of the column and reliably transmits a large beam reaction force to the column.
c) Absorb energy with a hysteretic damper placed in the axial direction of the column at the junction between the column and the beam, and limit the damage to this replaceable damper part;
A seismic isolation and vibration control mechanism.