Previous earthquakes have highlighted the seismic vulnerability of bridges due to excessive movements at expansion joints. This movement could lead to the catastrophic unseating failure if the provided seat width is inadequate. Moreover, seismic pounding is inevitable during a strong earthquake due to the limited gap size normally provided at the expansion joints. Various types of restrainers, dampers and other devices have been proposed to limit the joint movement or to accommodate the joint movement so that the damages caused by excessive relative displacements could be mitigated. To select and design appropriate devices to mitigate the relative displacement-induced damages to bridge structures during earthquake shaking, it is important that results from the previous studies are well understood. This paper presents an overview on various pounding and unseating mitigation devices that have been proposed by various researchers. Based on an extensive review of up-to-date literatures, the merits and...

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Devices for protecting bridge superstructure from pounding and unseating damages: an overview

The performance of concrete shear keys as restraining devices for laminated rubber bearing–supported highway bridges was examined in past earthquakes such as the 1999 Chi-Chi and the 2008 W...

Yielding Steel Dampers as Restraining Devices to Control Seismic Sliding of Laminated Rubber Bearings for Highway Bridges: Analytical and Experimental Study

Using seismic isolation systems for highway bridges modifies the structure’s principal vibration modes and effectively reduces the seismic base shear conveyed from the superstructure to the substructure. However, for some low-damping rubber isolation bearings, large displacements can be a problem. Supplemental hysteretic dampers can be introduced into the base-isolated bridge, which might nevertheless increase the structure base shear, and the merit of adding dampers has to be evaluated properly. In this paper, a simplified method was implemented for the design of a low-cost hysteretic damper, and the resulting isolator-damper system was tested experimentally. The design method used is based on an equivalent linearization approach. A full-scale elastomeric isolation bearing was characterized and used in the design of a hysteretic damper. Both the isolator and the damper went through cyclic testing and real-time dynamic substructuring (RTDS) methods to verify the capacity of the method to design ba...

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Implementation of a Simplified Method in Design of Hysteretic Dampers for Isolated Highway Bridges

Investigation of equal strength mild steel tenons as displacement restraining devices for long-span railway arch bridges

In certain areas of Canada, seismic loads can be very high and seismic rehabilitation of existing bridges is inevitable and very expensive. A standard method of rehabilitation is to provide the existing structure with steel, concrete or fibre reinforced plastic jackets in order to increase strength and ductility of piers that are the main resisting members to earthquake. This paper provides some directions for the use of simple isolation devices as elastomeric bearing to rehabilitate existing bridges, specifically lifeline and emergency bridges. With this kind of very simple methods, it is possible in some cases to reduce seismic loads without expensive strengthening methods. The result of this study could also be used for the design of new bridges. This paper as the basis of the research has served to recognize the influence of different parameters as in the code CSA S6 (2006) in the seismic design of the base isolated bridges in comparison with the conventional bridges. CHAPTER4. ISOLATED BRIDGE PARAMETRIC STUDY 50

Simplified design method for energy dissipating devices in retrofitting of seismically isolated bridges

Isolation bearings and dampers are often installed between piers and superstructures to reduce the seismic responses of bridges under large earthquakes. This paper presents a novel steel damper for bridges. The damper employs steel plates as energy dissipation components, and adopts a vertical free mechanism to achieve a large deformation capacity. Quasi-static tests using displacement-controlled cyclic loading and numerical analyses using a finite element program called ABAQUS are conducted to investigate the behavior of the damper, and a design methodology is proposed based on the tests and numerical analyses. Major conclusions obtained from this study are as follows: (1) the new dampers have stable hysteresis behavior under large displacements; (2) finite element analyses are able to simulate the behavior of the damper with satisfactory accuracy; and (3) simplified design methodology of the damper is effective.

Qiang Xie

Papers

Development of steel dampers for bridges to allow large displacement through a vertical free mechanism