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

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 Wenchuan earthquakes, where the widely observed shear key failure and bearing sliding significantly increased the risk of span unseating. To avoid such scenarios, economical yielding steel dampers are proposed to replace conventional shear keys as restraining devices on bridges. If designed properly, the steel dampers are expected to control bearing displacement within limit without imposing much additional demand on the substructure. The primary objective of this study was to develop a simplified procedure for designing the yielding steel dampers to control sliding displacement of the laminated rubber bearings to a specified value for the considered earthquake hazard. By treating the global bridge system as a serial-parallel combination of different components, the correlations of various parameters were investigated. On that basis, a simple formulation was developed, followed by a series of nonlinear time history analyses and a shake table test as verifications. The outcome of this study highlights the cost-effectiveness of using yielding steel dampers and laminated rubber bearings as an earthquake-resistant system for highway bridges compared with other popular isolation systems. The proposed design procedure was also verified to be quite efficient in properly designing the yielding steel dampers for a satisfactory bridge seismic performance.