Experimental Study of Bridge Elastomeric and Other Isolation and Energy Dissipation Systems with Emphasis on Uplift Prevention and High Velocity Near-Source Seismic Excitation

Keywords: Bridges. Prestressed isolators. Modeling. Two span bridges. Linear viscous dampers. Nonlinear viscous dampers. Elastomeric bearings. Elastomeric isolation systems. Isolator testing machines. Axial loads. Lateral displacement. Rotation. Isolation systems. Energy dissipation systems.

Abstract: This report provides an assessment of the benefits offered by damping systems in near-source earthquakes and of the accuracy of currently available tools for analytical prediction of their seismic response. A two-span continuous deck bridge configuration was used in the test program. First an isolator testing machine was designed and constructed that was capable of testing small bearings under controlled conditions. Next, three vastly different bearings (flat sliding, friction pendulum, and elastomeric) were tested prestressed in the developed testing machine. Test results provided strong evidence for the capability of prestressing to prevent uplift or tension in isolation bearings. Finally, an experimental study of bridge elastomeric isolation systems with emphasis on near-source high velocity seismic excitation was preformed. The addition of the damping devices caused a substantial reduction in displacement, provided relief to the vulnerable pier, caused a reduction in the total shear force transmitted to the bridge substructure, and provided for redistribution of the reduced inertia forces from the vulnerable pier to the presumed strong abutments.