Performance of seismically isolated bridges under beyond design shaking

Professor, Department of Structural Engineering 

Mervyn Lea Rudee Endowed Chair in Jacobs School of Engineering

Associate Dean for Equity, Diversity and Inclusion, Jacobs School of Engineering

Director, Caltrans Seismic Response Modification Device Facility

University of California, San Diego

Seismic isolation is a proven strategy for protecting critical infrastructure from the damaging effects of design-level earthquake shaking. Under stronger shaking, the seismic isolation system can be subjected to displacement demands beyond its design capacity, resulting in yielding of the bridge substructure, failure of the bearings or exceeding the clearance and pounding against the abutment back-walls. Caltrans design recommends that seismic isolation function as the primary structural seismic resisting system. Beyond the design capacity, a secondary earthquake resisting system engages in the form of substructure column plastic hinging.

To assess the effectiveness of this design approach, the response of a seismically isolated highway bridge is examined with a detailed nonlinear model to capture the progression of damage and potential failure modes. The numerical results indicate that plastic hinging reduces the effectiveness of the isolation system, however, the damage to the columns is controlled and protects from bearing failure under increasing seismic demands. An experimental shake table program is currently under way to verify the result of the numerical models and plans for testing will be presented.

Gilberto Mosqueda is a professor in the Department Structural Engineering and the Mervyn Lea (M. Lea) Rudee Endowed Chair in Jacobs School of Engineering at the University at California San Diego. Previously, he was an assistant then associate professor at the University at Buffalo. He received his PhD from the University of California at Berkeley, MS from Massachusetts Institute of Technology, and BS from the University of California at Irvine all in civil engineering.

Professor Mosqueda is the Director of the Caltrans Seismic Response Modification Device Test Facility testing full scale seismic isolation and damping devices. He received the Colegio de Ingenieros Civiles de Mexico, Jose A. Cuevas Award in 2020, American Society of Civil Engineering Moisseiff Award in 2019, NSF CAREER award in 2008.