Use of a seismic early warning system to calibrate variable dampers for structural control of a highway bridge

The possible exploitation of a seismic early warning system (SEWS) in the framework of semi-active (SA) structural control using magnetorheological (MR) dampers is herein investigated. This control system is considered as a complex and emerging technology for seismic protection of civil structures, able to interact actively and in real time with the structure during an earthquake. The main idea consists in changing the MR dampers behavior applied to the hosting structure, according to an anticipate estimate of the peak ground acceleration (PGA) provided by the SEWS. In details, the PGA value is used to build the elastic 5% damped spectrum according the Eurocode 8 rules. Then, the spectral acceleration, evaluated at the fundamental period of the hosting structure, is used to set the voltage in the MR devices according to an appropriate algorithm. The adjustment is supposed to happen only once, just before the quake strikes. In this case, the SA structural control framework becomes relatively simple, if compared to classical semi-active control systems. The present paper describes the application of this protection technique to a case-study, a highway bridge located in southern California. The seismic response of the benchmark bridge is investigated by nonlinear time-history analyses by adopting 28 real earthquake ground excitations. The 28 accelerograms cover a wide variety of magnitudes, distances to fault and soil types. The effectiveness of the proposed control strategy is assessed and compared to more consolidated control techniques.