Structural Control Strategies for Seismic Early Warning Systems

Abstract eng:
A seismic early warning system (SEWS) is a set of actions that can be taken from the moment when a seismic event is triggered, with a significant reliability, to the moment the quake strikes in a given location. The leading (pre-information) time can be estimated in the range of few seconds to dozens of seconds. Current research activities on SEWS include the anticipate estimate of the peak ground acceleration (PGA) and/or of the response spectrum of the incoming earthquake. Possible interactions between SEWS and structural control are related to the exploitation of the anticipate estimation of the PGA in the framework of semi-active control strategies, in particular using magnetorheological (MR) dampers. The latter are time-varying properties devices able to achieve a wide range of physical behaviors using low-power electrical currents. Changing the current in the damper causes a very fast modification of the mechanical properties of the MR fluids, due to the particular magnetic field applied. The main idea of this work is to change the MR damper behaviour according to the forecasted intensity of an upcoming earthquake provided by the SEWS, in order to obtain the optimal seismic response of the hosting structure. A reinforced concrete bridge is considered herein as a case-study. Three different control strategies are designed and compared, each one being based on the use of the following devices respectively: rubber isolator, viscous damper, semi-active magnetorheological (MR) damper, the latter working with a SEWS in the way described above. The effectiveness of each considered control technique is discussed with reference to several different seismic input.

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