Smart Damping Strategies for Seismic Protection of Urban Structures

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This investigation is aimed to develop a broad and integrated foundation for innovative smart structures concepts for earthquake hazard mitigation in heavily urbanized regions. The research plan is divided into two complementary efforts: low/medium-rise buildings and bridges, and medium/high-rise buildings. For low/medium-rise buildings and bridges, an adaptive base-isolation system will be studies that are able to accommodate the severe ground motion generated by high-velocity, long-period, seismic events associated with near-fault earthquakes. The proposed adaptive isolation system is comprised of low-damping isolation bearings used in conjunction with smart dampers employing magnetorheological (MR) fluid and can effectively adapt to unpredictable excitation levels and types. The proposed architecture employing isolation bearings and the MR damper overcomes many expenses and technical difficulties, which preclude the broad-scaled realization of controllable isolation system.For medium/high-rise buildings, smart dampers interconnecting buildings will be investigated. An alternative approach to the popular method of hybrid mass driver, which has high potential for reducing structural responses due to large earthquake and wind excitations is to use a class of active control systems that places control actuators between adjacent buildings with different dynamic characteristics. Yet, concerns over reliability, external power, capital cost and maintenance remain. Smart dampers such as the MR damper have been shown to possess the adaptability of the active control approach while maintaining reliabilities familiar in passive dampers. Development of appropriate MR dampers for this application shows great promise.This project will focus on understanding and integrating the two complementary smart structures concepts into viable means for protecting civil structures against near-fault earthquakes. The research will involve development of: (1) smart base isolation concepts, (2) smart interconnected buildings concepts, and (3) control strategies that can exploit the unique features of the adaptive system in mitigating urban earthquakes. Proof of concept experiments for several structural system configurations will be carried out at the University of Notre Dame, and a 200 kip prototype damper will be developed. This project is awarded under NSF 98-36 "US-Japan Cooperative Research in Urban Earthquake Disaster Mitigation.