Energy-based damage assessment on structures during earthquakes

Several seismic damage indices have been developed using the energy concept in attempt to compensate for the inadequacy of ductility criteria. However , these indices are either based on implicitly defined energy as a cumulati ve effect on ductility or are unable to consider energy in a quantitative m anner. In this paper, a method of assessing the structural performance duri ng earthquakes based on both explicitly computed plastic rotation and plast ic energy at every hinge of a moment-resisting frame is proposed. This meth od uses the force analogy method to evaluate the structural response and en ergy in the inelastic domain. Inelastic deformation is expected to occur du ring major earthquakes, and active control based on an instantaneous optima l control algorithm is used to improve the structural performance. Comparis ons are made between uncontrolled response and instantaneous optimal contro l response based on a single-degree-of-freedom system to demonstrate the co mputation of plastic energy. Damage analysis of a six-storey moment-resisti ng steel frame is then presented to evaluate the performance and applicabil ity of the proposed damage measure. Results show that the proposed damage a ssessment criteria are feasible and that active control can reduce plastic rotation and plastic energy, thereby reducing damage to a certain acceptabl e limit. Copyright (C) 2001 John Wiley & Sons, Ltd.