Analysis of seismic structural damage using earthquake records

Models for the analysis of global structural damage based on equivalent modal parameters are introduced and applied on reinforced concrete structures subjected to earthquake loads. A model for the analysis of seismic structural damage consists of a finite number of numerical indicators (damage indices) and of a procedure for their computation. A structure exhibits a nonlinear behavior when it experiences a damaging earthquake. Nonetheless a time variant equivalent linear structure can be defined. An algorithm for the estimation of the modal parameters of a linear structure has been developed and implemented. Global damage indices are then defined from the vibrational parameters of the equivalent linear structure considered.;The relationship between parameter based global damage indices and local damage variables is then studied. For reinforced concrete structures stiffness degradation and permanent deformation describe damage at the local level. It is shown that the global damage indices introduced here result from averaging operations in space and in time of the local damage variables.;The serviceability analysis of a structure is first considered. It is shown that the problem of identification of the serviceability limit state is equivalent to the problem of detection of seismic structural damage. A limit state can be defined as a surface in the space of the damage indices relative to the model considered. Experiments on small-scale models are analyzed to obtain an analytical definition of the serviceability limit state. Since many uncertainties are present in any damage analysis problem, a probabilistic definition is obtained, in terms of the probability that the structure considered is damaged after a seismic event. In order to validate the proposed procedure, records from large-scale models and actual full-scale structures are analyzed. The model proposed performs very well in detecting seismic structural damage.