Uncertainty evaluation of after-earthquake damage detection strategy

After-earthquake assessment of buildings in terms of safety and usability is nowadays performed by technicians who are called to give their judgement based on in-field surveys and visual inspections, often conducting the surveys in the absence of objective data. This implies additional inconvenience for residents and economic losses in the affected area. A near real-time assessment based on objective data related to the seismic response of the structures is possible through the use of monitoring systems that provide observations on the state of the monitored structure, obtaining information on its dynamic response. One of the most reliable parameters that can be correlated to the state of a structure after an earthquake is the ductility demand, expressed in terms of interstory drift. Using acceleration time-history records from the ITACA (Italian Accelerometric Archive) strong-motion database, we investigate the main sources of uncertainties in the estimation of displacement time-histories and interstory drift, using the method of double integration of the acceleration measurements alone. We have found that in general the instrumental uncertainties have less importance than the uncertainties of the model, in particular in the presence of residual displacements at the end of the seismic motion.