Seismic Loss Assessment Based on Real Repair/Retrofit Costs

Abstract eng:
Recent seismic events confirmed the high vulnerability of existing buildings and highlighted the importance to quantify the attained losses and optimize the economic resources in the reconstruction phases. According to modern seismic design standards, damage to structural and non-structural elements are expected during the design-level seismic event. However, the building reparability and the associated costs should be evaluated in detail. This aspect is even more relevant considering that existing building may experience significant nonstructural damage after medium-to-low intensity (short return period) seismic events. Thus, nowadays, the challenge of a comprehensive seismic assessment is the estimation of the earthquake-induced losses, including the “3Ds”, death, dollars and downtime. Expected losses need to be considered in the retrofit design process and can be a selective criteria to identify the proper strategy and technical solution. According to these evidences, several refined or simplified approaches have been proposed in literature and they are currently under developments. Although they use rigorous methodologies, the predicted overall repair costs may require further validations. The recent seismic events represented the occasion for monitoring and collecting the direct repairing costs and real downtimes related to massive reconstruction processes (e.g. L’Aquila, 2009 and Christchurch, 2011). This paper presents a comparison of the predicted repair costs with the actual costs collected in the L’Aquila reconstruction process. The adopted methodology is described in detail and applied to case study reinforced concrete (RC) private residential buildings damaged by the L’Aquila earthquake. Refined numerical models have been developed to properly assess the seismic performances of structural and non-structural components. The predicted damage scenario well reproduce what observed during the aftermath surveys. The ATC-58 (2012) procedure, along with the recent upgrades in the fragility database, has been adopted to estimate the repair costs. The predictions are closely compared with actual repair costs grouped in meaningful categories of similar components. Similarities and differences are discussed. Further improvements to extend the adopted methodology to the Italian building stock are suggested.

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