A simplified methodology for seismic repair costs assessment in RC buildings: an application to L’Aquila 2009 event

The estimation of direct and indirect losses due to earthquakes is a key issue in the Performance Based Earthquake Engineering framework. The analysis of damage data in literature highlights the key role played by damage to nonstructural components on the resulting losses, namely, infills and partitions, in Reinforced Concrete (RC) Moment Resisting Frames (MRF). Therefore, the use of simplified methods leading to the definition of repair costs, fatalities, and repair time due to earthquake, reproducing the influence of infills on the global behaviour of RC frames, is very attractive for insurance and risk management strategies. In commonly adopted loss computation tools, no specific data related to masonry infill panels, widespread in moment-resisting-frame residential buildings, are available to perform a probabilistic assessment of losses. To fill this gap, specific fragility and loss functions have been recently proposed in the literature. To assess their validity and estimate the relevance of the repair costs due to infills after earthquakes with respect to the total reconstruction process, the present work analyses a subset of Reinforced Concrete residential buildings with masonry infills struck by the 2009 L’Aquila (Italy) earthquake, focusing on “lightly” damaged buildings, where only damage to masonry infills occurred. In such a way, the evaluation of repair costs can be made by neglecting the contribution due to repair activity to other structural components (namely vertical structures, horizontal structures, stairs, roofs). Based on available data related to these buildings, the observed damage scenario after L’Aquila earthquake is first obtained. Then, a simplified mechanical method – PushOver on Shear Type models (POST) – for seismic vulnerability assessment of infilled RC buildings is used to obtain a predicted damage scenario to be compared with the observed one. The repair costs for infills are estimated given the observed and the predicted damage scenarios, by means of the cost functions at given damage states (DSs) reported in the most recent literature for infill panels. Additionally, the resulting estimated repair costs are compared with the actual repair costs presented in the available literature for the investigated subset of buildings, and the percentage influence of infills on the total repair costs due to earthquakes for residential buildings is lastly computed.