Alternative Retrofit Strategies For Pre'70 R.C. Buildings: Vulnerability Models and Damage Scenarios

Abstract

The inherent seismic vulnerability of existing R.C. buildings, designed prior to the introduction of adequate seismic code provisions in the early/mid-1970s, has been dramatically confirmed by the catastrophic socio-economical consequences of earthquake events occurred worldwide in the past decade. Several alternative seismic retrofit/rehabilitation solutions have been studied in the past, few of which have been successfully implemented in practical applications on single buildings. However, due to the typical one-off peculiarity of a retrofit intervention, issues of costs and invasiveness and practical implementation still remain the most challenging aspects for their wide adoption. Recent developments and numerical/experimental validation of viable and low-cost retrofit solutions for pre-1970 buildings within a multi-level retrofit strategy approach, suggest the possible implementation of “standardized” solutions at a urban or territorial scale. In this contribution, the efficiency of such a structural mitigation strategy is investigated, within the framework of a seismic risk analysis approach. To this aim refinements of the models typically adopted for territorial scale vulnerability assessment have been suggested to better represent pre-1970 R.C. building behaviour before and after retrofit intervention, as recently observed in numerical and experimental investigations. Comparative evaluation of the reduced level of the expected damage after alternative retrofit solutions have been carried out and described in terms of fragility curves. Further exemplification of the effects of retrofit strategies planned at a territorial scale have been provided via damage scenarios referred to a case study region in Italy.