POST-EARTHQUAKE ASSESSMENT OF DAMAGED NON-DUCTILE BUILDINGS: DETAILED EVALUATION FOR RATIONAL REPARABILITY DECISIONS

Abstract

Non-ductile reinforced concrete frame structures represent a large portion of the existing building stock all over the world; the lacking of important reinforcement details on such constructions render them vulnerable and a significant source of hazard to life in future earthquakes as well as a of economic losses during moderate to severe seismic ground motions. Ideally, effective risk mitigation may be obtained with structural retrofit or by building demolition and replacement. However, economic and social constraints impair abrupt application of those solutions, requiring the study of alternative policies to encourage owners of more vulnerable structures to undertake risk assessment and mitigation. One important aspect in debate on risk mitigation is the treatment of buildings damaged by earthquakes and their possible reparability; different solutions may be adopted in order to make cities safer and more resilient to earthquakes. Building reparability strongly depends on the expected future performance of damaged building and the required repair costs. After earthquakes, the exhaustive assessment of the costs requires detailed on site surveys to establish the damage level, amount of needed interventions to restore the building in all its structural and nonstructural components and the computation of related costs. On the other hand, analytical prediction of damage level due to earthquakes could help significantly to forecast expected costs; also, applying performance-based earthquake engineering methods can contribute significantly to this scope and further allow the sound evaluation of safety variation due to damage, in addition to costs. The main objective of this research is to explore and test different methods and tools for the assessment of buildings reparability taking into account both the expected safety variation and costs. In particular, two main level of analyses for the assessment of damaged buildings are explored, namely detailed analysis based on non-linear time-histories, that is finalized to accurate estimation of expected safety variation for mainshocks corresponding to increasing return period and related repair costs, and pushover based ones, that allows simplified, practice oriented, assessment of variation of the residual capacity and performance loss due to assigned earthquakes.