Time-dependent tsunami fragility analysis for reinforced concrete building stock

The increasing awareness about tsunami risk for urban coastal communities worldwide leads to the development of tools for disaster risk management and loss quantification in a Probabilistic Tsunami Risk Assessment (PTRA) framework. In this study, a time-dependent tsunami fragility analysis framework for physical assets is developed to produce large-scale analytical fragility functions for the Italian Reinforced Concrete (RC) residential building stock. The time-dependent ageing deterioration is simulated on RC buildings for different exposure conditions (i. e., in-land, near the coastline) and deterioration level (i.e., if regular maintenance works are guaranteed or not). A mechanics-based method for the damage assessment of frames under tsunami loading is adopted for the fragility analysis of RC building portfolios, able to account for the building-to-building variability and the tsunami flow variability. The building height and date of construction are selected as main attributes for the definition of homogeneous building classes for the study region. Monte Carlo simulation is performed for the generation of 105 building realizations for each class, accounting for uncertainties in both capacity and demand. Missing information about structural details of RC components are completed through a simulated design procedure, according to the design criteria in force at the time of construction for the study region. Preliminary sets of analytical fragility functions are derived for the Italian residential building stock at different structural and non-structural damage levels, and results are compared with fragility models from the literature, attesting the soundness of the proposed method. The results show that uniform corrosion slightly affects the fragility curves, whilst pitting corrosion increases the probability of occurrence of intermediate damage levels.