Impact of Long-Duration Earthquakes on Successive Earthquake-Tsunami Fragilities for Reinforced Concrete Frame Archetypes

Abstract

This study quantifies the effects of long-duration earthquakes on the behavior of reinforced concrete (RC) buildings subjected to successive earthquake-tsunamis through the development of fragility surfaces. The suite is comprised of both ductile and nonductile systems, representing a portfolio of RC structures that could be found in a (coastal) community. Previous research has shown that long-duration earthquakes can significantly influence the structural responses and even the collapse behavior of building systems. Earthquakes with large moment magnitudes that produce tsunamis are often long duration events, yet ground motion duration has not been fully considered when generating tsunami fragility curves or successive earthquake-tsunami fragility surfaces. This study incorporates earthquake loading through a nonlinear time history analysis (NLTHA) and subsequent tsunami loading with a nonlinear static procedure. Detailed probabilistic structural models are subjected to both long-duration and regular-duration earthquakes through the NLTHA phase of the successive simulation to explore the possible impact of long-duration earthquakes on earthquake-tsunami fragility surfaces used to represent the behavior of these RC buildings. Results show that failure probabilities from the fragility surfaces are increased by up to 40% in some cases, with low- to mid-rise RC structures (ductile and nonductile; up to 8 stories) being adversely affected by long-duration earthquakes. Furthermore, this study reports the governing parameters of scalar and vector-valued fragility functions in the proposed RC portfolio exposed to long-duration earthquakes and tsunami hazards. These fragility surfaces can be useful in developing community-level models in risk-based or resilience-based decision-support for disaster mitigation.