Seismic energy distribution and fragility assessment of reinforced concrete multi-span highway bridges

Abstract

The seismic resilience of highway bridges is critical to ensuring the safety and functionality of transportation networks during earthquakes. The quantification and distribution of seismic energy associated with seismic hazards is imperative for structural performance evaluation and is crucial for understanding the structural behavior until collapse. This study aims to investigate the seismic energy dissipation patterns, including hysteretic and damping energy, at the component and global structural level and assess the fragility of a reinforced concrete (RC) multi-span highway bridge. For this purpose, a high-fidelity finite element model was developed, and an extensive non-linear time history analysis was carried out for the given ground motion suite. The energy dissipation mechanisms are quantified for key bridge components, such as columns, bearings, deck unseating, and shear keys. The relative contribution of each component to global hysteretic and damping energy dissipation is investigated. Fragility curves, which establish the likelihood of different damage states for the given seismic hazard, are developed using probabilistic seismic demand models for the bridge components and system. Results reveal that hysteretic energy dissipation dominates the response of RC bridges, particularly in bearings. Damping energy exhibits a more stable response and is dominated by the structural mass and bearing. The fragility analysis indicates that the component with high energy dissipation is the governing component. Similarly, components with the least energy dissipation show reduced probabilities of exceeding critical damage thresholds. The proposed energy-based fragility framework enhances understanding of seismic demand distribution in RC bridge systems and offers valuable insights for the development of performance-based design and retrofitting strategies, contributing to the broader goal of resilient infrastructure in seismic-prone regions.