Bridge Hazard Analysis and Evaluation Considering the Combined Effects of Pier Scour and Seismic Action

Abstract

Bridges are critical components of transportation infrastructure, and their safety and resilience are significant to ensure public welfare. This study presents a comprehensive analysis and evaluation of bridges under multi-hazards, focusing on the interplay between two significant factors: pier scour and seismic action. The joint effects of these natural hazards present a substantial challenge for bridge engineers and require further analysis and assessment.This study presents a framework for assessing the vulnerability of bridges under combined seismic and scour hazards. It employs nine bridge categories, defined by the NCHRP 24-34 project, based on bridge lengths and pier sizes. A probabilistic approach was introduced for hazard curve development, focusing on local pier scour depth as the intensity measure. The probability distribution of scour depth was derived from nominal values of the HEC-18 scour equation and uncertainties evaluated in the NCHRP 24-34. Key random variables, including Manning’s n value, channel bed slope, discharge, and cross-section area, were analyzed for uncertainty, leading to their respective probability distributions. Monte Carlo simulations were then used to generate generalized scour hazard curves for each bridge category, allowing for the estimation of the probability of scour exceeding a given depth at any given day or during extreme events. Seismic fragility analysis was conducted using nonlinear dynamic analysis to evaluate the probability of bridge failure under seismic loading, with the limit states of bridge components like piles and bearings. The study further integrates seismic fragility with scour hazard curves to assess the joint probability of failure due to both hazards. A case study is included, applying the proposed methods to a specific bridge, demonstrating how site-specific ground motions, finite element modeling, and dynamic characteristics are considered in evaluating the bridge's response to these combined hazards. This work provides a comprehensive approach for improving bridge risk assessments and prioritizing mitigation strategies, offering valuable insights into the interaction between scour and seismic vulnerabilities.