Reliability analysis of pier under combined effect of scour and earthquake

The current bridge design method evaluates each load type independently, potentially underestimating failure risks. A probabilistic approach that considers simultaneous extreme events is essential for bridge safety. This study employs the First-Order Reliability Method (FORM) to analyze the combined effects of scour and earthquakes on a reinforced concrete bridge pier. Pier reliability was assessed across varying peak ground accelerations (PGA) in combination with scour at the Sangam, Ram Munshi Bagh, and Asham stations located along the Jhelum River, with a detailed analysis of basic variables affecting scour. System reliability analysis was applied to evaluate combined extreme events, revealing that pier reliability decreases significantly as PGA increases. For instance, the reliability index dropped from 3.19 to 1.37 under combined conditions with a safety factor of 1.00. These results were compared with design codes to propose scour load modification factors. This framework provides a robust tool for updating design standards to account for extreme events and can be extended to other natural hazards.