Effect of bridge design parameters on multihazard performance of river crossing bridges

Abstract

River crossing bridges in seismically active regions are typically susceptible to two natural hazards – earthquakes and floods. For such bridges, design parameters related to piers may play major roles on bridge multihazard performance. The current study explores the same for key bridge design parameters – aspect ratio and longitudinal reinforcement ratio for piers, and differential ground elevation between multiple bents. Multihazard condition at the southeast part of Nepal is considered as hazard condition at testbed. Regional seismic hazard is represented with a suite of earthquakes generated based on regional seismic design spectra. Due to the regional flood hazard, expected pier scour of investigated bridges are estimated from 100-year flood discharge (including climate change projection) in the Koshi river, Nepal. Three-dimensional finite element models of chosen bridges, without and with scour, are developed including ±10% variations in the stated design parameters. Fragility and risk curves of the investigated bridges are developed and compared to assess relative influences of the design parameters on performance of these bridges. Observations signify that pier aspect ratio and longitudinal reinforcement ratio can significantly influence the multihazard performance of riverine bridges. Research outcome also demonstrates how design parameters may be revised to perform risk-targeted multihazard design of bridges.