Improving life-cycle performance of degrading bridges under floods through retrofit measures

Global bridge failure statistics indicate that hydraulic actions, particularly hydrodynamic forces and scour, play major roles in bridge failure during floods. The scenario is specifically critical for ageing bridges in harsh environments. Because of continuous exposure to such environments, RC bridges with time become more susceptible to load demands during flood events. Hence, appropriate retrofit strategies are essential that can be implemented at any instance during service lives of bridges. This study identifies potential flood retrofit strategies for bridges and develops a framework to measure their effectiveness by analysing a simply supported RC riverine bridge before and after retrofit. As the bridge experiences scour as well, opted retrofit strategies include superstructure and scour retrofit. Computational fluid dynamics simulations are performed to calculate hydrodynamic forces on bridge superstructure, whereas code provisions are followed to calculate the same for piers. Finite element analysis of the bridge at various life-cycle years under different combinations of inundation ratio and flood velocity found that the ageing bridge, without and with scour retrofit, fails to sustain during extreme floods; yet, it becomes safe when superstructure retrofit strategies are implemented. Thus, obtained results demonstrate the effectiveness of retrofit strategies in mitigating flood risk of ageing bridges.