Sustainability-Driven Seismic Resilience Assessment and Multiobjective Optimization of DSM-Retrofitted RC Bridges on Liquefiable Ground

Sustainability and seismic resilience are increasingly essential for infrastructure systems, prompted by the demand to endure more frequent extreme events while minimizing environmental impacts. This paper presents a sustainability-driven, multiobjective framework for assessing and optimizing the seismic resilience of RC bridges on liquefiable ground retrofitted with deep soil mixing (DSM). As such, a nonlinear three-dimensional finite element bridge–ground model is developed to capture the dominant soil–pile interaction mechanisms associated with liquefaction-induced lateral spreading, incorporating various DSM configurations defined by cement content, area replacement ratio, and ground treatment volume. The influence of these DSM parameters on probabilistic seismic demands, fragilities, recovery trajectories, and resilience of the bridge is systematically explored. In addition, the total cost and carbon footprint associated with DSM are estimated based on the established life-cycle assessment data, and three optimization strategies are implemented, including (1) single-objective cost and resilience optimization, (2) multiobjective optimization, and (3) sustainability-driven optimization with simultaneous cost and carbon footprint constraints. The results demonstrate that DSM optimization is essential for balancing seismic performance with economic and environmental considerations. Both budget-driven and sustainability-driven approaches provide cost-effective and environmentally responsible solutions, achieving substantial resilience improvements while remaining within acceptable economic and environmental limits.