Deteriorating bridges, particularly in regions most vulnerable to natural hazards, pose a threat to public safety. With increasing concern regarding sustainability, there is need to consider not only economic, but also environmental and social indicators of performance for bridges under natural hazards. This thesis presents two frameworks: a life-cycle sustainability analysis for quantifying risk-based sustainability indicators of bridge performance and a multi-objective optimization framework for selecting optimal retrofit and repairs based on sustainability objectives. Results highlight impacts retrofits have on reducing expected values of lifetime sustainability indicators and reveal relationships between lifetime environmental, economic, and social sustainability indicators for bridges subject to multiple threats. The frameworks are anticipated to help guide selection of retrofit and repair combinations by providing a set of optimal solutions, which enhance sustainability while ensuring safety and mitigating damage from natural disasters.