Risk-Based Approach for Optimum Maintenance of Bridges under Traffic and Earthquake Loads

Structures deteriorate as a result of material aging, aggressive environmental conditions, and increasing loads. During their lifetime, structures are also possibly exposed to some extreme events. The associated consequences of failure caused by progressive deterioration or extreme events can be devastating. Therefore, risk assessment and risk mitigation are necessary to keep structural performance within tolerable levels. This paper proposes an approach for assessing the time-dependent risks caused by traffic and earthquake loads and establishing the optimal preventive and essential maintenance strategies of bridges. The efficiency of the proposed approach is demonstrated using a highway bridge. Socioeconomic and environmental losses are investigated in a consequence-based framework. The vulnerability analysis under traffic loads is performed using time-dependent deterioration and traffic load models. The time-dependent failure probability for given earthquake loads is computed by comparing displacement ductility capacity and demand obtained via nonlinear dynamic analysis. The risks from 196 earthquake scenarios associated with four magnitudes and 49 earthquake strike locations are compared, and the highest one is selected as representative of the seismic risk. Based on the available maintenance options and the associated costs, the optimal lifetime essential/preventive maintenance strategies for total risk mitigation are developed.