Life-cycle cost optimisation on a set of bridges

Abstract

This manuscript presents a life-cycle cost optimisation methodology for a set of roadway bridges, during a medium or a long period of time. The methodology analyses multiple scenarios and evaluates the performance and cost consequences of implementing different types of interventions, in different periods of time, for each bridge. The methodology takes into consideration the direct and indirect costs associated with different types of interventions, in addition with a degradation model to predict the deterioration along time. The optimisation is performed with a genetic algorithm to find the optimised intervention plan, over the desired analysis period. That process takes into consideration the life cycle cost minimization and the boundary constraints which could be fixed by the decision maker, either in terms of performance or cost. The methodology was tested on set of concrete Portuguese roadway bridges and the results of its application is presented. Attending to the nature of the problem, data’s uncertainty is considered and Monte Carlo simulation Method is used to present the results in a probabilistic manner. To better support the decision, a multi-objective optimisation is also presented. The gathered results are useful to minimize the associated high life-cycle costs of bridges and also to prepare an eventual extra-budget request argumentation. The methodology is then an approach to support decisions related to the scheduling of the necessary interventions on a set of bridges over time, ensuring the required performance level and taking the available budget into consideration.