Bridge Management Strategy Based on Extreme User Costs for Bridge Network Condition

This paper presents a practical approach for prioritization of bridge maintenance within a given bridge network. The maintenance prioritization is formulated as a multiobjective optimization problem where the simultaneous satisfaction of several conflicting objectives includes minimization of maintenance costs, maximization of bridge deck condition, and minimization of traffic disruption and associated user costs. The prevalence of user cost during maintenance period is twofold; the first case refers to the period of dry season where normally the traffic flow is diverted to alternative routes usually resurfaced to regain traffic access. The second prevalence refers to the absence of alternative routes which is often the case in the least developed countries; in this case the user cost referred to results from the waiting time while the traffic flow is put on hold awaiting accomplishment of the maintenance activity. This paper deals with the second scenario of traffic closure in the absence of alternative diversion routes which in essence results in extreme user cost. The paper shows that the multiobjective optimization approach remains valid for extreme cases of user costs in the absence of detour roads as often is the scenario in countries with extreme poor road infrastructure. 1. Bridge Maintenance Management Problem The Tanzania Roads Agency (TANROADS) has developed a bridge maintenance management system called TANBRIDGEMAN, which in its current version of 2002 has the following features:(i)annual bridge inventory data;(ii)bridge inspection data (which incorporates condition rating of critical components of the bridge and recommendation on remedial measures);(iii)maintenance cost computations.TANBRIDGEMAN however prioritizes the maintenance on basis of the condition rating and maintenance cost only. The discussion at hand is to expand the maintenance prioritization by incorporating user cost. In any facility management scenario, such as in bridge management system, the issue becomes how to prioritize bridge maintenance by satisfying three conflicting objectives simultaneously. The three types of targeted objectives-oriented prioritization are the following:(1)damage condition rating-based prioritization: the projects will be ranked in terms of condition rating; that is, the project with the highest condition rating (the most damaged condition state) will be given first priority;(2)maintenance cost-based prioritization: the projects will be ranked in terms of maintenance cost; that is, the projects with the lowest maintenance cost will be given first