Exploiting linear system behaviour to determine structure level costs based on element condition states

Due to the deterioration of bridges, interventions are required to ensure that they will continue to provide an adequate level of service over a specified time period. The determination of preservation intervention strategies that maximize the benefit to all stakeholders requires consideration of not only the condition of the elements of which a bridge is comprised, but also the performance of the structure as a whole. This is required because although some costs can be related to the condition of the elements, others, such as the costs of accidents for those travelling on the bridge, cannot. In this paper, a methodology for relating structure performance to element condition states for the purpose of determining structure level costs is presented. An exact method, which yields accurate results but is computationally demanding, as well as an approximate method, which yields less accurate results but is computationally much less demanding, are presented and demonstrated using examples. It is seen that the use of the approximate method for estimation of the values of the performance indicators results in only a small discrepancy in the estimate of total costs that would be incurred over the expected life time of the example bridge when compared with the use of the exact method.