ABSTRACT
As bridges deteriorate over time, maintenance work programs (WPs) are required to ensure that adequate level of service is provided to the society. The systems that determine WPs for bridges have principally defined the optimal WP as being the one that results in the lowest economic impacts incurred by the owner of the infrastructure, i.e., impacts directly related to the execution of interventions (Green and Richardson 1994, Thompson, et al. 1998). Owners, however, are not the only stakeholders affected by bridge performance. There are also, for example, the users of the bridge who can be negatively affected by poor bridge performance. The interventions, should be executed in a way to minimise the lowest overall negative impacts to all stakeholders, i.e., the most sustainable work programs should be followed. A challenge in the determination of these work programs is that only some impacts, such as intervention costs, are attributable to elements. Others, such as accident costs, are only attributable to the bridge as a whole, directly, and the bridge elements, indirectly. The latter requires more modeling effort than what is currently done in many bridge management systems, and, therefore, requires a different methodology to be used (Mirzaei and Adey 2015).
In this paper, a methodology is proposed to determine the most sustainable work programs for single bridges that systematically takes into consideration both element level and structure level impacts. In this methodology, the bridge is considered to be composed of groups of elements and multiple elements group sets are made. These multiple element group sets are exhaustive. All possible times between the execution of interventions (referred to as intervention interval sets) on these groups of elements are investigated. The element level and bridge level impacts are estimated taking into consideration how the deterioration of, and interventions on, the element group affect the structural behaviour. The relationship between the condition of the elements in each of the element groups and bridge performance is modeled by using performance limit state functions.
The proposed methodology is demonstrated by using it to determine the most sustainable work program for an example bridge. It is shown that using the new methodology it is possible to investigate a comprehensive set of candidate WPs including the interventions on all groups of elements and all sets of intervention intervals. Both element level and structure level impacts were appropriately taken into consideration. Through the evaluation of the candidate WPs it was found when the condition of an element affects the bridge performance, it affects the time of execution of interventions on the other bridge elements when the elements are grouped. When an element has no effect on the bridge performance and it is not grouped with the other elements, the optimal WP is determined directly based on the impacts incurred during the execution of interventions.
