International Association for Bridge Management and Safety (IABMS 2010)
July 11-15, 2010
J. Weidner, J. Prader, N. Dubbs, F. Moon and E. Aktan
A large portion of the nation’s bridges has exceeded its original design life. The loads to which these bridges are subject to are often much larger than the designers anticipated. Today’s typical State DOT is juggling a massive number of structures with limited personnel and inadequate budgets on a daily basis. As such, the maintenance of bridges cannot be focused on prevention. Problems are addressed as they appear based on urgency. The combination of large populations alongside budgetary and personnel constraints put considerable importance on every decision made by the bridge owner. There are tools available to help inform decisions, such as structural identification (St-Id) and life-cycle cost analysis. Individually these tools are effective, but problems sill arise with application as well as candidate selection. It is therefore beneficial for a bridge owner to consider an asset management (AM) system, which can utilize both St-Id and life-cycle cost analyses to help optimize where and when funds are allocated to projects in an effort to get the most out of both the budget and the bridge population. AM systems are entirely dependent on the quality of data which is utilized to influence decision making.
The process of St-Id as a means of mitigating uncertainty in the analysis and basic decision-making for a single structure is an established and reliable tool for an engineer or bridge owner. The authors have been utilizing St-Id over the past 20 years for structures varying from highway overpasses to signature long-span bridges. However, the application of St-Id as a tool for management of large population of assets is a relatively new concept. This paper will address how St-Id can best be utilized within the umbrellas of AM for a population of similar bridges; a common situation a State DOT may face. The foundation of using St-Id in AM is to estimate vulnerability of a population of structures in order to assess risk and facilitate the determination of appropriate candidates for further investigation from a cost-benefit perspective.
It is in obtaining quality, reliable data that structural identification (St-Id) can play a role in an AM program. It is difficult for an engineer to associate the qualitative, visual appearance of a structure with hard numbers like capacity. Often there is too much uncertainty resulting from the complexity and redundancy typical to civil structures.
St-Id is by no means the solution to the nation’s aging infrastructure problem. The in-depth St-Id process is far too expensive and time consuming to apply in a global manner to a large population of structures. It follows that full-scale St-Id is most applicable to a single or small population of assets.
The application to single assets will be presented in the context of a review of five bridges tested over the past several years. The detail of these tests including modeling, experimental design, and testing are presented in various conference papers (Prader et al 2008, Weidner 2009a,b). The results of these tests, in terms of the decisions made by the bridge owner are summarized and discussed briefly herein as an example of the benefit of St-Id.
The St-Id process is viable for large population, with adjustment to each step. This sparse, rapid version of St-Id can provide excellent performance metrics for incorporation into and AM system.