1 BRIDGE NETWORK COSTS VS. TRUCK WEIGHT LIMITS: METHODOLOGY AND COMPUTER SOFTWARE DEVELOPMENT

Abstract. The US National Cooperative Highway Research Program is developing, under project 12-51, a new methodology and decision support tool to be used by highway agencies to estimate the network-level bridge costs due to changes in truck weight limits. Combined with other tools for pavements and other affected assets, the system will help agencies to assess the full costs and benefits of allowing heavier trucks to use the highway network, or even restricting the network to lighter trucks. Using bridge inventory data, the methodology addresses four cost impact categories: steel fatigue consumption, deck fatigue consumption, overstress deficiencies, and higher new bridge design loads. For the first two categories, it quantifies the change in the number and magnitude range of loading cycles and assesses the probability of fatigue damage for cost estimation. For the latter two categories, it estimates the change in load rating requirement and design load requirement, respectively. Then the impact costs are estimated based on these requirements. To enable practical application of the methodology, a decision support tool is being developed in Microsoft Excel and Visual Basic. The system consists of a connected set of workbooks for preparing inventory data, describing scenarios of weight limit changes, and analyzing the impacts. Paul D. Thompson, et al.