Bridge Load Models and Truck Weight Regulations

Abstract

Historically, truck regulations have instituted control on axle and gross weights with bridge formulas based on limiting nominal stresses in certain types of bridges. These stress limitations do not usually lead to consistent or defensible safety levels and further ignore the cost impact of the weight regulation on all highway systems. This paper illustrates how new truck weight regulations can be developed which balance economy and provide acceptable safety levels. Target safety levels are derived from existing AASHTO bridge evaluation and rating procedures which have shown adequate performance safety levels. Reliability indices are used to relate the statistics on existing and proposed truck weight regulations and the dynamic behavior and resistance variables of existing bridges, bridge costs associated with new truck weight regulations are presented. These costs have been estimated by using the bridge inventory data of the Federal Highway Administration and statistics established for bridge capacity rating, span, material type and geometry.