Traditional bridge design and bridge rating are based upon codified procedures that examine a bridge's capability to resist traditional highway-type vehicles (e.g., trucks). It is known, however, that other vehicles (e.g., farm/agricultural vehicles or implements of husbandry) use these bridges. These farm vehicles have characteristics that are quite different from traditional vehicles; specifically, they tend to have different wheel spacing, different gage widths, different wheel footprints, dynamic coupling characteristics, and others. Further, these vehicles are carrying heavier loads as the agriculture industry has desired them to do so. Currently, the Iowa DOT Bridge Rating Engineer must make assumptions about how highway bridges resist these non-traditional vehicles. Thus, a research study is needed to more accurately characterize how applied loads from these implements of husbandry are resisted. Specifically, it is desired to understand how these agriculture loads are distributed through the structural elements comprising the bridge and to assess the magnitude of the dynamic loads these vehicles impose. Further, it is desired to know what methods of analyzing bridges for these loads are acceptable, so that accurate bridge ratings may be produced.

The objective of this study is to determine how the implements of husbandry distribute their load within a bridge structural system and to provide recommendations for accurately analyzing bridges for these loading effects. To achieve this objective the distribution of live load and dynamic impact effects for different types of agricultural vehicles will be determined by load testing and evaluating two general types of bridges. The types of equipment studied will include but will not be limited to; grain wagons/grain carts, manure tank wagons, agriculture fertilizer applicators, and tractors. Once the effect of these vehicles has been determined, recommendations for the analysis of bridges for these non-traditional vehicles will be developed.

The research is proposed to be conducted in two phases. Since Iowa DOT has already identified bridges needing evaluation, Iowa DOT is providing the funding sufficient for the completion of Phase I. Iowa State University (ISU) researchers associated with the Bridge Engineering Center will be performing the tasks associated with Phase I. A proposed Phase II will provide the opportunity for other states to participate, including suggesting additional bridges/bridge types for evaluation or for the expansion of the Phase I plan to include a more comprehensive analytical component. The number of bridges to be evaluated depends upon the number of states/organizations participating in the pooled fund, the level of cooperation of local implement operators, and other factors. For example, if the bridges to be tested in Phase II are all located in the State of Iowa it is estimated that the cost per additional bridge would be $10,000. If, however, the bridges selected for inclusion in Phase II are outside of Iowa, it is estimated that the per bridge cost would be approximately 20% higher.

Minimum 2 states @ $10,000 per year for 5 years Requirements of partners: - Financial support - TAC participation - Provide bridge information files as requested by the research team - Provide access to tested bridges - Provide needed traffic control during testing - Provide a tandem axle dump truck for testing