Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer, BEC
About the research
Deflection criteria typically used in the design of highway bridges are currently based on arbitrary limits. Although the need for having deflection limits is undisputed, there exists a need for live load defection criteria for timber superstructures and decks based on actual structural behavior, performance of wearing surfaces, and user perception. In addition, current deflection limits are based solely on total deflection. However, past experience has shown that differential deflection may be a more important parameter. As a result, a need exists for research related to the importance of and allowable limits for differential deflections as they relate to the long-term performance of timber bridges.
Project features include the following: 1)Completion of a survey of state and local bridge owners on the use of live load deflection criteria. 2) Field testing and in-depth condition assessment of 20-30 timber bridges with varying superstructure and deck types. 3)Analytical modeling and extrapolation of timber bridges for a sensitivity analysis. 4) Development of deflection criteria (e.g., total, differential) based on results of field testing and analytical modeling.