Design Criteria for Portable Timber Bridge Systems: Static versus Dynamic Loads

Summary: Design criteria are needed specifically for portable bridges to insure that they are safe and cost effective. This paper discusses different portable bridge categories and their general design criteria. Specific emphasis is given to quantifying the effects of dynamic live loads on portable bridge design. Results from static and dynamic load tests of two portable timber bridges showed that dynamic loads can be significantly greater than static loads. Under smooth bridge entrance conditions, the mean dynamic bridge deflections were 1.13 times greater than static bridge deflections. Under rough bridge entrance conditions, mean dynamic bridge deflections were 1.44 times greater than static bridge deflections.