Floating Bridge Drawspan Maintenance

A methodology for making maintenance decisions to avoid fatigue failure is proposed. The maintenance procedures developed for the drawspan mechanism of the Evergreen Point Bridge are used as an illustration of the methodology. The methodology includes, development of the stress/environment relationship for the critical member, collection of long-term environmental data and the computation of long-term stress distribution, determination of cycles at each stress level from the return period, and duration of various environmental conditions and the member frequency at the associated stress level, determination of the fatigue characteristics of the member (S-N) from a limited number of full-scale tests using the Prot procedure, and determination of yearly damage and, life expectancy using Miner's hypothesis.