Fatigue Evaluation of Bridges

The present work applies the AASHTO guide specifications to fatigue evaluation of several actual bridges. Estimates are compared with predictions made using linear elastic fracture mechanics principles where the time required for an initial flaw to propagate to a critical length is calculated. It is found that actual steel highway bridges demonstrate that fatigue predictions based solely on safe life result in excessively low fatigue lives. Mean life predictions on the other hand tend to be too long. It can be possible to calibrate the AASHTO specifications so there is a closer agreement with the fracture mechanics predictions.