Benefits of post-weld treatment to improve tubular bridge fatigue performance

In looking for ways of improving the fatigue performance of tubular bridge structures, the use of residual stress based post-weld treatment methods, such as needle peening, has been suggested. To study this possibility, a number of large-scale fatigue tests were performed on untreated and treated tubular bridge joints. Following these tests, a probabilistic fracture mechanics-based treatment model was developed and used to perform a number of studies. In examining the results of these studies, the mean applied stress level was seen to strongly influence the treatment benefit at the various potential crack sites in a typical tubular bridge structure. Based on this observation, the possibility of post-weld treatment in the field (i.e. after the dead load stresses are introduced) is examined herein, and seen to result in a significant increase in the treatment benefit.