Fatigue Tests on Post-tensioned Bridge Decks

In the Netherlands a large number of concrete bridges with post-tensioned concrete decks are in service and are constructed in the 60s and 70s of the previous century. These decks need to be investigated regarding their structural safety because of increased traffic loads in both number and intensity. An important type of prestressed bridges present in the Netherlands is constructed using prestressed T-girders and transversely post-tensioned cast in-between slab panels.

During static tests in the Stevin laboratory of the Delft University of Technology (DUT) on this type of concrete bridge decks it was found that compressive membrane action has been generated which results in a higher static bearing capacity. On the other hand it was found that when a load is applied stepwise with only three load cycles per step in about 8 h, the load capacity reduces about 16% with respect to the static capacity.

The Dutch Ministry of Infrastructure and the Environment and DUT decided that further experimental research on the influence of cyclic loading on the fatigue strength for this type of bridge deck was necessary. In total 3 static and 9 fatigue tests were performed. Based on the experimental results a relation was found between the relative fatigue strength and the logarithm of the applied number of load cycles. For 1 and 100 million load cycles a relative fatigue strength of respectively 0.54 and 0.42 was found.