Experiments on punching shear behavior of prestressed concrete bridge decks

In the Netherlands, most of the bridges were built more than 50 years ago and it is essential for bridge authorities to find out if these bridges are still safe for modern traffic loads for which they were not designed initially. Experiments on a 1:2 scale were carried out in the laboratory of the Delft University of Technology (TU Delft) to investigate the bearing capacity of bridge decks with varying levels of transverse prestressing subjected to concentrated wheel loads. All the tests showed failure in punching shear. It was found that, as a result of compressive membrane action (CMA) by virtue of lateral restraint effects, in combination with the transverse prestressing, the punching shear resistance of the decks was much larger than predicted by most international codes that do not consider the effect of CMA. It appears to be worthwhile to regard CMA when assessing the bearing resistance of existing bridges to avoid unnecessary strengthening measures.