Experimental and numerical investigation of the bearing capacity of transversely prestressed concrete decks

In the Netherlands, there are a large number of transversely prestressed bridge decks that were built in the last century and need to be investigated for safety against the modern traffic loads. The shear capacity as prescribed by the codes is more conservative in the recently implemented EN 1992-1-1:2005 (CEN 2005) than in the formerly used Dutch NEN 6720:1995. As a result, many existing bridges are found to be critical in punching shear when assessed using the Eurocode. To check if such bridges were safe against the wheel load of the Eurocode Load Model 1, laboratory tests on a 1:2 scale model of a prototype bridge, consisting of a thin, transversely prestressed concrete deck slab cast in-situ between the flanges of long prestressed concrete girders were carried out. All the tests failed in punching shear mode. A 3D nonlinear finite element model was also developed in the FEA software package DIANA to study the structural behavior and investigate compressive membrane action in deck slabs. A comparative study of the numerical and the experimental results leads to the conclusion that existing bridges still have significant residual strength due to the presence of transverse prestressing and the membrane forces. It was observed that sufficient saving in cost can be made if calibrated numerical models are employed to investigate existing structures rather than doing expensive experimental studies.