Behaviour and strength of existing bridges with low amount of shear reinforcement

In this paper, the strength of prestressed girders with low amount of shear reinforcement or with defective anchorage is investigated by means of a test programme carried out at the Ecole Polytechnique Fédérale de Lausanne on 10 prestressed and 2 reinforced concrete girders (10 m long, 0.78 m high). The results show that if certain conditions are fulfilled, these structures can perform suitably and provide the expected strength according to plastic design approaches. For comparisons, the elastic-plastic stress fields method is used to predict the specimens’ strength leading to excellent correlations between the measured-to-predicted behaviour and strength. Furthermore this approach allows a sound understanding of the various shear-carrying mechanisms developed in the girders and of the various failure modes observed.