Shear strength of pretensioned concrete T-girders: a combined stress field model and experimental investigations

Abstract

The key to understanding the shear failure mechanism of prestressed concrete girders lies in how to properly deal with the combined effects of the applied load, the support reaction, as well as the prestressing force. This paper firstly conceptualizes a combined stress field model, which integrates these effects by manifesting several subfields to disclose the potential failure patterns at different locations in the short shear span. Then, shear tests of four full-scale pretensioned concrete T-girders with a height of 1.6 m and two kinds of shear-span-to-depth ratios were carried out. The test results showed that all the specimens failed in a web-crushing pattern near the support accompanied by a bond-slip of the deflected strands. By analyzing the deviated compression subfields in the highly stressed webs and introducing a failure criterion for cracked concrete, the ultimate shear strength of pretensioned concrete girders was formulated. Finally, the shear strength evaluated by the proposed formula and by some other design codes were compared, and it was proved that the results of the proposed model were closer to the test.