FRP strengthening of web panels of steel plate girders against shear buckling Part-I_ Static series of tests

Asist. Prof. Dr.  Zaid Al-Azzawi

This paper examines a novel FRP strengthening methodology intended to improve the shear capacity and shear buckling of thin plate girder webs. Slender plates are used in a variety of structural engineering applications because of their high strength-to-weight ratio and, in certain configurations, their post buckling reserve capacity. However, out-of-plane displacements may be induced by in-plane loads close to or exceeding the buckling load, which in turn induces secondary bending stresses at welded plate boundaries. Under cyclic loads, as in the case of bridges with repeated axle loads, this phenomenon is referred to as breathing, and may cause cumulative fatigue damage to plate girders, which may influence the limit state of the girder. This may contribute to overall deterioration of bridges, which is a topic of critical importance in Europe, North America and Japan. The effectiveness of the novel FRP strengthening technique under static loading has already been demonstrated through tests by the authors. The optimum strengthening technique; which involves bonding a preformed, corrugated FRP panel to one side of the steel plate girder web; was adopted for the second series of tests, which examine cyclic loading to simulate repeated axle loads in real bridges. The variables considered in this work are the type of the strengthening material (CFRP and GFRP) and the load intensity. Six specimens were manufactured to simulate the end panel of a plate girder with potential length of 15m. Test results along with non-linear finite element modelling proved the efficiency of the strengthening technique in reducing the critical stresses and consequently increased the fatigue life of the tested plate girders.