Ultimate strength of I-girders under eccentric patch loading: Derivation of a new strength reduction coefficient

In structural applications I-girders are subjected to eccentric patch loading since even a small eccentricity of applied loads relative to the web plane is unavoidable in practice. Experimental research shows that the behaviour of eccentrically loaded girders differs from that of concentrically loaded girders. A reduction in ultimate strength due to eccentricity is evident, and some expressions for the reduction have been proposed. We show that these expressions overestimate the reduction in capacity for large eccentricities. In this paper, results of 102 tests on I-girders subjected to eccentric patch loading are presented and the variables involved in the phenomenon are evaluated based on a parametric study of experimental data and the results of several finite element models. The parametric study confirms that the parameters previously identified for evaluating the effect of small eccentricities are sufficient for addressing cases with larger eccentricities. New mathematical expressions are proposed herein to represent the reduction in strength across the full range of eccentricities considered.