Quantifying Lateral Support of Steel Girders Directly Connected to Trapezoidal Sheeting

Abstract

Flexural and lateral–torsional buckling (LTB) may govern the construction stage of steel and steel–concrete composite girders, when the compression flange is not yet restrained by composite action. Trapezoidal profiled steel sheeting, used as permanent formwork and often directly fastened to the top flange, can contribute to construction‐stage lateral restraint; however, current European guidance is largely framed around secondary cold‐formed purlin members. This paper quantifies the sensitivity of LTB response indicators to evaluate deck‐to‐flange restraint levels by combining analytical considerations with linear eigenvalue buckling analyses using a warping‐enabled (7‐DOF) beam formulation, benchmarked with higher fidelity modelling approaches. A parametric study is performed for representative hot‐rolled girder sections and unbraced lengths, while the connection rotational stiffness is varied and treated as an idealised stiffness level to span flexible‐to‐stiffer restraint regimes. The results indicate that the stabilising influence of the attached sheeting becomes more pronounced with increasing unbraced length and that increased restraint can improve LTB performance even for relatively stocky sections, supporting the use of computationally efficient 1D models for scoping assessments. The study provides a preliminary basis for subsequent calibration through refined contact modelling and/or targeted experimental investigation.