Experimental investigations of the flexural‐torsional buckling resistance: Steel rolled I‐section beam‐columns under moment gradient

Abstract

AbstractBeam‐columns of uniform rolled or equivalent welded sections are the member types most commonly used in steel skeletal structures. EN1993‐1‐1 [1] provides two design procedures of such members, one based on the interaction equations for the section resistance and the member buckling resistance, and the other one based on the so‐called General Method (GM) that tends to follow that of Ayrton‐Perry's procedure used for extreme cases of compression without bending and bending without compression. Above cited design procedures yield similar results when the beam‐column is predominantly under bending but sometimes results being away from each other when the beam‐column is predominantly under compression. Recently, a novel version of GM has been proposed [2], providing a tool of more rational design that yields the results from Eurocode 3 interaction equation procedure in both extreme cases. The proposed procedure is based on the Euclidean norm of dimensionless action effects and evaluation of Maquoi‐Rondal imperfection factor interpolated between those for compression without bending and bending without compression. This analytical procedure was verified with a wide range of advanced numerical simulations incorporating geometrical and material imperfections (residual stresses). In order to validate the accuracy of the proposed procedure, an experimental study on the buckling resistance of rolled I‐section beam‐columns was carried out the results of which are presented in this paper. Firstly, an overview of the experimental programme carried out on subframe specimens is given and then followed by the summary of measurements of deformations as well as global load vs. displacement characteristics for selected specimens. Finally, an assessment of the beam‐column buckling resistance, experimental vs. predicted by Eurocode 3 interaction equations procedure, is presented and conclusions with regard to the preliminary validation exercise are drawn.