Lateral torsion-flexure buckling of corrugated web steel girders

Abstract

Resistance to lateral torsion-flexure buckling of steel I-girders with plane webs is a very important design requirement. Codes of practice allow designers to use the critical moment of a simply supported beam subject to a constant moment and relate it to the critical moment of any other loading case via an ‘equivalent moment factor’. On the other hand, the compression flange outstand-to-thickness ratio which controls the flange local buckling is another important design parameter. According to most codes of practice this ratio, together with web-to-thickness ratio, defines the I-section class and compactness. Recently, plate girders with corrugated steel webs have been used in different structural applications and bridges. The girder's flanges provide the flexural capacity with no contribution from its corrugated web which provides the girder's shear capacity. Lateral torsion-flexure buckling and local flange buckling of corrugated web girders still need to be investigated. A numerical analysis based on the finite-element technique was performed on these girders. The critical moment causing lateral instability was numerically determined. The finite-element model results were used to investigate the applicability of the critical moment design equations, currently used for a girder with a plane web, to corrugated web girders. The validity of the equivalent moment factor concept to corrugated web girders was also examined. The numerical model was then used to scrutinise the local buckling behaviour of the compression flange for girders with corrugated webs. The applicability of the currently used limiting values for flange outstand-to-thickness ratio which define the section class to corrugated web girders was also examined.