Critical buckling moment in plate girders with stiffeners, discrete lateral torsional restrains and a combination of both

This paper presents the method and results from a finite element parametric investigation of the elastic critical buckling moment of bridge girders. The effect of discrete torsional restraints with variable spring stiffness values as well as variable stiffeners arrangement was numerically investigated. A buckling ratio was introduced to enable the comparison and the derivation of equations. This is the ratio between the elastic buckling moment of the parametrically investigated beam compared to a simply supported beam without any stiffeners or intermediate torsional restraints. The addition of stiffeners resulted in a linear correlation between the buckling ratio and the number of web panels between stiffeners. The elastic critical buckling moment increased by 16% when a 10m girder incorporated 20 vertical stiffeners on each side. The buckling ratio increased in a quadratic correlation with increased thickness of the stiffeners. Increasing the thickness of the stiffeners from 10mm-30mm resulted in an average increase of the buckling ratio of approximately 8%.