Behaviour and Strength of Steel Twin Girder Systems with Torsional Braces

Abstract

This study is motivated to investigate the behaviour and strength of beams with only discrete torsional bracing. The experimental program of a scaled twin-girder system with different arrangements of lateral and torsional bracing was conducted. Concurrently, a finite element model was developed and verified with the test results. A parametric study using the finite element model was conducted to study further the effect of girder spacing, cross-frame stiffness, and number of cross-frames on the lateral torsional stability of the twin-girder system. Results showed that the girder spacing and number of cross-frames had the most significant effects on the critical moment of girders braced with only torsional braces. Changing the cross-frame member stiffness did not result in any marked change in the critical moment. The comparison of numerical results with design equations contained in the current CSA S16 (2010) and S6 (2006) standards showed that a stiffness requirement for the torsional brace should be implemented.