Brace Forces in Horizontally Curved Steel Box Girder with Two Types of Lateral Bracing System by Using ANSYS Program

Abstract

The U-shaped steel trapezoidal box girder is designed to work compositely with the concrete deck to form a closed-section for live loading. The critical stage of these girders are during construction since the fresh concrete and the whole construction load must be support by the non-composite steel section. At the top flange level, a lateral bracing system is typically mounted to form a quasi-closed section and thus increase the torsional stiffness at construction stage. In the current study, A horizontally curved steel box girder with two and three spans were used, lateral bracing includes two types of bracing system; Single Diagonal (SD) and a Crossed Diagonal (XD). Equations from prior studies estimate the lateral bracing forces for box girders with a good accuracy. The axial forces evaluated by 3-D Finite Element Analyses (ANSYS 19.2) are compared with the axial forces computed from the equations, there are excellent correlations between the finite element analysis and the equations, where the average of difference in the first case study with SD and XD was equal to 0.66% and 2%, respectively, while in the second case study it was 1.3%. Also it can be note that the deflection diagram for girder with XD bracing type is more uniform than the girder with SD bracing type. ANSYS software has been an efficient, inexpensive method and easy to use for designers of bridges.