Finite Element Analysis and Optimization of Hollow Flange Steel Girders

Abstract

abstract Optimization techniques may be effective in finding alternative geometries of steel girders to improve their structural behavior, particularly avoiding or reducing the bending moments. In structural, architectural and bridge engineering, conventional steel I-girders are fabricated generally by welding two plate flanges, a flat web and a series of transverse or longitudinal stiffeners together. This study investigates the structural behavior of hollow flange steel girders. A nonlinear finite element model for the analysis of hollow flange steel girders was developed. The numerical analysis was conducted by the finite element ANSYS software and was carried out on different hollow flange steel girders chosen from literature. A parametric study was conducted to investigate the effect of several selected parameters on the overall behavior of hollow flange steel girders. These parameters include the effect of cross-section, web openings shape, size and location. The results showed that the ultimate capacity increase when the section hollow, the load failure of HFSPG increased 28% and 59.6% as compared with UHFSPG and LHFSPG, the ultimate capacity of HFSPG with 4 square openings decreased 4.8% compared to HFSPG without openings, the ultimate capacity of HFSPG with circle openings increased compared with HFSPG with square openings and the ultimate capacity of HFSPG with web opening near support increased 5.23% and 3.25% compared with HFSPG with web opening in quarter and center of girder respectively. VI The finite element software package ANSYS (v 12.1) was used to find the optimum volume of the hollow flange steel plate girders. Two cases were considered, which are optimization of steel girder under three-concentrated loads and two-concentrated loads. The objective function is minimization of total volume of the girder. The constraints are tensile stress in steel, shear stress in steel and displacement at mid-span of the girder. The design variables are the height of top and bottom hollow flanges, width of top and bottom hollow flanges, the thickness of top and bottom hollow flanges, the height and thickness of the web. The result showed that the optimum volume for the steel girder decreased about 13 % than the initial for the steel girder under three-concentrated loads and decreased 34.8 compared with HFSPG under two-concentrated loads.