Experimental and Finite Element Analysis of Lateral Torsional Buckling of Concrete Filled Tubular Flange Steel Girders

Abstract

The structural behavior of concrete filled Tubular Flange Girders (CFTFGs) has been studied in this research. This study aims to investigate the ability of tubular flange to increase resistance of steel girders against Lateral- Torsional Buckling (LTB). For this purpose, experimental, and numerical analysis were carried out.The experimental work consisted of fabricating and testing of five specimens. The first specimen with flat plate flange considered as a control specimen and the other specimens with tubular flanges. In tubular flanges specimens the effect of filled and non-filled tubular flanges with concrete also, the geometry effect of tubular flange sections, i.e. depth (40 and 20 mm) were studied. These specimens have the same length (1920 mm) and the same overall depth (170 mm). The specimens were tested under two point loads applied at the third-span points. The second part was a numerical one using the finite element method by software package (ANSYS 14), then employed to investigate the nonlinear behavior of tubular flanges girders and a similar numerical study of conventional I-girders was conducted, then the results compared with those of tubular flange girders.The measured experimental results were; the ultimate load capacity, load- vertical deflection, load- lateral deflection and load- twisting angle. Finally, the tubular flange specimens increased the lateral torsional buckling capacity comparing with the standard I-shaped steel members by about (66-97%), while bending strength increased by about (33-55%) for tubular flange section filled with concrete of 42.5 MPa. The concrete filled tubular flange increased the LTB capacity by about (14- 22 %) comparing with the unfilled specimens, also increased the flexural strength by about (13-22%). Thus, tubular flanges girders allowed using for large unbraced girders due to increasing the torsional stiffness of the girder. The numerical models were carried out by software package (ANSYS 14). The results were found to be in a convergent state with those obtained from the experimental tests.

Keywords: Lateral–torsional buckling, finite element analysis, and tubular flange girder.