Experimental study on the ultimate bending resistance of steel tub girders with top lateral bracing

This paper presents a series of experimental test results on the flexural resistance of a steel tub girder with top lateral bracing. Three test girders were fabricated with high tensile strength SM570 TMC (nominal yield strength, Fy=460MPa) steel plates. The test girders had a half-size cross section of practical bridge girders whose depth and length were approximately 1000 mm and 12,000 mm, respectively. The pure bending test was conducted on the tub girder specimens using a universal test machine. Incremental nonlinear analyses were also performed on the tested girders and compared with the tested results. The incremental nonlinear analysis with finite element modeling was confirmed to be applicable to simulating inelastic buckling behavior and evaluating the ultimate bending strength. The effect of cross-frames and top lateral bracings on flexural strength was then discussed. The flexural resistance capacity specified in the AASHTO LRFD design specifications was compared with the evaluated ultimate strengths, and the validity of the design specifications was verified.