Influence of Brace Slenderness on the Fracture Life of Rectangular Tubular Steel Bracing Members Subjected to Seismic Inelastic Loading

Axial compressive strains that develop in rectangular steel tube braces subjected to cyclic inelastic loading can lead to local buckling and brace fracture. In this study, the influence of the brace effective slenderness on this strain demand is examined as an attempt to assess the effect of brace slenderness on brace fracture. Past test data indicating an impact of brace slenderness on brace fracture is first reviewed. Brace axial deformations at onset of buckling and at first yielding in compression are evaluated using elastic buckling theory. Finite element analysis of bracing members exhibiting different effective slenderness ratios is carried out to evaluate the strain demand after inelastic buckling has occurred and plastic hinging has formed. The strain demand prior to brace buckling and plastic hinging is small and has negligible effect on brace fracture. Compressive strains that develop after brace buckling has occurred and plastic hinging has formed generally decrease as the brace effective slenderness ratio is increased.