STR-883: CYCLIC RESPONSE OF STRUCTURAL STAINLESS STEEL PLATE UNDER LARGE INELASTIC STRAINS

Contemporary seismic design of steel braced systems is based on dissipating earthquake energy through significant inelastic deformation in the bracing members under cyclic excursions. The structure is designed such that the first significant yield occurs at ground intensity levels that are at or above the design earthquake forces. Thus, delaying the yielding of brace elements is deemed a good design but it could also lead to subsequent loss of stiffness and strength, large residual deformation or even dynamic instability and collapse. To enhance the post-yield performance of the brace system, a steel component with high strain hardening character may be required. The stress-strain behaviour of structural stainless steel, the austenitic 304L type, shows an early deviation from linearity at a much lower stress level than carbon steels, but with a much stronger strain hardening character. In this study, the austenitic 304L stainless steel material is characterised under large inelastic cyclic strains. Coupons were carefully designed and machined from 304L stainless steel and 350WT carbon steel plates, and were tested under constant cyclic strain amplitudes. Results of these tests have shown that 304L stainless steel exhibits greater cyclic hardening with maximum cyclic stress values up to nearly three times the yield stress. However, the carbon steel showed greater low-cycle fatigue life