ABSTRACT
Advanced high-strength cold-formed steel has much greater strength than conventional cold-formed steel. The material properties must be properly determined for eventual application to structural design. Three topics pertaining to its material properties characterization are discussed. Firstly, a series of tension coupon tests for AHSS with a nominal grade of 690 MPa were conducted. Material properties including modulus of elasticity, yield stress and ultimate strength were determined. Various existing Ramberg-Osgood models were studied to correctly represent the stress-strain relationship from coupon tests, but none provided reasonable fitting. Therefore, an updated 3-stage Ramberg-Osgood model was proposed. In this model, a reasonable but uncommonly used proof stress was selected to represent the yield strength. An energy method was utilized to compare with common material models and verify the use of the proposed offset as yield stress. Results indicated that the proposed offset was a good match to represent the yield stress.
