Strength and ductility of HPS flexural members

Abstract

An experimental and analytical research program was recently completed that examined in detail the parameters affecting the strength and ductility of high-performance steel (HPS) flexural members. HPS is a term used to describe a new class of steels being produced under strictly controlled conditions that have high strength, usually greater than 448 MPa (65 ksi) and exceptional toughness and weldability. The mechanical characteristics of these steels are different from conventional steels, leading to concerns over their use in some structural applications. Under earthquake loading, flexural members are expected to deform inelastically, so members fabricated with HPS steels must possess adequate ductility. This paper discusses the inelastic behavior of welded, I-shaped flexural members fabricated from an HPS steel, HSLA-80, having a nominal yield stress of 550 MPa (80 ksi) and an ultimate strength between 610–690 MPa (90–100 ksi) and compares the results to similar flexural members fabricated from conventional A36 steel. The effects of material properties: yield stress, strain-hardening modulus, yield stress-to-ultimate strength ratio, and strain at ultimate stress; cross-section geometry: flange slenderness, web slenderness, and lateral slenderness; and loading condition: monotonic moment gradient, monotonic uniform moment, and cyclic moment gradient are described from the results of experimental testing and analytical modeling. The results are evaluated against the existing design criteria established in the AISC-LRFD specifications and recommendations are made for revising the specifications.