Uniaxial Cyclic Stress‐Strain Behavior of Structural Steel

Abstract

A simple mathematical model for the uniaxial cyclic stress‐strain behavior of structural steel is proposed for arbitrary loading histories in the inelastic range. The model uses the monotonic and cyclic stress‐strain curves as references and assumes the existence of stress bounds which cannot be exceeded in any given cycle. The movement of the bounds, which is controlled by hardening, softening, and mean stress relaxation, is determined by the strain amplitude of the last excursion and the previous stress‐strain history. The rates of hardening, softening, and mean stress relaxation are determined from experimental data. The nonlinear portions of the stress‐strain curves are defined by a continuously changing tangent modulus whose magnitude is a function of the distance between the stress bound and the instantaneous stress. A comparison is made of predicted and experimentally obtained stress‐strain histories. Although the model is developed specifically for types of histories associated with seismic excitations (small number of cycles), it should be applicable as well to low cycle fatigue problems involving large numbers of cycles since it is based on the stabilized cyclic stress‐strain curve.