Cyclic Metal Plasticity: Experiments and Theory

Stress-strain curves are presented for random inelastic cyclic loadings of 2-in. (51-mm) diameter, thin-walled ASTM A106 seamless steel tubes subjected to uniaxial and torsional experiments. The mechanical properties of the selected steel resemble those of the A36 steel widely used in building construction. The experiments simulate the extreme conditions which may occur in some elements of structural steel frames during severe earthquakes. The uniaxial cyclic tests correspond to the conditions which may develop in the flanges of beams; whereas the torsional tests simulate those in the panel zones of the beam-column joints. Employing the effective stress and the effective plastic-strain invariants and a hereditary concept a procedure is described for using the experimental results from uniaxial tests for obtaining consititutive relations for generalized loadings, including complete load reversals. Comparisons of the calculated results with experiments are given showing good agreement.