ELASTIC-PLASTIC BUCKLING BEHAVIOR OF STEEL MATERIAL UNDER COMPLEX CYCLIC LOADING PATHS

After compressive yielding, local buckling will occur on steel tubes in concrete-filled steel tubular column under complex seismic loading. In a bar-system finite element model (FE model), the seismic response of steel structure members cannot be effectively simulated by steel constitutive models without considering the influence of buckling. To study the buckling behavior of steel under complex cyclic loading, 30 steel specimens with strength grades Q235 and LYP160 were designed, and various complex cyclic loading paths were adopted to obtain the stress-strain hysteretic relation and elastic-plastic buckling behavior of steel under various complex cyclic loading. On the basis of three steel cyclic constitutive models in the literature:Légeron Model, GA Model and DM Model, the predicting results were compared and analyzed with the test results. It can be seen that Légeron Model fails to stimulate the buckling effect of post-compressive yielding steel, and in GA Model, the stress-strain properties of compressive buckling agree well with the experimental results. The unloading stiffness of tension and compression calculated by the DM Model agrees well with the test results.