The incremental inelastic stiffness matrix of the composite column is derived. In the column, high-strength four precast-concrete panels are fixed to the steel square tube with high strength headed studs. Strain softening type stress-strain relation of precast concrete panel is assumed from the test results of short column whose length is equal to the failure length decided by Mohr-Coulomb criterion. Hysteretic rule concerning shear force-to-slip relation of headed stud is also proposed based on the test results. Analytical results agree well with the hysteretic behavior of composite columns subjected to constant axial force and anti-symmetrical repeated moment.
