Mechanical properties and constitutive model of Q345GJ thick steel plate in China

The Q345GJ steel plate is a common Chinese product that has an increasingly wide usage in civil engineering. However, previous research on Q345GJ steel plates with thicknesses of no less than 60 mm is limited, especially the systematic cyclic loading tests, causing an inadequate understanding of the cyclic behaviour and corresponding constitutive parameters of thick steel plates. To further investigate the mechanical property of Q345GJ thick steel plates and fill the gap of test databases, layered specimens obtained from five different thickness positions of the 60-mm and 100-mm thick Q345GJ steel plates were tested under monotonic tension and five cyclic loading protocols. The mechanical properties of specimens in different thickness positions were compared and analysed. Moreover, parameters of the Chaboche cyclic constitutive model were calibrated and then validated by finite element analysis (FEA). Results indicated that the surface-layer specimens exhibited greater strength and lower ductility than the middle-layer specimens. Furthermore, the hysteretic curves of all the specimens were plump, where the energy dissipation of the surface-layer specimens was greater than that of the middle layer, particularly for the 100-mm thick plate. Based on the test results and calibrated parameters of the Chaboche constitutive model, significant isotropic softening characteristics were observed for all thickness positions. Following the tests and analysis, the cyclic constitutive model calibrated in this study was verified to support further numerical simulations.