Abaqus CFST model: contact not engaging concrete core properly?
Hi, I’m modeling a CFST member in Abaqus under bending. I used surface-to-surface contact between the inner steel tube and the outer concrete core. For the interface, I used hard contact in the normal direction and penalty friction in the tangential direction with a friction coefficient of 0.4, with separation allowed. In this case, the model gave about 200 kN peak load.
Then I replaced the concrete with steel properties as a sensitivity test, and the peak load still stayed around 200 kN, although the response curve was slightly different. But when I tied the core to the steel tube using tie constraints, the concrete-core model increased only slightly, while the steel-core model jumped to about 450 kN.
Does this mean the contact model is not engaging the core properly? What am I doing wrong, and how should the concrete-steel composite behavior in a CFST be modeled correctly?
Thanks!