Abstract
In this paper, as a structure to integrate a high axial force subjected CFT column and the supported RC upper floor slab in a large underground box, a T-shaped joint is proposed, where the top end of the column is embedded in the floor slab. The loading capacity of the proposed joint is evaluated by means of a 3-D nonlinear FEM. This evaluation method is first developed and justified by analyzing the past reported results of the loading tests for a plus-shaped joint that integrates a penetrating CFT column and the supported RC intermediate floor slab. This proposed evaluation method reasonably estimates the damage area and its expanding extent under specific loading cases. The method can also derive the possibility of joint fracture taking place prior to the fracture of adjacent members, based on the change in rotating rigidity due to the rotation angle difference generated between the column axis and the slab axis. The established evaluation method is then applied to the proposed T-shaped joint, and it is confirmed to possess the required load capacity against the expected level of seismic forces without resulting in any preceding fracture or punching sheer fracture of the joint.
