Progressive collapse of post-tensioned subframes following the removal of an interior column

Abstract

Experimental investigations about the post-tensioned concrete substructures are still imperative to be conducted to assess the structural performances against progressive collapse. Four half-scaled framed substructures were tested to evaluate the dynamic resistant behaviors under a scenario of sudden removal of an interior column. Then, to evaluate the performances against progressive collapse at the large deformation stage, the residual substructures were tested under the pseudo-static loading regime. Various responses at the prescribed locations were monitored with the experimental instruments. The variables in the research included diameters of the post-tensioned strands (PTS), bonded form of PTS, and unboned form of PTS. By comparison, the differences among the reinforced concrete counterpart (RC), bonded post-tensioned concrete substructures (BPC), and unbonded post-tensioned concrete substructure (UPC) were highlighted. Dynamic experimental results indicate that the PTS can have significant influences on damping ratio and enhance the vertical stiffness of RC specimens. Moreover, the ultimate bearing capacity of UPC can reach 2.09 times larger than that of the RC substructures, and the PTS with a larger diameter can enhance the ultimate bearing capacity more than that with a small diameter. Additionally, the proposed analytical model can well agree with the failure modes at the catenary action (CA) stage, and the theoretical formulas can be well utilized to evaluate the ultimate bearing capacity.