Experimental and numerical investigation of the progressive collapse of precast reinforced concrete frame substructures with wet connections

Abstract

In precast reinforced concrete frame structures, beam-column joints suffer severe damage under large deformations, which may significantly influence their performance in resisting progressive collapse. A static progressive collapse test was conducted on one conventional reinforced concrete beam-column substructure (RC) and four precast reinforced concrete beam-column substructures with wet connections (PCWC). A quasi-uniformly distributed load was applied to the substructures to simulate gravity loads. The first group of PCWC specimens consisted of two specimens with different layouts of mechanical sleeves, in which the beam and column reinforcements were connected through mechanical sleeves and grout-filled coupling sleeves, respectively. In the second group of PCWC specimens, the beam and column reinforcements were joined through a 90° bend anchorage and lapping in grout-filled holes, respectively. In one of the PCWC specimens in this group, unbonded prestressed strands (UPS) were also adopted. For the first group, premature failure of the mechanical sleeve connections occurred, which reduced the collapse resistances of the PCWC specimens compared with that of the RC specimen. For the second group, the damage mode and collapse resistance of the specimen without UPS were similar to those of the RC specimen. Furthermore, the collapse resistance of the specimen with UPS, which generated additional axial force along the beam, was greater than that of the RC specimen. The connections of the column reinforcements in all PCWC specimens exhibited robustness under large deformations of progressive collapse, even though large horizontal deformations and slips along the grout-layer were observed in the specimen with UPS. An analytical model was then developed to study the collapse resistances of the specimens, particularly the contributions of the compressive arch action and the catenary action. Finally, numerical simulations were used to optimize the configurations of PCWC connections, namely the arrangements of the mechanical sleeves, levels of the UPS, and strength of the cast-in-situ concrete, to improve their performance in resisting progressive collapse.