Static collapse resistance performance assessment of precast concrete beam–column substructures using wet connections under uniformly distributed load

Precast concrete (PC) frame structures using wet connections consist of composite beam and column including prefabricated and cast-in-situ concrete parts, characterized by specific complex load mechanisms when large structural deformation is induced during progressive collapse. Therefore, PC beam–column substructures using specific construction methods of wet connections were focused: 1) in PCWC-1, connected beam reinforcements through mechanical sleeves and anchored reinforcements using anchor plates; 2) in PCWC-2, anchored beam reinforcements by bending the end into 90°; 3) in PCWC-1, connected column reinforcements by grouting sleeves with thread connections in one end, while in PCWC-2 by similar sleeves with overlapping reinforcements in one end. Collapse tests were conducted under quasi-static uniformly distributed load (UDL) to get actual responses close to engineering practice. And the corresponding collapse resistance mechanisms were examined analytically. The experimental results indicated that: 1) in the compressive arch action (CAA) stage, higher concrete strength of the cast-in-situ parts was vital for improving the collapse resistance performance of the PC substructures, with the peak load reaching 134 kN, 23 % greater than the 109 kN in the reinforced concrete (RC) substructure; 2) in the catenary action (CA) stage, anchor plates reduced the substructure’s ductility, but the 90° bending enabled the PC substructure to achieve a collapse resistance of 168 kN, comparable to the RC’s 158 kN. The analytical results demonstrated that: 1) in the CAA stage, beam flexural action primarily contributed to the collapse resistance, with higher-strength cast-in-situ concrete increasing the contribution in the PC substructures by 29 % compared to the RC substructure; 2) adopting cast-in-situ concrete at each beam-end segment resulted in more balanced bending moment developments at the beam-end sections near the middle and side columns, compared to using concrete toppings alone, with moment ratios of 3.5/10 and 1.5/10, respectively, at the peak load stage; 3) in the CA stage, the bending moments developed along the beam due to UDL that induced curved beam deformation, together with the axial force of the reinforcement jointly contributed to the collapse resistance. However, the bending moment contributed less in the PC substructures (9 % ∼ 13 %) than in the RC one (18 %), due to weakened cooperation of the prefabricated and cast-in-situ beam parts. ● Conduct progressive collapse tests under uniformly distributed loads. ● Include both wet connections of the prefabricated beam and column. ● Reveal load transfer capacities of wet connections during collapse scenarios. ● Analytically uncover collapse resistance mechanisms involving wet connections. ● Analytically quantify wet connection influence on collapse resistance.