Study on the resistance to progressive collapse of dry-connected precast concrete beam-column substructures

Extensive research has been conducted on the seismic performance of dry-connected precast concrete structures, while studies on their resistance to progressive collapse and related experimental investigations remain limited. To address this gap, a dry-connected precast beam-column substructure was selected as the test specimen. One reinforced concrete (RC) specimen and one precast concrete (PC) specimen with corbel supports and bolted beam-column joints were designed to investigate the resistance to progressive collapse after the removal of the middle column. Through experimental testing, the resistance to progressive collapse, failure modes, and stress development at critical sections of the substructure were obtained. The experimental outcomes suggest that the RC specimen exhibits three distinct resistance mechanisms during progressive collapse, i.e., purely flexural action (PFA), compressive arch action (CAA), and tensile catenary action (TCA). In contrast, the dry-connected PC specimen presents only PFA and CAA, indicating a slight reduction in ductility. Compared to the RC specimen, the peak loads of the PC specimen increase by 25.2 % and 15.5 % in the PFA and CAA phases, respectively, enhancing its resistance to progressive collapse during the pre-damage phase. The ultimate displacement observed in the RC specimen is 256.5 mm, whereas the PC specimen records an ultimate displacement of 177.4 mm, which accounts for 69.2 % of the value for the RC specimen. Concurrently, a finite element model of the specimen was established through ABAQUS software to perform numerical simulations. After validating the finite element model, a parametric analysis was conducted to evaluate the strength of the connection bolts. It is observed that upgrading the connection bolts to Grades 6.8 and 8.8 yields improvements of 14.9 % and 21.7 % in the peak load of the CAA phase, respectively, in contrast to the original tested PC specimen. Moreover, the newly tested PC specimen attains the TCA phase, with ultimate loads being 53.9 kN and 62.7 kN, respectively. The numerical simulation results closely matched the experimental failure modes of the prefabricated structure. Enhanced bolt strength can significantly improve the resistance to progressive collapse of the prefabricated substructure. The findings from this experimental study establish a theoretical foundation for the design of such dry-connected joints.