Progressive Collapse Resistance of Bonded Prestressed Precast Concrete Frames with Buckling-Restrained Rods

Bonded prestressed precast concrete (PC) frames have garnered attention for the great seismic resilience, but their progressive collapse resistance requires further investigation. Therefore, four bonded prestressed PC substructures designed with equivalent seismic resistance were examined through pushdown tests. The effects of strand profiles (straight versus parabolic) and energy-dissipating buckling-restrained rods (BRRs) were considered. Test results indicated that parabolic strands required a lower pretension than straight strands: reducing the prestress prevents premature strand rupture, significantly enhancing the deformation capacity and catenary action capacity, whereas, reducing strand cross-sectional areas decreased the vertical resistance throughout the loading process. The employment of BRRs reduced the required strand usage but maintained the catenary action capacity and notably improved the compressive arch action capacity. Moreover, using slot-bolted connections avoided tensile rupture of the BRRs during collapse and enhanced the structural continuity and robustness. A full-range resistance model was further established, quantitatively incorporated with the tension–slip relationship of bonded strands at the joint and the horizontal restraint of side columns.