Progressive collapse resistance of prestressed precast concrete substructures with slot-bolted top-seat angles

Abstract

Prestressed precast concrete frames rely on post-tensioned strands and energy dissipaters to interconnect members, but their progressive collapse resistance is often limited by the low deformation capacity of the dissipaters. This study introduced a novel top-seat angle connection with slotted bolt holes that enabled controlled slippage under large deformations, delaying premature failure. A comprehensive mechanical model was first developed to characterize the full-range force-deformation behavior of slot-bolted angles. Four frame substructures were then tested under a column removal scenario: one monolithic concrete specimen and three precast concrete specimens—one without angles, one with column-leg-slotted angles, and one with double-slotted angles. Results demonstrated that the precast specimen without angles outperformed the monolithic specimen under catenary action (CA) but showed weaker compression arch action (CAA). Incorporating slotted angles significantly improved CAA stiffness and resistance, achieving performance comparable to monolithic construction. Notably, the slotted angles provided a deformation capacity twice that of conventional designs and contributed approximately 20 % of total resistance at the ultimate state of collapse. The double-slotted angles could further enhance the load-bearing capacity of the substructure over the column-leg-slotted angles. These findings validated the effectiveness of slot-bolted top-seat angles in enhancing progressive collapse resistance of prestressed precast concrete frames.