Progressive Collapse Resistance of Precast Concrete Frames with Discontinuous Reinforcement in the Joint

Boundary conditions of precast concrete frames play a crucial role in their progressive collapse resistance under middle column removal scenarios. Interior and exterior frames behave differently as a result of different horizontal restraints on side columns. This paper presents an experimental study on four precast concrete frames with either 90° bend or lap-splice of the bottom reinforcement in the beam-column joint. The resistance of interior and exterior frames were determined quantitatively. Reinforcement detailing in the beam-column joint dominated structural resistance and deformation capacity of interior frames. Side columns of interior frames remained intact under compressive arch action (CAA) and catenary action, in spite of significant horizontal deflections and severe cracking because of initial horizontal compression at the CAA stage and subsequent tension at the catenary action stage. However, one exterior frame exhibited flexural failure of the side column when subject to catenary action, evidenced by concrete crushing in the compression zone. In side beam-column joints, diagonal shear cracks were observed at the CAA stage, and shear links were mobilized to sustain the shear force. Finally, relevant conclusions on the progressive collapse design of precast concrete frames are drawn from the experimental findings.