Progressive Collapse Resistance of Emulative Precast Concrete Frames with Various Reinforcing Details

Abstract

In this paper, three precast concrete (PC) frames and one cast-in-situ reinforced-concrete (RC) frame were cast and tested to investigate the load-resisting mechanisms of emulative PC frames with various reinforcing details to resist progressive collapse. In the beams of PC frames, the top reinforcement was continuous without curtailment while the bottom reinforcement had different anchorage strength. Test results indicated that, in the event of middle column removal, similar to RC frame, beam action, compressive arch action (CAA), and tensile catenary action (TCA) could be developed sequentially in PC frames with emulative connections, PC frames with sufficient anchorage strength or additional bottom U-shaped bars passing through the middle joint could obtain similar level of CAA capacity as RC frame. However, they may achieve relatively lower TCA capacity due to higher bond strength between the top reinforcement and cast-in-situ topping layer in beams, owing to higher concrete strength in the topping layer, resulting in earlier fracture of the beam top reinforcements. Conversely, PC frames with insufficient anchorage could achieve comparable TCA capacity as RC frame. However, their CAA capacity was less than that of RC frames due to pulling-out failure of bottom reinforcements, preventing further development of strain hardening at beam action and CAA stages. Based on test results and analytical studies, it was found that, similar to RC frames, PC frames with emulative connections could provide sufficient rotational capacity to ensure development of tie-force as required by the design guidelines.