Progressive collapse resistance of RC beams

• An analytical model reliably estimates large displacement response of a 2-span beam.
• Response of beams bridging over lost column up to collapse are characterized.
• Effects of beam axial compressive force on beam response are quantified.
• For collapse resistance, beam’s strength may be more important than its ductility.
• Displacement response of ordinary and special frame beams are compared and described.

The current guidelines for evaluating progressive collapse potential of existing and new buildings require analyzing and evaluating the structure for the case of an instantaneous loss of a primary vertical support, such as a column. In this paper, the response of a continuous beam bridging over a lost column is evaluated. A series of beam models are developed by changing structural characteristics such as lateral load design type (ordinary vs. special frames), axial stiffness at the beam boundaries, steel yield stress, amount of integrity reinforcement at bar cut-off locations and the beam span to study their effects on the performance of the beam. The modeling technique used for the analyses of the beams has been validated by comparing experimental and analytical results of an RC beam subjected to large deformations. Push-down analyses are carried out in order to study and characterize the full range of response and compare the behavior of the beams. For each case, the behavior of the critical sections are evaluated and used to describe load transfer mechanisms. The effects of different structural characteristics on the performance of the beam to resist progressive collapse are discussed by comparing the results of the analyses.