Effect of Beam Design on Progressive Collapse Resistance of RC Framed Structures

This study presents numerical findings of an investigation into the effect of beam dimensions and sagging and hogging reinforcement ratios on progressive collapse response of reinforce concrete (RC) frame sub-assemblages when faced with an interior column loss. Also the flexibility of the beams in terms of height to span ratio which is directly correlated with compressive arch action and catenary action mechanisms is not directly emphasized. To this aim, four RC frame sub-assemblages of constant span lengths and different beam dimensions and reinforcement ratios were designed. Built on earlier calibrated numerical models using fibre element approach, nonlinear static push-down analyses capable of accurately simulating structural response to large deformations were performed for the four frame sub-assemblages with different beam designs. The study demonstrates that the beam design influence is significant as it completely changes the progressive collapse resistance and behavior of such frames while the beam span lengths are kept constant. Frames with small beam cross sections showed ductile behaviour due to catenary action, whereas frames with larger beam cross sections displayed brittle failure and predominate arch action.