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.

The ability to predict the resistance of reinforced concrete (RC) structures to progressive collapse as a result of an interior column removal has become a need in structural design. In general, three resistance mechanisms characterize the structure resistance to progressive collapse, flexural action, compressive arch action, and tension catenary action. The objective of this study is to investigate the effects of floor system configurations on the progressive collapse-resistance of RC frame sub-assemblages and the amount of energy dissipated in each resistance mechanism. This investigation employs a fiber element-based modeling technique to present findings into the effects of beam size and reinforcement details on the progressive collapse-resistance and energy dissipation of RC beam-column sub-assemblages with four equal spans. Three different span lengths of 5, 6, and 7 m were considered. A total of 38 floor system designs for gravity loads were performed in accordance with the ACI 318-14 design code. The modeling technique employed in this study was validated and utilized by the authors in previously published works. The study shows that beam size and the presence of slab are critical as they significantly affect the energy dissipation and progressive collapse-resistance and failure pattern of the sub-assemblage frames. Moreover, the presence of a slab was found to increase the energy dissipation by around 28%.

Predicting reinforced concrete (RC) framed structure resistance to progressive collapse as a result of column removal scenario has recently become a necessity in the design of such structures. Such removal leads to large deformations impairing the functional performance of the structure. To predict the progressive collapse resistance, most of the researchers have developed numerical models to simulate the behaviour of test frames. However, these numerical models are confined to the test frames and would need to be modified when simulating different frames. This study discusses the resistance of RC framed structure to progressive collapse due to column exclusion from the viewpoint of numerical modelling issues using fibre element approach. The numerical results using fibre element approach were compared with a reported database of ten test RC framed buildings. The study shows that developing a simple numerical model, as an alternative to destructive tests, based on the fibre element approach with few elements and properly selected model parameters to adjust can accurately predict the resistance of structures subjected to interior column removal with minimal computational time and effort, and can be utilized in lieu of performing difficult advanced geometric and material nonlinear finite element computations.