Behavior of Non-Ductile Beam-Slab Systems under Support Failure Scenarios

Non-ductile reinforced concrete structures built prior to the introduction of seismic codes are susceptible to severe structural damage during an earthquake. Past earthquakes have demonstrated, for example, the high likelihood of shear failure of non-ductile columns. Failure of a column within a building system creates a discontinuous load path due to loss of axial load carrying capacity. When this occurs, the system has to redistribute loads to other load bearing members to prevent progressive collapse. Although several studies have been conducted to understand the behavior of the beam-column frame system under support failure, the role of the beam-slab system under such failure scenarios has observed much less attention in the literature.;Large-scale experiments were conducted on two one-third scale reinforced concrete beam-slab models to investigate their behavior under different support failure scenarios. Test results demonstrate that the beam-slab system was able to continue to carry large vertical forces despite the occurrence of a simulated column failure, while redistributing the loads to the adjacent support locations. Compared to predictions using Yield Line Theory, an enhancement in load capacity of more than 50% was observed. This reserve capacity is largely attributed to the presence of in-plane forces that develop as the system redistributes load.;A nonlinear finite element model is implemented and its property selection and model protocol parameters evaluated by comparing its response to that observed in the tests. Subsequently, the validated finite element model is used to conduct a parametric analysis varying the different design parameters to common ranges found in practice. The emphasis of this aspect of the study is on characterizing the ultimate load carrying capacity of the system under the more critical corner support failure scenario. Results from the parametric analysis on the beam-slab system numerical model further corroborate observations from the experimental phase of the study. Namely the presence of in-plane membrane forces and increased load carrying capacity on average by 50% compared to the Yield Line Theory estimates. An analytical model is presented, which proves to increase the reliability of estimating the ultimate load carrying capacity of the system by considering the in-plane membrane forces that occur due to the presence of the slab.