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    Progressive collapse resistance of RC beams
    (ELSEVIER SCI LTD, 2015) Livingston, Elisa; Sasani, Mehrdad; Bazan, Marlon; Sagiroglu, Serkan
    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. (C) 2015 Elsevier Ltd. All rights reserved.
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    Progressive Collapse-Resisting Mechanisms of Reinforced Concrete Structures and Effects of Initial Damage Locations
    (ASCE-AMER SOC CIVIL ENGINEERS, 2014) Sagiroglu, Serkan; Sasani, Mehrdad
    Computational simulations for analyzing progressive collapse resistance of structures following initial damage require specific attention to structural modeling of floor systems. In collapse analysis of RC structures, it is shown that the degrees of freedom of nonlinear beam, joist, and slab sections must include flexural and axial deformations. It is also shown that ignoring torsional cracking of beams can lead to a significant overestimation of the progressive collapse resistance of structures. Evaluating the response of a seven-story RC structure following 15 simulated single column removal scenarios, it is shown that a top floor column removal is more likely to cause structural collapse than failure on a lower floor. This is in part due to the lack of Vierendeel frame action after a top floor column removal. For the simulated scenarios in which the structure resists progressive collapse without experiencing large vertical displacements, the resistance is primarily provided by Vierendeel frame action and axial compressive force-moment interaction of beams. The importance of the floor system in-plane action in axial-flexural response of beams is discussed. The effect of accounting for the elevation difference between the centerlines of floor slabs and beam elements within the building model is studied.