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Progressive collapse analyses of steel framed moment resisting structures

by Lim, Joonhong.

Abstract (Summary)
Progressive collapse has been an important issue in building failures since the collapse of the Ronan Point apartment building in 1968. Progressive collapse is a failure sequence that relates local damage to large scale collapse in a structure. If any load exceeds the load-carrying capacity of any member, it will cause additional local failures. Such sequential failures can propagate through the structure. Therefore, a local member failure analysis is the basic element for the progressive collapse analysis. Three different failure criteria have been considered in this study. They are material failure, buckling failure, and connection failure. Material and buckling failures were analyzed by using a second-order inelastic method. Connection failures were analyzed by using a moment-curvature relationship calculated by a power model using three parameters. The finite element code ABAQUS/Explicit has been used for the analyses. Single column failure results from the ABAQUS/Explicit simulations and from the NFA developed for this study based on the second-order inelastic method were compared for a verification purpose. Various numbers of spans and stories with rigid, semi-rigid, and reinforced semirigid frames were studied for 2D frame analyses. As the number of spans increased, the collapse mode tended to change from total collapse to partial collapse. As the number of stories increased, the collapse mode tended to change from partial collapse to total collapse. However, the analyses of the semi-rigid frames showed different trends. All semi-rigid iii frames collapsed partially by joint failures. The 2D frame analyses showed that a vertical failure was caused by connection failures, a horizontal failure was caused by column buckling. The 3D frame analyses showed a different tendency. Four different span frames with rigid and semi-rigid connection with a single column size, were used for six initial failure cases. The assumed rigid and semi-rigid connection did not make a big difference in the 3D cases. Therefore, semi-rigid connection would not be a critical factor if the initial damage is localized. Inner columns were more critical than outer columns. However, the single column initial failure caused total collapse for the most of the frame with a more realistic design. The 3D frame with realistic designs showed three facts. First, a more realistic design, using two different column sizes, is more vulnerable to progressive collapse than a single size column design. Second, a semi-rigid connection could trigger total collapse of a structure, while a rigid frame just caused internal damage. Third, the lengths of columns did not affect collapse modes. However, it could be a factor when the frame is overdesigned to resist progressive collapse. iv
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School:Pennsylvania State University

School Location:USA - Pennsylvania

Source Type:Master's Thesis

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