Energy flow in progressive collapse of steel framed buildings

Abstract

This paper provides the methodology for an energy-based progressive collapse assessment of multistory buildings. The progressive collapse of steel-framed buildings is analyzed based on an energy flow perspective. The energy based assessment of structural members is introduced, and compared with conventional force and deformation approaches discussed in the literature. Consecutively, the advantages of energy flow analysis in interpretation of extreme dynamic events are discussed. On the global level, a building can arrest the collapse, and achieve its stable configuration only if the kinetic energy is completely dissipated by the structure. Otherwise, the remaining kinetic energy will cause the collapse to continue. In a conventional building, kinetic energy is dissipated within structural members by the transformation into their deformation energy. Structural members can dissipate finite amounts of energy before becoming unstable. The column deformation energy was shown to be a better stability indicator under dynamic loading than the maximum dynamic force. The energy flow analysis is illustrated with a collapse assessment of a typical steel building.Keywords: progressive collapse, energy flow, energy dissipation, structural robustness, steel building, global stability, column buckling, collapse analysis Murrah Federal Building collapse proved that the possibility of progressive, catastrophic failure is remarkably real and must be addressed [2]. An increasing number of buildings are locally damaged due to explosions and construction errors. Progressive failure can potentially spread throughout the building and result in a catastrophic failure that involves numerous deaths [3,4,5,6]. This study aims at providing new insights into the dynamic, transient phase of collapse propagation. The main objective of this work is to enable the development of an energy-based analysis of progressive collapse of steel buildings by focusing on the role of the energy flow. The specific objectives are:• Compare the energy flow method to traditional force-based approaches, and demonstrate their equivalence in well-understood situations,• Provide an illustrative example of how to interpret and employ the energy-based analysis of progressive collapse. BackgroundProgressive collapse can be viewed as a "domino effect" because a local failure triggers successive failures, progressing in time to a collapse encompassing a disproportionately large portion of a building. The in-depth overview of progressive collapse mitigation approaches and robustnessoriented design can be found in [7]. Grierson et al. [8] proposed an incremental, sequential static procedure. Grierson's method is an extension of a plastic hinge approach. Each step of the procedure ends at the formation of a new set of plastic hinges until the building collapses or reaches a stable state.This approach includes connection failure and accounts for impact forces from falling members.3 Izzuddin et al. [9] focused on connections between beams and columns as triggers of p...

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