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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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The safety of building occupants during and immediately after disasters, such as a major earthquake, is highly dependent on the way in which people interact with the damaged physical environment. While there are extensive studies on evacuation from undamaged structures and on structural behavior under seismic and other hazards, research on the influence of building damage on human evacuation behavior is limited. This study presents a framework by which models for buildings and human behavior can be coupled to analyze the dynamic influences of building damage on the evacuation process. The framework combines nonlinear dynamic finite-element modeling of structures, probabilistic modeling of damage, and agent-based modeling of human occupants to investigate the behavior of people as they interact with each other and with their dynamically-deteriorating environment as they attempt to evacuate the building. A case study is presented for a typical three-story commercial office building subjected to the ground motions of the 1994 Northridge, California earthquake. By using exit flow rates and other measures related to evacuation time histories as the outcomes of interest, it is shown how the proposed framework can be used as a tool to enhance building design and to develop recommendations for improved evacuation strategies. An important future extension of the work is expanding the framework for multiple buildings for community-wide models of postdisaster behavior

Experimentally measured mechanical properties of hollow sphere steel foam are the subject of this paper. The characterization of the hollow sphere foam encompasses compressive yield stress and densification strain, compressive plastic Poisson's ratio, and compressive unloading modulus, as well as tensile elastic modulus, tensile unloading modulus, tensile yield stress, and tensile fracture strain. Shear properties are also included. These tests provide sufficient information to allow calibration of a macroscopic, continuum constitutive model. Calibrated foam plasticity parameters are tabulated, and unique feature of foam plasticity are explained. Also, initial development of mesoscale simulations, which explicitly model voids and sintered hollow spheres, is reported. This work is part of a larger effort to help the development of steel foam as a material with relevance to civil engineering applications.