Towards the Design of Cold-formed Steel Foam Sandwich Columns

In this paper a design method for the compressive capacity of sandwich panels comprised of steel face sheets and foamed steel cores is derived and verified. Foamed steel, literally steel with internal voids, provides the potential to mitigate many local stability issues through increasing the effective width-to thickness of the component for the same amount of material. Winter’s classical effective width expression was generalized to the case of steel foam sandwich panels. The provided analytical expressions are verified with finite element simulations employing brick elements that explicitly model the steel face sheets and steel foam cores. The closed-form design expressions are employed to conduct parametric studies of steel foam sandwich panels with various face sheet and steel foamed core configurations. The studies show the significant strength improvements possible with steel foam sandwich panels when compared with plain steel sheet/plate

Interfacing Building Response with Human Behavior Under Seismic Events

The goal of this paper is to model the interaction of humans with their built environment during and immediately following a natural disaster. The study uses finite element simulations to evaluate the response of buildings under input ground motions and agent-based dynamic modeling to model the subsequent evacuation of building occupants in the study area immediately following the seismic event. The structural model directly captures building damage and collapse, as well as floor accelerations and displacements to determine nonstructural damage, injuries and fatalities. The goal of this research is to make connections between building damage and occupant injuries, with geographic automata as the information handler for the agent-based platform. This research demonstrates that human behavior and evacuation patterns can be evaluated in the context of realistic structural and nonstructural damage assessments, and that prior knowledge of evacuation patterns is critical for adequate preparedness of cities to severe earthquakes

Interfacing Building Response with Human Behavior Under Seismic Events

The goal of this paper is to model the interaction of humans with their built environment during and immediately following a natural disaster. The study uses finite element simulations to evaluate the response of buildings under input ground motions and agent-based dynamic modeling to model the subsequent evacuation of building occupants in the study area immediately following the seismic event. The structural model directly captures building damage and collapse, as well as floor accelerations and displacements to determine nonstructural damage, injuries and fatalities. The goal of this research is to make connections between building damage and occupant injuries, with geographic automata as the information handler for the agent-based platform. This research demonstrates that human behavior and evacuation patterns can be evaluated in the context of realistic structural and nonstructural damage assessments, and that prior knowledge of evacuation patterns is critical for adequate preparedness of cities to severe earthquakes

Steel foam for structures: A review of applications, manufacturing and material properties

The objective of this paper is to provide a state-of-the-art review for the structural application, manufacturing, material properties, and modeling of a new material: steel foam. Foamed steel includes air voids in the material microstructure and as a result introduces density as a new design variable in steel material selection. By controlling density the engineering properties of steel components may be altered significantly: improvement in the weight-to-stiffness ratio is particularly pronounced, as is the available energy dissipation and thermal resistivity. Full-scale applications of steel foams in civil structures have not yet been demonstrated. Therefore, existing applications demonstrating either proof-of-concept for steel foam, or full-scale use of aluminum foams in situations with clear civil/structural analogs are highlighted. Adoption of steel foam relies on the manufacturing method, particularly its cost, and the resulting properties of the steel foam. Therefore, published methods for producing steel foam are summarized, along with measurements of steel foam structural (modulus, yield stress, etc.) and non-structural (thermal conductivity, acoustic absorption, etc.) properties. Finally, existing models for predicting foamed steel material properties are summarized to highlight the central role of material density. Taken in total the existing research demonstrates the viability of steel foams for use in civil/structural applications, while also pointing to areas where further research work is required. © 2011 Elsevier Ltd. All rights reserved

Probabilistic approach to progressive collapse prevention. Physics based Simulations

Physics based collapse simulations of moment resisting steel framed buildings are presented.Survival probability of a building occupant is proposed as a single scalar measure to quantify resistance to progressive collapse of a particular structure at hand. Practical procedure for the survival probability calculations by means of physics based simulations and theorem of total probability is shown in the paper. Simulations of structural response to the sudden removal of a key structural member have been carried out for a number of failure scenarios. Such analysis is at the forefront of civil engineering modeling because it involves material nonlinearities, large deflections, finite strains, and certainly requires dynamic analysis. Saving human lives in the case of abnormal loadings and/or unexpected hazards is equivalent to minimizing the area of collapsed floors. Such approach should also minimize the financial loss to a building owner.The area of collapsed floors can be extracted from the physics based simulations. It is proposed to quantify the goodness of design with the survival probability of a building occupant. Such single scalar measure provides an opportunity to employ optimization algorithms to produce the safest and the most economic structural design. © 2009 ASCE

Dynamic energy based method for progressive collapse analysis

Physics based collapse simulations of moment resisting steel frame buildings are presented with an emphasis on the development of energy flow relationships. It is proposed that energy flow during progressive collapse can be used in evaluation of moment resisting, steel frame building behavior and specifically, localized failure. If a collapsing structure is capable of attaining a stable energy state through absorption of gravitational energy, then collapse will be arrested. Otherwise, if a deficit in energy dissipation develops, the unabsorbed portion of released gravitational energy is converted into kinetic energy and collapse propagates from unstable state to unstable state until total failure occurs. The energy absorption of individual members provides very transparent information on structural behavior as opposed to oscillating internal dynamic forces in structural members. Therefore, critical energy absorption capacity is hereby proposed as a stable failure criterion in progressive collapse analysis. Energy flow quantification is shown to be readily available from the dynamic finite element simulations. The proposed dynamic, energy based approach to progressive collapse, provides insight and a simple yet robust analysis for producing structures capable of resisting abnormal loadings and/or unexpected hazards. © 2009 ASCE

Dynamic energy based method for progressive collapse analysis

Physics based collapse simulations of moment resisting steel frame buildings are presented with an emphasis on the development of energy flow relationships. It is proposed that energy flow during progressive collapse can be used in evaluation of moment resisting, steel frame building behavior and specifically, localized failure. If a collapsing structure is capable of attaining a stable energy state through absorption of gravitational energy, then collapse will be arrested. Otherwise, if a deficit in energy dissipation develops, the unabsorbed portion of released gravitational energy is converted into kinetic energy and collapse propagates from unstable state to unstable state until total failure occurs. The energy absorption of individual members provides very transparent information on structural behavior as opposed to oscillating internal dynamic forces in structural members. Therefore, critical energy absorption capacity is hereby proposed as a stable failure criterion in progressive collapse analysis. Energy flow quantification is shown to be readily available from the dynamic finite element simulations. The proposed dynamic, energy based approach to progressive collapse, provides insight and a simple yet robust analysis for producing structures capable of resisting abnormal loadings and/or unexpected hazards. © 2009 ASCE

Probabilistic approach to progressive collapse prevention. Physics based Simulations

Physics based collapse simulations of moment resisting steel framed buildings are presented.Survival probability of a building occupant is proposed as a single scalar measure to quantify resistance to progressive collapse of a particular structure at hand. Practical procedure for the survival probability calculations by means of physics based simulations and theorem of total probability is shown in the paper. Simulations of structural response to the sudden removal of a key structural member have been carried out for a number of failure scenarios. Such analysis is at the forefront of civil engineering modeling because it involves material nonlinearities, large deflections, finite strains, and certainly requires dynamic analysis. Saving human lives in the case of abnormal loadings and/or unexpected hazards is equivalent to minimizing the area of collapsed floors. Such approach should also minimize the financial loss to a building owner.The area of collapsed floors can be extracted from the physics based simulations. It is proposed to quantify the goodness of design with the survival probability of a building occupant. Such single scalar measure provides an opportunity to employ optimization algorithms to produce the safest and the most economic structural design. © 2009 ASCE

Effects of random imperfections on progressive collapse propagation

Progressive collapse is an increasing concern in the structural engineering community, especially after the collapse of the World Trade Centre Towers. While numerous papers have been published on the subject, the effects of random imperfections on failure paths have not yet been studied. The presented simulation study investigated the effects of random geometric imperfections on the formation of alternative paths after the removal of the first story column(s). Eccentricities and curvatures were introduced as independent random variables for each structural element. Gaussian distributions with means and standard deviations selected on the basis of a handbook of construction tolerances were applied to represent the real life imperfections. The selected, representative seismic building was repeatedly simulated under the same column(s) removal scenario with different imperfections randomly introduced in each simulation. The presented design exhibited competing failure modes. The dominant failure mode was observed in 80% of the simulations, while the secondary failure mode manifested itself in the remaining 20% of the simulations (the same column(s) removal scenario). The presented probabilistic study revealed that real-life imperfections may result in the alternate failure paths. Monte Carlo simulations shall be employed to detect such secondary load redistribution paths and/or collapse modes. © 2010 American Society of Civil Engineers

Effects of random imperfections on progressive collapse propagation

Progressive collapse is an increasing concern in the structural engineering community, especially after the collapse of the World Trade Centre Towers. While numerous papers have been published on the subject, the effects of random imperfections on failure paths have not yet been studied. The presented simulation study investigated the effects of random geometric imperfections on the formation of alternative paths after the removal of the first story column(s). Eccentricities and curvatures were introduced as independent random variables for each structural element. Gaussian distributions with means and standard deviations selected on the basis of a handbook of construction tolerances were applied to represent the real life imperfections. The selected, representative seismic building was repeatedly simulated under the same column(s) removal scenario with different imperfections randomly introduced in each simulation. The presented design exhibited competing failure modes. The dominant failure mode was observed in 80% of the simulations, while the secondary failure mode manifested itself in the remaining 20% of the simulations (the same column(s) removal scenario). The presented probabilistic study revealed that real-life imperfections may result in the alternate failure paths. Monte Carlo simulations shall be employed to detect such secondary load redistribution paths and/or collapse modes. © 2010 American Society of Civil Engineers