A review of progressive collapse research and regulations

History has demonstrated that buildings designed to conventional design codes can lack the robustness necessary to withstand localised damage, partial or even complete collapse. This variable performance has led governmental organisations to seek ways of ensuring all buildings of significant size possess a minimum level of robustness. The research community has responded by advancing understanding of how structures behave when subjected to localised damage. Regulations and design recommendations have been developed to help ensure more consistent resilience in all framed buildings of significant size, and rigorous design approaches have been specified for buildings deemed potentially vulnerable to extreme loading events. This paper summarises some of the more important progressive collapse events, to identify key attributes that lead to vulnerability to collapse. Current procedures and guidelines for ensuring a minimum level of performance are reviewed and modelling methods for structures subjected to localised damage are described. These include increasingly sophisticated progressive collapse analysis procedures, including linear static and non-linear static analysis, as well as non-linear static pushover and linear dynamic methods. Finally, fully non-linear dynamic methods are considered. Building connections potentially represent the most vulnerable structural elements in steel-framed buildings; their failure can lead to progressive collapses. Steel connections also present difficulties with respect to frame modelling and this paper highlights benefits and drawbacks of some modelling procedures with respect to their treatment of connections

Progressive collapse analysis of steel structures under fire conditions

This is the post-print version of the final paper published in Engineering Structures. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.In this paper a robust static-dynamic procedure has been developed. The development extends the capability of the Vulcan software to model the dynamic and static behaviour of steel buildings during both local and global progressive collapse of the structures under fire conditions. The explicit integration method was adopted in the dynamic procedure. This model can be utilized to allow a structural analysis to continue beyond the temporary instabilities which would cause singularities in the full static analyses. The automatic switch between static and dynamic analysis makes the Vulcan a powerful tool to investigate the mechanism of the progressive collapse of the structures generated by the local failure of components. The procedure was validated against several practical cases. Some preliminary studies of the collapse mechanism of steel frame due to columns’ failure under fire conditions are also presented. It is concluded that for un-braced frame the lower loading ratio and bigger beam section can give higher failure temperature in which the global structural collapse happens. However, the localised collapse of the frame with the higher loading ratio and smaller beam section can more easily be generated. The bracing system is helpful to prevent the frame from progressive collapse. The higher lateral stiffness of the frame can generate the smaller vertical deformation of the failed column at the re-stable position. However, the global failure temperature of the frame is not sensitive to the lateral stiffness of the frame

A macro-element based practical model for seismic analysis of steel-concrete composite high-rise buildings

This is the post-print version of the final paper published in Engineering Structures. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2012 Elsevier B.V.Seismic behaviour of steel–concrete composite high-rise buildings, composed of external steel frames (SFs) and internal concrete tube (CT), with rectangular plan is investigated in this paper. A macro-element based model is established for seismic analysis of composite high-rise buildings aiming at predicting their global responses under earthquakes. By employing this macro-element based model, natural frequencies and vibration modes, storey and inter-storey drifts, overturning moments and storey shear forces of composite structures, induced by earthquakes, are able to be obtained with much less computation time and cost compared with using micro-element based analytical models. To validate its efficiency and reliability, the macro-element based model is employed to analyse a 1/20 scaled-down model of a 25-storey steel–concrete composite high-rise building subjected to simulated earthquakes with various intensities through a shaking table. Natural frequencies and storey drifts of the model structure are obtained from numerical analyses and compared with those from shaking table test results. It has been found that the calculated dynamic responses of the composite model structure subjected to minor, basic, major and super strong earthquakes agree reasonably well with those obtained from experiments, suggesting that the proposed macro-element based model is appropriate for inelastic time-history analyse for global responses of steel–concrete composite high-rise structures subjected to earthquakes with satisfactory precision and reliability. This research thus provides a practical model for elastic and inelastic deformation check of high-rise composite buildings under earthquakes.Ministry of Science and Technology of Chin

Performance and Design of Composite Modular System with Tenon Connections for Multi-Storey Buildings

Modular building is an innovative construction method based on advanced manufacturing technologies, which is a more eco-friendly, effective, and cost-saving alternative than conventional methods. The primary objective of this thesis is to design a sufficient composite modular system for multi-storey applications and provide design recommendations based on system-level analyses under earthquakes, winds, and sudden column losses. In the course of this thesis, a numerical model is first created for an existing tenon-connected inter-module connection to investigate its effects on the building’s lateral resistance. A cohesive interface model is used to account for the weld fracture. Due to the semi-rigid connectivity, there are around 53% and 28% reductions in the yield and maximum capacity of the building, respectively. The displacement coefficient method per American guidelines FEMA-356 is then adopted to predict the maximum deformation of the modular buildings under different design seismic loads. To strengthen the modular buildings, a novel composite modular system is newly proposed, which consists of concrete-filled steel tubular columns, laminated double beams, and integrated composite slabs. The structural responses of the composite modular buildings are assessed under design wind actions per Australian Standards AS 1170.0-2. The results indicate that the proposed buildings have sufficient design capacity but insufficient deflection control. The progressive collapse analysis is performed on the buildings in sudden column loss scenarios per Unified Facilities Criteria UFC 4-023-03. The results show that alternate load paths are activated after the notional column removals, and the progressive collapse is unlikely for the scenarios under consideration. Finally, the suitable dynamic increase factors of 1.90 and 1.60 are recommended for the 4- and 12-storey modular buildings, respectively, allowing peak dynamic responses to be predicted using the static approach

Assessment of progressive collapse in multi-storey buildings

Accepted versio

Dynamic Behaviour and Catenary Action of Axially-restrained Steel Beam Under Impact Loading

In this paper, the dynamic behaviour and catenary action of axially restrained steel beam under impact loadings is examined through a combination of experimental and numerical investigations. It describes and discusses the results of six impact tests on the axially restrained welded H-beams by means of the drop hammer test machine. The main behavioural patterns and the key response characteristics including the development of impact force, deformation and strain, as well as failure modes are examined, with emphasis on the effect of impact energy and the width to thickness ratio of beam flange. Finite element models are also developed and validated against the available testing results. It is demonstrated that the detailed FE model can capture the response of the welded H-beams under impact loadings. Moreover, the mechanism of catenary action was identified based on the development of the internal force in the welded H-beams

Seismic and Robustness Design of Steel Frame Buildings

In this paper, a design procedure that combines both progressive collapse design under column removal scenario and capacity design to produce a hierarchy of design strengths is presented. The procedure develops in the context of the European Standards, using the classification of European steel sections and considering the seismic design features. Three-dimensional models of typical multi-storey steel frame buildings are employed in numerical analysis. The design for progressive collapse is carried out with three types of analysis, namely linear static, nonlinear static and nonlinear dynamic. Since the behaviour following sudden column loss is likely to be inelastic and possibly implicate catenary effects, both geometric and material nonlinearities are considered. The influence of the fundamental parameters involved in seismic and robustness design is finally investigated

An overview of progressive collapse in structural systems

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (leaves 54-55).It has become evident recently that abnormal loads need to be considered in the design of structures so that progressive collapse can be prevented. Building collapses such as the Ronan Point, Alfred P. Murrah, and World Trade Center have shown the catastrophic nature of progressive collapse and with an increasing trend towards more terrorist action in the future, it is clear structural design must include progressive collapse mitigation. The most critical abnormal loadings that have potential to cause progressive failure are blast and impact. These loads are impulsive and dynamic in nature with the potential to induce destructive forces, and to further complicate matters is the random nature of occurrence which makes it difficult to predict adequate levels of design. Much research has been conducted over the past several decades, but to this day very little standardized language has been published to help designers create progressive collapse resistant structures. What is known is that robust structures can be built economically by following a general design philosophy of redundancy, ductility, and overall structural integrity. Reinforced concrete structures are especially well suited for resisting progressive collapse by specifying steel reinforcement detailing such as continuous top and bottom reinforcement, close spacing of stirrups, strategic locations of splices, continuous reinforcement through joints, and designing slabs for two-way action. Steel structures have good ductility, but connection detailing is usually the weakest point and requires special design, such as the use of the SidePlate (tm) connection.(cont.) Regardless of the type of material used, the design should strive for a uniform, regular layout of the structural system with limited span lengths and close spacing of beams and columns. Perimeter defense systems should be employed as this decreases the threat of an abnormal loading. Since there has been little consideration of extreme loadings, existing structures may be inadequate and require retrofit. Although more difficult, it is possible to achieve improved progressive collapse resistance through the use of externally applied retrofits, such as concrete encasement or the application of composite polymer materials.by Phillip J. Georgakopoulos.M.Eng

Disproportionate collapse analysis of mid-rise cross-laminated timber buildings

This paper investigates the structural behaviour of a twelve-storey Cross-Laminated Timber (CLT) building subjected to sudden removal of internal and external ground floor loadbearing walls, and computes the probability of disproportionate collapse. Analyses are carried out at three different structural idealisations, accounting for feasibility and complexity of finite elements models to understand their performance at: i) the global, ii) the component, and iii) the connection level. Focus is devoted on force and deformation-demands obtained from nonlinear dynamic analyses of the building. The demands are compared against the supply from common CLT panel sizes and the rotational stiffness (k) of the joints, detailed with off-the-shelf angle brackets and self-tapping screws. The study demonstrates that the applied forces and deformations required to develop resistance mechanisms are too large to be supplied by the proposed element and connection designs, if an internal ground floor wall is removed. The considered building has a probability of failure as high as 32% if designed without considerations of the complexities associated with disproportionate collapse. Consequently, to resist the effects of internal wall removal, the floors need to be redesigned and improved structural detailing with sufficient strength, stiffness, and ductility is necessary to trigger collapse resistance mechanisms