Sudden Column Removal Research Articles

Experimental Study on the Progressive Collapse Resistance of a Two-Story Steel Moment Frame

AbstractIn this study, the progressive collapse resistance of a two-story steel moment frame was investigated after the sudden removal of a perimeter column in the first floor through an experimental study. Two finite-element models with and without concrete slabs were developed and compared with the experimental results. The results indicate that the numerical model with slabs agrees well with that of the experiment and the concrete slabs play a significant role during the process of load redistribution. After the removal of the column, the partial loads previously carried by the removed column were transferred to its adjacent columns by the slabs. In addition, the concrete slabs and steel beams formed composite beams through shear connectors to resist the loads after the removal of the column. As a result, the stresses in the beams and the vertical displacements above the removed column were reduced significantly.

Progressive collapse design of seismic steel frames using structural optimization

This paper uses structural optimization techniques to cost-effectively design seismic steel moment frames with enhanced resistance to progressive collapse, which is triggered by the sudden removal of critical columns. The potential for progressive collapse is assessed using the alternate path method with each of the three analysis procedures (i.e., linear static, nonlinear static, and nonlinear dynamic), as provided in the United States Department of Defense United Facilities Criteria (UFC) Design of Buildings to Resist Progressive Collapse. As a numerical example, member sizes of a two-dimensional, nine-story, three-bay regular steel immediate moment frame are optimally determined such that the total steel weight is minimized while the design satisfies both AISC seismic provisions and UFC progressive collapse requirements. Optimization results for the example frame reveal that the traditional minimum weight seismic design, which does not explicitly consider progressive collapse, fails to meet the UFC alternate path criteria associated with any analysis procedure. Progressive collapse design optimization using the linear static procedure produces the most conservative and consequently heaviest design against progressive collapse. In contrast, the more accurate nonlinear static and dynamic procedures lead to more economical designs with UFC-acceptable resistance to progressive collapse, at the expenses of considerable modeling and computing efforts.

3-D nonlinear dynamic progressive collapse analysis of multi-storey steel composite frame buildings — Parametric study

A 3-dimensional finite element model built by the author was used in this paper to analyze the progressive collapse of a multi-storey steel composite frame building. The proposed model can represent the global 3-D behavior of the multi-storey building under the sudden column removal scenarios. Based on this model, parametric studies were carried out to investigate the structural behavior with variations in: strength of structural steel, strength of concrete and reinforcement mesh size. Through the parametric study, the measures to mitigate progressive collapse in the future design were recommended.

Progressive collapse of multi-storey buildings due to sudden column loss—Part II: Application

The companion paper presents the principles of a new design-oriented methodology for progressive collapse assessment of multi-storey buildings. The proposed procedure, which can be implemented at various levels of structural idealisation, determines ductility demand and supply in assessing the potential for progressive collapse initiated by instantaneous loss of a vertical support member. This paper demonstrates the applicability of the proposed approach by means of a case study, which considers sudden removal of a ground floor column in a typical steel-framed composite building. In line with current progressive collapse guidelines for buildings with a relatively simple and repetitive layout, the two principal scenarios investigated include removal of a peripheral column and a corner column. The study shows that such structures can be prone to progressive collapse, especially due to failure of the internal secondary beam support joints to safely transfer the gravity loads to the surrounding undamaged members if a flexible fin-plate joint detail is employed. The provision of additional reinforcement in the slab over the hogging moment regions can generally have a beneficial effect on both the dynamic load carrying and deformation capacities. The response can be further improved if axial restraint provided by the adjacent structure can be relied upon. The study also highlights the inability of bare-steel beams to survive column removal despite satisfaction of the code prescribed structural integrity provisions. This demonstrates that tying force requirements alone cannot always guarantee structural robustness without explicit consideration of ductility demand/supply in the support joints of the affected members, as determined by their nonlinear dynamic response.

Design Oriented Approach for Progressive Collapse Assessment of Steel Framed Buildings

This paper introduces a relatively simple yet accurate methodology to evaluate the efficacy of steel framed buildings against progressive collapse initiated by sudden local column failure. The proposed procedure can be implemented at various levels of structural idealisation, considering either the full damaged structure or critical substructures. In either case, the procedure accounts for the dynamic effects of column failure, where three main assessment stages are proposed. The first stage involves determination of the nonlinear static response of the structure/substructure under gravity loading using either simplified or detailed modelling techniques. The second stage employs a newly developed simplified dynamic approach, where the maximum dynamic response is estimated from the nonlinear static response using an energy equivalence criterion. The final stage assesses the vulnerability to progressive collapse by comparing the ductility demand in the connections, corresponding to the maximum dynamic response, to the ductility supply, considering the deformation capacity of individual connection components. The applicability of the proposed approach is demonstrated through a case study, which considers sudden removal of a peripheral column in a typical steel framed composite building. This study shows that such structures can be prone to progressive collapse. Several remedial measures are investigated, including the benefits of additional slab reinforcement over the connections.