Progressive collapse analysis of composite steel frames subject to fire following earthquake

• Published in: Fire safety journal Vol. 103; pp. 49 - 58
• Main Authors: Suwondo, Riza, Cunningham, Lee, Gillie, Martin, Bailey, Colin
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier Ltd 01.01.2019; Elsevier BV
• Subjects: Catastrophic collapse; Collapse mechanism; Columns (structural); Composite building; deformation; Deformation effects; Deformation resistance; Earthquake damage; Earthquakes; Fire damage; Fire resistance; fires; Load redistribution; Post-earthquake fire; Progressive collapse; Seismic activity; steel; Steel frames; Steel structures; Three dimensional analysis; Three dimensional models; Time lag; Travelling fire; Two dimensional models; Collapse mechanism; Progressive collapse; Post-earthquake fire; Earthquake damage; Composite building; Travelling fire; Load redistribution
• ISSN: 0379-7112; 1873-7226
• DOI: 10.1016/j.firesaf.2018.12.007

This paper presents three-dimensional progressive collapse analyses of composite steel frames exposed to fire following earthquake. The scenarios of heating columns located in various different fire compartments (internal, edge and corner bay) are first studied to investigate load redistribution paths and members’ interactions within the composite frame. The results show that the loads previously supported by the heated columns are redistributed to adjacent columns along two horizontal directions, a phenomenon which cannot be captured in a 2D model. Then, the 3D model is adopted to investigate the effect of residual deformation after an earthquake on the progressive collapse behaviour of the composite building. It is found that neither the load redistribution path nor the fire resistance of the building is considerably affected by the residual deformation. A series of progressive collapse analyses subjected to travelling fires resulting from fire compartment damage is also performed. It is concluded that the survival of the building can be greatly affected by the spatial nature of the travelling fire as well as the inter-zone time delay. •Three-dimensional modelling of composite frames is essential in order to simulate load redistribution between columns as a result of heating. The loads previously supported by the heated columns are redistributed to adjacent columns along two horizontal directions, a phenomenon which cannot be captured in a 2D model.•The loading ratio plays an important role in the collapse resistance of the building. A lower loading ratio can prevent the building from collapse. This is because the load previously sustained by the heated column can be safely transferred to the adjacent columns without causing buckling.•During the cooling phase, the heated columns experience large tension resulting in extra load being transferred to the adjacent columns. Therefore, the cooling phase should be considered in the robustness analysis of the building.•In the frame examined, residual deformation due to the design earthquake has a minor effect on the load redistribution or progressive collapse mechanism.•Travelling fire and inter-zone time delay significantly affect the collapse resistance of the building. Therefore, the designer should consider a range of travelling fire scenarios.