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.

Fire loading following earthquake loading is possible in any building in a seismic prone area. However, most design approaches do not consider fire following earthquake as a specific loading case. Moreover, seismic design philosophies allow a certain degree of damage in structural elements which make structures more vulnerable when subjected to post-earthquake fire. This study uses three dimensional numerical models to investigate the effect of earthquake damage on the fire resistance of composite steel-frame office buildings. Two types of earthquake damage, fire insulation delamination and residual lateral frame deformation, are investigated. It is concluded that earthquake damage can significantly reduce the fire resistance of composite buildings, with delamination of fire protection having the greatest effect. The results of this study can be used by designers to improve the post-earthquake fire resistance of composite buildings.

This study presents robustness analyses of a three-dimensional multi-storey composite steel structure under the action of multiple fire scenarios. The main objective of the work is to improve current understanding of the collapse resistance of this type of building under different fire situations. A finite element approach was adopted with the model being firstly validated against previous studies available in the literature. The modelling approach was then used to investigate the collapse resistance of the structure for the various fire scenarios examined. Different sizes of fire compartment are considered in this study, starting from one bay, three bays and lastly the whole ground floor as the fire compartment. The investigation allows a fundamental understanding of load redistribution paths and member interactions when local failure occurs. It is concluded that the robustness of the focussed building in a fire is considerably affected by the size of fire compartments as well as fire location. The subject building can resist progressive collapse when the fire occurs only in the one-bay compartment. On the other hand, total collapse occurs when fire is located in the edge three-bay case. This shows that more than one fire scenario needs to be taken into consideration to ensure that a structure of this type can survive from collapse in the worst-case situation.

It is well-known that tensile membrane action in concrete floor slabs can enhance the fire resistance of a composite steel frame building. Vertical supports provided by protected beams along the edge of the slab panel play an important role in the development of the tensile membrane actions. The present study investigates the effect of fire insulation delamination on the protected beam, as might occur in an earthquake, on the fire resistance of composite floors subject to fire following an earthquake. The results show that fire insulation delamination considerably reduces the development of tensile membrane action. Based on the results obtained, two methods of improvement are presented to enhance the development of tensile membrane action concurrent with fire insulation delamination. It is found that increasing slab thickness and improving fire protection rating can enhance the fire resistance of the whole building even with fire insulation delamination.

This paper presents modelling of the progressive failure of steel moment frames subjected to localised fire. A finite element approach using the software ABAQUS has been developed to analyse the structure. An explicit-dynamic solution was adopted to solve the non-convergence problems caused by element buckling. A series of validation analyses were carried out to ensure that the results were within an acceptable level of accuracy. The analysis results are shown to match well with the previous experimental data and analysis. This modelling approach allows detailed insights to be obtained into the structural robustness of such frames in fire situations.