The response of steel frame structures under fire conditions
In June 1990 a fire occurred in a large contractors' hut on the first floor of a 14 storey steel framed building in the Broadgate development. Despite large deflections the structure behaved well and there was no collapse of any of the beams, columns or floors. A major investigation was underta...
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University of Edinburgh
1997
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| Online Access: | http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653661 |
| Summary: | In June 1990 a fire occurred in a large contractors' hut on the first floor of a 14 storey steel framed building in the Broadgate development. Despite large deflections the structure behaved well and there was no collapse of any of the beams, columns or floors. A major investigation was undertaken of the fire and the structural performance. It was concluded that the building behaved as a framework of elements though designed as a collection of isolated elements. The connections were able to accommodate large deformations and forces without failure. Hence when the framework acts as a total entity structural stability is significantly improved. The investigation recommended that more research and analysis was required to study the characteristics of frame action in fires. This thesis details a study of the behaviour of multi-storey frames at elevated temperatures. A series of pairs of five storey two bay plane steel frames were designed to demonstrate restrained column collapse behaviour and column collapse due to hinges forming in the restraining beams at ambient temperatures. In a pair, both frames collapse under the same applied load but each frame displays one of the collapse mechanisms. This thesis chronicles the construction of the frames and the tests carried out at ambient temperatures and under various heating configurations. A non-linear elastic frame analysis was developed based on the slope deflection method. The reduction in flexural stiffness of the critical column due to bending plasticity is modelled with a non-linear spring. This analysis is used to predict the collapse load and collapse state of each frame tested. Comparisons are made with predictions from the EC3 simple column design method. The non-linear elastic frame analysis is also used to investigate the frame responses which occur due to the presence of elevated temperatures. |
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