Temperature of a partially embedded connection subjected to fire

When subject to fire, structural steel and connectors lose both their strength and stiffness. Structures expand when heated and contract on cooling. Furthermore, the effect of restrained thermal movement can introduce high strains in both the steel member and the associated connections. Fire tests on steel structures have shown that the temperature within the connections is lower compared to the connected steel members. The beneficial effect of the partial embedding of a connection in a concrete slab for its resistance in fire conditions was already intuitively utilised by structural engineers. Three sets of tests provide the measuring of the accuracy of the developed numerical and analytical model for heat transfer and temperature distribution in the partially embedded connections. The connection shadow factor is proposed further to allow the prediction of temperatures in connections from the calculated gas temperature during a post-flashover fire.

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► The paper focusses to beam to column and beam to beam header plate connections.
► Partially embedded connections were tested at elevated temperatures.
► A numerical model of transfer of heat was developed utilising shadow factors.
► An analytical model of transfer of heat to this connection was prepared.
► The prediction models were evaluated on tests with good accuracy.