Temperatures in unprotected joints between steel beams and concrete-filled tubular columns in fire

This paper presents experimental, numerical and analytical results of temperatures in different components of unprotected joints between steel beams and concrete-filled tubular columns in fire, which forms part of a research project to investigate joint behaviour under fire conditions and robustness of steel structures under accidental fire attack. Accurate calculation of connection temperatures is an essential first step of this process. The joint types include fin plate, endplate, reverse channel and T-stub. The results of the experiments indicate that the different components that are in the same region of a joint may be considered to have the same temperature. This suggests that the lumped mass temperature calculation equation in EN 1993-1-2 for unprotected steelwork may be used to calculate joint temperatures, by using an equivalent section factor for all the joint components in the same region of the joint. Therefore, the main objective of this study is to derive suitable expressions to calculate the section factors for the different components of the joints tested in this study. The experimental results have also been used to assess the simple temperature calculation method in Annex D of EN 1993-1-2, which relates the joint temperatures to the temperature of the connected beam. It has been found that this method generates grossly inaccurate results.