P 1162 – Minimum dowelling of composite beams in case of fire
The effects of elevated temperatures on the composite joint of a composite beam were examined within the scope of the research project. With the results of the research project, the safe usage of the partial connection theory shall be enabled. For this purpose boundaries of the application of a reduced degree of shear connection in case of fire, especially the minimum degree of shear connection, where investigated.
Besides the standard time-temperature curve also determined natural fire curves were investigated. The thermal loads on a composite beam have been calculated based on possible fire scenarios for typically application areas of composite structures. Four large scale fire tests have been conducted, each with two 9 m composite beams. In the fire tests the longitudinal slip of the composite joint, the vertical deflections and the temperature of the steel beam, of the concrete chord and the core temperature of the headed stud shear connectors have been recorded. Detailed solid models were developed, using the finite element program Abaqus. These models were validated with the experimental results. Extensive parametric studies and numerical investigations were conducted with the validated models.
A multiplicity of influences on the composite joint in case of fire where described and evaluated with the help of the experimental and numerical investigations. Some of the more important results are the identification of three dominating effects of elevated temperatures of the composite joint, the recognition of the decisive load combination for the composite beam in fire, as well as the description of dominating influences on the composite joint. Some of these influences are the stiffness of the composite joint, the degree of shear connection of the composite beam and the relation between the tensile capacity of the concrete chord to the shear capacity of the composite joint. Finally, practice-oriented design rules and limits for the safe use of the partial connection theory for composite beams in fire are given.
Prof. Dr.-Ing. M. Mensinger, Dr.-Ing. S. Pfenning, Prof. Dr.-Ing. J. Zehfuß