Fire Safety Design of Structures in Steel-Timber Hybrid Construction

In the structural design of steel-timber hybrid constructions, linear steel load-bearing elements such as columns and beams protected by timber linings, as well as frame systems, which are completed by a secondary load-bearing structure consisting of plane CLT elements can be used. However, for associated multi-storey buildings, there are also high fire protection requirements that must be met to ensure the overall safety of the building. A consistent and widespread implementation of this construction method in building practice is, therefore, currently failing due to corresponding knowledge gaps. The findings and results on the fire behaviour of steel-timber hybrid structures from the first tests series obtained to date as part of the ongoing research project will be presented in the following paper. A campaign with three different experimental test setups was conducted. Small scale specimens were used to derive and validate thermal properties for numerical simulations. Furthermore, the protective effect of timber linings for steel members was investigated in beams, columns and floor systems. The tests have shown that the charring behaviour of the timber linings and therefore the failure time depend on numerous factors like the number of sides exposed to fire, the profile factor of the protected steel member as well as of the joints in the applied linings.