A big topic on the project of the Gare Maritime was fire safety. It was difficult for the renovation project to comply with existing fire safety Belgian standards and a derogation file had to be drawn up.
Concerning the timber structure, an advanced study for fire stability has been performed for this project in collaboration with the University of Liège. Indeed, we were asked to demonstrate that the structure could withstand a longer period of time than originally planned while maintaining the same sections.
When necessary, it was chosen to work with an intumescent transparent paint specially developed for wood. Many products exist on the market to improve the fire reaction of wood but it was not easy to find a paint that improves the fire resistance with technical datas to understand how to calculate the impact of this painting over the timber section during fire. The painting found had valid datas for a floor with a certain load and span. As these assumptions were not met, the project configuration was tested to validate that the values used were still applicable and so a fire test on a real scale mock-up of the floor has been performed in order to validate the complex.
In addition to the fire test, we did further numerical analysis.
A finite element modelling of some joints has been done with the software SAFIR to perform thermal and mechanical analysis and study the behaviour of those joints after a determined time without any protection or with de addition of an intumescent paint.
In case of fire, the behaviour of the timber depends not only on the temperature of the material but also on the type of solicitation (tension, shear, …). To be able to determine the load bearing capacity of a dowel, we modelled a beam (the dowel) supported by stiffeners whose stiffness varies along the dowel according to the evolution of the mechanical properties of the wood. The stiffener was thus representing the behavior of the wood depending on its temperature.
With the first general model of the joint, we knew the temperature of the wood along the cross section of the beam so we were able to characterize the stiffeners along the dowel. Then we applied at the position of the slotted plate a load that was incremented until the load bearing capacity of the dowel was reached.