Comportement au feu des dalles mixtes en béton léger

Abstract

Composite structures are composed of two or more different materials called composite elements. These elements have many benefits due to their combined properties that allow them to behave as a single unit to perform better in overall this work is about the Composite slabs, which are horizontal elements used for many types of buildings. They are made by casting concrete above a profiled steel sheet. The main objective of this research is to study the influence of lightweight concrete on the thermal-mechanical behaviour of composite slabs by developing a 3D finite element model the study is divided into three major parts. Starting with a literature review of experimental and numerical works on the thermal-mechanical behaviour of Composite slabs passing to a thermal analysis using ANSYS; this study shows that the moisture content of lightweight concrete significantly impacts fire resistance time. When the moisture content exceeds 3%, the Eurocode method predicts a lower fire resistance time compared to the simulation method. The prediction models indicate that to achieve the same fire resistance time, a normal-weight concrete section must be 7% thicker than a lightweight concrete section. Finally, a thermal-mechanical analysis was conducted using a hybrid method based on the thermal results of the finite elements study and the analytical equations mentioned in the Eurocodes. The results of this study show that concretes with higher mechanical performances result in a significant residual moment after heating, while the stability is still monitored. The development of the deflection is more important in LWC than in NWC and the positions of the rebars have a significant impact on the thermal and mechanical results of the composite slab.