Experimental study on the m-v interaction of a hybrid steel connection used in concrete floor-to-balcony junction

Abstract

The energy efficiency standards impose to reduce thermal bridges in buildings. In France, in the case of internal thermal insulation, a commonly used technique for concrete buildings, thermal break systems must be placed at the slab-to-wall junction. They maintain the continuity of the insulation through the slab, but must evidently comprise structural elements, that ensure the transfer of shear forces from the slab to the wall, and bending moments in front of bal-conies. On one hand, as these structural elements have a low thermal resistance, they must be limited. On the other hand, the architects and future occupants of the buildings ask for larger balconies. In order to meet both thermal and structural requirements, concrete constructors have to find optimized solutions. SLABE® system is such a robust and ductile system: Stainless steel Z-shaped profiles are used as shear keys, embedded at both ends in the concrete and complemented by horizontal reinforcement bars to increase the bending moment resistance. Its behaviour is quite complex: The M-V plastic interaction of Z shaped steel profiles is not well known, the plastic ductility of the steel elements may be limited by punching of the concrete, and the stiffness of the system is strongly depending on the anchorage of the steel rebars and on the support conditions of the steel profiles. As a consequence an experimental study of the system has been carried out, covering different M/V ratios varying from 0.1 to 0.8. It includes an original test setup in order to handle cases where the load is applied near the connection. An analytical model have been deduced in order to predict the resistance at ULS of the thermal break.