Experimental study of the behavior of a steel-concrete hybrid thermal break system under vertical actions
Résumé
The level of energy performance requirements in buildings has substantially increased over the last twenty years. As a consequence, a large thickness of thermal insulation has to be used and the reduction of thermal bridges is necessary. This reduction becomes a main concern for structural design, particularly, at wall to balcony connections which cannot be left monolithic for concrete buildings with external thermal insulations in. For that kind of connections, a thermal break system (TBS) must be interleaved. The structural roles of this element are not only to transfer a vertical force and a bending moment but also to ensure the horizontal flexibility in order to absorb the relative displacements induced by thermal expansion of the balcony and to have a sufficient horizontal resistance for wind and seismic actions, where relevant. Moreover, this connection must answer to some minimal requirements of robustness. When considering all these aspects, the conventional TBS, made of stainless steel bars, appear to be inadequate. For that reason, a new solution of TBS, so-called SUNE, has been developed. It consists of tensioned rebars, U-shaped steel sections and special shear keys. In this article, the experimental tests to study the structural behavior of the SUNE under vertical actions are presented. An analytical formulation for determining the ultimate load of TBS and an analytical model for computing the flexural stiffness have been proposed and validated using the experimental results. © Springer International Publishing AG 2018.