Experimental study on racking resistance of timber double-skin façade elements

Abstract

The use of double-skin façade (DSF) is a quite new approach in building renovation process, complementing conventional renovation strategies. A double-skin facade is an envelope wall construction that consists of two transparent surfaces separated by a cavity and can essentially improve thermal and acoustic resistance of building envelope. Main double-skin wall components are usually composed of hardened external single glazing pane and internal three-layer insulation glass unit (IGU) which are rigidly bonded to the frame structure. Recently, many studies have analysed thermal and acoustic performance of DSF elements, but practically none in a sense of structural behaviour, especially in determination of racking resistance of such wall elements. Moreover, in terms of reduction of global warming potential, an eco-friendly timber frame instead of common used steel, aluminium or plastic frame is investigated in this analysis. The developed load-carrying real-size composite timber-glass DSF wall elements are subjected to experimental racking test using two different types of adhesives (polyurethane and epoxy) and consequent bonding type alternatives of connecting the internal three-layered thermal glazing to the timber frame. The obtained results for the maximal fracture force and racking stiffness are compared with previously tested prefabricated timber-glass wall elements using a single-skin three-layered thermal insulating glazing only. The results evidently demonstrate that this new approach of prefabricated load-bearing double-skin façade elements can essentially improve racking resistance and stiffness comparing with previously studied timber-glass wall elements and can thus be fully recommended especially in structural renovation process of old buildings. However, a lot of parameters still significantly effect racking resistance of such elements and thus have to be further numerically or parametrically investigated.