Wooden window frames with structural sealants: manufacturing improvements and experimental validation of a finite element model

This paper proposes a finite element (FE) model of a novel wooden window frame typology and validates it by experimental tests on a whole window frame and corner joint specimens. The focus is on double glazing glass frames and dowelled butt corner joints. The innovation consists on the application of the structural silicone sealant only at the interface between wood and one of the thin glass layers of the double-glazing glass, so achieving a low application depth. This application mode reduces the sealant quantity and allows the disassembly and substitution of the glass from the frame in case of breakage. In order to inform the FE model of the whole frame, the corner joint strength is measured by specific experimental tests. The test are carried out on meranti wood species and using a SIKA WT-40 structural silicone. The results show an high correlation between the FE model and the experimental results in the range of small frame deformations, that are of interest for this application. The model is then applied to various wooden frame geometries in order to evaluate if the silicone application mode and dowelled corner joints allow an acceptable stiffness of the frame, and in particular low deformations of the bottom corner joint, in order to maintain the wooden frame functionality under external loads. This approach could be useful in the assessment of optimal wood-sealant-glass joint geometries, corner joint geometries and window frame geometries to limit the bottom corner joint deformation in the required range.