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

Abstract

This paper proposes a finite element (FE) model of a novel wooden window frame typology and validates it by experimental tests on window frames and corner joint specimens. The innovation consists of 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 technique 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 dowelled butt corner joint strength is measured by specific experimental tests. The results show a good correlation between the FE model and the experimental results in the range of small frame deformations, which are of interest for the proposed application. In particular, the FE curve overestimates the bottom corner displacement of about 17% at 1000 N load, 7% at 2000 N and less than 5% at higher applied force on the upper corner. The model is then applied to various wooden frame geometries in order to evaluate if the proposed silicone application mode and dowelled corner joints type 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 when subject to external loads. The approach could be useful when assessing optimal sealing application modes, wood-sealant-glass joint geometries, corner joint geometries and window frame geometries to limit the bottom corner joint deformation within the required technical specifications. IntroductionWood frames are used in several manufacturing applications, such as kitchen, doors, windows, partitions, etc. In particular, novel architecture and structural engineering are characterized by thin frames and large spans where glass represents a structural element and contributes to the energy performance of the buildings. These requirements increase the interest in structural sealants' applications, in novel joining techniques and in the overall assessment of frames structural performances under various applied loads. Moreover, the growing interest on the energy performance of buildings has increased the scientific research in the area of glass and façade in architecture, and in novel chemical and mechanical approaches to the structural sealants and window

Determination of the Bending Moment of a Dowel and Tenon Joint on Window Profile IV 92 of a Wooden Window

“…Dowel joints were pulled out of the wood on the inner side during tensile test, or on the outer side during compression test. This behaviour explains the different failure mode of the dowels in the Fig 5b. For the expression of the stress distribution in the wooden window frame connected with dowels, Pantaleo et al (2013) previously used finite element modelling. The fact that strength of the corner joint increases with increasing bonding surface was discussed in the Introduction, and such a dependency already has been established by many authors such as Warmbier and Wilczyński (2000), Wilczyński and Warmbier (2003), and Hajdarević and Šorn (2012).…”

“…The dowels are therefore able to compete with the tenon and mortise joint by accepting a lower strength (Efe et al 2005;Hrovatin et al 2013a;İmirzi et al 2015). Despite the overall lower strength of dowel joints (Pantaleo et al 2013), the experimental tests and modelling using the finite element method have established that dowelled window sashes with the application of structural silicon still have sufficient stiffness. Generally, the size of a bending moment and the stiffness of dowel joints can be affected by the dowel spacing, diameter, and depth of dowels (Warmbier and Wilczyński 2000).…”

“…Dowel joints are the most frequent alternative to tenon and mortise (Bahlmann 2011;Hrovatin et al 2013a;Pantaleo et al 2013). Dowel joints provide many advantages for manufacturers.…”

“…Larger profiles allowed for thermally insulating double and triple glazing to be fitted, which helped with decreasing the heat transfer coefficient by as much as 75%, compared to single glazing (Hochberg et al 2010). Through their glazing, windows represent a structural element that contributes to improving the energy performance of the entire building (Pantaleo et al 2013). However, due to the weight of the insulating glass, increased demands are placed on the strength of the corner joints.…”