On parameters affecting the racking stiffness of timber-glass walls

Abstract

An extensive parametric numerical study was performed after completed experimental campaign of timber-glass hybrid walls (TGW and TGWE). 36 timber-glass models (TG) with different outer dimensions were built and analysed with a goal to capture the basic response of mechanically tested timber-glass walls and to determine the racking stiffness of the calculated numerical models. Timber frame was modelled using linear beam elements with hinges in all four corners, an IGU was modelled as a multilayer shell and finally a layer of adhesive was modelled with linear and nonlinear springs, which were distributed circumferentially around the edge of IGU and connected onto a timber frame. Normal and shear stiffness coefficients for linear-elastic springs were calculated, while for nonlinear springs a special series of mechanical tests on polyurethane (PU) adhesive was performed since a lack of data available in addition to the desired amount of information needed for the numerical analysis. Uniaxial tension, compression and shear tests were made to obtain the results in form of the load-displacement curve, which presented a direct input for nonlinear normal and shear springs of the mathematical model. For each compression and tension mechanical test three specimens were prepared and tested up to rupture, while a double-lap shear test was conducted using two specimens giving two results each. PU adhesive specimens of the first series had dimensions of 50 mm $$\times $$ 50 mm and thickness of 5.0 mm. Mechanical tests were repeated for two additional thicknesses of PU adhesive, namely 7.0 mm and 9.0 mm. After completed experimental investigation on PU adhesive joint, together 108 numerical models with different external dimensions were analysed in commercial code SAP2000. Having the correct information about the stiffness of the single TG shear wall one can calculate the stiffness of the entire timber-glass building built with such walls.