Structural Analysis of Glulam Frame of a Modular Timber–Aluminium Hybrid Façade System in Nordic Climate

Abstract

This article presents the results of mechanical testing and structural analysis of the glulam frame supporting novel external façade envelope elements made of aluminium, glass, and insulation. The glulam frame forms the basic structural support for the new modular hybrid façade system, an industrial product designed by STATICUS company with an aim at reducing environmental impact. The ultimate and serviceability limit states are considered to assess the durability of the design in terms of possible deformations affecting air and moisture tightness as well as the level of stresses leading to potential damage accumulations and fatigue. The analysis combines the horizontal environmental loads, that is, wind loads over 4 years of real wind speed data in 2021–2023 together with the permanent self-weight loads for the representative mid-rise building in different characteristic coastal locations in Norway: Oslo, Trondheim, and Tromsø. The constructed load models are applied to the geometrically non-linear numerical mechanical model of the glulam frame. Explicit modelling of the screw connections in the frame was validated by static mechanical testing in a laboratory set-up. Continuum elements with an orthotropic material model are used for wood. The stress level in reference to the ultimate strength was established for all wind loads and characteristic failure mode was identified as local compression perpendicular to grain in the screw connection. The mechanical fatigue life of the glulam frame is estimated at a minimum of 32 years (Tromsø) and a maximum of over 100 years (Oslo, Trondheim) based on the calculated stress level and real expected number of cycles of loading over the service life.