Modification factors for predicting the mechanical properties of light-frame timber shear walls for nonlinear static analyses

Accurately predicting the mechanical response of timber shear walls is essential for the seismic design of light-frame timber (LFT) structures, particularly when using nonlinear static analyses. Existing models and standard-based equations often fail to provide reliable estimates of stiffness, load-carrying capacity, and ductility due to the complex and highly nonlinear behaviour of timber connections. This study presents a methodology to predict the load-displacement response of LFT shear walls through the use of multiplicative corrective factors, referred to as α-factors. These factors are derived from regression analyses on experimental data and serve to adjust analytical or code-based predictions of stiffness, strength, and ductility to better reflect mean values required in nonlinear static analyses. A comprehensive experimental campaign comprising 15 cyclic tests was conducted on full-scale LFT shear walls with oriented strand board (OSB) and gypsum fibre board (GFB) sheathings, connected with nails and staples to support the development of the methodology. The test results reveal that GFB-sheathed walls generally exhibit higher stiffness and load-carrying capacity, due to the greater density and mechanical strength of GFB, but lower deformation capacity and more brittle failure modes compared to OSB-sheathed walls. Nail and staple fasteners showed comparable strength, although nails resulted in higher deformation capacity. The proposed methodology enables more reliable implementation of nonlinear static analyses by correcting for the limitations of existing models and better capturing the average seismic response of LFT shear walls.