Four cross-laminated timber (CLT) two-storey houses were tested at the UNBC Wood Innovation and Research Laboratory in Prince George. The houses were 1.5 m x 2.0 m in plan and 5.3 m tall. The lateral load resisting system was composed of platform-framed coupled panel shear walls, made of 5-ply CLT panels 2.5 m x 1.0 m for a 2.5:1 aspect ratio. The shear walls were connected to the base with high-capacity hold downs attached with fully threaded Ø12 x 120 mm self-tapping screws (STS), and shear keys that decoupled the uplift from the sliding resistance. As panel-to-panel connections, 19.1 mm thick D-fir splines were surface mounted with Ø10 x 100 mm STS.
A total of ten quasi-static tests (two preliminary monotonic and eight reversed cyclic) were conducted, investigating the impact of following parameters:
i. Mass on the floors;
ii. Shear bracket connections between floors;
iii. Tension strap connections between floors;
iv. Presence of acoustic insulation layers on both sides of first level floor;
v. Presence of perpendicular shear wall.
The main findings can be summarizes as follows:
1) Increasing the strength of the shear brackets at the bottom of the second storey shear wall and adding dead load to each floor (#H1c vs #H2a) significantly improved performance.
2) The impact of screw installation angle at the tension straps(#H2a vs #H2b) had only minimal impact on overall performance, although this might be influenced by re-testing the house.
3) The impact of STS installation angle at the tension straps (#H2a vs #H2b vs #H3a) had only minimal impact on overall performance, although this might be influenced by re-testing house #2 in the test where all STS were installed at 45°.
4) Substituting the bolts for STS in shear connections between floors (#H3a vs #H3b) improved overall performance, leading to the highest load-carrying capacity and the most equal storey drifts of all houses tested without a perpendicular wall.
5) The added acoustic layer (#H4a vs #H3b) had a small detrimental effect on performance.
6) The perpendicular walls (#H4b vs #H3b) significantly increased load-carrying capacities.