This project developed engineering solutions to enhance the performance of NLT shear walls. Proposed methods were first tested as small-scale connections and then in full-size walls. The connection tests showed that by installing inclined screws or bracings between studs, the stiffness could increase up to ten times and the peak load could double compared to a regular sheathing connection. Based on the small-scale test results, three configurations of the ENLT wall were designed: screw reinforcement (SC), steel bracing (SB), and wood bracing (WB). The nominal dimension of the wall was 2.44 m × 2.44 m (width × height, 96 in × 96 in). Two specimens were manufactured for every configuration: one tested under monotonic loading and the other under reverse-cyclic loading. One repaired wall was also tested after replacing sheathings. The tests were conducted in accordance with ASTM E564-06 (2018) and ASTM E2126-19.
The peak load of ENLT was more than doubled compared to regular NLT with single face sheathing (SH1) and its stiffness increased by at least 60%. The repaired wall also exceeded the peak load of SH1 by a wide margin. Most ENLT walls had holdown failure at the peak. When compared to regular NLT with double face sheathing, the advantage of ENLT was more significant under the reverse-cyclic loading, in which case, the peak load had a gain of 30% or more, from 53.8 kN to 68.2-72.3 kN. And the improvement at the reverse cycle was also substantial. All ENLT walls showed consistently better performance under reverse-cyclic than monotonic loading. Amongst the three ENLT configurations, steel bracing had higher stiffness than the other two. Wood bracing led to the highest load as recorded in the test, but the difference was not easy to determine due to holdown failures in most cases.
Common failure modes found in various configurations of the wall were discussed, and recommendations for industrial production and future development were also given.
