Leading Innovation in Hybrid Trusses
Pursuing our growth strategy of developing building solutions for large scale, low rise commercial buildings, Canada Wood has been busy testing three different truss configurations at the Ehime Forest Research Center in Kumakogen town in February and March of 2022. The test specimens comprised of Canadian dimension lumber and Hem-fir(N) squares. These truss configurations will open up new possibilities for Canadian lumber species (for SPF as well as Hem-Fir and Douglas Fir). Normally, nail-plates to fabricate trusses are used in these applications, however this method poses two problems. The first is an equipment issue. Although several companies do possess nail plate equipment, many panel companies do not and purchasing such equipment requires considerable capital investment. The second issue is poor aesthetic appearance of nail plate trusses. Traditionally Japanese people prefer to see only clean wood surfaces and do not like to see exposed metal connectors. For this reason, nail-plate trusses do not resonate with Japanese preferences.
Working with leading Japanese structural engineers Canada Wood designed and conducted full-scale bending tests on these trusses this past fiscal year. The test program is advancing well and we are in the final phase of this development program in fiscal 2022-2023. The test specimen truss joints use screws and do not require any special fastening equipment. This means that the trusses can be fabricated anywhere and this will result in cost advantages. Also unlike metal plate systems, the Canada Wood screw based hybrid trusses are non-proprietary and will be available for all Japanese builders to use. The test specimen sections were fabricated in panel plants and were subsequently assembled together at the test center. Also, the screw connections used in joints are low profile to do not draw attention, allowing the trusses a cleaner and visually attractive design aesthetic.
The trusses have different strength, aesthetic, and span characteristics. Two trusses are engineered for spans of up to 20 meters and one truss is designed to span up to 10 meters, but due to test facilities limits, tests were conducted with 10m spans. This year Canada Wood will be developing full design details and span tables to support commercial adoption of these trusses and open the door for increased Canadian lumber use in Japanese roof assembly applications.