Evaluation of the Mechanical Behaviour of Novel Latticed LVL-Webbed Joists

Background:

Solid-web I-joists are some of the most commonly used engineered wood products in residential and commercial buildings for floor and roof assemblies. Web openings, which are required to accommodate services in a building, can reduce the shear capacity and structural integrity of the joists. Open-web joists, which do not require modifications on-site, can overcome this problem.

Objective:

The objective of this study is to create an all-timber open-web joist product utilising engineered timber with reduced environmental impact compared to existing I-joist products. Joists are manufactured by combining latticed web-components made from Laminated Veneer Lumber (LVL) with solid timber flanges. The structural performance of these novel joists is investigated.

Methods:

Bending and shear tests were carried out on latticed LVL-webbed I-joists of two different depths, namely, 241 mm and 305 mm. The load-displacement behaviour and failure mode were recorded. The characteristic bending moment and shear force capacity are compared to that of commercially available I-joist products manufactured with a solid web.

Results:

Failure of the I-joists was found to occur in the web, good load capacities were achieved and the response was predominantly linear elastic to failure. Joists manufactured using PRF adhesive were found to outperform those manufactured using UF adhesive.

Conclusion:

The latticed LVL web I-joists compared favourably with similar-sized solid-web I-joists with regard to moment and shear capacity and have been shown to be a suitable alternative to commercially available I-joists that can also facilitate openings for services without adversely affecting the structural integrity of the joist.

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