Study on a newly developed diagonal connection for hybrid timber trusses made of spruce glulam and beech laminated veneer lumber

ABSTRACT

The paper presents a truss concept characterised by structural simplicity and economic efficiency. The intended materials are spruce glulam for chords as well as posts and beech LVL (laminated veneer lumber) for diagonals, which are stressed in tension. Connections between the truss members are preferably be realised using self-tapping screws. The main focus of the paper is on a newly developed diagonal connection where the diagonals are screwed on to both outsides of the chords with countersunk screws and special washers. For this diagonal connection, a calculation model of the load-bearing capacity and the connection stiffness is presented. Tests were performed which encompass local and global stiffness examinations between screwed-on beech LVL diagonals and chords even for technically different screw connections. The corresponding test results agree with analytical values according to the proposed calculation model. A corresponding small-scale truss prototype was designed and tested. Computer-aided analyses of the truss deformations give first evidence for the actual feasibility of the truss concept employing the newly developed connection.

KEYWORDS:

• Hybrid truss
• beech laminated veneer lumber
• axially loaded self-tapping screws

Acknowledgements

The authors thank their project partner Holzbau Bruno Kaiser GmbH, Bernau, for the collaboration and the manufacture of test specimens.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge the financial support of the Federal Ministry of Food and Agriculture (BMEL) via the Agency for Renewable Resources (FNR) as project executing organisation (Code 22010017).