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Performance of self-tapping screws under climate-induced degradation in Australian chemically treated timber: experimental evaluation and preliminary insights
Conference paper   Peer reviewed

Performance of self-tapping screws under climate-induced degradation in Australian chemically treated timber: experimental evaluation and preliminary insights

Zidi Yan, Tripti Singh and Liam Ottenhaus
Proceedings IRG Annual Meeting, pp.1-19
Annual Meeting of International Research Group on Wood Protection (IRG), 56th (Beijing, China, 25-May-2026–28-May-2026)
IRG Secretariate
2026
url
https://www.irg-wp.com/irgdocs/details.php?4ff12ed3-7a27-4d19-b167-ea603a796ae3View
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Abstract

Timber engineering Timber durability self-tapping screws preservative treated timber timber degradation withdrawal capacity shear capacity outdoor exposure
Self-tapping screws are increasingly used in Australian timber construction, yet their performance under climate induced degradation in chemically treated timber remains insufficiently quantified. This paper reports a pilot study from a broader programme, examining two preservative systems (H2F and CCA) and two screw coatings (hot dip galvanised, GAL, and Tufcote, TU) under two exposure regimes: full outdoor exposure (FE) and controlled water exposure (WE). Test samples were tested at 0-month (control), 3-month, and 6-month durations. Structural performance was evaluated using screw withdrawal (SW) and screw shear (SS) tests, with density corrected results reported and compared with the latest Eurocode 5 prediction equations. Overall, withdrawal behaviour was more sensitive to exposure. FE led to clear capacity reductions by 6 months in multiple groups, while WE produced mixed responses, including short term gains in some cases that were not always retained at 6 months. Coating and treatment interactions were evident, with TU generally showing larger early reductions under FE. These findings provide preliminary evidence to support environment specific fastener selection and motivate durability informed connection design for Australian treated timber systems.

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