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Abstract
In this study, varying ambient climates were simulated in a test building by changing temperature and relative humidity. Beech glued laminated timber (glulam, Fagus sylvatica, L.) was freshly installed in the test building and monitoring of the change in wood moisture content of the glulam resulting from the variations in climate was carried out. Subsequently, finger-jointed beech specimens were exposed to the variations in relative humidity measured in the course of the monitoring experiment on a laboratory scale, and thus an alternating climate regime was derived from the conditions in the test building. Its influence on the delamination of the finger-joints was evaluated. In addition, it was examined whether beech finger-joints using commercial adhesive systems fulfil the normative requirements for delamination resistance according to EN 301 (2018) and whether different bonding-wood moisture levels have an effect on the delamination of the finger-joints. In the context of the monitoring experiment, there was a clear moisture gradient in the beech glulam between the inner and near-surface wood. The applied adhesive systems showed almost the same delamination resistance after variation of relative humidity. The normative requirements were met by all PRF-bonded and by most PUR-bonded beech finger-joints with higher bonding wood moisture content.
Highlights
Extreme climatic conditions often exist during the application phase of timber construction products [1] and especially during transport to or installation on the construction site
References [6,7,8] showed that individual adhesive systems can fulfil the normative requirements for delamination resistance, but their results were, at the same time, dependent on a large number of parameters
Various one-component polyurethane and two-component aminoplast adhesive systems used for finger-jointing beech and oak showed negative results compared to the normative requirements for delamination resistance [6]
Summary
Extreme climatic conditions often exist during the application phase of timber construction products [1] and especially during transport to or installation on the construction site. Since wood construction products are almost exclusively made of coniferous wood and in particular of Norway spruce (Picea abies, L.) [3], the delamination test is designed for spruce [4,5] Hardwood bondings such as those of beech, the most abundant hardwood in Central Europe, are tested according to the standard designed for spruce, and currently there are only adapted requirements for the hardwood species oak (Quercus spp.) [4]. References [6,7,8] showed that individual adhesive systems (partly without proof of applicability for hardwood) can fulfil the normative requirements for delamination resistance, but their results were, at the same time, dependent on a large number of parameters. The integration of adhesive systems and bonding technology is essential for this
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