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The effect of moisture gradients on tensile strength perpendicular to grain in glulam

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Abstract

Experimental results are presented concerning tension perpendicular to grain in glulam sections where internal stresses induced by climate changes are present. The results reveal that moisture induced internal stresses may affect the tension capacity both in a positive and a negative way compared to reference specimens, free from moisture gradients. The tension capacity is reduced during moistening from RH 40% up to RH 80% whereas it is increased during drying from RH 80% to 40%. The tension capacity during wetting is only 50% of that observed for drying specimens. This behaviour can be explained by the combination between initial moisture induced stresses and stresses from external loading. The same tendency was observed for specimens exposed to cyclic climate changes, where it was also found that time and numbers of cycles do not affect the tension capacity in any specific direction.

Zusammenfassung

Es werden experimentelle Ergebnisse präsentiert, betreffend der Zugfestigkeit senkrecht zur Faser in Glulamabschnitten, in denen durch Klimaänderungen induzierte interne Spannungen vorhanden sind. Die Ergebnisse zeigen, dass durch Feuchte induzierte interne Spannungen die Zugkapazität sowohl positiv als auch negativ beeinflussen können im Vergleich zu Kontrollproben, die frei von Feuchtegradienten sind. Die Zugkapazität wird während des Feuchtevorgangs von 40% bis zu 80% relative Feuchte reduziert, wobei sie sich während der Trocknung von RH 80% auf 40% erhöht. Die Zugkapazität während des Befeuchtens beträgt nur 50% derjenigen, die bei der Probentrocknung beobachtet wird. Dieses Verhalten kann durch die Kombination zwischen initial feuchte-induzierten Spannungen und Spannungen von externer Belastung erklärt werden. Die gleiche Tendenz wurde bei Proben beobachtet, die Wechselklima ausgesetzt waren, wobei man auch herausfand, dass Zeit und Anzahl der Wechsel die Zugkapazität nicht in irgendeiner bestimmten Richtung beeinflussten.

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  1. Div. of Structural Engineering, Lund University, Box 118, 221 00, Lund, Sweden

    J. Jönsson & S. Thelandersson

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  1. J. Jönsson
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  2. S. Thelandersson
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Correspondence to J. Jönsson.

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Jönsson, J., Thelandersson, S. The effect of moisture gradients on tensile strength perpendicular to grain in glulam. Holz Roh Werkst 61, 342–348 (2003). https://doi.org/10.1007/s00107-003-0405-6

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  • DOI: https://doi.org/10.1007/s00107-003-0405-6

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