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Johan Hans Jönsson
Internal stresses in glulam due to moisture gradients in the grain direction
Keywords: contact free measuring technique, cross-grain direction, glulam, internal stress, moisture gradients, released deformation, slicing technique
An experimental study on the internal stress state perpendicular to grain in glued laminated timber induced by moisture variations along the grain is presented. The stress is evaluated by using measured modulus of elasticity and strain. Different types of tests are performed, in which specimens are exposed to artificial climate change when the specimens are in either a wetting or a drying state, and specimens are exposed to a cyclic climate change. Test results from the specimens that were in a drying state show that the tensile stresses near the end of the specimens at some point exceeds the strength of the wood and cracks. In the opposite test, when the specimens are in a moistening phase, the maximum tensile stresses are lower and in the order of 0.2 MPa during the tested period. The cyclic test, which continued during 20 weeks, showed that there were no accumulated effects regarding strain and stress values. In this test, the average maximum tensile and compression stresses were of the order 0.20 and 0.10 MPa, respectively.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 59, 01/2005
Pages: 18 - 22