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Mechanical Behaviour of Wood Exposed to Humidity Variations.

Mårtensson, Annika LU (1992) In TVBK-1006
Abstract
The effects on wood of simultaneous mechanical and moisture loading are studied. In order to clarify the mechano-sorptive behaviour of wood, a review of different phenomena presented in the literature is included. Compressive tests have been performed on spruce. The tests have been performed with both constant load and varying load. The humidity has been varied during the tests. The properties of the material used have been investigated both before and after the main testing was performed. Based on the review of mechano-sorptive phenomena and the test results presented in this study, a constitutive model is developed. The model was quantified on the basis of test results presented both in this thesis and in the literature. The validity of... (More)
The effects on wood of simultaneous mechanical and moisture loading are studied. In order to clarify the mechano-sorptive behaviour of wood, a review of different phenomena presented in the literature is included. Compressive tests have been performed on spruce. The tests have been performed with both constant load and varying load. The humidity has been varied during the tests. The properties of the material used have been investigated both before and after the main testing was performed. Based on the review of mechano-sorptive phenomena and the test results presented in this study, a constitutive model is developed. The model was quantified on the basis of test results presented both in this thesis and in the literature. The validity of the model was checked

independently against other tests. Finally a number of practical load situations were studied.

In these simulations both humidity and load were varied.

The calculations show that the model is capable of describing the response of wood with reasonable accuracy. The simulations indicate that the response of small test specimens is more difficult to describe than that of larger beams. Some differences in behaviour are found to depend on loading mode and nature of moisture cycling. Very large and fast moisture cycles seem to give larger mechano©sorption than smaller variations. The results of the simulations show that there is a significant influence of strain on the shrinkage and swelling response.



Studies of the effect of varying load show that a temporarily applied load has little effect on

the long term deflection of structural timber. A simulation of snow load variation shows that

the long term deflections are rather small in comparison with the case when the characteristic

load is assumed to be constant over time. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Ranta-Maunus, Alpo, VTT, Finland
organization
publishing date
type
Thesis
publication status
published
subject
keywords
KstrWood
in
TVBK-1006
pages
189 pages
publisher
Structural Engineering, Lund University
defense location
John Ericssons väg 1
defense date
1992-06-01 10:00
ISSN
0349-4969
language
English
LU publication?
yes
id
db9df985-2dac-494a-a5fc-3c282ef3af13 (old id 933293)
date added to LUP
2011-02-17 16:40:33
date last changed
2016-09-19 08:44:56
@phdthesis{db9df985-2dac-494a-a5fc-3c282ef3af13,
  abstract     = {The effects on wood of simultaneous mechanical and moisture loading are studied. In order to clarify the mechano-sorptive behaviour of wood, a review of different phenomena presented in the literature is included. Compressive tests have been performed on spruce. The tests have been performed with both constant load and varying load. The humidity has been varied during the tests. The properties of the material used have been investigated both before and after the main testing was performed. Based on the review of mechano-sorptive phenomena and the test results presented in this study, a constitutive model is developed. The model was quantified on the basis of test results presented both in this thesis and in the literature. The validity of the model was checked<br/><br>
independently against other tests. Finally a number of practical load situations were studied.<br/><br>
In these simulations both humidity and load were varied.<br/><br>
The calculations show that the model is capable of describing the response of wood with reasonable accuracy. The simulations indicate that the response of small test specimens is more difficult to describe than that of larger beams. Some differences in behaviour are found to depend on loading mode and nature of moisture cycling. Very large and fast moisture cycles seem to give larger mechano©sorption than smaller variations. The results of the simulations show that there is a significant influence of strain on the shrinkage and swelling response. <br/><br>
<br/><br>
Studies of the effect of varying load show that a temporarily applied load has little effect on<br/><br>
the long term deflection of structural timber. A simulation of snow load variation shows that<br/><br>
the long term deflections are rather small in comparison with the case when the characteristic<br/><br>
load is assumed to be constant over time.},
  author       = {Mårtensson, Annika},
  issn         = {0349-4969},
  keyword      = {KstrWood},
  language     = {eng},
  pages        = {189},
  publisher    = {Structural Engineering, Lund University},
  school       = {Lund University},
  series       = {TVBK-1006},
  title        = {Mechanical Behaviour of Wood Exposed to Humidity Variations.},
  year         = {1992},
}