Bienvenue

1
Effect of moisture content variation on short
term dowel-bearing strength
Nicolas SAUVAT, Octavian POP, Seddik MERAKEB,
Frédéric DUBOIS
Laboratory ()GEMH, University of
Limoges Egletons, France
() Heterogeneous Material Research Group Civil
Engineering and Durability Team
frederic.dubois_at_unilim.fr
2
Effect of moisture content variation on short
term dowel-bearing strength

• Scientific context
• Materials and methods
• Instantaneous tests
• Short term tests
• Conclusions and remarks

3
Scientific Context

• Timber structures under climatic environment

• Effects of
• Duration of loading
• Moisture content variations
• Moisture content history
• Creep evolution
• Structure ageing

4
Scientific Context

• Timber joint behavior under climatic environment

5
Scientific Context

• Dowel bearing vs moisture content, an
  experimental contribution

Moisture
Time

• Instantaneous tests on green to dry wood, with
  natural drying
• Short term tests with 2 initial moisture
  contents, and 2 service conditions

6
Materials and methods

• Experimental setup

Zwick testing machine with a climatic chamber
Douglas fir specimen
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Materials and methods

• Loading procedure Instantaneous tests

1
max,est
F / F
0,8
0,6
0,4
0,2
0
0
120
240
360
480
600
720
Force-controlled pre loading
Time (s)
8
Materials and methods

• Loading procedure Short term tests

1
max,est
F / F
0,8
5 days
0,6
0,4
0,2
0
Force-controlled pre loading
360 s
Time
9
Materials and methods

• Wood specimens

width
d
Specie Douglas fir (France)
Direction parallel to fiber
Instantaneous tests
Short term tests
Geometry
d 8 mm
d 8, 14 and 20 mm
7 d
Width 2 d and 4 d
Width 2 d
Repetition 2 2
Repetition 5
6 d
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Materials and methods

• Moisture content conditions

Instantaneous tests
Short term tests

• 2 hygrothermal conditions are used for initial
  stabilization and service conditions
• 20C and 70 Hr
• 30C and 90 Hr

Regularly cut from green to dry
Testing condition 25C and 60 - 70 Hr
Seasoned Dry condition Unseasoned Wet
condition Seasoned Wet condition Unseasoned
Dry condition
Low moisture High moisture Moistening Drying
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Instantaneous tests

• 4 examples / w

20
13
30
12
Instantaneous tests
13
Instantaneous tests

• No effect of width homogeneous moisture content

14
Instantaneous tests

• Failure type

14
19
15
Short term tests

• Moisture content history

1- Seasoned Dry condition 2- Unseasoned Wet
condition 3- Seasoned Wet condition 4-
Unseasoned Dry condition
Low moisture High moisture Moistening Drying
16
Short term tests

• Creep response

(Average values)
uinst
17
Short term tests

• Relative differed displacement during creep phase

(Average values)
Softening effects
Hardening effect (mechano-sorption)
18
Short term tests

• Moisture content history effects on bearing
  strength

1- Seasoned Dry condition 2- Unseasoned Wet
condition 3- Seasoned Wet condition 4-
Unseasoned Dry condition
Low moisture High moisture Moistening Drying
Bearing strength only dependent on service
condition No effect of initial moisture
content. No effect of a 5 days creep
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Short term tests

• Moisture content history effects on bearing
  strength

Max strength and failure dependent on final
condition
20
Conclusions and remarks

• Instantaneous tests

Dowel bearing strength reduction according to an
increase of moisture content Failure type can be
crushing or splitting according to moisture
content
21
Effect of moisture content variation on short
term dowel-bearing strength
Nicolas SAUVAT, Octavian POP, Seddik MERAKEB,
Frédéric DUBOIS
Thanks for your attention
Laboratory ()GEMH, University of
Limoges Egletons, France
() Heterogeneous Material Research Group Civil
Engineering and Durability Team
frederic.dubois_at_unilim.fr