1 Introduction
2 Literature review on relationship of compressive strength and wood moisture content
2.1 Present code provisions
2.1.1 European timber design code
2.1.2 US code provisions
3 Review of published tests
3.1 Small and medium sized clear specimens
Reference detailsa
| Reference strength | Moisture modification factors
\(k_{moist, mean, green} (u)\)
| |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Species – | Moisture % | Density kg/m\(^3\)
|
\(\rho _0\)
kg/m\(^3\)
|
A MPa |
C
MPa |
\(B=b\)
% |
a
– |
c
– |
\(f_{c,0,dry}\)
MPa | 18 % – | 24 % – | 30 % – | 50 % – |
Roš (1936), Fig. 20. | |||||||||||||
spb
| 0;18; >30 | 300–500 | 400 | 54.5 | 16.1 | 0.076 | 1.342 | 0.423 | 38.1 | 0.79 | 0.66 | 0.57 | 0.46 |
wfc
| 0;18; >30 | 300–500 | 450 | 65.9 | 18.0 | 0.077 | 1.492 | 0.408 | 44.2 | 0.78 | 0.64 | 0.56 | 0.44 |
Roš (1936)), Fig. 22. | |||||||||||||
spb
| 0;18; >30 | 300–500 | –d
| 29.6 | 19.2 | 0.064 | 0.898 | 0.583 | 33.0 | 0.87 | 0.78 | 0.71 | 0.62 |
Kollmann (1955), Fig. 652. | |||||||||||||
spb
| 0–100 | –d
| –d
| 111.4 | 19.7 | 0.117 | 2.367 | 0.419 | 47.1 | 0.71 | 0.56 | 0.49 | 0.43 |
Kühne et al. (1955), Fig. 9a. | |||||||||||||
spb
| 0–160 | 400–450 | 400 | 61.1 | 18.1 | 0.090 | 1.571 | 0.465 | 38.9 | 0.78 | 0.65 | 0.57 | 0.48 |
wfc
| 0–160 | 400–450 | 450 | 88.6 | 24.0 | 0.118 | 1.948 | 0.528 | 45.5 | 0.76 | 0.64 | 0.58 | 0.53 |
spb,e
| 6–22 | 330–660 | 400 | 95.0 | 19.8 | 0.126 | 2.329 | 0.485 | 40.8 | 0.73 | 0.60f
| 0.54g
| 0.49g
|
spb,e
| 6–22 | 330–660 | 450 | 100.7 | 18.7 | 0.104 | 2.116 | 0.393 | 47.6 | 0.72 | 0.57f
| 0.49g
| 0.40g
|
Averageh
| – | – | 425 | 75.9 | 19.2 | 0.097 | 1.758 | 0.463 | 41.9 | 0.77 | 0.64 | 0.56 | 0.48 |
3.2 Full sized pile specimens
4 Materials, specimens, and test program
4.1 Log material
4.2 Pile specimens
4.3 Small clear specimens
5 Conditioning and moisture content of specimens
6 Compression tests parallel to the fiber
6.1 Small clear specimens
6.2 Pile specimens
7 Test results for small clear specimens
7.1 Data and observations
Physical, mechanical property or ratio | Statistical quantity | Small scale clear wood specimens | |||
---|---|---|---|---|---|
Dry (MC = 12 %) | Green (MC \(>\) 30 %) | ||||
Specimen type | Specimen type | ||||
DIN 52185 | EN 408 | DIN 52185 | EN 408 | ||
No. of specimens tested | 42 | 42 | 42 | 42 | |
No. of specimens used for evaluation | 35 | 38 | 35 | 38 | |
Moisture content in % |
\(x_{mean}\) (COV in %) | 13.9 (1.9) | 13.9 (2.5) | 200 (16) | 181 (18) |
Compressive strength \(f_{c, 0}\) in MPa |
\(x_{mean}\) (std) | 44.3 (9.9) | 41.6 (8.5) | 21.9 (5.4) | 20.1 (4.4) |
COV in % | 22.4 | 20.3 | 24.7 | 22.0 | |
\(x_{min}\)
| 30.2 | 29.0 | 14.6 | 12.5 | |
\(x_{max}\)
| 72.4 | 60.7 | 36.4 | 31.2 | |
\(x_{05}\)
| 29.3 | 28.4 | 13.9 | 13.0 | |
Density \(\rho _{12}\) in kg/m\(^3\)
|
\(x_{mean}\) (std) | 442 (75) | 442 (58) | 439 (64) | 442 (60) |
COV in % | 16.9 | 13.0 | 14.7 | 13.6 | |
\(x_{min}\)
| 349 | 334 | 353 | 348 | |
\(x_{max}\)
| 653 | 580 | 659 | 604 | |
\(x_{05}\)
| 326 | 347 | 337 | 344 | |
Compressive strength ratio
\(f_{c, 0, EN}/f_{c, 0, DIN}\)
| at \(x_{mean}\) level | 0.94 | 0.95 | ||
at \(x_{05}\) level | 0.97 | 0.94 |
7.2 Evaluation of moisture impact
Specimen size | Specimen type | MOR and MOE ratios | |||
---|---|---|---|---|---|
\(k_{moist, green}\;=\;\frac{f_{c, 0, green}}{f_{c, 0, dry}}\)
|
\(\dfrac{E_{c, 0, green}}{E_{c, 0, dry}}\)
| ||||
\(x_{mean}\)
|
\(x_{05}\)
|
\(x_{min}\)
|
\(x_{mean}\)
| ||
Small defect free | DIN 52185 | 0.49 | 0.47 | 0.48 | – |
EN 408 | 0.48 | 0.46 | 0.43 | – | |
Structural sized | Round wood | 0.57 | 0.66 | 0.60 | 0.89 |
8 Test results for the pile specimens
8.1 Data and observations
Physical, mechanical property or ratio | Statistical quantity | Moisture state of specimen | Ratio | |
---|---|---|---|---|
Dry | Wet | Wet/dry | ||
No. of specimens tested | 17 | 17 | 17 | |
Moisture content in % |
\(x_{mean}\)
| 12.5 | 89.4 | |
Pile diameter at failure plane \(d_f\) in mm |
\(x_{mean}\)
| 214 | 196 | |
Bottom/top diameter \(d_{bottom, top}\) in mm |
\(x_{mean}\)
| 220/205 | 204/190 | |
Compressive strength \(f_{c, 0}\) in MPaa
|
\(x_{mean}\)
| 30.8 | 17.6 | 0.57 |
std(x) | 6.1 | 2.3 | ||
COV in % | 19.8 | 13.1 | 0.66 | |
\(x_{05}\)
| 20.3 | 13.4 | 0.66 | |
\(x_{min}\)
| 21.9 | 13.3 | 0.60 | |
\(x_{max}\)
| 39.9 | 21.0 | 0.53 | |
Density \(\rho _{12}\) in kg/m\(^3\)
|
\(x_{mean}\)
| 453 (48) | 447 (34) | 0.99 |
COV in % | 10.6 | 7.5 | 0.71 | |
\(x_{min}\)
| 398 | 389 | 0.98 | |
\(x_{max}\)
| 566 | 550 | 0.97 | |
\(x_{05}\)
| 370 | 387 | 1.05 | |
MOE E
c
,0
a in GPa |
\(x_{mean}\)
| 12.1 | 10.7 | 0.89 |
std(x) | 1.9 | 1.6 | ||
COV in % | 15.9 | 14.9 | 0.93 | |
\(x_{05}\)
| 8.6 | 7.9 | 0.92 | |
\(x_{min}\)
| 8.9 | 7.7 | 0.87 | |
\(x_{max}\)
| 15.0 | 14.3 | 0.95 |