2004 Decay of timber and its mechanical characteristic 1075015
1075015 1. 1 1. 2. 3. 4. 5. 4.5. 2. JIS 3. 3.1 3.1.1 ( ) ( ) i
3.1.2 3.1.3 10 3.2 ( 3% ) 4 3% ii
Decay of timber and its mechanical characteristic Kochi University of Technology Dept. of Infrastructure Systems Engineering 1075015 Michihiro ENDOU 1. Objectives Recently, needs for timber structures have increased because they are human-friendly and eco-friendly. The timber is expected as the material that can achieve the sustainable development. However, in case of using the timber as structural material, it has some problems as follows; 1. Cost 2. Fire resistance 3. Decay of timber 4. Variations in mechanical characteristic 5. Anisotropic of the material Regarding No. 4 and 5, there are many studies and they are solved practically by the laminated timber technology. However, there are little data on the mechanical characteristics of the decayed timber. The lack of the data mentioned above may be one of the major reasons that reduce the reliability of the timber structures. 2. Research procedure In this research work, only Japanese cedar is studied, because the forests of Japanese cedar are the serious environmental problem in Kochi and the utilization of cedar is required urgently. Test piece making, decaying process and loading test are carried out, following JIS regulations with some modification. The flow of research is as follows; Test piece making Loading test on the timber before decay Decaying Loading test on the timber after decay 3. Test results 3.1 Mechanical characteristic of timber before decay 3.1.1 Unit weight and strength iii
It is generally said that the strength of timber is strongly associated with the unit weight. The loading test shows that the correlation between the strength and unit weight is high only in the fibrous direction. Regarding the strength in other direction, the effect of the ration of the latewood to the earlywood in volume is larger than the effect of the unit weight. 3.1.2 Fracture mode Several different fracture modes are observed in the test, even if they are loaded in the same way. For example, if there is some eccentricity in load, the stress concentration occurs at some area and only the earlywood breaks and the whole test piece crashes finally. In the case that the force is loaded uniformly, the test piece breaks in the mode of split-off. Because of the difference in fracture mode, the strengths of the test pieces show the large scattering. 3.1.3 Load direction and yield stress Yield stress and Young s modulus in fibrous direction are about ten times of those in other directions. Therefore, in the structural design of the timber structure, the timber should be used so that the major loads act in the fibrous direction. 3.2 Effect of decay The level of the decay was judged by the reduction in weight. The results of the weight measurement do not necessarily agree with the appearance of the test pieces. In this study, the decaying process was not successful and the sufficient numbers of decayed test pieces were not obtained. The reduction in the yield stress and Young s modulus of decayed test pieces are significantly large. 4 Conclusion The strength of timber is strongly associated with weight in the fibrous direction. The ration of earlywood to latewood in volume affects the strength in other directions. There are several different fracture modes, even in the test pieces are loaded in the same way. The level of decay is difficult to estimate from the appearance. The effect of decay on mechanical characteristics is large. iv
Abstract iii i 1 1.1 1 1.2 2 1.3 2 1.4 3 2 2.1 4 2.1.1 4 2.1.2 4 2.1.3 5 2.1.4 5 2.2 2.2.1 2.2.1.1 5 2.2.2 6 2.2.3 6 2.2.4 8 2.2.5 9 2.2.6 11 2.2.7 11 2.3 2.3.1 12 2.3.2F 14 2.3.3 14 2.3.4 14 2.3.5 18 2.3.6 20 3 3.1 22
3.1.1 22 3.1.2 23 3.2 25 3.3 25 3.3.1 3.3.1.1 26 3.3.1.2 26 3.3.1.3 26 3.3.2 3.3.2.1 26 3.3.2.2 26 3.3.3 3.3.3.1 28 3.3.3.1 28 4. 31 4.1.1 31 4.1.2 31 4.1.3 31 4.1.4 32
1 15% 4 2 5 1No 6 2No 6 3No 6 4No 6 5No 6 6No 6 7No 7 1 2 9 8 10 3 10 9 11 10 11 4 12 11( ) 12 12( ) 13 3 4 No 14 5 No 14 6 No 14 5 15 6 16 7 7 No 16 8 No 16 9 No 16 10 No 17 11 No 17
12 No 17 13 18 14 18 8 20 9 20 10 20 15 No 20 16 No 20 17 No 21 18 No 21 19 No 21 20 No 21 21 No 21 22 No 22 23 No 22 24 No 23 25 No 23 26 No 24 27 No 24 28 No 24 29 No 25 30 No 25
1. 1.1 1 97% 3% 1. 2. 3. 4. 5. 1,3,4,5 1. 4.5. 4.5. 1
JIS 3. 1.2 2 1.3 S2 S1 S3 S2 S3 S2 S3 2
1 H 1.4 1.1 3
2. 2.1 2.1.1 2 10 110 2.1.2 3 3 6 3 3 6 3 4
2.1.3 2 10 4(ABCD) 1)3 120 10 4(ABCD) 3 120 10 4(ABCD) 1 40 1) 2.1.1 ABCD 4 2.1.4 JIS ( ) 2.2.4 17 202040 mm 202030( 102010) 3202020 2.2 2.2.1 2.2.1.1 15% 15% 1 1 ABCD 4 2 ABCD 10 ( 20 ) A B A 1 15% 5
= m / v a a a 1 a: (g/cm 3 )ma: (g)va: (cm 3 ) 2 2.2.2 0 3 No. No. No. 2.2.3 ( mm) 17 6
1No 2No 3No 4No 5No 6No 7
7No 2.2.4 20 70 15 10 10 7 7 10 10 1 1 8
2.2.5 JIS JIS (1) (2) 9.8N/mm 2 4.52N/mm 2 4 (3) (20mm)1/2 23 PpPm 2.3 (1)(3) 3 Ε c = Ρl lα (1) σ cp Ρ = p Α (2) σ c Ρ = m Α (3) Ec: (N/mm 2 ) cp: (N/mm 2 ) c: (N/mm 2 ) P: (N) l: (mm) l: P (mm) 9
A: (mm 2 ) Pp: (N) Pm: (N) (1) (2) 45 2 (3) 0.49N/mm 2 0.38N/mm 2 4 (4) (20mm)1/2 (1)(2) 3 Ε c90 Ρl = lα (1) σ cp90 Ρ = p Α (2) Ec90: (N/mm 2 ) cp90: (N/mm 2 ) P: (N) l: (mm) l: P (mm) A: (mm 2 ) Pp: (N) 2 2 10
2.2.6 (1) 8 8 (2) 5.88N/mm 2 3.92N/mm 2 3.32N/mm 2 (3) ( ) 3 τ Ρ = m Α (1) : (N/mm 2 ) Pm: (N) A: (mm 2 ) 3 3 2.2.7 (1) a: 20mm 14 280mm 11
(2) (3) 9 10 9 10 (4) 14.7N/mm 2 9.15N/mm 2 3 (1)(3) 3 Ε b = 3 Ρl 48Ι y (1) σ bp Ρ l p = 4Z (2) σ b Ρ l m = 4Z (3) Eb: (N/mm 2 ) bp: (N/mm 2 ) b: (N/mm 2 ) P: (N) 12
: P (mm) 3 bh I: 2 Ι = (mm 12 4 ) l: (mm) b: (mm) h: (mm) 3 bh Z: Z = (mm 3 ) 6 Pp: (N) Pm: (N) 4 4 2.3 2.3.1 1112 11 12 2% 0.8mm(11 ) 11 ( ) 13
12 ( ) 2.3.2F (F ) F F 2.3.3 3 3 2.3.4 14
46 79 2.3.3 (A,B,C,D ) 4 No 5 No 6 No 13No 14No 15
15No No No 10 o N No No No F 2 No No F (No) ) (No) No C,D F C,D C,D 16
No ( 5... ) ( 6 ) ( 7 ) ( ) 5 6 17
7 7 No 8 No 9 No No No 2.3.5 1012 18
10 No 11 No 12 No No ( ) No No, 16No 17No 19
18No No No No 2.3.6 1314 13 14 20
19No F C-D A-BB-C 21
3 3.1 3.1.1 JIS 1 2 1 2 (1): 280 JIS 50100cm 2 500800ml 555cm 2 9800ml 8 (2) 2500gpH5.56.0 (3)800ml (4) (2) : JIS K 8222 1 1 (3) : 4% 0.3% 1.5% JIS K 8824 1 (4) : 120 30 800ml 0.149mm 2.4g 2 26 ± 2 30ml 26 ± 2 70% 1 26 ± 2 70% 22
JIS 2 2 1 57 8 9 10 3.1.2 1521 () 15 No 16 No 23
17 No 18 No 19 No 20 No 21 No 5 3% ( ) 3% 24
3.2 3.3 3% 3.3.1 3.3.1.1 No B 4 No B 1 No 1 5, 3.3.1.2 3% ( ) 2223 22 No 23 No 25
No F No B 8% F 3.3.1.3 2425 24 No 25 No No 3.3.2 3.3.2.1 3.3.2.2 2628 26
26 No 27 No 28 No 20No A 21No C No,, No A 7% 78%C 5% 64%No A 4% 69%D 7% 50% No 27
3.3.3 3.3.3.1 ), 3.3.3.2 ABC D 2930 29 No 30 No 28
22No A 23No B 24No C D No A 6% 47% 47%B 4% 36% C 6% 40% 14% A 3 B 1.5 C 2 29
30
4. ( ) 4.1.1 = 4.1.2 4.1.3 (No) (No) (No) 10 4.1.4 31
( ) 1 2 32
33
1 1 510 34
: 2 No 3 No 4 No 5 No 6 No 7 No 8 No 35
: 9 No 10 No 11 No 12 No 13 No 14 No 15 No 36
: 16 No 17 No 18 No 19 No 20 No 21 No 22 No 37
( ) 23 No 24 No 25 No 26 No 27 No 28 No 38
( ) 29 No 30 No 31 No 32 No 39
( ) 33 No 34 No 35 No ( ) 36 No 37 No 40
38 No ( ) 39 No 40 No ( ) 41 No 42 No 41
V n n 1 s 2 1 = V1: n: s: V 2 n = n 1 s 2 V2: V F 0 = V 2 1 F 43F )F0 F 44 ( ) 45 ( ) 46 ( ) 42
47 (No No ) 48 (No No ) 1 49 ( ) 50 ( ) 17 1 No 2 No 43
3 No 4 No 5 No 6 No 7 No 44
8 8 ( ) 45
3 46
7. 4 2004/03/30 1980/2/26 1963/4/20 JIS http://www.jisc.go.jp/ http://members.jcom.home.ne.jp/souzounakano/wood-b.html 47