CIB-W18 Timber Structures – A review of meeting 1-43 2 MATERIAL ...

More documents

Recommendations

Info

Figure 2: Test arrangement Summary The tensile strength perpendicular to grain of 187 wood specimens was determined using the test arrangement of EN 1193 (see figures 1 and 2). 53 % of these specimens failed right at the bond line at the intermediate wood. By Finite Element calculations it was shown that stress intensities are evoked at the bond line and the stress distribution in the specimen is non-uniform. An important aim of the project was to determine the correlation of tensile strength perpendicular to the grain with other properties, especially with the density. By separating the largest group of the tangential specimens by the location of rupture, the result was a comparatively high coefficient of correlation for specimens which failed at the joint and a very small coefficient of correlation for those with failure in the wood. One possible hypothesis for this result is based on Weibull's probabilistic fracture theory. It has to be emphasised that the tests were done with nearly clear wood specimens without visible cracks or splits, which often occur in structural size timber. Especially because of cracks, the tensile strength perpendicular to grain in structural timber will be lower than the values given in table 5. 32-6-4 H J Blass, M Schmid Tensile strength perpendicular to grain of glued laminated timber Introduction The tensile strength perpendicular to grain of glued laminated timber according to the European standard EN 1194 is based on the following equation: (1) ft,90,g,k = 0,2 + 0,015 ft,0,l,,k where ft,90,g,k is the glulam strength perpendicular to grain and ft,0,l,k is the tensile strength parallel to grain of the planks. According to Eurcode 5 this characteristic strength ft,90,g,k is related to a reference Volume of V0 = 0,01 m 3 . A test method for determining the tensile strength perpendicular to grain of glulam using this reference volume V0 is given in EN 1193. Test series according to this test procedure are reported by Aicher und Dill-Langer. The material they used was especially produced for their research project. The planed planks of strength class C40 had a constant thickness of 33 mm. Planks including pith were excluded (so called 3x-log sawing, centre boards with pith were sorted out). The aim of the project presented here was to determine the tensile strength of glued laminated timber of different strength classes commonly used in Germany. The material of the test specimens should forma representative sample taken out of numerous beams manufactured by different glulam producers. Conclusions The tensile strength perpendicular to the grain shows no significant correlation with wood density and does not differ for different glulam strength classes. This contradicts EN 1194. The lowest values determined in tests are close to zero. Structural details with tensile stresses perpendicular to the grain should be avoided or the timber should be reinforced perpendicular to the grain. CIB-W18 Timber Structures – A review of meeting 1-43 2 MATERIAL PROPERTIES page 2.132
More important than the volume effect according to Weibull seems to be the presence of macroscopic defects as for example ring shake. Macroscopic defects lead to failures governed by stable crack growth. Based on the test results the volume effect seems to be stronger than assumed by EC5. The exponent k was determined as k = 3 compared to k = 5 given in Eurocode 5. CIB-W18 Timber Structures – A review of meeting 1-43 2 MATERIAL PROPERTIES page 2.133
Page 1 and 2:
CONTENT 2.1 COMPRESSION PERPENDICUL
Page 3 and 4:
23-12-4 H Riberholt, J Ehlbeck, A F
Page 5 and 6:
30-17-1 F Rouger A new statistical
Page 7 and 8:
CIB-W18 Timber Structures - A revie
Page 9 and 10:
2.1 COMPRESSION PERPENDICULAR TO GR
Page 11 and 12:
for solid sawn lumber and glulam ha
Page 13 and 14:
The discussion is supplemented by t
Page 15 and 16:
Figure 3. Load-deformation curves f
Page 17 and 18:
The results indicate a clear affini
Page 19 and 20:
which has been already mentioned ab
Page 21 and 22:
served when testing whole CLT panel
Page 23 and 24:
2) The mechano-sorptive effects in
Page 25 and 26:
and codified; optimised strategies
Page 27 and 28:
36-11-1 R H Leicester, C H Wang, M
Page 29 and 30:
For handling of moisture effects in
Page 31 and 32:
- The short-term tests had a mean m
Page 33 and 34:
criteria, they may offer decisively
Page 35 and 36:
Conclusion The relation between the
Page 37 and 38:
the laminations were determined and
Page 39 and 40:
27-12-3 E Serrano, H J Larsen Influ
Page 41 and 42:
shear stress offered by competing s
Page 43 and 44:
e alarmed when a significant check
Page 45 and 46:
Measurement of shear deflections du
Page 47 and 48:
41-12-2 M Frese, H J Blass Bending
Page 49 and 50:
tures". The Centre Technique du Boi
Page 51 and 52:
By setting γG = γQ1 = γQ2 = …
Page 53 and 54:
ment. For instance, extreme distrib
Page 55 and 56:
method which was commonly used in c
Page 57 and 58:
2.7 LOAD DURATION 6-9-3 T Feldborg,
Page 59 and 60:
son curve", derived from small clea
Page 61 and 62:
19-9-4 U Korin Non-linear creep sup
Page 63 and 64:
24-9-1 T Toratti Long term bending
Page 65 and 66:
Summary Based on the analysis of th
Page 67 and 68:
when a dry period is followed by a
Page 69 and 70:
- Jansson and Leijten both demonstr
Page 71 and 72:
- The used methods and technologies
Page 73 and 74:
ISO, generally through the technica
Page 75 and 76:
ed. The significance of the choice
Page 77 and 78:
However, there is another equally i
Page 79 and 80:
25-17-3 D W Green, J W Evans Moistu
Page 81 and 82: tion of settings. Since this proced
Page 83 and 84: posed approach is that the reliabil
Page 85 and 86: Conclusion It was concluded that th
Page 87 and 88: - The difference between E in edge
Page 89 and 90: On the basis of long-term experienc
Page 91 and 92: Conclusions The possibilities of vi
Page 93 and 94: Finland and Norway). Consequences w
Page 95 and 96: Fig. 1. A wind-induced compression
Page 97 and 98: emphasis on the modelling of the ef
Page 99 and 100: some trends are apparent. Based on
Page 101 and 102: - A higher COV of the raw material
Page 103 and 104: Visual grading of wood into strengt
Page 105 and 106: 4 X(1 � X) Y �1� X � 3s�1
Page 107 and 108: F112 and F122. It is however shown
Page 109 and 110: strength tends to increase with ris
Page 111 and 112: y assuming a normal distribution. E
Page 113 and 114: 19-12-3 F Colling Influence of volu
Page 115 and 116: - WF/Ww: 2:1 The single span three
Page 117 and 118: 40-6-2 M Poussa, P Tukiainen, A Ran
Page 119 and 120: 2.12 SIZE AND CONFIGURATION FACTORS
Page 121 and 122: While the estimates of the size eff
Page 123 and 124: ters for all grades and species. Si
Page 125 and 126: Modelling of length-wise distributi
Page 127 and 128: different things that affect the si
Page 129 and 130: sponds to the statistical approach
Page 131: fects. As a summary we may, for the
show all

CIB-W18 Timber Structures – A review of meeting 1-43 2 MATERIAL ...

Create successful ePaper yourself

Delete template?

Save as template?