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

23-6-1 U Korin
Timber in compression perpendicular to grain
Summary
The compressive strength of timber perpendicular to grain was investigated.
The study reports tests conducted on whitewood specimens 40 mm x
90 mm x 180 mm in size in central loading or end loading for varying
lengths of loading sectors l/L. Upgrading experiment of bearing capacity
of the timber by Nail-plates reinforcement was found to be unsuccessful.
Discussion and Conclusions
1 It is necessary to agree on a clear strength-bearing capacity criterion for
timber in compression perpendicular to gain.
2 Eurocode 5 brings a parameter Kc,90:
�c,90, d � Kc,90 fc,90,
d
Kc,90 depends upon the length of the overhangs of the loaded member.
The following table presents a comparison between the values of Kc,90
calculated for the loading conditions in this investigation and the experimental
results of this investigation. The differences between the compared
values are very large and should be further studied.
3 The investigation covered so far only one kind of timber and one cross
section (d/b=2). There is a room for a much wider investigation on the
subject.
Table 2 Comparison between Kc,90 and experimental results.
l/L Central Sector loaded End sector loaded
Kc Experimental
results
Kc Experimental
results
1 1 1 1 1
0.875 1 1.063 1 1.063
0.75 1.006 1.188 1 1.156
0.625 1.025 1.375 1 1.281
0.50 1.061 1.625 1 1.438
0.375 1.124 1.969 1 1.625
0.25 1.237 2.344 1 1.875
0.125 1.478 2.781 1 2.156
27-6-1 C Lum, E Karacabeyli
Development of the "critical bearing" design clause in CSA-086.1
Abstract
There are currently inconsistencies in the compression perpendicular-tograin
(C-perp) design procedures in the Canadian code for Engineering
Design In Wood, CSA-086.1-M89. For example, a single specified design
value is given for a species group irrespective of the loading condition, or
the lumber grade. On the other hand, different values are assigned to
Douglas-fir lumber and Douglas-fir glulam (glued-laminated timber). These
inconsistencies not only make the design code confusing to designers,
but they also hinder the introduction of appropriate C-perp strength values
for products such as machine stress rated lumber. A research program focused
on resolving these inconsistencies in the C-perp design procedures
CIB-W18 Timber Structures – A review of meeting 1-43 2 MATERIAL PROPERTIES page 2.10