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positive effects on the load-carrying capacity in grain direction than in
force direction perpendicular to the grain. Therefore the presented structural
model corresponds with experimental results.
Exceptions are perpendicular to the grain loaded joints on structural
members with low girder depth (approx. H < 30 cm). Here the low stiffness
results in compressing cracks with a lower distance from the loaded
edge. The consequence is an overestimation of the load-carrying capacity.
The numerical model also supplies an overestimation of the fracture loads
of perpendicular to the grain loaded joints arranged above the axis of gravity.
For such joint configurations other failure criteria become authoritative.
35-7-9 M Yasumura
Determination of fracture parameter for dowel-type joints loaded perpendicular
to wooden grain and its application
Introduction
During the CEB-W 18 Meeting in Delft, 2000, a formula to predict the lateral
capacity of dowel-type joints loaded perpendicular to the wooden
grain was proposed (Paper 34-7-9). This formula includes what we call
the "fracture parameters" consisting of G and Gc. Instead of applying individual
material properties of G and Gc which are difficult to determine
from the material tests, fracture parameters will be obtained by conducting
simple tension test of dowel-type joints consisting of a single or multiple
dowel fasteners. This study proposes the test method to determine the fracture
parameter for dowel-type joints loaded perpendicular to the wooden
grain. Tension tests of dowel-type joints were conducted with different
edge and end distances, and the suitable configuration of specimen and
dowel disposition are proposed with the aid of FE analysis. The obtained
fracture parameters were applied to validate the formula for predicting the
failure load of dowel-type joints.
36-7-7 M Ballerini, A Giovanella
Beams transversally loaded by dowel-type joints: Influence on splitting
strength of beam thickness and dowel size
Abstract
The paper reports the results of a new set of experimental tests on beams
loaded perpendicular-to-grain by dowel-type connections. The experimental
programme consists of two different test series. The first one,
which concerns large specimens with multiple dowel connections, has
been performed essentially to investigate the actual influence of the beam
thickness on the splitting strength. The second one, which involves smaller
specimens with single dowel joints, has been carried out to confirm the
soundness of the results of a previous research and to demonstrate the limited
effect of the connection strength on the splitting resistance of beams.
The experimental results of both test series are illustrated and discussed
with reference also to the results of previous research. Finally, the failure
loads are compared with the bearing capacity predicted by the final drafts
of the new European and German design codes for timber structures.
Conclusions
The results of a new experimental programme on the splitting strength of
beams loaded perpendicular to the grain by dowel type connections, performed
to investigate the actual influence of the thickness of the beams
and of the fasteners size, have been illustrated and discussed in detail.
The main features of this experimental research are the dimensions of
the beams of the first series (800 mm high beams with a width ranging
form 80 to 200 mm), and the size of fasteners' diameter.
The analysis of the results allows the following statements:
– the tests data show that beam thickness affects linearly the splitting
strength;
– the tested joint configurations show to have no, or a very limited influence
on the strength;
– the results on beams with single dowel connections show that the dowel
diameter (and consequently the embedding strength of the joint) doesn't
affect the splitting strength of beams;
– consequently, the tests results of the present research confirm the
soundness of the results reported in Paper 32-7-2.
Finally, the comparison of tests results with the design formulae included
CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.35