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due to splitting tendency are reducing the embedding strength parallel to
grain. This is generally assumed in all design codes, where load-carrying
capacities or allowable loads for nailed joints are independent of the loadgrain
angle. In this case, k90 � 1.
Proposals
Based on these investigations the following proposals are given to be used
in the Eurocode 5 for characteristic embedding strengths for
bolted and dowelled joints:
f
h,0, k
h, � , k �
2 2
k90sin
� cos
� �
f � 0,082� 1� 0,01d
h,0, k k
k �1,35 �0,015
d (softwood)
90
k �0,90 �0,015
d (hardwood)
90
f
� �
nailed joints (d < 8 mm)
�0,3
h, k � �k
� �
h, k k
�
f 0,082 d
(not predrilled holes)
f � 0,082 � 1� 0,01 d � (predrilled holes, as for bolts)
It can be seen from the tests that the embedding strengths of hardwoods
are approximately 10% higher than those of softwoods with same density.
This could be made allowance for in design codes if further investigations
verify this observation.
29-7-8 L Davenne, L Daudeville, M Yasumura
Failure of bolted joints loaded parallel to the grain. Experiment and
simulation
Abstract
This paper deals with the analysis of failure of joints with dowel-type fasteners
in glued laminated timber under static loading. The single bolt loads
the wood parallel to the grain. The joint failure is due to a cracking along
the grain direction.
An experimental program was carried out on joints for different structural
parameters and bolt diameters.
Fracture is analysed by use of linear elastic fracture mechanics concepts.
Possible pure or mixed modes of fracture are investigated. The
crack propagation condition is assumed to be based on a comparison of the
energy release rate with a critical value. An analysis of elastic stresses is
carried out for the prediction of the onset of cracking.
The critical energy release rate value was obtained from experimental
results of fracture tests under three point bending. The comparison between
experimental and numerical results for the simulation of fracture in
joints shows that the linear elastic fracture mechanics provides a good approximation
of load-bearing capacity of bolted joints and may help improve
design codes.
Conclusion
LEFM is a simplified approach consisting in the comparison of the energy
release rate with a critical value. This method has been applied for the determination
of the load carrying capacity of a mechanical joint with a single
bolt. The loading was parallel to the grain. The fracture mode that
leads to failure is the mode I of opening. The critical energy release rate
was chosen equal to the fracture energy value issued from bending tests.
Comparisons of the load carrying capacity obtained experimentally and
numerically with the Finite Element method is encouraging by considering
the coarse assumptions of the simplified approach.
Adjust this simplified approach for calculation rules might provide an
improvement for the determination of the ultimate load in the design of
bolted or nailed joints.
30-7-6 A Mischler
Influence of ductility on the load-carrying capacity of joints with doweltype
fasteners
The load-carrying capacity of joints with laterally loaded dowel-type fasteners
is, in Eurocode 5, based on a plastic design method, which was developed
by Johansen (1949). In this model, it is assumed that both the
dowel and the timber behave like rigid-plastic materials. Brittle failure
modes such as splitting or plug shear are not taken into account by this design
method. Plastic analysis methods are only valid to describe the load-
CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.20