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4.11 NON-METALLIC DOWELS
22-7-3 J Ehlbeck, O Eberhart
Design of double shear joints with non-metallic dowels. A proposal for
a supplement of the design concept
Introduction
At the University of Karlsruhe a research programme was undertaken to
determine the load-carrying capacity and the deformation behaviour of
glulam joints with non-metallic dowels of resin-impregnated compressed
wood. This material consists of multi-layered densified 2 mm beech veneers
glued together and fully impregnated with phenolic resins. One of
the objectives of this research work was to find out if Johansen's theory for
determining the ultimate load-carrying capacity of joints with dowel-type
fasteners can also be applied for such type of material having pronounced
brittle properties.
The test data in principle confirmed the applicability of this design
model which was introduced in the CIB-Code as well as the draft Eurocode
5 for limit state design calculations. It turned out, however, that an
additional failure mode may occur which makes it advisable to introduce a
supplementary design formula.
Conclusions
Tests with brittle non-metallic dowels in glulam joints proved an additional
failure mode compared to those used in the "classic" Johansen theory
which is -the basis for calculating the ultimate load-carrying capacities of
joints with dowel-type fasteners in the CIB-Code and the draft Eurocode 5.
It is proposed to add to the design formulae another one describing this
failure mode where there is only one brittle bending failure in the middle
member. Furthermore, in case of brittle dowel materials it is proposed to
substitute the yield strength by the bending strength of the material.
32-7-11 R D Drake, M P Ansel, C J Mettem
Non-metallic, adhesiveless joints for timber structures
Abstract
The construction of wide-span timber structures is strongly dependent on
the effective design of joints, which are usually fabricated from steel
plates, bolts and dowels. Such joints tend to be heavy, costly, prone to corrosion
and vulnerable to fire with poor aesthetic qualities. This paper investigates
the potential for replacing steel fasteners with nonmetallic elements
based on fibre-reinforced plastic pultrusions for the design of medium-to
large-scale timber structures. Techniques have been developed for
calculating the load bearing capacities of a range of non-metallic joints including
stress analysis using finite element methods. Non-metallic joints
for wood composites have been manufactured using friction-fitted, reinforced
plastics in the form of dowels and plates. The reliability of these
techniques has been confirmed by full scale laboratory testing of compo-
CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.72