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4.6 GLUED-IN RODS
19-7-2 H Riberholt
Glued bolts in glulam
Summary and conclusions
An economic and convenient production method for glued-in bolt connections
has been developed. The bolts were placed in oversized holes and
glue was then injected. For practical reasons only threaded rods were used.
The axial capacity of these is not very sensitive to minor defects in the
bonding to the steel.
The tests show that the bolt connection can be used even for large
changes in the moisture content of the wood. The steel surface is to a certain
degree protected against corrosion by the employed polyurethane and
epoxy glues. But under severe corrosive conditions zinc coatings or similar
should be used.
The axial and lateral load-carrying capacity of a bolt connection has
been found experimentally. The capacities were similar to those reported
in the literature, but here essentially smaller distances to the wood edges
and in between the bolts were used. Further, the axial capacity was found
to be higher for the more flexible polyurethane glue.
For axial loaded bolt connections long-term tests were carried out in
which the moisture content of the wood was changed. It appears that for
out door service the-long term capacity is approximately half the shortterm
capacity of dry specimens.
Further for some selected types of connections with glued-in bolts, tests
were carried out in order to verify the proposed calculation methods and
theories of the static behaviour. The following were investigated:
– Moment stiff column-foundation joint
– Trimmer joint
– Moment stiff frame corner
– Splitting of laterally loaded glulam beams
In general it can be, stated that glued-in bolt connections can be designed
with a capacity comparable to that of a glulam element. As an example the
moment capacity of the tested moment stiff column-to-foundation joint
was found to be approximately 75 % of that of the glulam column. And
the connection could easily be designed stronger.
The tests with a frame corner revealed that, if several glued bolts are intended
to carry the load together, then it is essential to design the connection
so that the forces can be distributed evenly. Otherwise, the glued
length employed has to be of a size that the bolt yields before being pulled
out. Because in this way an initial uneven force distribution can be equalized
before failure occurs due to ductility of the bolt connection.
Object
The object of the project was:
A. Development of a reliable production method.
B. Development of corrosion resistant glued bolt connections for outdoor
service.
C. Determination of the axial strength and the lateral load-carrying capacity
for glued bolt connections. Further determination of minimum
distances for obtaining the load-carrying capacities.
D. Accomplishment of some full scale tests to elucidate suitable applications
and as background for dimensioning methods.
As starting basis the project had the report: “H Riberholt, Glued bolts in
glulam, Department of Structural Engineering, Technical University of
Denmark, 1977” which deals with threaded rod connections glued with
resorcinol glue.
26-7-4 J Kangas
Design of joints based on V-shape glued-in rods
Abstract
In this study a method is presented how to design the capacity of moment
resisting, joints of glued laminated timber structures based on the properties
of in V- shape glued-in rods. Design rules for anchorage capacity of
the rods and capacity of timber in the joint area are given. Design rules are
based on an experimental research, which is briefly introduced.
The, technology has originally been developed in TSNIISK in Moscow.
It was introduced in CIB-W18 in Paper 22-7-11. Research work began already
in 1975. It has been almost unknown for the rest of the world mainly
because the publications were in Russian.
The method is based on ribbed steel rods, which have been glued at
skew angles into the glulam. The rods take effectively the forces in their
CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.47