30 the influence of bolt hole and reduce

30
BFRP specimens have been tested under tension load, to study the effect of
different connection techniques (bolted, bonded, bonded-bolted, and injected
bolts) on the behaviour of the connection. Bonded-bolted technique is
characterized by combining the advantages of both bolted and bonded techniques
which have high bearing capacity, high rigidity, and fatigue performance. The
adhesive layer weakens the influence of bolt hole and reduce the stress
concentration. The bonded-bolted connections have been prepared as follow:

1-     BFRP
plates were cut to the desired length and width.

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2-     Six
bolts’ holes were drilled in according to the required dimensions with 12.6 mm
diameter as shown in fig. 3-4.

3-     Clean
the plates’ surface using sand blasting and wipe with alcohol after cleaning.

4-     Then,
Sanyu resin was used with 1 mm in the overlap distance.

5-     Finally,
bolts were put in their places and tightened with finger tight.

6-     Left
the connections seven days to cure.

For
injected bolts, this technique offers several advantages such as 1) there is no
need for sealing the bolts holes, 2) large clearance can be used, 3) bolts with
threaded parts can be used through the FRP plates parts, 4) connections with
injection bolts are stiffer than connections with ordinary bolts. The injected
bolted connections have been prepared as follow:

1-     BFRP
plates were cut to the desired length and width.

2-     Six
bolts’ holes were drilled in according to the required dimensions as the bolted
specimens in fig 3-4 but with 14 mm hole diameter.

3-      Bolts were put in their places but without
tightened the nuts.

4-      Due to difficulty of drilling a hole in the
BFRP and HSFRP bolt’s head to inject the resin, Sanyu resin was injected into
the clearance between the hole and the bolt using the syringe then tightened
the nut with a finger tight.

5-     Finally,
left the connections to cure for 7 days.

6
bolts with 12 mm diameter have been used for bolted, bonded-bolted, and
injected bolts. Furthermore, three bolts type (i.e., SS, BFRP, and HSFRP) were
used with each technique.

For
the bonded technique, preparing the connections was similar to the
bonded-bolted connection but without using bolts.

In
addition to these connection techniques, the effect of adding an additional
layer of BFRP to the plate surfaces in the overlap distance, in the transverse
direction to the applied load as shown fig. 3-8, were tested. Specimens’
dimensions were similar to the bolted connection as shown in fig.3-4. Finger
tightened BFRP bolts with 12 mm diameter were used with these specimens.

Table
3.7 shows the details and results of the specimens tested to investigate the
effect of the connection techniques and the effect of the additional layer.

Regarding the designation of the
specimens, the designation follows the MDO-X-Y-L-Z order where M is the type of
the connection (B for bolted connection, BB for bonded-bolted, and IB for
injected bolts); DO is the diameter of the bolt where O is the number; X is the
number of bolts; Y is the bolts type (S for SS, F for the BFRP, and H for the
HSFRP); and Z is the number of the connection of the three identical specimens
for each parameter; L is for the additional layer specimens. For example,
BBD12-6-F-1 represent a bonded-bolted BFRP connection with 6 BFRP bolts with 12
mm diameter and it is the first specimen.