30BFRP specimens have been tested under tension load, to study the effect ofdifferent connection techniques (bolted, bonded, bonded-bolted, and injectedbolts) on the behaviour of the connection.
Bonded-bolted technique ischaracterized by combining the advantages of both bolted and bonded techniqueswhich have high bearing capacity, high rigidity, and fatigue performance. Theadhesive layer weakens the influence of bolt hole and reduce the stressconcentration. The bonded-bolted connections have been prepared as follow:1- BFRPplates were cut to the desired length and width.2- Sixbolts’ holes were drilled in according to the required dimensions with 12.6 mmdiameter as shown in fig.
3-4.3- Cleanthe 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- Leftthe connections seven days to cure.Forinjected bolts, this technique offers several advantages such as 1) there is noneed for sealing the bolts holes, 2) large clearance can be used, 3) bolts withthreaded parts can be used through the FRP plates parts, 4) connections withinjection bolts are stiffer than connections with ordinary bolts. The injectedbolted connections have been prepared as follow:1- BFRPplates were cut to the desired length and width.
2- Sixbolts’ holes were drilled in according to the required dimensions as the boltedspecimens in fig 3-4 but with 14 mm hole diameter.3- Bolts were put in their places but withouttightened the nuts.4- Due to difficulty of drilling a hole in theBFRP and HSFRP bolt’s head to inject the resin, Sanyu resin was injected intothe clearance between the hole and the bolt using the syringe then tightenedthe nut with a finger tight.5- Finally,left the connections to cure for 7 days.
6bolts with 12 mm diameter have been used for bolted, bonded-bolted, andinjected bolts. Furthermore, three bolts type (i.e., SS, BFRP, and HSFRP) wereused with each technique.
Forthe bonded technique, preparing the connections was similar to thebonded-bolted connection but without using bolts.Inaddition to these connection techniques, the effect of adding an additionallayer of BFRP to the plate surfaces in the overlap distance, in the transversedirection 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.
Fingertightened BFRP bolts with 12 mm diameter were used with these specimens.Table3.7 shows the details and results of the specimens tested to investigate theeffect of the connection techniques and the effect of the additional layer.Regarding the designation of thespecimens, the designation follows the MDO-X-Y-L-Z order where M is the type ofthe connection (B for bolted connection, BB for bonded-bolted, and IB forinjected bolts); DO is the diameter of the bolt where O is the number; X is thenumber of bolts; Y is the bolts type (S for SS, F for the BFRP, and H for theHSFRP); and Z is the number of the connection of the three identical specimensfor 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 12mm diameter and it is the first specimen.