Experimental Research On The Strengthening Of Concrete Beams For Shear And Torsion Resistance With Direct Shear Bolting Plates

The method of strengthening Reinforced Concrete by bolting plate is a newtechnique which has developed since recent years. While strengthened by the boltingplate, the holes must be drilled so the anchor bolt could be planted into the beam, andthe plate could be fixed on the beam by the anchor bolts. So the component and thebolting plate can performance as a system, when the component is deformed by loading.Thus the capacity of the component will be improved. Though it’s a new technique,compared with the technique of bonded plate and the technique of bonded carbon fiberto strengthening Reinforced Concrete, it can avoid desquamation effectively and is goodon fire-resistance. Enjoying so many advantages the bolting plate method also has itsshortage. The prepared holes on the plate must left enough space for the anchor bolts inorder to install convenient. When the plate deformed by loading, there will appear someproblem that some bolts are not yielded by loading until others begin to be forced,which can not make all of the bolts cooperative bearing by shear and it severelydecrease the shear capacity of group anchor system. The experiment in this articleemploys the method of strengthening Reinforced Concrete by direct shear bolting platewhich not only enjoy the advantages of bolting plate, but can overcome thedisadvantage of the bolts can not cooperative bearing the loads. The plate is fixed on themember by the direct shear bolts instead of formal bolts to achieve the goal that thebolts and plate can contact closely. Then it can give a full play to shear stiffness andcapacity to ensure strengthening effect. In order to study the effect of the method ofstrengthening Reinforced Concrete by direct shear bolting plate, the static loadingexperiment of three beams on combined force of bending moment, shear and torsion hasbeen done. Based on the observation and analysis of the capacity, stiffness and the crackdevelopment of the experiment, the effect of the direct shear bolting plate method onanti-shear-torsion will work out.The main research includes that:①Summarizing the torsion strengthening methods at the present stage, anddrawing a conclusion of the study on the strengthening of bolts plate.②Introducing the scheme of the experiment, the beams will be only strengthenedon flank sides without the U-shape hoops. The plate and the beam are combined by thedirect shear bolts without being bonded by adhesive. And the load will be applied by a vertical load on the cantilever end, which can provide bending moment, shear andtorsion at the same time. Based on the results of the experiment, the manchanicalbehavior of the beams have been improved which proved that this strengthening methodis effective.③By contrasting the experiment phenomena of the capacity, the developmenttrend of the crack and the stiffness of the three beams, the conclusion that the directshear bolting plate has a good performance on improving the capacity and inhabit thestiffness of the beams has been drawn. So the study of direct shear bolting plate onanti-shear-torsion is necessary.