Shear Behavior Of Large Scale Beam Reinforced With Hand-wound CFRP Stirrups

Fiber reinforced Polymer(FRP)are used in reinforced concrete structures featuring its lightweight,high strength and corrosion resistance properties.Application of FRP stirrups and longitudinal bars instead of traditional reinforcement in concrete structures can effectively solve the durability problem caused by steel corrosion.However,prefabricated bars may can’t be used if there are any design modification at the construction site whereas the CFRP sheets(Carbon Fiber Reinforced Polymer)can be wound directly around longitudinal reinforcements as hand wound CFRP stirrups,which can solve this problem on behalf of its flexibility and construction convenience and its closed shape can avoid the slip of overlapped legs in the use of pultruded bars.While there is very limited existing research about mechanical property of hand-wound stirrups and the shear behavior of beams with hand-wound stirrups.In view of this,the test of large scale beam reinforced with hand-wound CFRP stirrups was carried out to prove feasibility and applicability of this type of reinforcement.The main research contents are:(1)The tests of straight and bend part of stirrups were designed and carried out with the aim to study how production process and cross section dimension affect the bend strength and the effectiveness of FRP stirrups.The results showed that the ratio of bend part over straight part of hand-wound stirrups is about 50% higher than that of pultruded bar stirrups.(2)12 large scale beams with hand-wound CFRP stirrups were tested to observe the effect of reinforcement variables(stirrups inclination angle,type of reinforcement material and cross section of stirrups)on shear behavior of beams.Evidence showed that hand-wound stirrups can enhance the capacity and shear stiffness of beam whereas this effectiveness can be increased by using inclined stirrups.(3)American ACI(2015)and Canadian CSA(2012)design code recommendations were selected to predict and compare with experimental results in order to examine whether these recommendations can be used to design beams reinforced with new developed hand-wound stirrups.Analysis proved that prediction of CSA(2012)matches well with results while ACI(2015)overestimates the capacity up to 20%.