Experimental Study On Shear Behavior Of RC T Beams Without Stirrups Strengthened With CFRP Sheets Under Impact Loading

In recent decades,Fiber reinforced polymer(FRP)has been wildly used to strengthen various reinforced concrete(RC)structures.As a most popular reinforcement material,CFRP possesses many advantages,like high strength to weight ratio,good erosion resistance and ease of construction.It has been demonstrated that FRP can greatly increase the load capacities and ductility of structures,while there are more requirements for the impact resistance of structures with the increase of extreme loads,such as explosions and various terrorist attack.There is few researches about the impact behavior of FRP strengthened RC beam,and most of the available investigations are on the flexural strength of FRP strengthened RC beams.Shear failure mode is a critical failure mode when beams are under impact loads,but there is a lack of investigation on the FRP contribution to shear strength.This study aims to investigate the shear mechanism and FRP contribution of CFRP strengthened RC beams without stirrups under impact loading,and the results are compared with static tests.Specific results of this study are summarized as follows:(1)Five CFRP strengthened T-Beams without stirrups were tested under static loads to investigate the effect of plate end anchorage utilizing fabric wrap,FRP spike anchors or Hybrid bonding system.The load-deflection curve,the crack patterns and the strain distribution of CFRP strips were studied.The FRP contribution under static tests was derived and compared with the theoretical value.(2)Twelve CFRP strengthened T-Beams without stirrups were tested under impact loads to investigate the influence of impact energy and different anchorage methods.The characteristics of strain time history of steel,concrete,and FRP strips were analyzed and the characteristics of time history of impact loads and reaction loads were summarized.The time-lag of reaction force,the crack patterns of beams under impact loads were derived.(3)Based on the analysis of various time history curves,the shear mechanism of CFRP strengthened RC beams without stirrups under impact loading was obtained.The method to reasonably evaluate the impact resistance of beams and the FRP contribution was carried out,which could offer reliable reference to practical engineering.