Investigation On Mechanical Performance Of RPC Beams Prestressed With External CFRP Tendons

With high compressive strength and excellent durability,Reactive Powder Concrete(RPC)could replace the ordinary Concrete as a structural material.With high strength,superior corrosion resistance and good fatigue performance,Carbon Fiber Reinfoced Plastics(CFRP)could replace the steel stranded wire as externally prestressed tendons.The combination of RPC and CFRP is expected to achive high performance of mechanical behavior and durability for externally prestressed concrete structure.It can effectively reduce the structure self-weight,increase the structure span ability,and improve the durability of the structure.In addition,in marine concrete structures prepared with seawater and sea sand,the steel bars in RPC beams prestressed with external CFRP tendons should be replaced with FRP bars to form a high durability RPC structure.At present,more researches have been done on the mechanical properties of RPC and CFRP materials at domestic and abroad,but there are few studies on the mechanical properties of RPC structure reinforeced with CFRP,especially the study of RPC beams prestressed with external CFRP tendons.Therefore,under the support of the National Key Research and Development Program of China“Key Technology Integration and Demonstration for the New Structural Application of Fiber Reinforced Composites”(No.2017YFC0703008),Experiments and theoretical studies of RPC beams prestressed with external CFRP tendons were conducted,the main contents of which are as follows:(1)Four RPC beams prestressed with external CFRP tendons with different shear-span ratio,jacking stress and partial prestressing ratio(PPR)were tested.The results of the load-deflection curves,cracking load,yield load,ultimate load,external prestressing increment,failure characteristics,crack distribution and development,concrete strain,steel strain,etc.were obtained.Based on the test results,the influence of various parameters on the mechanical properties of the beam was analyzed in detail.(2)Based on the results of bending performance test,an incremental calculation model for external prestressing of external prestressed concrete beams based on beam deformation was established,and the calculation method for the increment of external prestress was deduced.And the feature of failing processes for the beams was clarified,and the equations for predicting the cracking and ultimate moments of the beams were proposed.The nonlinear numerical analysis program is used to analyze the bending performance of RPC beam prestressed with external CFRP tendon,and the bending performance of the beam is analyzed comprehensively by the program.(3)In order to research the influence of partial prestressing ratio(PPR),jacking stress and shear-span ratio,seven RPC beams with internal GFRP reinforcements and prestressed with external CFRP tendons were tested.The results of the load deflection curves,cracking load,ultimate load,external prestressing increment,failure characteristics,crack distribution and development,concrete strain,GFRP strain,etc.were obtained.According to the test results and combining with relevant specifications and literature research,the formula for shear capacity of full-FRP prestressed RPC beam is proposed and the applicability of the formula is verified.