Fatigue Experimental Research For Reinforced Concrete Beam Strengthened With Prestressed CFRP Plate

With the improvement of economic level,people put forward higher request to the safety,serviceability and durability of the building,so it is a hot topic in the field of construction to reinforce and transform the structure.Due to its light weight,high tensile strength and good durability,carbon fiber board(CFRP)has attracted widespread attention in the field of Engineering reinforcement.In the previous studies,the static load test of Prestressed CFRP plate reinforced concrete beams has made remarkable achievements,but the research on fatigue test and prestress loss test is very little,the specimen of a small size,low level,poor reliability of prestressed anchorage and restrict the development of CFRP in engineering field.Two sets of anchorage equipment are developed,the prestressed CFRP board is fixed by anchorage MJ1,then the fatigue test research is carried out(three static load,three fatigue).Six concrete beams is fixed by prestressed CFRP plate with MJ1 and MJ2.Then the theory and experimental research of prestress loss are carried out.The research contents and results are as follows:1.This paper analyzes and introduces the anchor tensioning device of independent research and development,Theoretical calculation of reinforced concrete beams strengthened with prestressed CFRP plates is carried out,by comparing the theoretical value with the experimental value,the agreement is high.2.By analyzing the Change of strain,deflection and crack development of specimens,the conclusion is drawn from the development of cyclic loading.The fatigue performance of the damaged specimen is similar to that of the intact specimen,and the results show that the prestressed CFRP plate can achieve the same reinforcement effect as the intact beam;Mid-span deflection of the 60% prestressing specimen is less than that of the 40% prestressing specimen;Compared with the 40% prestressing specimen,the number of cracks,the crack spacing and the crack width is small in the 60% prestressing specimen.3.The CFRP board of the six concrete beams tension test,effectively solves the problems of previous research of anchorage slip occurred,the contact surface of the CFRP plate and the clamp is used as the base cloth and the structure is used for smoothing the gauze,and then the measuring force wrench is used for tightening.4.The anchorage tension which is slotted or not,prestress level and type of anchorage is considered as the prestress loss factors under the influence of comparative analysis.The total loss rate of the beam bottom slot is smaller than that of the non-notched specimen,which shows that the prestressed loss can be effectively restrained by the method of grooving at the bottom of the beam;With the increase of the prestress level,the total loss rate of prestress is increased,which shows that in order to prevent the loss of effective prestress,the appropriate prestressing level should be selected;the total loss rate of MJ1 is less than that of MJ2 prestress,which shows that the reliability of MJ1 is higher..