Experimental Study On Flexural Behavior Of Concrete Beams Strengthened With Prestressed CFRP Tendons

Carbon fiber composite materials have been widely used in the field of building reinforcement due to their high strength and corrosion resistance.According to the previous literature,it can be seen that when the ordinary carbon fiber material is used for in-line reinforcement,the flexural capacity of the member can be effectively improved,but the effect of improving the deflection and crack under normal use is limited,and the crack development cannot be effectively suppressed..When the prestressed carbon fiber material is used for in-line reinforcement,not only the flexural capacity of the member can be effectively improved,but also the crack resistance of the member is greatly improved,and the high-strength property of the carbon fiber material can be fully utilized.In the conventional reinforcement methods,most of the anchoring and tensioning are carried out at both ends of the component,but since the pillars or beams are often present at both ends of the actual component,there is a great difficulty in the use in actual engineering.The reinforcement method used in this paper can be better applied to the actual project,making up for the limitations of the single beam of the laboratory.In order to study the bending resistance of concrete beams strengthened with prestressed CFRP tendons,a total of six test beams,including one comparative beam and five reinforcing beams,were produced in this paper,and the following work was carried out accordingly:(1)Prestressed CFRP reinforcement is carried out by using the bonded anchors independently developed by the research group and the tension anchoring device.After the reinforcement is completed,the prestress loss of the three strengthened beams is monitored and the prestress loss is analyzed.And calculation,the calculation results show that the total pre-stress loss value agrees well with the experimental value.(2)Carry out the static load test on the components,record and analyze the relevant data of prestressed CFRP tendons,tensile reinforcement tendons and concrete load-strain relationship during the test,and the deformation process of the test beams and the development process of cracks and deflections.Through the record analysis,the cracking load,yielding load and ultimate load of the test beam were obtained,and the bending performance of the test beam under different tensile reinforcement ratios and different prestressing levels was compared and analyzed.The results show that the characteristic load of concrete beams strengthened with prestressed CFRP tendons is improved,the development of cracks is restrained,the stiffness of test beams is improved,and the deflection deformation is reduced,which is used to provide reference for the actual engineering of concrete beams strengthened with prestressed CFRP tendons in the future.(3)Based on the experimental research,the ABAQUS finite element software simulation analysis of the reinforced beams was carried out.The simulated values of the load-deflection curve and the ultimate bearing capacity were compared with the experimental values,and the comparison results were analyzed.(4)Based on the experimental research and finite element simulation analysis,the calculation formula of ultimate bearing capacity is derived,and the ultimate bearing capacity of the member is calculated.The calculated results agree well with the experimental results.The "Code for Design of Concrete Structures" is adopted.The deflection formula of the middle beam is used to calculate the deflection of the test beam,and the theoretical value is compared with the experimental value,and the error is within 15%.