Study On Performance Of Reinforced Concrete Beams Based On Ductile Prestressed

In the past 20 years,China's economy has developed rapidly.The reinforced concrete structure accounts for a large proportion of the construction market.When the structure is degraded or the service conditions change,which leads to the structure cannot continue to work in the current state,in order to save costs and facilitate construction,the primary consideration is to strengthen the structure.Therefore,it is of great significance to develop technologies with lower cost,better bearing capacity,stronger stiffness performance and better ductility in the reinforcement of structure.The technology of using prestressed carbon fiber material to enhance concrete is mainly used for the improvement of traditional bonding and reinforcement to make the strength utilization of carbon fiber material more obvious,the bearing effect better,But the problem of lowering the ductility of the structure has not been solved,and the component size studied is small,which result to the limitations to the guidance of the actual project.According to the insufficiency of previous research factors,this paper carried out the design of prestressed carbon fiber reinforced anchors with improved ductility on the basis of large-sized components,and carried out the tests based on this set of anchors.The main research contents include the following aspect:1.Designed anchorage to improve ductility,and independently developed the tensioning technology of the anchorage on the basis of this design anchorage,and applied to the reinforcement system in this paper.The short-term prestress loss monitoring of the tensioned carbon fiber material was maintained for 5-7 days.The effects of different tensile forces,different "fuse" diameters,and the presence or absence of adhesion on the prestress loss were studied.It is found that the short-term prestress loss is concentrated at 14%-20%.The "fuse" diameter and the presence or absence of adhesion have little effect on the short-term prestress loss;the larger the initial tensile force,the more the short-term pre-stress loss.2.The static load test of reinforced concrete structures strengthened with prestressed carbon fiber materials was carried out to study the bending performance: including structural bearing capacity,ductility and carbon fiber material utilization influenced by different reinforcement amounts,different initial tensile stresses,different screw diameters.It is found that the bearing capacity of reinforced concrete flexural members strengthened with unbonded prestressed carbon fiber is increased by 10%-30%.The increase of cracking load is greater than the yield load and ultimate load.The greater the initial tensile force,the more the bearing capacity is improved;The "fuse" diameter can increase the deflection of the structure by 30%,and the ductility of the reinforced structure is greatly improved;the utilization of the carbon fiber without reinforcement pre-stress reinforcement is lower than that of the bonded prestressed reinforcement.3.The co-stressed analysis of prestressed carbon fiber materials,steel bars and “fuse” was carried out at different stages of the structural load-bearing process to understand the effects of different stress stages of the three structures,and whether the unbonded prestressed reinforcement still conforms to the flat section assumption.The results show that the height of the neutralization axis of the strengthened test piece is lower than that of the comparative test piece,and the lower the concrete strength,the more the height of the neutralization axis is lowered.4.Model establishment and calculation verification for components with different damage states.The verification results show that the model is suitable for the bending calculation of reinforced concrete flexural members without unbonded prestressed reinforcement.