The Oretical Research And Finite Element Simulation Of Concrete Eccentric Loaded Columns Strengthened With CFRP Sheets Under Secondary Load

Carbon fiber reinforcement technology is an emerging reinforcement technology,its superior performance by more and more attention.CFRP features include deformation ability,high tensile strength,light weight,corrosion resistance,good durability,fatigue resistance,high temperature,thermal expansion coefficient is small and so on.Since the eighties of last century,carbon fiber reinforcement research,and more concentrated in the axial compression cylindrical column,and the actual project in the concrete column is rectangular and bear eccentric load,while the ordinary CFRP provides a passive constraint,can not give full play to its high-intensity characteristics,so in recent years,some experts and scholars put forward the reinforcement method of prestressed CFRP,improve material use efficiency.In this paper,combined with engineering practice,taking into account the secondary force of concrete columns.Based on the above problems,the main contents of this paper are as follows:(1)On the basis of the ordinary reinforced concrete circular column of CFRP,the circular shape of RC column strengthened by prestressed CFRP was deduced by the sectional shape coefficient,the corner weakening coefficient and the common work coefficient.Constraint stress calculation formula.(2)On the basis of existing calculation models,the expressions of ultimate compressive strain,ultimate compressive stress and stress-strain model of rectangular concrete eccentric compression columns strengthened with prestressed CFRP under secondary loading are deduced by introducing the reduction coefficient.(3)Based on the characteristics of prestressed CFRP and eccentric compression columns,the formula for calculating the normal cross-section capacity of reinforced concrete columns under eccentric compression is deduced.(4)Based on the above theoretical derivation,the influence of concrete strength grade,slenderness ratio and initial eccentricity on the mechanical behavior of RC columns strengthened with prestressed CFRP sheets under the first and second loadings are compared and analyzed.The results show that,The mechanical properties of the biased column under the secondary load are slightly less than the one time.The effect of the ring reinforcement on the bearing capacity of the small eccentric compression column is more significant.(5)The whole process of loading of rectangular concrete columns strengthened with prestressed CFRP sheets under one load and two loads was simulated by using ABAQUS.The results show that the preloading method further enhances the biasing force The compressive strength and load-carrying capacity of the column and the maximum loading of the prestressing force to 20% are better.The mechanical properties of the column are greatly improved by the two-layer CFRP reinforcement,but the effect of the three-layer reinforcement is remarkably decreased,In the two-tier reinforcement can achieve the desired results.