Study On Seismic Behavior Of Reinforced Concrete Beams And Columns

Strengthening and rehabilitation of existing structures is one of emerging professions in the present construction industry,in which strengthening of concrete structures approximately represent more than 50 percent.The current research on the seismic performance is far less than the normal bearing capacity of enlarged cross-section columns with RC focusing on the axial and eccentric compression columns.Hens,it is essential to study on the seismic performance of enlarging section column.At the same time,the calculation formula of normal bearing capacity of the bonded FRP by the code recommended in our country is mostly refer to the foreign standard and expert’s experience.Therefore,it’s necessary to analyze the reliability of the formula and consider the effect of earthquake action on the strengthening effect.Combining with some actual reinforcement project,the mechanical behavior of reinforced concrete beams and columns are studied via the experiment,the finite element numerical simulation and formula calculation in the specification,which provides scientific basis and technical support for the establishment of building reinforcement retrofit scheme and the formula correction of the standard.A finite element model of enlarging cross-section columns with RC is proposed in this paper.Compared with experimental hysteretic curves,the results of nonlinear analysis show that computational results are acceptable,indicating that the model proposed could be applied to the seismic analysis of reinforced RC columns.The analysis results of different parameters show that: the full extent of load-displacement hysteretic loops of the RC columns by enlarging section reduced and the number of displacement cycles minimized after yield with increasing axial compression ratio.Furthermore,the horizontal bearing capacity and stiffness of the reinforced columns is significantly improved with increasing the new longitudinal reinforcement ratio.In addition,the ductility of RC columns by enlarging section is obviously improved with increasing the diameter of the new stirrup and reducing its spacing during encryption area.According to the 56 test data of beams strengthened with fiber reinforcement polymer,the analysis of the flexural bearing capacity formula of beams strengthened with FRP in specification is performed.The results show that the data calculated using the design formulas in Code for Design of Strengthening Concrete Structure has 86 p-ercent below the test values.Upon the test data of the flexural bearing capacity,the prediction formula and design formula of the flexural capacity of the strengthened beams is proposed.Based on the bending test beams strengthened with CFRP,paper verifies the finite element model of reinforced beams,changes the loading mode,and the carries out the nonlinear analysis,upon which seismic bearing capacity calculation formula of strengthened beam are put forward.