Experimental Study On Axial Compression Reinforced Concrete Columns Strengthened With Encased Steel

In our country,there are large number of buildings with reinforced concrete structures which have been in service for many years,these buildings are often due to many reasons leading to lack of capacity,so they needs to be strengthened to improve the structure of the carrying capacity to meet the structural reliability requirements.The reinforced concrete columns are the most important force and reinforcement components in engineering,increasing section reinforcement method and clad steel reinforcement method are the two most commonly used reinforcement methods,according to the steel and the original component connection is different,outsourcing steel reinforcement method is divided into externally bonded steel strengthening method（Also known as wet-type steel reinforcement method）and Unbonded outsourcing steel reinforcement method（also known as dry-type steel reinforcement method）,the two kinds of outsourcing steel reinforcement methods are obviously deficiencies.The article to the shortcomings of the above two kinds of reinforcement methods,a new type of steel reinforced concrete column strengthened with angle steel is put forward,namely through part of cast-in-place self compacting concrete will angle（through the steel plate connected to each other）and the original component closely.So that the two parts are able to work together to improve the rigidity of components and bearing capacity,overcome the durability problem of the external reinforcement steel reinforcement method and the co-operation problem of the unbonded outsourcing steel reinforcement method.The subject based on theoretical analysis,model test and finite element simulation,the reinforced concrete columns under the influence of factors such as steel ratio,plate spacing and new concrete thickness are studied.The reinforced concrete columns are subjected to axial compression.Force performance and failure characteristics,and put forward some suggestions and practical calculation methods for the design of new reinforced angle steel reinforcement columns.In order to complete the above research contents,the article has carried out the following main research work:（1）Experimental research of columns used to carry out new composite reinforced concrete axial compression bearing capacity.Design of 16 axial compression column specimens,including a primitive concrete compression column,three single outer steel reinforced concrete compression column and 12 to consider the self-compacting thickness,batten spacing,angle steel and other parameters of the parameters of the external viscous steel reinforced concrete column.Through the compression failure test,the stress process and failure characteristics of the various compression columns were observed,and the bearing capacity test results of the new reinforced angle steel reinforced specimen and the wet type steel reinforced specimen were compared.The reinforcement mechanism and carrying capacity The contribution of self-compacting concrete,the spacing of plates,the type and amount of angle steel to the bearing capacity of compression-strengthened columns are explored.（2）The application of classical theory and normative knowledge structure reinforcement（including theory of increasing section method and steel reinforcement method）,based on the experimental phenomena and results,the article analyzes the mechanical properties of the reinforced concrete columns subjected to the compression behavior of the reinforced concrete beams,and analyzes the mechanical properties of the reinforced concrete columns subjected to the reinforcement of the cross section method and the reinforced steel reinforcement method.The effect of new self-compacting concrete joint layer,the amount of angle steel and the effect of patch spacing on the bearing capacity is studied.The expression formula of the bearing capacity of the reinforced concrete column is strengthened by the new method.Based on the experimental data,the relationship between the strength coefficient of angle steel and the constraint index of concrete confined with steel frame system is expressed as follows:α_sv=4.1λ_t+0.11And as a basis for the reinforcement of the axial load of the bearing capacity of the expression:N_u=0.95f_cc(A_c+A_c0)+f_yA_s+（4.1λ_t+0.11）f _yaA_ya.（3）With the help of finite element analysis software ANSYS,the constitutive relation of the materials,the yield criterion for nonlinear analysis,using ANSYS modeling for numerical simulation,based on the results of the simulation analysis model of stress angle steel reinforced concrete columns under axial compression,changes and reasons of the strain and the displacement parameters and bearing capacity test results,and with the test phenomenon,compared the results of theoretical analysis,the simulation model of ANSYS angle steel reinforcement of reinforced concrete columns subjected to axial compression results with experimental values,classic theory results,confirmed the finite element simulation results are effective.So in the future of the reinforced structure Study on the reinforcement effect by numerical analysis method,analysis powerful application ANSYS finite element simulation method,appropriate modeling,in order to compensate for the defects such as test consumables consumption,increase the volume of test data acquisition technology,saving time and space supplies,optimize research results.（4）On the basis of summing up the research results,this paper puts forward the existing problems of this research,and also has a clear plan on how to carry out the later research work.