Numerical Analysis Of Axial Compression Performance Of Pre-damaged RC Columns Reinforced With Steel Casing And Steel Fiber Cement Mortar

Compared with the traditional reinforcement method,the steel casing reinforcement method has advantages of high bearing capacity,good seismic performance,and convenient construction.At present,the research on the steel casing reinforcement method mainly focuses on the reinforcement of complete columns,while the influence of damage on the reinforcement effect should be considered in the reinforcement and renovation of existing buildings.Therefore,to improve the mechanical properties of the steel casing reinforcement method and apply it to the reinforcement of damaged columns,a new type of reinforced material steel fiber cement mortar is introduced,and a new type of composite structure of steel casing and steel fiber cement mortar for the reinforcement of pre-damaged RC columns has been proposed in this dissertation.In the previous experiment,the damage degree of RC column,concrete discretization,and steel casing thickness were all taken as influencing factors,7 steel casing-steel fiber cement mortar pre-damaged RC columns were designed and made to carry out the axial compression test.But these influencing factors were still not comprehensive due to various objective limitations.Therefore,based on the experimental study,the corresponding reinforcement column was then established based on ABAQUS finite element calculation model,and its rationality also was verified in this study.The key factors affecting the axial compression performance of such reinforced columns(steel casing thickness,steel strength,loading method,The strength of steel fiber cement mortar and the strength of concrete)also was analyzed by nonlinear parameters.The research results were as follows:(1)The simulated analysis of 5 reinforced columns(Only one of the three discrete reinforced columns was selected for simulation)was carried out,and the simulated deformation pattern,load-displacement curve,axial bearing capacity,and stress nebular diagram of each component were compared with the experimental results respectively,which verified the correctness of the finite element calculation model established.(2)Based on the finite element calculation model established by the experiment,the key factors affecting this kind of reinforced column were analyzed by variable parameters,and 19 calculation models were constructed in total.Through the comparison of the load-displacement curve and axial bearing capacity,it could be seen that the ultimate bearing capacity of reinforced columns would increase with the improvement of steel casing thickness,steel strength,and steel fiber cement mortar strength;The change of steel casing thickness possessed a greater impact on the ductility of reinforced columns,while the increase of steel fiber cement mortar strength harmed the ductility;The hooper loading method could obtain higher lifting effect of bearing capacity and deformation performance;With the same damage degree,the concrete strength of the inner column had little influence on the performance of the reinforced column.(3)According to the superposition principle and the limit equilibrium theory,the calculation formulas for the axial compression bearing capacity of steel casing-steel fiber cement mortar reinforced pre-damaged RC columns were deduced respectively.The comparison of the results concluded that the calculation formulas for the axial compression bearing capacity derived based on the superposition principle were more consistent with smaller errors,which provided a reference for the application of this kind of reinforced column in real engineering projects.