Nonlinear Analysis Of RC Column Strengthened With Envelop Angle

Encased steel strengthening method, which had advantages of small workload, little influence on architectural space and short construction period, quickly developed in the structure reinforced field and widely used to strengthen concrete structural thing of reinforced concrete and so on. Specially, when it was applied to strengthen reinforced concrete members, it could significantly improve the characters of these reinforced concrete members, such as, bearing capacity, stiffness, ductility. Therefore, it is meaningful study in our reality life to analyze the nonlinearity of reinforced concrete column strengthened with encased steel.Many scholars proceeded a lot of trial research for reinforced concrete column strengthened with encased steel and got many considerable conclusions. Based on the previous work, this article aimed at study mechanical properties of reinforced concrete column under secondary load influenced by unloading force. According to relevant clause of Code for Design of Concrete Structures and Design Code for Strengthening Concrete Structure, Elastoplastic damage constitutive model for concrete and the linear strengthening elastic-plastic constitutive model of rebar and encased steel were used to build six models of reinforced concrete column strengthened with encased steel with different unloading force in the general finite element software ABAQUS. And the bearing capacity, ductility, use ratio of encased steel of reinforced concrete members that influenced by unloading force were studied by nonlinear research of the six models under the axial load and eccentricity load. Five finite element model were built to analyze the reinforcement performance that influenced by thickness, strength, batten plate spacing, batten plate sectional dimension, stress history of encased steel. The results show: the increase of bearing capacity is biggest and the ductility is the best when the unloading force is about 60% for the reinforced concrete column under the axial load, while unloading force is about 40% for the reinforced concrete column under the eccentricity load; t he bearing capacity and use ratio of encased steel increases and stress level decrease with the increase of thickness of encased steel; the smaller batten plate spacing is, the better bearing capacity of reinforced concrete column strengthened with encased steel is, but the relationship between them is not nolinear, when the batten plate spacing is about 250~300mm, the increase of bearing capacity is biggest and reinforcement effect is best; reinforcement effect is better when increase sectional dimension of angle iron can than increase sectional dimension of batten plate, and the limit valve increased of bearing capacity can reach 34.11%. Based on formula of ultimate bearing capacity of reinforced concrete column strengthened with encased steel and formula of use ratio of encased steel in Design Code for Strengthening Concrete Structure, compare simulation result and theoretical calculating value and the result shows the simulation result is within the limits specified by standard and the model is reasonable. The content of the article can provde theoretical foundation and reference valve for the engineering projects.