Formulation of a generalized truss analogy for the analysis of shear behavior of short jacketed columns

Abstract

Short columns in a story of a reinforced concrete building tend to fail in shear during an earthquake. They can be strengthened using concrete jacketing. A performance-based evaluation requires the modeling of nonlinear lateral load versus deformation behavior of such a column. While previous studies are available to analyze the behavior of a flexure-critical column, computationally simple method of analysis of the shear behavior of a short column is lacking in the literature.A generalized truss analogy is proposed to predict the shear behavior of short columns beyond diagonal cracking and till failure. Its formulation satisfies equilibrium of forces in the concrete strut and reinforcing bar ties, compatibility of strains in the concrete and ties of the web region of a column, and suitable constitutive relationships of the materials. First, the formulation and computation algorithm as applicable to an original column, are presented in this paper. Next, the method is extended to columns strengthened by concrete jacketing. Its application to a composite jacketed section is implemented using a sandwich model.The validation of the proposed method is presented, comparing the predictions with the lateral load versus deflection behavior curves obtained from the tests of five large-scale shear-critical column specimens (two original and three jacketed), tested as part of this research. The good correlation of the predicted and test results confirmed the application of the proposed method for the nonlinear analysis of shear for short columns.