Nonlinear 3D FEM was utilized to carry out inelastic response analysis of RC piers subjected to earthquake motions in order to analyze the role of shear reinforcement on final failure mode of the piers. Final failure mode of RC piers with different ratios of shear reinforcement, axial stress level, main reinforcement ratios and L/h ratios was determined considering different typesof damage indices of concrete such as; shear and normal stresses and strains, axial and lateral strains, plastic strains in axial, lateral or principle directions and cracking patterns. In the analysis, plastic strains (axial, lateral, and principle) were focused since the level of collapse depends on the quantity and sign of the plastic strains. Final failure mode of piers is highly affected by shear reinforcement ratio and axial stress level, remarkably affected by pier size and slightly affected by main reinforcement ratio. Failure mode changes significantly from severe diagonal failure to flexural failure by increasing shear reinforcement ratio and the rate of change depends on the mentioned parameters. From such comprehensive analysis, we plotted design curves from which the designers can determine the required shear reinforcement ratio at which failure mode changes from diagonal shear failure to flexural failure. A model was proposed to determine the plastic hinge height at which high plastic strains occur. Experimental results were carried out using cyclic loading tests and the results were used to verify the analytical ones.
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