Energy Balance Based Ultimate Strain Capacity Model for Rectangular Concrete Columns with Limited Confinement Details

Abstract

In the evaluation of existing structures, it is still common to find reinforced concrete elements designed with non-seismic or sub-standard transverse reinforcement details. Typically, these details consider poorly anchored 90° hooks that limit the confinement capacity of stirrups and crossties leading to a premature loss in strength or even failure. This study presents a simplified energy-balance-based model for the estimation of a practical value of the ultimate strain capacity of reinforced concrete columns with limited confinement details. This model is based on the well-known energy-balance principle to develop specific modification for the assessment of poorly detailed transverse reinforcement configurations. The model is calibrated using results from an analytical analysis-oriented ultimate strain model, considering a set of combinations that are representative of existing RC columns. Finally, the proposed scheme is validated against published lateral load tests of columns with sub-standard transverse reinforcement configurations. Results suggest good agreement between predicted confinement triggered failure and experimental failure lateral displacement for reinforced concrete columns with limited confinement. Furthermore, the validation shown that the proposed model accurately reproduces the lateral load capacity degradation.