Mechanics-Based Hinge Analysis for Reinforced Concrete Columns

The lateral deformation behavior of a RC column is particularly important because it not only magnifies the moment but also affects the ability of the columnand, subsequently, the frameto sway and absorb energy at all stages of loading. The lateral deformation is affected by disturbed regions, such as tensile cracks or compression wedges, which are often simulated with the help of hinges whose properties are derived empirically. Being empirical, these hinges can only be used within the bounds of the tests from which they were derived, and in this respect are of limited use. In this paper, a mechanics-based hinge is developed that can be used at all stages of loading (that is, at serviceability through to ultimate) and also during failure. The mechanics-based model is based on the principle of plane sections remaining plane, shear-friction theory that quantifies the behavior of RC across sliding planes, and partial-interaction theory that allows for slip between the reinforcement and the encasing concrete. Being mechanics based, it can be used for any type of RC column; that is, for any type of reinforcement and for any type of concrete as long as the material properties are known. The mechanics model is shown to be in good agreement with published test results and can simulate not only multiple cracks if necessary but also the formation of wedges.