Analytical model for torsional behavior of RC members combined with bending, shear, and axial loads

In this study, a torsional behavior analysis model is developed for reinforced concrete (RC) members subjected to combined loads. In the analytical model, a member section is considered to be idealized as panel elements, on which a flexural analysis is first done considering axial forces to derive normal stresses acting on the cross-section. The panel elements are then analyzed with the normal stresses using the smeared truss model that satisfies the equilibrium and compatibility conditions. The various member forces are combined in terms of stress, in which the initial crack angle, the effective thickness affected by the combined stresses, and the distribution of the longitudinal reinforcement are reflected. From the combined stresses in the idealized panel elements, the member strengths are determined by applying multi-potential capacity criteria in which aggregate interlock failure, concrete crushing, and spalling of concrete cover are considered. The analytical model is verified by comparing it with existing test results, and it is found that the proposed model well evaluates the torsional behavior of RC members with and without shear force, bending moment, and axial force.