Nonlinear sectional analysis of reinforced concrete beams and shells subjected to pure torsion

This paper presents a sectional analysis tool which can compute the complete torque-twist behaviour of reinforced concrete beams and shells. The cross section is modelled as a 2-D grid of triaxial elements representing the concrete and uniaxial elements representing the longitudinal reinforcement. Fixed strain patterns based on kinematic assumptions are used instead of using the finite element method to calculate strain distributions corresponding to sectional strains. Constitutive models for the concrete are based on the Modified Compression-Field Theory, though tension stiffening is neglected in the proposed model's current implementation. A key assumption used in this model is that the shear strain distribution caused by twists obtained from a linear elastic analysis can be used to describe the nonlinear behaviour of a member following cracking. The validity of this assumption when applied to rectangular sections is confirmed based on a study of 115 tests from the literature. Excellent agreement of peak strength and overall torque-twist behaviour are observed when comparing the model predictions and experimental data from these tests. Areas of future work are to improve the capabilities of the model are identified. (C) 2019 Elsevier Ltd. All rights reserved.