Smeared crack analysis for plain concrete in torsion

This is the first of two papers addressing the efficient approach of the torsional behavior of concrete elements through smeared crack analysis. This paper presents the development of an analytical model for the behavior of concrete elements in increasing torsion. The model is based on a special numerical technique that employs constitutive relations expressed in terms of normal stress and crack width, for the behavior of the crack process zones. The width of a crack process zone is considered as a material property and is estimated through comparisons between analytical and experimental data. The method is not restricted by the cross section shape because the analysis includes numerical mapping. Examination of the objectivity of the proposed analysis in relation to the used mesh density is included in the study. The proposed approach is also applicable to concrete elements subjected to torsion combined with flexure, sheer, and axial force. Validation of the analytical model derived in this paper is demonstrated in a companion paper using extensive comparisons between predicted and experimentally obtained behavior curves and ultimate torque values.