Near surface mounted (NSM) technique has become one of the most prominent methods in retrofitting and strengthening structural elements. The literature does not provide a systematic and clear way to model the material of RC beams under combined torsion and bending loading, and is mostly experimental. A calibration procedure was carried out using the nonlinear finite element analysis program “ANSYS" in order to provide such a way of modeling.
The experimental RC beams specimens upon which the calibration process is applied are deficient in stirrups and with no side bars, hence the control beam specimen is deficient in torsional capacity, this is to provide room for torsional retrofitting. This study focuses on the needed rationale and parametric values to model concrete retrofitted with NSM continuous rectangular spiral reinforcement using Drucker-Prager Concrete material model combined with hardening, softening and dilatation (HSD) exponential material model, to be provided in order to reach good numerical results.