In this research, a study for the composite beam subjected to torsion in sagging moment regions was presented both experimentally and numerically. Two full scale composite beams with corrugated steel sheet were utilized in this study. The beams were tested under the same loading combination; shear, torsion and positive bending; with different percentages of load to produce torsion of about 25% and 33% of the total applied load to the beam. Three push-out tests were performed to obtain the characteristic strength of the used stud shear connectors. A non- linear analysis for the tested composite beams with partial interaction between the steel I-beam flange and the composite slab was presented. The composite beam was simulated using the software package ANSYS 8.1, where seven different elements were utilized to simulate the different components of the composite beam. The change in the stud behaviour was accurately recorded using a newly proposed simulation. In addition, two other beams with different percentages of torsion were studied using the presented model. The study insured the accuracy of the proposed model revealed some important results concerning the behaviour of the composite beam under the effect of torsion, shear and positive bending moment