Torsion experiment and analysis on steel-encased concrete composite beams

In order to study the torsion behavior of steel-encased concrete composite beams,experiments were conducted on two specimens with varied stir-up ratios subjected to pure torsion and on three specimens with varied ratios of torsion to bending moment.The torsion ratio,torsion-strain relationship,strain distribution for steel and concrete,and the strain distribution along slab width direction were all mea-sured.Experiments showed that the torsions accord with three stage deformation rule and the rupture of concrete board conforms with common reinforced concrete.On the basis of experiment,according to the elastic and plastic theory and analysis on the bearing capacity by using spatial truss model with variable angle,cracking torque and ultimate torque of composite beams are obtained.The results are in good agreement with measured ones.