Pure Torsion and Combined Torsion Behaviors of Steel-concrete Composite Beams

In order to study torsion behavior of steel-concrete composite beams,pure torsion and combined torsion tests were conducted on five specimens of the new type steel-encased concrete composite beams.Authors studied this new steel-encased concrete composite beam's destruction shape,worked mechanism and the crack development and distributed situation under pure torsion and combined torsion,and also compared and analyzed composite beam's relationships of torsion and torsion ratio,load and strain,bending and deflection,load and crack development.On the basis of elasto-plastic theory,the calculation formulas about cracking torsion of pure torsion and combined torsion were presented;and using spatial truss model with variable angle,formulas for ultimate torsion strength of pure torsion and combined torsion were proposed.The results are in good agreement with measured ones,and provide a basis for safty and stability evaluation of structures.