Torsion of Steel Beams
- Emeritus Professor Nick Trahair
- Dr Yon-Ling Pi (formerly University of Sydney, now University of New South Wales)
- Dr Lip Teh (Formerly University of Sydney, now Seimens Dematic)
Previous projects have included studies of the plastic torsion collapse of thin-walled open sections, the development of torsion design methods and design aids, the prediction of the inelastic large twists of I-section torsion beams, and the flexural buckling of torsion members.
This project is concerned with large twist rotations of elastic thin-walled open section beams which induce additional longitudinal stresses which exert non-linear “Wagner” stiffening torques.
The non-linear behaviour of a narrow rectangular beam is first analysed and then this is extended to elastic beams of general cross-section. Expressions are derived for the non-linear “Wagner” section constants for narrow rectangular sections, doubly symmetric I-sections, and mono-symmetric equal angle sections.
A general finite element method of analyzing non-linear torsion is described, and used to develop a computer program which can analyse a beam of general cross-section under any combination of concentrated and distributed torques and concentrated bimoments, and which may be prevented from twisting or warping at points along its length. The program is validated by comparison with closed form or numerical solutions for a number of simple examples.
Publications
- Trahair, NS and Pi, YL, 'Simplified Torsion Design of Compact I-Beams', Steel Construction, AISC, Vol. 30, No. 1, 1996, pp 2-19. Also see School of Civil Engineering Research Report R686.
- Trahair, NS, and Teh, LH, 'Second Order Moments In Torsion Members', Engineering Structures, Vol. 23, 2001, pp 631-642. Also see School of Civil Engineering Research Report R800.
- Trahair, NS, 'Non-Linear Elastic Non-Uniform Torsion', Journal of Structural Engineering, ASCE, 131 (7), 2003, pp1135-42. Also see School of Civil Engineering Research Report R828.