Strength of Prestressed Solid and Hollow Beams Subjected Simultaneously to Torsion, Shear, and Bending

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Title: Strength of Prestressed Solid and Hollow Beams Subjected Simultaneously to Torsion, Shear, and Bending

Author(s): J. Misic and J. Warwaruk

Publication: Special Publication

Volume: 55

Issue:

Appears on pages(s): 515-546

Keywords: beams (supports); bending; bending moments; crack propaga-tion; failure mechanisms; loads (forces); prestressed concrete; shear strength; stress-strain relationships; torsion

Date: 8/1/1978

Abstract:
This paper presents details of an analysis for strength at failure of prestressed beams subjected to a complex system of applied loads consisting of combined torsion, shear and bending. It is based on a modified skew bending approach incorporating the use of strain compatibility over the beam cross-section to permit recognition of a "non-flat" yield region typical for cold drawn reinforcement. A significant feature of this analysis is the use of a biaxial strain criterion to recognize that the magnitude of the limiting strain in the compressed concrete at failure varies with different combinations of torsion, shear and bending. Other contributors working on this problem have used either a constant limiting concrete strain of magnitude 0.003 as for pure flexure, or some constant fraction of this amount throughout all possible load combinations involving torsion, shear and bending. Incorp-orated also in the determination of the ultimate strength is the ' recognition of the presence of shear stresses on the uncracked failure surface. Results of tests made on eighty four beams were used to verify this analysis. An excellent and consistent correlation was obtained between theoretical and test values for bending moments and resisting torques.