Derivation of optimized shape equations for ducts in deviation saddles

초록

In externally prestressed concrete girders, a deviation saddle should be designed to support the deviation force when deviation saddle is attached to concrete section. The deviation saddle can be designed more effectively if the deviation force is uniformly distributed on a duct in the saddle. In this paper, equations of normal and deviation forces on the duct, in which the tendon force is decreased by curvature friction, have been derived. The optimized shape equation of the duct has been derived for curvature radius which satisfies the allowable deviation force in design codes for any tangent angle. Semi-major and semi-minor axes of an elliptic shape duct have been proposed. The elliptic shape duct shows behavior similar to those of the optimized shape duct. The efficiencies of the optimized and elliptic shape ducts have been proved by comparing size effects and distributions of deviation forces with those of a circular shape duct. © 2018 by Korea Concrete Institute.

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