New Methodology for the Analysis of Beams Prestressed With External or Unbonded Tendons

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Title: New Methodology for the Analysis of Beams Prestressed With External or Unbonded Tendons

Author(s): Antoine E. Naaman

Publication: Special Publication

Volume: 120

Issue:

Appears on pages(s): 339-354

Keywords: beams (supports); cracking (fracturing); flexural strength; partial prestressing; prestressed concrete; prestressing; serviceability; structural analysis; structural design; unbonded prestressing; Structural Research

Date: 6/1/1990

Abstract:
A simple methodology for the solution of beams prestressed or partially prestressed with external or unbonded tendons in the linear elastic cracked and uncracked range of behavior is described. It leads to equations allowing the computation of stresses in the concrete section, the tensile reinforcing steel, the compression reinforcing steel, and the prestressing steel. In particular, it is shown that the stress in unbonded tendons is a function of the applied loading, the steel profile, and the ratio of the crack width (or crack band width) to the span. These factors can all be accounted for through the use of a strain reduction coefficient ê for the uncracked range of behavior and a similar coefficient êc for the cracked range of behavior. It is shown that, when the strain reduction coefficients ê and êc are taken equal to unity, the solutions developed here revert to the solutions developed earlier for partially prestressed beams with bonded tendons.