Long Term Behavior of Prestressed and Partially Prestressed Concrete Beams: Experimental and Numerical Results

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Title: Long Term Behavior of Prestressed and Partially Prestressed Concrete Beams: Experimental and Numerical Results

Author(s): Bernard Espion and Pierre Halleux

Publication: Special Publication

Volume: 129

Issue:

Appears on pages(s): 19-38

Keywords: beams (supports); camber; cracking (fracturing); deflection; creep properties; failure; loads (forces); partial prestressing; prestressed concrete; prestress loss; serviceability; shrinkage; strains; stress analysis; structural design; General

Date: 12/1/1991

Abstract:
Tests results from long-term experiments on prestressed and partially prestressed concrete beams are reported. Tests were carried out on 10 rectangular beams spanning 2 m and undergoing sustained loading for five years. After that time, there was no evidence of stabilization of the time-dependent behavior of concrete. Numerical modeling of the deformation of the midspan section explains experimental observations and confirms that the presence of ordinary reinforcing steel in a prestressed concrete section leads to a redistribution of stresses between concrete and steel which should be taken into account in serviceability limit-state computations. Tests to failure of the beams at 5 years yield no significant differences in carrying capacity with tests executed at an early age. It is suggested that the deflection limit state is a major consideration in design and that the degree of prestressing should be chosen in function of ratio of permanent load to total design load (permanent and live).