Influence of Passive Reinforcement on Creep and Shrinkage of Concrete: Long-Term Observations

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Title: Influence of Passive Reinforcement on Creep and Shrinkage of Concrete: Long-Term Observations

Author(s): K. Audenaert and L. Taerwe

Publication: Special Publication

Volume: 246

Issue:

Appears on pages(s): 217-228

Keywords: creep; long-term behavior; shrinkage; stress redistribution

Date: 9/1/2007

Abstract:
In most concrete structures, a gradual stress transfer occurs between concrete and steel due to the time-dependent concrete deformations. This aspect is of particular interest in partially prestressed concrete members where significant tensile stresses may develop due to the restrained concrete deformations. To study this effect, a long-term research project was started in the 1970’s. In 1979, 16 concrete prisms with dimensions 140 x 150 x 4000 mm were manufactured. They differed by the amount of passive reinforcement (rs respectively 0; 1.5; 3 and 6 %) and by the level of the applied compressive stress (sc = 0; 5; 10 or 15 N/mm²). The compressive force was applied at 28 days by means of unbonded strands. The prisms were placed in an air-conditioned room at 20 ± 1 °C and 60 ± 3 % R.H. During more than 25 years, deformation measurements were carried out to determine the redistribution of stresses due to the restraining effect of the passive reinforcement on shrinkage and creep of concrete. In this article the results of the deformation measurements will be given and compared with an analysis based on the model for creep and shrinkage given in the CEB-FIP Model Code 1990.