Title: Crack Control In Reinforced And Prestressed Concrete Beams

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Publication: CIA

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Date: 2/13/2011

Abstract:
The current crack control procedures recommended by various building codes are examined by calculating the crack widths for a series of beams and comparing the results with allowable limits. The crack width is determined using the stresses and strains of the steel bars between adjacent cracks enclosed by a rectangular concrete prism. The bond force acting at the interface of concrete and reinforcement is evaluated using a common bond stress-bond slip relationship available in the literature. The new analytical method is first verified by comparing the calculated crack widths with the values measured by previous investigators on a large number of test beams. The resulting crack width is then calculated for a series of beams, with the bar diameter, bar spacing and the steel stress selected to satisfy the code requirements. The results indicate that the crack width under service loads becomes larger than the acceptable limit, when the recommendations given in current AS3600 (2001) are used. On the other hand, the ACI318 (1995) procedure is found to be acceptable. Finally, for the development of reliable crack control procedures for prestressed beams, more research is needed to establish bond characteristics in prestressing strands, as the bond strength is a major parameter affecting the crack width.