Shrinkage Cracking in Fully Restrained Concrete Members

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Title: Shrinkage Cracking in Fully Restrained Concrete Members

Author(s): R. Ian Gilbert

Publication: Structural Journal

Volume: 89

Issue: 2

Appears on pages(s): 141-149

Keywords: cracking (fracturing); crack width and spacing; creep; deformation; reinforced concrete; serviceability; shrinkage; slabs; structural members; Structural Research

Date: 3/1/1992

Abstract:
This paper considers the problem of cracking in fully restrained members subjected to direct tension caused by dry shrinkage. The mechanism of direct tension cracking is discussed, and some popular misconceptions concerning the behavior of restrained members are exposed. Paper presents a rational approach for the determination of the number and spacing of cracks and the average crack width in a member, which is fully restrained and subjected only to an axial restraining force caused by shrinkage. The approach is based on the principles of mechanics and is illustrated by worked examples. Predictions agree well with observed cracking in restrained members. The procedure is used to calculate the quantities of steel required for crack control in a number of practical situations. Finally, the results of the investigation are compared with the provisions for shrinkage and temperature reinforcement in the ACI Building Code (ACI 318-89) and AS 3600-1988.