The Tension Stiffening Mechanism in Reinforced Concrete Prisms

Tension stiffening is an important phenomenon in reinforced concrete because it controls not only deflections but also crack spacings, crack widths and the formation of multiple cracks. It is now common practice to study the effects of tension stiffening in concentrically loaded prisms, which is the subject of this paper, and use these behaviours as guidance for the effects of tension stiffening in reinforced concrete beams. As tension stiffening is a mechanism for stress transfer between the concrete and reinforcement, the interface bond stress-slip (tau-delta) properties are of utmost importance. In this paper, partial interaction theory is used to develop generic closed form solutions for crack spacings and widths, the load to cause primary, secondary cracks and subsequent cracks. Four different types of interface bond characteristics (t-d) are considered: a linear ascending bond slip which is useful at serviceability; a linear descending bond slip which is useful at the ultimate limit state; a nonlinear bond slip characteristic which closely resembles material bond slip behavior at all limits; and the CEB-FIP Model Code 90 (CEB 1992).