Hybrid tension stiffening approach for decoupling shrinkage effect in cracked reinforced concrete members

Abstract

Even at first loading, restrained shrinkage of concrete might significantly affect cracking resistance and short-term deformations. Correct assessment of this effect is of vital importance in constitutive analysis. Recently the authors proposed a methodology for eliminating the shrinkage effect from short-term moment-curvature and tension stiffening relationships. However, owing to rather complex issues of convergence and numerical integration, this approach was difficult to apply in practice. The present study proposes an improvement making the methodology a transparent and mechanically sound tool for analysis. The key strategy for the modification was to reduce a large number of concrete layers to two layers, one tensile and one compressive, the latter being assumed to be linear elastic. The study introduces a new concept of tension stiffening, the hybrid model, combining features of the reinforcement-related and the concrete-related approaches. Like the reinforcement-related approach, it assumes that tension stiffening stresses act in the same area in which tensile reinforcement occurs. To account for the shrinkage effect, tension stiffening is related to the concrete - a material capable of shrinking.