Effect of Secondary Cracks for Cracking Analysis of Reinforced Concrete Tie

In order to obtain adequate serviceability and good durability of structures, international standards limit the crack width either through a direct calculation or by adopting specific measures. However, cracking behaviour is very complex because of the huge number of parameters that can have a significant effect on it. This complexity is also confirmed by the high scattering of the test results or by the several formulae that are adopted to theoretically govern the phenomenon. The cracking behaviour of reinforced concrete structures under bending, with or without axial forces, can be described with a model based on the bond stress-slip relationship, tau-s, between concrete and steel. A model of this type based on the bond law proposed by CEB-FIP Model Code 1990 was developed in the literature to predict the mechanical behaviour of a reinforced concrete tie subjected to a monotonic loading, both in the crack formation phase and the stabilized cracking phase. However, the adoption of the bond stress-slip relationship as it is fails to comply with the equilibrium condition and contradicts the experimental condition of fixed crack pattern. These inconsistencies can be overcome considering the effect of the so-called Goto cracks or secondary cracks which leads to a decreasing trend of the bond stresses around the crack. The effect of secondary cracks on the cracking behaviour of an r.c. tie in the stabilized cracking phase is also analysed through a parametric analysis, which highlights how and to what extent their influence zone varies as a function of the axial force, the concrete strength, the reinforcement ratio and the bar diameter.