Cracking analysis of r.c. ties considering the effect of internal secondary cracks

The cracking behaviour of an r.c. tie subjected to a monotonic loading, in the stabilized cracking stage, can be described with a model based on the bond stress-slip relationship, tau-s, proposed by fib Model Code 2010 that considers the effect of the so-called Goto cracks or internal secondary cracks. This leads to a decreasing trend of the bond stresses around the crack, along a reduced bond length whose extension increases when the axial load increases. It is shown, in particular, that the average bond stress along the transmission length, on which the crack width calculation method proposed by fib Model Code 2010 is based, depends, other than on the concrete strength, also on the reinforcement ratio and the bar diameter. To this regard, tabulated theoretical values of the average bond stress are proposed as a function of the aforementioned parameters and allow to improve the calculation method proposed by fib Model Code 2010. Finally, the theoretical results of crack spacing and crack width obtained with the general method are compared to the experimental data available in the literature.