An Improved Method for the Calculation of Crack Spacing and Width in RC Beams

On the basis of the cracking analysis of an RC tie subjected to a monotonic loading, that considers the effect of the secondary cracks in the stabilized cracking stage through a linear distribution of bond stresses close to a primary crack, a general crack prediction model has been set up. The mathematical model is based on equilibrium and compatibility conditions as well as constitutive laws for bond and normal stresses. It results that the average bond stress along the transmission length can be assumed as a function of the concrete strength, the reinforcement ratio and the bar diameter. This assumption has allowed to improve the calculation method of crack spacing and crack width, proposed by fib Model Code 2010. The improved method is here applied in the case of RC beams. This extension is based on the concept of effective area of concrete in tension surrounding the reinforcement that is considered in fib Model Code 2010 and Eurocode 2. The theoretical results of crack spacing and crack width obtained with the improved method are compared to the experimental data available in the literature as well as the results obtained with standards.