This paper theoretically and experimentally investigates the semi-empirical formulas recommended by Eurocode 2 (EC2), fib Model Code 2010 (MC2010), and Eurocode 2 with the German National Annex (DIN) for calculating crack widths in reinforced concrete. It is shown that the formulas can be derived from the principles for the idealized behavior of RC ties. However, instead of explicitly solving the resulting differential equations, the use of simplifications leads to inconsistent formulas. An experimental study was carried out involving the testing of eight RC ties to discover the modeling uncertainty of the formulas. It was found that EC2 substantially overestimated the crack widths for the RC ties. MC2010 and DIN seemed to predict the crack widths better, but gave rather a large number of nonconservative crack width predictions. These experimental results, combined with the theoretical study, suggest that a more consistent calculation model should be formulated by explicitly solving the resulting differential equation.

@en

Concrete structures shall be designed and constructed to limit cracking and crack widths for durability, functionality and aesthetic reasons. Current design methods and requirements are, however, only in a limited manner verified for large-scale concrete structures and long service life, as well as for new binder and concrete types. To facilitate an improved design basis for large-scale reinforced concrete structures, the present project on evaluation and improvement of calculation methods for large-scale concrete structures in Service Limit State has been initiated. Initially, the occurrence of shear cracks and excessive deformations in concrete cantilever bridges has been investigated. A calculation model based on the Modified Compression Field Theory was established under the assumption that creep in principal compression direction may cause the occurrence of diagonal shear cracks in webs of the cross section. In a shear cracked state, the shear stiffness will be significantly reduced, which further results in increase of shear deformations. The calculation model was applied to, and verified on a real segmentally cast cantilever bridge: the Sålåsund Bridge with main span L = 120 m, where this type of cracking was observed.@en