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Option to consider reopening of cracks

Last modified by Iwona Budny Bjergø on 2022/02/25 13:07

An option for the consideration of reopening cracks is available in the configuration settings on RC design tab:


According to EN 1992-1-1 7.1 (2), the section should be assumed uncracked, if the maximum tensile stress is lower than fctm. In these cases, the crack width calculation is not performed, and the cracked section analysis is using the uncracked material and section properties in the current iteration.

However, if we assume that the structure has been\will be subjected to higher load levels throughout its lifetime (comparing to the SLS crack combinations), than what is actually happening is the reopening of already existing cracks instead of the development of new ones, which requires lower stress level. By checking the Reopening cracks option, the 7.1 (2) criteria is ignored in crack width and cracked section calculation, and the crack calculation is performed in any case (except for fully compressed sections).

It is important to note that the calculation methodology itself remains the same, as well as the tensile strength of the concrete. Thus, in case of crack width calculation, the crack width values on the shells remain unchanged, however it is determined and display in more nodes. The next figure shows the results without (left) and with (right) the consideration of reopening cracks:


During cracked section analysis, the stiffness and section properties of bars/shells are interpolated between the uncracked and fully cracked state (EN 1992-1-1 Eq. 7.18), depending on the stress level of the current iteration. As at these low stress levels the section is very close to the uncracked state, its stiffness is also going to be very close to the uncracked inhomogeneous stiffness, which means that this option cause only a slightly difference in the deflection results.

NOTE: The crack width calculation only affects the shells, as for bars the parabolic material model is used (EN 1992-1-1 3.1.7 (1)) with zero tensile strength for the calculation of the internal stress distribution.