Regarding the analytical calculation of SLS, you should note that the calculation is based on a provided or applied reinforcement for SLS.
The provided reinforcement can result, for example, from the ultimate limit state design, the defined basic reinforcement, or the automatically determined required reinforcement for SLS. The reinforcement applied to the SLS design can be displayed graphically.
Problem Cause
If, in some areas, a reinforcement that is too small or no reinforcement results from the ULS or from the basic reinforcement and if, at the same time, no required reinforcement is determined for the SLS, then the serviceability limit state design is performed without reinforcement or with a reinforcement that is too small. In this context, very high results may occur during the deformation, for example. Also, there may be poor convergence.
Problem Solution
It is necessary to ensure that there is a reinforcement in each area of the structural system. For this, you can apply a basic reinforcement or a minimum reinforcement, for example.