The Complete Message:
The concrete class used cannot be lower than C25.
In the article 188.8.131.52 ( a) of BDY 2018 , in reinforced concrete elements that will meet the earthquake effect; Among the concretes given in TS EN 206, C25 to C80 concrete classes will be used, there is a condition.
Based on this condition, if a reinforced concrete element with a strength lower than C25 is defined in the project, this message is given.
Define C25 or higher concrete class and assign it to reinforced concrete elements.
The new concrete class can be defined from the building tree.
Assigning concrete class is done in the properties of the elements, in the Static / Reinforced Concrete tab, from the static material list.