In the article 7.2.5.3 ( 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 higher than C80 is defined in the project, this message is given.
Solution
Define C80 or lower concrete class and assign it to reinforced concrete elements.
The new concrete class can be defined from the building tree.