The Complete Message:
Structural system type A15 (in X / Y direction) is selected. Shearwalls should be used in A15 structural systems.
The A15 structural system is defined in the earthquake code as buildings where all the effects of earthquakes are met with high ductility level reinforced concrete walls.
However, the shearwall is not defined in the project.
Shearwalls should be added in the requested direction in accordance with the A13 structural system in the project .
If a Shearwall will not be used in the structure, in the Analysis Settings / TBDY 2018 Earthquake Code Wizard, A11 for High Ductility Level Systems and A31 for Systems with Limited Ductility Level can be selected.