This is triangle hollow block You must create the R,D,A of the structure by entering the WIZARD. You did not enter it. If it is taken as you did, it will not give 0.75 error. It would be fooling the program, but actually deceiving yourself. You cannot solve this type of structure with so few pitches. You should increase the pitches as follows. (When TBDY2018 was first published As an example, I fixed a project in the forum to save it.) Ünver ÖZCAN