FAQ, CEDRUS, Question 2

Why do the moments resulting from a limit state specification not match the results of a corresponding result combination?

For limit state specificaions you only get reinforcement moments (limit values for mx would hardly make sense). The reinforcement moments ma_xt, ma_yt, ma_xb, ma_yb are based on a linearized yield criterion. For ma_xt (top layer reinforcement moment in x direction) e.g. not only the component mx of the involved loadings are taken into account but also the m_xy. Therefore reinforcement moments may not be compared with single component results (e.g. m_x) from result combinations.

Note: A limit state specification consisting of only one permament loading can lead to different values for ma_xt and ma_xb. In a point with pure torsion (m_x=m_y=0) you will get the results ma_xt=-|m_xy| and ma_xb=+|m_xy|.