When reactions are imported from a super structure software solution such as STAAD, ETABS or GT Strudl, a standard right handed coordinate system as displayed below is assumed to be used.
In GT Strudl, the gravity axis can be either the Y axis as displayed below or Z axis. An option in GT Strudl allows the gravity axis to be Y or Z before exporting the node and reaction information to Mat3D.
For reaction import from STAAD & ETABS, the coordinate system as displayed below is assumed. It is possible to change the gravity axis on the Node Locations tab of the workspace summary page.