DIAPHRAGM FORCES
1.- Apply diaphragm forces (define diaphragm using semi-rigid option)
2.- Display any stress or shell force for the relevant load case
3.-For maximum chord forces, Draw or define a section cut where maximum chord forces are expected
4.- Moments in Z are the in-plane moment in slab make sure angle is zero, refresh as required
5.- The value of Z moment divided by slab width is equal to compression and tension chord forces
6.- Shear and collector forces at slab-shear wall connection , draw or define section cut next to support following wall direction
7.- Make sure angle is zero, in this case shear/collector force is equal to F2 or 2559lbs as expected
See also: https://wiki.csiberkeley.com/display/etabs/Rigid+vs+Semi-rigid+Diaphragm