Shear wall is modelled in Staad by Surface entity . Now a surface entity is composed of internal plate elements .
Staad internally generates the meshed plate elements in a surface panel . The default meshing division is based on the 10 division each edge .One can also reduce this divison and the mesh density by SET DIV command .
Program analyzes the internal plate elements while solving the stiffness matrix . The Surace entity is specially introduced in Staad only for the shear wall design . This entity internally extracts all the plate stresses thus developed and then convert them to the six different forces as specifed and required by the design code for shear wall design .
Mz in the shear wall force output represents in-plane bending force.
Fxy in the shear wall force output represent in-plane shear force.
Fy in the shear wall force output represent in-plane compression force.
My in the shear wall force output represent out-of-plane vertical bending force.
Mx in the shear wall force output represents out-of-plane horizontal bending force.
Qy in the shear wall force output represents out-of-plane shear force.
One need not has to model a shear wall seperately by plate entity and then manually deduce the required focres from the different plate stresses . Instead of that he can directly use teh Surface option.
For more detail on the sherawall modelling and design , refer to the chapter no. 2.2 13.5
in Staad Technical reference Manual .