When using rigid diaphragm analysis in RISA-3D it can be useful to evaluate the story shear in each frame. This is a perfect application for the Internal Force Summation Tool. The first step is to solve the desired load combination.
Using the selection tools on the far left side of the screen, unselect (gray out) everything in the model except for the frame which you are interested in. Next, snap the model into an elevation view of the frame. These two steps are very important.
Click on the icon with a blue sigma in the lower left corner of the screen. Then click on two joints of the frame that are at the same elevation to define a horizontal cutting plane.
Once the cutting plane is defined (by clicking the second joint) you can slide the plane up and down your frame, and the force results will be displayed at the bottom of the screen. Click a third time for a dialog box which explains what each force is. F1 represents the story shear.