... box. Thesevalues control the shape of the 5% damped spectrum. Refer to ATC-40, Chapter 4, for adiscussion of, and appropriate values for, Ca and Cv.• The Show Family of Demand Spectra check ... of the table defineswhich joints are referred to as the center, corner and edge joints. Note that no mass is assignedto joints 22 and 26 at the roof level. These are the joints at the top of ... Center, Edge and Corner JointsLevel Center Joint Edge Joints Corner JointsRoof 24 20, 23, 25, 28 19, 21, 27, 29Second 14 11, 13, 15, 17 10, 12, 16, 18Joint Masses at Center, Edge and Corner Joints...