Floors with joist spacing’s of 4’ to 10’ tend to have increased total concrete slab depths and greater mass to resist floor vibration. SJI’s Technical Digest No. 5 Vibration of Steel Joist – Concrete Floor Slabs discusses in detail, methods for calculating vibration characteristics of CJ-Series steel joists. Calculation of vibration properties for SJI’s CJ – Series joists can readily be determined utilizing FloorVibe v3.0 by Structural Engineers, Inc.