Floor Vibrations in Composite Floor Systems

Floor vibrations contribute significantly to occupant comfort in new building construction. Relevant design standards include AISC's Steel Design Guide 11 and SJI's Technical Digest 5. This paper explores floor vibrations in composite floor systems using steel joists. A parametric study was conducted to determine the effects of modal damping ratio on peak acceleration calculations. Peak acceleration calculations are performed using both hand-calculations and FloorVibe, a software program coded to comply with AISC and SJI specifications. Analyses of a sample building were conducted with modal damping ratios that varied between 0.02 to 0.05 (2% to 5%). Additionally, the study also considered slight differences in joist spacing and depth of joist systems used. Results for peak acceleration indicate that vibrations increased when joists were spaced further apart, when smaller joists were used, and when lower modal damping ratios were used. Good correlation between computer analysis and hand-calculations was also observed.