Large open floor areas free of partitions or other damping sources are susceptible to annoying vibrations induced by human occupancy. Several references are available to determine the human perceptibility to transient floor vibrations. The vibration analysis performed by RAM Steel Beam Design employs two methods described in papers by Thomas Murray published in the American Institute of Steel Construction Engineering Journal:

1. Murray, Thomas M., “Design to Prevent Floor Vibrations”, Engineering Journal, American Institute of Steel Construction, Vol. 12, No. 3, Third Quarter, 1975.
2. Murray, Thomas M. and Hendrick, William E., “Floor Vibrations and Cantilevered Construction”, Engineering Journal, American Institute of Steel Construction, Vol. 14, No. 3, Third Quarter, 1977.
3. Murray, Thomas M., “Building Floor Vibrations”, Engineering Journal, American Institute of Steel Construction, Vol. 28, No. 3, Third Quarter, 1991.

Method 1 uses the modified Reiher Meister scale. It consists of determining the human perceptibility to vibrations based on amplitude and frequency of floor motion. The method is described in Reference 1, with refinements described in the later papers. It is commonly used in many design offices and is referenced in the AISC Manual of Steel Construction.

Method 2 is based on a more recent work by Murray (Reference 3), and consists of determining the percent of critical damping required by a floor system for the beams to be free of annoying vibrations. The damping requirement is calculated using an empirical formula based on the natural frequency and amplitude of the floor system. The engineer then must make a careful judgment of the amount of damping actually present in the floor system and compare it with the required damping. The method employed is as described for Residential and Office Environments.

For either method, the user may elect to either consider or ignore the contribution of the vibrational characteristics of the supporting members.

Although these methods have been incorporated into RAM Steel Beam Design, it should not be construed as an endorsement of either method. As with any aspect of engineering, it is the responsibility of the engineer to determine the applicability and accuracy of a design methodology employed for any given condition.