Comparisons of measured and predicted modal properties for steel framed floors

Floor vibration serviceability is a primary design consideration for steel framed floors. The accuracy of any floor vibration evaluation procedure depends on a reasonably accurate prediction of modal properties. To consider multiple modes in the acceleration prediction, the modeling procedure must also accurately predict the spacing of modal frequencies. The goal of this paper is to investigate the ability of current finite element modeling techniques to accurately predict natural frequencies, mode shapes, and accelerance FRF magnitudes. Two building floors were vibration tested and experimental modal analysis techniques were used to determine these modal properties. Analytical predictions were made using a commercially available finite element modeling program. The measured and predicted properties are compared to assess the accuracy of the modeling techniques. It is concluded that currently available finite element modeling procedures provide only very approximate predictions of natural frequencies, mode shapes, and FRF peak magnitudes.