The influence of in-plane floor flexibility on the normal mode properties of buildings

Abstract When the normal mode properties of multistorey structures are being calculated it is usual to assume that the floors are infinitely stiff in their own plane. For most framed buildings this is probably a reasonable assumption, but it is possible to visualize exceptional cases where, owing to a high length-to-width ratio of the floors or to a particular layout of resisting elements, appreciable flexing of the floors in their own plane will occur. In this paper an attempt is made to determine the possible extent of the influence of floor flexibility on the dynamic properties of structural frameworks by the consideration of two typical buildings. The investigation has been confined to symmetrical buildings on rigid foundations. The results indicate that the neglect of in-plane floor flexibility does not significantly change the computed dynamic properties.