Synopsis
Long-span (reinforced concrete, steel, composite, timber and timber-concrete) floors may show considerable vibration, which may disturb the occupants of such structures. The floor is often supported by columns and beams, which may reduce the natural frequency even in the range of human excitation. In this paper a model and simple explicit expressions are developed for the calculation of the natural frequency of plates, which take into account the deflections of the supporting beams. The floor is modelled as an orthotropic plate, while the effect of the supporting beams is taken into account either with Föppl’s expression or by the Rayleigh-Ritz method. The results are applied to timber and timber-concrete floors with various configurations, and the results are verified numerically. The derived expressions can serve either as an independent check of more sophisticated FE calculations or they can be used in the preliminary design stage.