Human Induced Vibration of Long Rectangular Steel and Composite Floors

Abstract

AbstractRecently several light‐weight, long span floors are built (e.g. steel‐framed structural systems), where the design is governed by vibration control. In these cases the acceleration due to human‐ or machine‐induced vibration can be very high, which may cause human discomfort. Long rectangular plates subjected to concentrated loads are often investigated by a replacement beam with a so called “effective width”, and the amplification factor is calculated according to a SDOF system, which in the case of resonance is equal to 1/2ξ, where ξ is the damping ratio. Since damping in lightweight, steel‐framed structural systems is very low (1–3%), dynamic amplification (calculated according to an SDOF system) can be rather high. However, the steady‐state dynamic response of beams and long plates subjected to periodic loads are significantly different. The steel‐framed floors are mechanically long even in that case when the ratio of the sides of the floor is around one due to the high orthotropy. For long plates, the response and the amplification factor are substantially different from those of beams. Hence, design based on effective width may lead to 2‐4 times higher acceleration than the real values. As an example the roof of a gymnasium under construction is examined, where different sport activities (walking, running, aerobic) will take place. The natural frequency of the floor supported by steel joists is small, close to the frequency of walking, therefore a detailed vibration analysis was performed.