Vibration serviceability of long-span concrete building floors - Part 1: review of background information

摘要

The current push towards stronger concrete materials and the use of prestressing is resulting in increasing slenderness and liveliness of long-span concrete floors in buildings. Although concrete floors have had a good vibration serviceability track record, this trend may lead to an increasing number of floors failing their vibration serviceability. This is the first part of a two-part paper which reviews literature pertinent to the vibration serviceability of long-span building floors made of concrete. As rationalization of any vibration serviceability problem requires characterization of the vibration source, path and receiver, the first part of the paper surveys 132 general references pertinent to these three key aspects of the problem. The second part of the paper builds on this background and reviews the approaches which integrate these three key aspects of the problem and propose ways for its mathematical modelling. The review of the vibration source found that humans are the most relevant excitation of building floors, which is practically impossible to isolate effectively. Moreover, mathematical models simulating human-induced excitation, such as 'near periodic' walking, running or jumping, do exist, but caution is required when using them on lightly damped floor structures. In this case, an assumption of pure resonance may lead to significant overestimation of responses due to the inability of humans to generate perfectly periodic forces. When considering concrete floors as vibration path caution is required as closely spaced modes of vibration tend to occur in orthotropic building floors having repetitive geometry. Also, evidence exists that in situ cast concrete columns tend to add stiffness to the floor system. These two facts mean that simplified modelling of concrete floors as SDOF systems based on the fundamental mode of pin-supported beams is likely to produce erratic results. Finally, typical receivers of floor vibrations are its human occupants or vibration-sensitive equipment. Characterization of humans as floor vibration receivers is probably the most difficult aspect of the floor vibration serviceability problem. Extreme caution is required when interpreting the plethora of procedures and parameters which exist in the literature related to human perception of vibrations. Most of these are not applicable to low-frequency low-level building vibrations. However, of those which are applicable there is an increasing trend to use either the root-mean-square acceleration or vibration dose value when assessing the vibration serviceability of building floors.