INTRODUCTION

The effects of vibration are becoming an increasingly important issue in the design of buildings and building elements. Modern construction methods mean that buildings are becoming lighter and have less structural damping. The response of such buildings to imposed vibration is therefore increased, so people using the buildings are more likely to experience vibration. If the vibration is large enough it can cause annoyance, motion sickness and ultimately panic. Over a number of years, different serviceability criteria have been developed to ensure that buildings and building elements are suitable for their intended activity.

Issues concerned with structural integrity (and hence safety) are not considered in this report. When a properly designed structure is subjected to vibration, people tend to become uncomfortable well before the limiting state of the design is reached. Hence, the serviceability requirements tend to be the critical factor in structures with human occupants. Although there are serviceability criteria associated with the appearance of building finish and public health, this report is limited to a consideration of the intrusive effect of vibration upon people.

The aim of serviceability criteria is to ensure that a structure is suitable for its intended use. Within the population there is a wide range of sensitivity to vibration. Generally, children are the most sensitive to vibration and adult males the least sensitive. Both the activity and posture of a person affect their perception of vibration. A person's expectation and exterior cues (such as sound) are also important factors. This wide number of complicating factors means that serviceability criteria can never be precise: what one person judges to be a tolerable level of vibration may be perceived by another to be annoying. Therefore, judgements often need to be made about the percentage of the population that would perceive the vibration conditions to be unacceptable; these judgements can have significant financial implications. For this reason, many codes of practice recommend that agreement is reached between the designer and the client beforehand about limiting vibration threshold levels.

As noted above, vibration serviceability criteria have been developed over many years. Some of these criteria have been developed for specific applications, whereas others have more general application. Although there are many similarities, there are also differences in the approaches used. Some of the methods relate to specified return time periods (eg one-year, five-year or 10-year periods), other methods relate to specific periods of vibration (eg a 16-hour day or eight-hour night). There is uncertainty about how criteria developed on the basis of simple vibration modes can be extended or interpreted for cases where a structure vibrates in a more complex way. Some methods give ranges of limiting accelerations, whereas other methods give a specific value. Also, some approaches conflict with other methods, and no two methods give consistent agreement with each other. There is not even consistent agreement about the units of acceleration, although the units are easily converted.

Many countries (eg the UK, the USA, Canada, Australia, New Zealand, The Netherlands, Japan, France, Germany and Denmark) have their own national codes of practice and standards, within which are contained building-related serviceability criteria. It is not the purpose of this report to compare and contrast the criteria adopted by each country. Instead, this study focuses on identifying and reviewing information that is relevant to buildings in the UK. Nevertheless, where appropriate, attention is drawn and references made to sources of information from other countries.

The UK falls under the scope of the following codes of practice and standards: the Building Regulations 2000 (England and Wales), Eurocodes (including the UK National Annexes), International (ISO) Standards and British Standards. There are also documents giving advice about specific building applications; these specialised approaches tend not to be consistent with other sources. The issue as to which standards and documents have precedence over others is touched upon in this review. However, a resolution of this matter is outside the scope of this report.

The aims of this review are:

1. To bring together state-of-the-art knowledge about vibration comfort criteria that are appropriate for three building-related areas in the UK where vibration has proved to be an important recurring issue, namely buildings, floors and grandstand risers.

2. To discuss dynamic test methods presently used.