BRE IP21/12 PDF

INTRO DUCTION

People perceive structural motion as ‘jerk', which is the rate of change of acceleration. Nevertheless, dynamic comfort criteria most commonly used in the UK relate to the acceleration itself. People have a wide range of sensitivity to acceleration, and this sensitivity depends upon what they are doing.

Accelerations can be continuous or intermittent, and the acceleration signals themselves can be relatively smooth or ‘spiky'. Accelerations can occur at a single frequency, at a few discrete frequencies or over a wide range of frequencies. The orientation of a person with respect to acceleration is also important. People are most sensitive to accelerations with frequencies between about 1–2 Hz for horizontal accelerations, and between 4–8 Hz for vertical accelerations. Dynamic comfort criteria have been developed to take into account all of these acceleration characteristics.

Before an informed discussion can take place, the concept of acceleration must be understood. It is also necessary to define statistical measures of acceleration. This is because dynamic comfort criteria give upper threshold acceleration limits. These limits relate to a particular statistical measure that is appropriate for a given situation. Comparing statistical measures that are measured (or predicted) with comfort threshold limits enables people's reaction to acceleration to be assessed.