DESIGN CRITERIA AND LOADS
W. H. Melbourne and J. C. K. Cheung
Background to the generation of perceptible accelerations in tall buildings is described with the conclusion that these tend to be dominated by the cross-wind response to wake (vortex) excitation. A sensitivity analysis demonstrates the dependence on wind speed, damping, building massiveness and the cross-wind force spectrum. The remainder of the paper gives guidelines to the way in which the shape or configuration of a building may be directed to achieve reductions in the cross-wind force spectrum and hence reductions in acceleration response to meet occupancy comfort criteria.
The design of many tall buildings has become increasingly determined by the requirement to keep motion from wind action to within acceptable levels for human occupation. The most significant response in this respect is the cross-wind response driven by the wake (vortex) excitation mechanism. There are a number of ways of shaping or configuring a tall building to reduce the cross-wind excitation, such that it can be hypothesized that there should never be any need to incorporate auxiliary damping into a tall building which has been appropriately shaped. This paper will discuss the parameter sensitivity of tall buildings to cross-wind response and develop some guidelines for the shaping of tall buildings to avoid excessive response to wind action.
The more technical aspects of the mechanisms of tall building response to wind action and acceleration criteria have been covered in several papers by Melbourne et al (1988, 1992, 1998). For the purpose of this paper the essential background information will be summarised.