Wind-induced
performance could be related to the dynamic responses of a building under wind
actions. Wind-induced responses, in terms of internal force, deflection, drift,
and acceleration, are comprehensively used to describe the building system behavior
or performance under wind excitations. It is clear that performance levels are
closely connected to the concept of limit-state design, which has been widely
adopted in most of modern design codes. Actually, the concept of performance
levels represent an evolution of prescriptive rules for limit-state designs
that have changed during years as more is learned about building behavior.

Although
it has been realized that wind-induced dynamic serviceability is generally the
major concerns in the design of tall buildings, research in structural design
and optimization for dynamic serviceability has not received as much as attention
as that for ultimate strength limit-state design of such structures. In fact, the
design of tall buildings in windy climates is generally dominated by
serviceability considerations in terms of wind-induced deflections and
vibrations, rather than by member strength requirements (Griffis 1993). The
deflections or deformations from all load types should not impair the strength
or effective functioning of a structure, supporting elements or its components,
nor cause damage to the finishes. For typical structures, the deflection limits
are recommended by various building design codes. The first step in doing a
serviceability design procedure is to define the acting load and then check its
effect on the building. Wind loading criteria for both strength limit states
and serviceability limit states in China are normally the same and typically
are based on a 50-year return period wind for normal buildings and a 100-year
recurrence interval wind for important structures. The design wind pressures
given in Hong Kong wind code (HKCOP 2004a, b) have been determined from the
hourly mean wind speed and peak gust wind speed having a return period of 50
years.