Tall buildings - Wind Loading of Structures - page 243

9.8.3 Interference effects on local pressures
Adjacent buildings can also have dramatic effects on local cladding loads on tall
buildings. An interesting, unusual example, based on wind-tunnel tests of a commercial
high-rise development, was described by Surry and Mallais (1983). In this case, a
downwind taller building resulted in an increase in the design local pressures by a factor
of about three. It was explained by the presence of the adjacent building inducing re-
attachment of the separated shear layers (see Section 4.1) on to the wall of the upwind
building (Figure 9.13).
Figure 9.13 Effect of a downwind building on
local cladding pressures (Surry and Mallais,
1983). Reproduced by permission from ASCE.
9.9 Damping
The dynamic response of a tall building or other structures, to along-wind or cross-wind
forces, depends on its ability to dissipate energy, known as 'damping'. Structural
damping is derived from energy dissipation mechanisms within the material of the
structure itself (i.e. steel, concrete, etc.), or from friction at joints, or from movement of
partitions, etc. For some large structures constructed in the last 20 years, the structural
damping alone has been insufficient to limit the resonant dynamic motions to acceptable
levels for serviceability considerations, and auxiliary dampers have been added. Three
types of auxiliary damping devices will be discussed in this chapter: visco-elastic
dampers, tuned mass dampers (TMD) and tuned liquid dampers (TLD).