Design approaches against wind excitation - Tall Buildings: Structural Systems and Aerodynamic Form - page 166

Curved (crescent) or zigzag plans can also be used to increase the stiffness of the
building against lateral loads. The behaviour of these forms against lateral loads is as
effective as the behaviour exhibited by folded plates against vertical loads (Schueller,
1977). The City Hall Towers (Toronto, 1965) ( Figure 6.17 ) and the Bow (Calgary,
2012), which have a curved plan form, are examples.

6.2 structural design approach

The control of the dynamic response of a tall and flexible building can be achieved
by increasing stiffness by the use of “shear-frame systems”, “mega column systems”,
“mega core systems”, “outriggered frame systems” and “tube systems” as a structural
design approach which is discussed separately in Sections 3.6 - 3.10 .

6.3 mechanical design approach

In designing tall buildings, engineers assume a certain level of inherent damping
in the structure when estimating the serviceability of the building under wind- and
earthquake-induced lateral loads.

The inherent damping capacity of a building is affected by:

• the structural system
• the materials used in the structural system
• the cladding and non-structural elements such as interior and exterior partition
walls
• the soil-structure interaction.

This is difficult to estimate and measure.

Figure 6.17

City Hall Towers, Toronto, Canada, 1965