The Structural Systems oF Tall Buildings - Tall Buildings: Structural Systems and Aerodynamic Form - page 28

Diagonal-bracing X-bracing
(a)

Chevron-bracing (V-bracing) Knee-bracing

Concentric-bracing

Eccentric-bracing
(b)

Figure 3.15 Types of bracing

elastic limits, while eccentric-braced frames do so within both elastic and inelastic
limits. Although the lateral stiffness and so deformation of eccentric-braced frame
systems are not as great as in concentric-braced frame systems, they are preferred in
seismic regions because of their energy dissipation capacity and ductility. In resisting
ultimate loads, energy produced by the external shear is dissipated/absorbed by
ensuring ductility through bending and shear in the lower and upper beams of shear
truss (truss frame).
The 21-storey, 92 m high Masonic Temple (Chicago, 1892), designed by the archi-
tects Burnham and Root in Chicago in 1892, was the first tall building in which a
shear trussed frame system was used.
The shear trussed frame system has been used in many tall buildings which held
the title of “the world's tallest building” in its time, including the 77-storey, 319 m
high Chrysler Building (New York, 1930) ( Figure 3.16 ), and the 102-storey, 381 m high
Empire State Building (New York, 1931) ( Figure 3.17 ) .

3.6.2 Shear walled frame systems

Shear walled frame systems consist of rigid frames and reinforced concrete shear walls
that are perforated or solid ( Figure 3.11b ). In general, shear walls are of reinforced
concrete; occasionally of composite formed by concrete encased structural steel, or of
steel plates. Columns and beams are reinforced concrete, steel or composite.
Some examples of tall buildings using the shear walled frame system with
reinforced concrete structural material include:

• the 32-storey, 127 m high Pirelli Building (Milan, 1958) (the irst reinforced
concrete building utilising the interactive system of rigid frames and shear walls)