Page 104 - Vertical City
P. 104
104 The vertical city
Just as the main supporting cables of a suspended
bridge, two groups of six principal oblique cables
connect the summit of the towers to the ground: the
first from the top of the central tower of 170 floors, the
second from the top of the six towers of 110 floors. 7
Like the vertical cables supporting the bridge deck
from the main cables, a net of horizontal cables on a
triangular mesh of 146,2 m (80,6 m) per side connects
the towers one to the other at levels 30, 50, 90 and 110.
The guys 8 ensure the structural damping of the
towers under dynamic loads (mostly wind, but also
earthquakes) and allow for lightweight constructions,
which greatly reduce the additional costs of the struc-
ture associated with the height of slender towers. It also
increases security towards terrorist attack.
The natural deformation of the cables under their
own weight also absorbs the effects of thermal dilata-
tion. 9
7 For L/B = 3,8 each cable is loaded at most at 100 GN (10.000 metric
tons), or a diameter of about 50 cm. It only requires 4.000 m³ of
concrete (or a cube of 16 m per side) at each abutment to balance
this effort.
8 The builders of large suspended or guyed bridges have addressed
the issues related to the vibration of the cables as well as to the
dangers of frost or accumulation of ice.
9 The maximum shortening or elongation of the cable on the size of
the city, for a difference in temperature of 30° C, or -10° C to +50° C
from an average temperature of 20° C, is 58.480 cm (32.240 cm) ×
30° C / 105, or 17,5 cm (9,7 cm), that is quite smaller than the move-
ments of these same towers without cables.
