Page 105 - Vertical City
P. 105
THE NEW SMALL VERTICAL CITY 105
These same cables, oblique and horizontal, can,
without additional costs, ferry gondolas between the
towers 10.
The use of guys also has the effect of submitting the
towers practically only to vertical forces, which permit
to apply the economic principle of load compensation
for the foundations. It consists of balancing the weight
of the tower by that of the excavated soil for its under-
ground structure, in such way that the stresses in the
ground are identical, whether or not there is a tower.
This also has the added advantage of avoiding subsi-
dence or deformation of the soil.
This leads us to plan for respectively 4, 6, 8, 11 and
17 underground floors beneath the towers of 30, 50, 70,
110 and 170 levels.
In our latitudes with L/B = 3,8, the bridges carrying
the networks of two or three levels (either 6,6 m or
9,9 m) for a span of 98,2 m, guyed at a third of their
length, present a structural slenderness ratio 11 between
98,2 m/ (6,6 m × 3) or 98,2 m/ (9,9 m × 3) or between 5
and 3,3. Their structure (with an indicator of volume 12
W ≃ 1) is therefore the lightest possible.
10 London has already built a cable car to cross the Thames, and urban
transportation by cable is the object of feasibility studies in the Paris
region (Televal and Porte de Bagnolet). The vitality of the company
Poma attests to the enthusiasm for this type of transportation.
11 This is the ratio between the span of the bridge and its height.
12 A structure is even lighter as its indicator of volume W, described
in my text on their morphology, is low. It cannot in all practicality be
inferior to 1 for a bridge.
