Page 84 - Vertical City

84 The vertical city

Progress in material science and technology lead now
to the use of concretes (up to 100 mPa) and steels (up to
700 mPa) more resistant, at lower relative cost, without
the augmentation of the resistance being accompanied
by that of its rigidity 2.

Constructions realized with these highly resistant
materials are thus lighter but also more flexible.

The necessary rigidity, to limit horizontal deforma-
tion under wind load, must be found in the morphology
of the tower 3.

It can be obtained by reducing its slenderness: for
example, for a given height H enlarging the width B
of the tower 4. The necessary volume should then be
excavated to ensure natural lighting and ventilation of
all habitable spaces, as I proposed for the 450 m-high
tower at La Défense in Paris.

Its photovoltaic multi-colored structural envelope
on a square plan of 54 m per side comprises a stack of
10 volumes, each 10 floors high in an L-shaped plan, with

2 The elasticity modulus E characterizes the rigidity of the material.
Also known as the Young modulus, it expresses (in Pa) the relation-
ship between the stress σ (in Pa) in the material with a deformation
σ and this deformation (a-dimensional number). E is constant for
steel (210 GPa) and proportional to √σ for concrete (E = 20 GPa
for σ = 10 MPa).

3 See Philippe Samyn, Étude de la morphologie des structures, à l’aide des
indicateurs de volume et de déplacement, Académie Royale de Bel-
gique, Mémoires de la Classe des Sciences, 3e série, t. V, Bruxelles,
2004.

4 The actual record of slenderness may well be the apartment tower
(the construction will begin soon) 111 West 57th Street in Manhat-
tan: 400 m in height, it presents an H/B = 24!