Also see the archival
list of the Essays on Science and Society.
ESSAYS ON SCIENCE AND
SOCIETY:
A Tale of Two Cities: Architecture and the
Digital Revolution
William J. Mitchell*
William J. Mitchell, is
professor in and dean of the School of Architecture and Planning at
MIT. His most recent book is High Technology and Low-Income
Communities, with Donald A. Schon and Bish Sanyal (MIT Press,
1999). His forthcoming E-Topia: Urban Life Jim--But Not As We
Know It, which explores the new forms and functions of cities
in the digital electronic era, will be published by the MIT Press in
Fall 1999.
CREDIT: ALLAN BURCH
The scientific and technological advances of the
industrial revolution radically transformed construction. New
materials and systems transcended previously critical constraints on
building size and complexity, allowing architects to create
skyscrapers, long-span structures, and mechanically and electrically
serviced interiors. By providing new intellectual tools, the digital
revolution is now producing a similar revolution in design, allowing
architects to imagine, develop, and explore innovative concepts that
would have proved impossibly difficult in the past.
Before a large and complex building can be constructed,
architects first need to produce drawings or some other precise and
detailed representation of it. Furthermore, architects and engineers
need to predict its performance under expected conditions of use:
They must establish acceptable levels of confidence that it will be
structurally adequate, that it will provide the necessary thermal,
lighting, and acoustic conditions, that it can be built on time and
on budget, and so on. Thus the architectural design process is
largely one of creating and analyzing representations of alternative
proposals, and then translating the completed representation of a
selected proposal into full-scale, physical reality. This extended,
highly collaborative process proceeds partly through flashes of
inspiration, but mostly through dogged trial and error.
In the past, the geometric and material possibilities that an
architect could explore in this process were severely constrained by
the limitations of available representation and analysis tools.
Traditional drafting instruments--parallel bars, triangles,
compasses, scales, and protractors--largely restricted designers to
a world of straight lines, parallels and perpendiculars, arcs of
circles, and Euclidean geometric constructions. The limitations of
analysis techniques based on precedent and rule of thumb meant that
the range of designs with predictable performances was even
narrower.
As a result, architects frequently found that they could sketch
configurations that they could not describe sufficiently precisely
or analyze sufficiently reliably, and therefore could not build. Of
course, it was still possible to create wonderful works under these
constraints, just as poets can create masterpieces within the severe
constraints of the sonnet form, but the fact remained that many
interesting design possibilities could never even be given serious
consideration.
Today, computer technology has changed all that. Modern CAD
(Computer Aided Design) systems allow designers to create very
complex three-dimensional (3D) geometric models with ease. In
addition, the availability of inexpensive computing power
facilitates the application of sophisticated analysis and simulation
algorithms to predict performance. These procedures need not rely on
unsubstantiated assumptions and rough approximations as in the past,
and the simulations can model the performances of structural and
environmental systems much more reliably. CAD/CAM technology--the
use of CAD models to drive numerically controlled fabrication and
assembly machinery--also allows the timely and economical
realization of designs that would once have proved impossibly slow
and costly.
To illustrate the extraordinary transformation that has taken
place in the digital decades, let us compare two architectural
masterpieces of the latter half of the 20th century: Jørn Utzon's
Sydney Opera House and Frank Gehry's Guggenheim Museum in Bilbao.
Both were regarded as breakthrough buildings of their time, both
caught the public imagination, and both became instantly emblematic
of the cities in which they were built.
The Sydney Opera House was the outcome of an international
competition held in 1956.*
Utzon's winning entry featured curved concrete shell vaults which,
the jury commented, "relate as naturally to the harbor as the sails
of its yachts." However, these spectacular vaults obviously
presented an extraordinary structural challenge, and the London
engineering firm of Ove Arup and Partners was therefore immediately
engaged to help figure out how to build them.
Utzon's very schematic competition drawings had depicted
free-form curved surfaces. The first task was thus to find a precise
and useful mathematical description. Arup commented: "Each of the
main shells consists of two symmetrical halves meeting in a ridge in
the vertical plane going through the longitudinal axis of the hall.
The ridge is part of a parabola. The two symmetrical surfaces
meeting in this ridge are roughly triangular in shape and descend on
each side to a point which forms a support for the shells.... By
thus defining the surface of the shells geometrically each point of
the surfaces can be given spatial coordinates and a basis has been
created for the calculation of the forces acting on the shells and
the stresses created in the shells."
From 1957 to 1961, Utzon and Arup struggled to find a feasible
structural solution, while simultaneously experimenting with shape
modifications intended to make the analysis and construction
problems more tractable. They explored single-skin concrete shells,
double concrete shells, systems of arches, and finally, ribs fanning
out from the base of each shell. The ridge profile became a circular
arc, then an elliptical one. Nothing worked, until the team
eventually hit upon a brilliant simplification. The surfaces of all
the shells could be defined, to a very close approximation of the
original sketched forms, as triangular patches on the surface of a
single sphere.
The ridge profile and the ribs thus reduced to arcs of circles,
and the uniformity of the surfaces now meant that they could be
constructed from prefabricated repeating elements, achieving
economies of scale and reducing the cost to a more acceptable level.
The working drawings could be generated using traditional drafting
instruments and standard techniques of descriptive geometry.
Furthermore, even with the relatively primitive algorithms and
minuscule computer power available at the time, the structural
analysis problem was simplified to the point where the necessary
calculations could be completed in a few months. By 1967, the
beautiful shells that we see today on Bennelong Point were finished.
Meanwhile, Utzon turned his attention to the design of the
auditorium ceilings, which he intended to be constructed from
suspended plywood panels. These had to conform to the shape of the
exterior shells, provide appropriate acoustic conditions, and create
visually compelling interior spaces. After lengthy experimentation
he proposed, in response to these demanding requirements, an
elaborate system of plywood box-beams shaped as sequences of convex
circular arcs.
To this second chapter of the story, though, there was to be no
happy ending. Arup came to believe that the box-beam design was
hopelessly impractical and should be replaced with a far more
conventional one. Increasingly, the virulent Australian press
pilloried Utzon for cost overruns and completion delays. Meanwhile,
a newly elected conservative state government was after the
architect's blood. (He was, after all, a foreigner, stubborn in
defense of his apparently outlandish ideas, and an appointee of the
previous Labor government.) In March 1966, Utzon was forced to
resign; he left Australia in bitterness and secrecy and was not to
return for decades. The interior project design was completed by
others, and--apart from the magnificent shells--has little of the
freshness and originality that Utzon and his supporters had hoped
and struggled for.
The tale of Bilbao--four decades later--began similarly but
turned out much more happily.
Gehry's initial sketches and models for
a museum beside the Puente de la Salve Bridge showed an even more
audacious assemblage of free-form curved surfaces than Utzon's. But
by this time, accurate modeling for analysis and construction
purposes was no longer a problem. For development of the design,
Gehry's office employed Catia--an advanced CAD system mostly used,
until then, in aerospace and automobile design. Like other such
systems available today, Catia provides a repertoire of spline
surfaces, ruled surfaces, and other surface types that can be
instantiated and assembled within a three-dimensional Cartesian
coordinate system to model just about any form a designer might
imagine. The Catia digital model, rather than a conventional set of
drawings, thus served as Gehry's definitive design representation.
During development of the design, this digital model was put to
many uses. Whereas Utzon had been forced to rely on laboriously
handmade drawings and scale models in his explorations of visual and
spatial effects, Gehry could employ visualization software to
produce, almost instantaneously, whatever views he needed. He could
also utilize rapid prototyping devices to generate physical models
automatically. The digital model also provided input data needed for
structural and other analyses. The complexity of these analyses no
longer presented a difficulty either: the available algorithms had
improved enormously in versatility and scientific accuracy since
Utzon's day, and the computer power needed to execute them had
become abundant and inexpensive.
Finally, at the construction stage, the digital model was used to
control CAD/CAM fabrication processes. This greatly reduced the
necessity for shape uniformity and component repetition. Gehry had
no need to seek heroic simplifications, like Utzon's resort to
spherical patches. The gap between what could be dreamed of and what
could be produced had been narrowed dramatically. Budget and
schedule were kept in close control, and the completed
building--remarkably true to the architect's first visionary
sketches--opened in 1997 to universal acclaim.
Bilbao illustrates a profound ongoing transformation of
architectural thinking and construction practice, the greatest such
shake-up since the industrial revolution. Replacement of drawings
done by hand with 3D CAD models and computer visualizations has
removed ancient constraints on architectural geometry and is
allowing exciting new languages of architectural form to emerge. The
use of sophisticated analysis and simulation algorithms, as well as
accurate calculations that take advantage of abundant computer
power, allows the behavior of these new forms to be understood and
predicted. Finally, supplementing industrial-era mass-production
with CAD/CAM mass-customization contributes to their speedy,
accurate, and inexpensive fabrication. For architects, the gap
between the imaginable and the feasible has narrowed dramatically.
The author is in the School of Architecture and Planning,
Massachusetts Institute of Technology, Cambridge, MA 02139-4307,
USA.
*The story of this project is told in detail,
with numerous illustrations, in Francoise Fromonot, Jørn Utzon:
The Sydney Opera House (Electa/Gingko, Milan, 1998).
Quoted in Fromonot, p. 65.
Francesco Dal Co, Kurt W. Forster, and
Hadley Arnold, Frank O. Gehry: The Complete Works
(Monacelli Press, New York, 1998).
