Civil Engineering Reference
In-Depth Information
1.9 Engineering as an art form
The effective start of modern building may be defi ned as the construction of the
Pantheon in Rome, in 120
AD
, Figure 1.14. This building exhibits engineering design
in the modern sense. The roof is a 44 m diameter spherical concrete dome, resting
on concrete walls that are some 30 m high. In order to reduce the thrust of the roof,
it is made of lightweight concrete, of which the density reduces towards the crown.
Also, the underside of the roof is relieved by caissons, which fulfi l the three roles of
saving materials, reducing weight and hence the thrust on the walls, while maintaining
stiffness, and decorating the interior.
The walls are 6 m thick, in plain dense concrete. Near their base they are relieved
by chapels on their inside face, made within their thickness. Again, these chapels have
multiple functions, economising on materials, displacing the centroid of the wall
outwards to improve its resistance to the thrust of the roof, providing a useful facility
and decorating the temple. The upper lifts of the wall are more massive, the weight
helping to resist the roof thrust.
Thus the appearance of this building is critically integrated with the engineering
concept, and in the author's opinion constitutes an art form which David Billington [2]
has called 'structural art'. This form of art depends on an engineering understanding of
the forces acting on the structure and the expression of these forces.
The design of the great mediaeval cathedrals shows a similar fusing of form and
function, where the roles of architect and engineer had not yet been separated,
Figure 1.15. Viollet-le-Duc, commenting in his
Dictionnaire de l'architecture française
on the design of these cathedrals, coined the phrase 'architecture raisonée', which
might be translated as 'analytical architecture'. This concept is appropriate to the
design of bridges, as described in the previous sections of this chapter.
As in any form of art, there is a continuum between the multitude of artisans, and
the small minority who reach the summits of skill and inspiration, who are known as
artists. There is no clear dividing line between the superb artisan and the artist, but
great artists are acknowledged as such by most people.
The young engineer who is designing the reinforcement for 100 pile caps for a
long viaduct may not see himself as a future artist. However, depending on how he
goes about this design, he may well be preparing himself for much more creative
engineering later in his career. He can do a boring, routine job, or alternatively there
are many ways in which he can carry out these mundane tasks creatively. For instance,
he can think about the mechanism whereby the vertical loads and bending moments
are transferred from the pier stem to the piles, he can compare strut-and-tie solutions
to classical bending theory, reconcile his understanding of good engineering with the
stipulations of the code of practice, question the purpose of each bar, fi nd reinforcement
arrangements that minimise off-cuts and waste and he can create a modular reinforcing
cage that expands easily with the span and depth of the pile cap.
There must of course be a chief designer who oversees his tasks, and who sets the
tone of the type of design he expects. If this chief designer is interested in producing
a design of quality, he will be prompting his assistant to think creatively about his
task, and giving him ideas to refi ne and develop. Although the majority of such chief
designers will never aspire to being recognised as artists, the best will.
It is common that artists are not recognised as such in their own lifetimes; it is
often in hindsight that their qualities are put in perspective and given the accolades
