Appropriately, the first project to be
discussed is the 1972 highway bridge
over the Rio Colorado (see Fig. 9) in
Costa Rica designed by T.Y. Lin In-
ternational and spanning 479 ft (145
m) between supports over a 300 ft (91
m) deep valley.
48
This new form
shows its structural logic clearly in the
almost polygonal lower chord, its deli-
cate verticals and its straight light hor-
izontal roadway.
The same sense of form appears in
the Chillon Viaduct (see Fig. 10)
along the northeast shore of Lake
Geneva and designed by Professor
Piguet of Lausanne, Switzerland.
Here, the design was chosen after a
competition in which the criterion of
aesthetics played a major role. The
double cantilever method used precast
concrete components post-tensioned
In a way, each of these three pro-
jects are by mature designers who
have worked with prestressing since
its early days. Thus, these engineers
are very much like the earlier pioneers
whose major contributions came after
a long contemplation of the behavior
of structures.
Whether these designers would
admit it or not, the crucial factor was
the study of history – not a study of
names and dates, but rather of forms
and of full-scale behavior. Ideas in
structure come from understanding
clearly the works of the recent past;
but they also come from abroad as
well as from home.
works of Freyssinet, Magnel, and Fin-
sterwalder, American engineers have
begun adapting prestressed concrete to
American conditions. In so doing, de-
signers like T. Y. Lin, engineers of the
state of California, and others across
the continent have shown how new
American forms can become a central
part of the recent past that engineers
everywhere will need to study.
Freyssinet’s difficult years from
1928 to 1935 have led to new forms
that have become symbols of how the
structural environment of the 21st cen-
tury can be built, not only to save ma-
terials and money but also to add ele-
gance and dignity to society equal to
any period in our history.
together. The total final cost of the 1 /2
1
mile (2 /2 km) long viaduct was only
$14 per sq ft.
1
49
Lastly, and departing slightly from
the historical focus, is the most recent
bridge of Switzerland’s most talented
contemporary bridge designer, Chris-
tian Menn. This magnificent structure,
the Ganter Bridge, is on the road going
over the Simplon Pass (see Fig. 11).
This structure reflects the continual
search for form in prestressed concrete.
In understanding more clearly the