“When bids for both the steel and the
concrete designs were opened, it was
clear that on a project of this kind steel
was no longer a serious competitor.”
The fourth report dealt with the
bridges for the Illinois Tollway on
which the decision had been made to
standardize precast factory-made pre-
stressed elements for 224 of the 289
bridges.
designs indicated the economy of
prestressed concrete. For the pre-
tressed concrete bridges, the unit costs
were $13.10 per sq ft whereas for the
steel option it was $16.50 per sq ft, a
very substantial difference.
The fifth and final American report
on bridges described a full-scale load
test of one bridge for the Illinois Toll-
way.
What these reports showed is that
by 1957 there was a major shift in
focus, compared to the bridge reports
at the MIT Conference six years ear-
lier, i.e., a shift away from individual
custom-made projects like the Walnut
Lane Bridge and towards mass pro-
duced fabrication on immense projects
or, as in the case of California, the use
of prestressed concrete by a single
public agency. There is no mention of
the Walnut Lane Bridge in any of
these articles and very little reference
to European experience. As Dean
stated in his opening remarks:
44
“It appears that in the field of rela-
tively small standardized, mass pro-
duced parts, United States construc-
tion is presently outstanding. In long
spans, continuous structures and the
more daring structural applications,
foreign technology leads.”
As if to pick up Dean’s challenge
about Europe’s lead in daring struc-
tures, T.Y. Lin, the conference chair-
man, closed the proceedings by pre-
senting a set of drawings by an
architect for daring structures of pre-
stressed concrete. Indeed, Lin’s own
career since that time substantiated
clearly the positive results of such fu-
turistic stimulus.
What I wish to add here is the paral-
lel stimulus of looking back at some
equally dramatic design ideas which
arose during those early years before
the Berkeley Conference. Especially
important are the ideas of Ulrich Fin-
sterwalder, who during that same pe-
riod in the 1950s embraced prestress-
ing and made it a construction tech-
nique as well as a design idea.