In a speech given at the First United
States Conference on Prestressed Con-
crete, Samual S. Baxter, later to be-
come president of the American Soci-
ety of Civil Engineers, stated that had
the original arch design for the new
Walnut Lane Bridge been bid below
the engineers’ estimate:
30
“It is also quite possible that this
First Conference on Prestressed Con-
crete might not now be in session . . .”
His claim was probably correct,
even though prestressing was already
being tried out elsewhere by 1951 and
some conference would most probably
have been arranged thereafter. Still,
this Philadelphia bridge served to
characterize the potential for pre-
stressed concrete because of its large-
scale, 160 ft (48.5 m) main spans, be-
cause of its construction economy, and
because of its acceptance, not only by
city engineers, but also by a powerful
city Art Jury, two types of people nor-
mally associated with traditional (con-
servative) attitudes.
As Baxter explained it, the stone-
faced arch design of 1974 obtained a
low bid of $1,047,790 compared to the
engineers’ estimate of $900,000. By
law, if the low bid exceeded the esti-
mate, it was rejected. Thus, the city
engineers began to search for another
solution, of which two arose.
The first solution was a plan to re-
move the stone facing which in the
low bid amounted to the astounding
sum of $486,490! Here, the Art Jury
objected to the mass of an unfaced
arch. The second solution suggested
itself almost by accident.
31
“The Bureau of Engineering, Sur-
veys and Zoning at that time was con-
structing large circular sludge tanks at
its new Northeast Treatment Works.
In a speech given at the First UnitedStates Conference on Prestressed Con-crete, Samual S. Baxter, later to be-come president of the American Soci-ety of Civil Engineers, stated that hadthe original arch design for the newWalnut Lane Bridge been bid belowthe engineers’ estimate:30“It is also quite possible that thisFirst Conference on Prestressed Con-crete might not now be in session . . .”His claim was probably correct,even though prestressing was alreadybeing tried out elsewhere by 1951 andsome conference would most probablyhave been arranged thereafter. Still,this Philadelphia bridge served tocharacterize the potential for pre-stressed concrete because of its large-scale, 160 ft (48.5 m) main spans, be-cause of its construction economy, andbecause of its acceptance, not only bycity engineers, but also by a powerfulcity Art Jury, two types of people nor-mally associated with traditional (con-servative) attitudes.As Baxter explained it, the stone-faced arch design of 1974 obtained alow bid of $1,047,790 compared to theengineers’ estimate of $900,000. Bylaw, if the low bid exceeded the esti-mate, it was rejected. Thus, the cityengineers began to search for anothersolution, of which two arose.The first solution was a plan to re-move the stone facing which in thelow bid amounted to the astoundingsum of $486,490! Here, the Art Juryobjected to the mass of an unfacedarch. The second solution suggesteditself almost by accident.
31
“The Bureau of Engineering, Sur-
veys and Zoning at that time was con-
structing large circular sludge tanks at
its new Northeast Treatment Works.
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