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[Music begins].
>> Male narrator: Who would have dreamed
that the introduction of a new application of concrete to
American construction would become the foundation of
50 years of human daring, risk and innovation?
Who would have imagined that the 1950 construction of the
Walnut Lane Memorial Bridge in Philadelphia would
so dramatically change the thinking of American Engineers
and designers?
No single event was more instrumental in launching
the pre-stressed and pre-cast concrete industry
in North America.
And no person was more significant in making
the Walnut Lane Bridge into a reality,
than professor Gustav Maniel of Belgium.
A charismatic, dynamic engineering genius,
Maniel developed the concepts for pre-stressed concrete
while at the University of Gent.
He brought his ideas to America during a visit in 1946.
Charles C. Zoleman, a former student and a Pennsylvania
consulting engineer, worked with Maniel
and together they outlined the benefits that pre-stressing
would provide to the concrete component.
Their report led to the testing of full-size bridge beams,
developed by Maniel.
Zoleman then worked with Ted Gut, of the pre-load
corporation, and officials in Philadelphia's
Bureau of Engineering, Surveys and Zoning,
to create a design that took full advantage
of pre-stressed concrete's benefits,
Bids for the project were taken on January 19, 1949.
The contract was awarded later that spring to the
Henry W. Horse Company in the amount of $698,000 .
Interest in the project was extremely high.
more than 300 engineers from seventeen states
and five countries watched a test of a girder like those
used in the Walnut Lane Bridge's main span.
The project proved to be an unqualified success.
The Walnut Lane Memorial Bridge met a variety of challenges
and proved that pre-stressed concrete could provide benefits
unmatched by any other material.
It was the culmination of many innovations developing
around this new technology during this period.
For instance, as early as 1944, the First Technical Committee on
Pre-stressed concrete was organized by ACI, and ASCE.
Then, in 1948 the first stress-relieved wire was
developed by John A. Roebling and Sons Company.
And in 1949, concrete products of Potstwon Pennsylvania created
the first pre-tensioning bed to make pre-tensioned bridge beams.
Soon came such innovations as the Michigan Block Beam system
which required only three components to produce.
The first pre-stressed girder's design for a building were
produced in 1951 in Tulsa Oklahoma, using button-headed
linear pre-stressing.
That same year, in Tacoma, Washington,
Anderson Brothers built their pre-stressing plant.
In 1952, pre-stressed concrete of Colorado produced
a double T design.
Marketed as the twin T, it was first used for the
cold storage warehouse for Beatrice Foods .
It allowed larger spans between beams and remains
a key component design to this day.
The Arroyo Seco Pedestrian Overpass in Los Angeles marked
the first use of pre-stress concrete in California.
It used a post-tension stressing system developed by
the Pre-stress Concrete Corporation of Kansas City.
In Florida, there were innovations such as 60-foot
pre-tensioned warehouse beams, new pre-stressing facilities
built by Florida Pre-stress Concrete in 1953.
And innovative ideas of all sizes and shapes.
A variety of bridge designs were created in Florida, spear-headed
by the Tampa Bay crossing 1951, which sustained the momentum of
the Walnut Lane Bridge.
During this time, box girders for short spans were designed
that took advantage of sonnevoids.
Testing these boxed girders in the early 1950s lead the
Pennsylvania Department of Highways to approve the use of
pre-stress box girders, for six expressway overpasses,
in downtown Philadelphia in 1955.
The project marked the first ever large scale application of
boxed girders in the country.
Throughout the 1950's, pioneers in the pre-stress concrete
industry continued to expand the materials design capabilities.
One, was Harry Edwards, president and founder
of LEAP Associates.
A consulting engineering firm in Lakeland Florida,
founded in 1950, LEAP has concentrated its services
almost exclusively on the development
and promotion of pre-tension concrete.
And the computerized analysis of pre-stress concrete structures.
Another early innovator was consulting engineer Ross H.
Brian of Nashville Tennessee.
Brian designed the first linear pre-stress structures
in the U.S., as well as the first structures using
deflected pre-tension strands.