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Time Line - 1982: Moorhead Pedestrian Bridge... |
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The finished Captive
Column Pedestrian Bridge. (27k) |
This Captive Column Pedestrian Bridge was installed at the
Moorhead Minnesota golf course in 1982. A similar sized steel bridge had already been
installed at a cost of about $5,000, compared to a project cost of $3,000 for the
prototype Captive Column. Mass production costs for Captive Column pedestrian bridges
would be lower than $3,000, especially since the prototype was made entirely by hand.
Transportation savings would drive costs down even further.
The total weight of the Captive Column bridge was approximately 850 pounds (including
finish and decking), compared to a weight of about 4,000 pounds for the similar sized
steel bridge. The light weight of the Captive Column allows the use of heavy equipment to
be avoided during installation. Excavation and footing costs can also be reduced because
of the light weight.
This bridge was constructed as part of a joint effort between Mr. Bosch and the
Moorhead Area Vocational Technical Institute. The following photos and text describe this
prototype:
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The Captive Column Pedestrian
Bridge was built entirely by hand, by two people. (22k) |
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Its weight was only 350 pounds
(without finish & deck). (22k) |
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The completed bridge arrived at
the site and was removed from the truck by hand. (23k) |
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The bridge was literally floated
across the creek. This was made possible by the protective fiberglass finish. After the
far end of the bridge hit the opposite bank, two of the workers crossed over. (26k) &
(27k) |
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The bridge was then lifted by
hand and placed in the poured concrete foundations. (24k) |
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The decking was bolted on and the
bridge was ready for use. This photo shows the opening ceremonies. (28k) |
After the bridge was installed, it was used until a particularly bad winter hit. During
this winter the creek flooded and froze over, knocking the bridge from its foundation and
carrying it downstream. Although the Captive Column was unharmed, the decking was damaged
and the bridge was not reinstalled. This was unfortunate, and could be avoided in the
future by altering the foundation design and increasing the distance between the bridge
and the water. This is precisely why prototypes are made -- to iron out the bugs.
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