Captive Column . Com

arrow1.gif (893 bytes) Time Line - 1982: Moorhead Pedestrian Bridge...
Finished Bridge   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:

Built By Hand The Captive Column Pedestrian Bridge was built entirely by hand, by two people. (22k)
Only 350 Pounds Its weight was only 350 pounds (without finish & deck). (22k)
Arrival The completed bridge arrived at the site and was removed from the truck by hand. (23k)
Floating AcrossFloating Across 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)
Placing In Foundation The bridge was then lifted by hand and placed in the poured concrete foundations. (24k)
Opening Ceremonies 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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Copyright 1998-2004 by Lawrence R. Bosch.