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:
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.
Copyright © 1998-2004 by Lawrence R. Bosch.