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Re; "portable" footbridges

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Sounds like you are looking for something like the *old* Bailey Bridge of WW2 
fame as long as aesthetics is not a consideration.  Meets all the 
requirements that you specified, plus some, except it is steel, not 
aluminum.  By combining sections, it can carry 60 ton tanks over rather long 
spans, and can be launched by man power with no one necessary on the other 
side of the breach (highly desirable when the people on the other side are 
the enemy and they are shooting at you).  I believe that Bailey Bridges (or 
their successor bridge) are now available thru a company called "Acrow" or 
something similar.  Their ads are frequently in ENR.

In the late 1950's, the Pima County Engineer purchased a bunch of surplus 
Bailey Bridge parts and used them for emergency bridge replacements and for 
"temporary" crossings where traffic volume had increased to the point that an 
all weather crossing was necessary but had not yet increased to the point to 
justify the cost of a permanent structure.  These were kept on hand until 
after two succeeding county engineers, a young engineer employee showed 
foresight and gleefully reported that they finally got rid of all those old 
bridge parts, leaving the county with no way to effect emergency repairs.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Thor A. Tandy wrote:

. > We are assisting in putting together concepts for the design, fabrication 
. > and assembly of footbridge(s) for the Baden_Powell Trail in the province 
. > of British Columbia.
. > 
. > Our first step is to collate concepts that are already in place.  We will 
. > be searching the internet for systems that conform to (but not limited 
. > to) the following general specifications.  
. > 
. > 1)    Spans: 30ft to 60ft. (10' increments)
. > 
. > 2)    Preferred Materials: Aluminum and/or timber
. > 
. > 3)    Assembly must be achievable with manpower or small transports.  We
. > envisage sections of 100lb +/-.
. > Must be modular or be in pre-fabricated sections for assembly with 
. > manpower on site. The trail can be expected to vary in width from two 
. > persons to vehicle width +/-. Environment is, of course, mountainous with 
. > bridges required at locations up mountainsides and stream crossings.
. > 
. > 4)    Off-the-shelf systems will be considered. From-scratch design will 
. > be carried out in the event no suitable proprietary systems are found.
. > 
. > Your comment or suggested sources would be appreciated.
. > 
. > Thor A. Tandy   P.Eng,  MCSCE,  MIPENZ
. >