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Re: Golf Course Bridge

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Eric,
 
I design wood bridges with a typical span between 25 and 125 ft all the time.  For the pedestrian bridges I use a LL = 85 to 100 psf but typically 100 psf.  Remember, the strength of wood can be increased for short durations so sometimes I use 85 psf if the situation appears to be justifiable (ask the owner).  Yes, you should get a copy of AASHTO and use it.  It will help you correctly define the load for each structural member on your bridge.  It's not uncommon for me to use a vehicle weight of 10K lbs and sometimes even 5K depending what the owner says will be necessary.  One thing I like to do is have them add those steel posts (can't remember the name) at the end of the bridge in such a way that a large vehicle could not mobilize onto the bridge.  Your sign wouldn't be a bad idea either.
 
I hope that helps!
 
Brian McMahon, E.I.T.
Timber Design
Universal Building Specialties, Inc.
Auburndale, Florida 33823
(863) 967-1131
----- Original Message -----
Sent: Monday, June 04, 2001 7:55 PM
Subject: Golf Course Bridge

I am designing two cart path bridges for a golf course.  First bridge is 3 span 70'+50'+50', second bridge has a single span of 70'.
 
Wonder of wonders, the owner and the contractor both want to minimize the cost on the structures, and are asking that I use the minimum live loading possible. 
 
The largest vehicle used on the golf course is a mower/utility vehicle with a gross weight of about 2 tons, well below H15 loading.  The bridges themselves are to be 10 feet wide, and the approaches are so hilly that it is unlikely that  a truck could even get to the bridges.
 
Soooo, my question is : Does anyone have experience regarding the use of loads substantially less than those required by AASHTO for the design of NON-highway bridges.  If so, are there standard loads?  I was thinking of using 5 tons as a minimum, and having the owner post a permanent sign showing the weight restriction.
 
Also, does the AASHTO manual govern the design of the bridges?  We are currently under UBC94, soon to switch to the IBC, but I am not all that familiar with AASHTO requirements (not much bridge work on Guam).  I would prefer to use UBC94, LRFD 2nd Ed for the girders, and refer to AASHTO for load distribution (based on 5 ton total weight) and seismic design.
 
Any suggestions?
 
 
T. Eric R. Gillham PE
PO Box 3207 Agana Guam 96932
Ph:   (671) 477-9224
Fax: (671) 477-3456
Cel  (671) 687-7115