From: "Juan C. Gray" <juangray(--nospam--at)col2.telecom.com.co>
Date: Tue, 05 Jun 2001 19:37:30 -0700
What I do for checking simple span prestressed bridges is essentialy the
same; at any given point of the span, the maximum moment is when you
have a concentrated load above it. With this , you can create a
spreadsheet to check actual vs. allowable stresses, and modify thecable
trajectory. At the end, yoy check moments for demand/capacity ratios.
Effland, Greg wrote:
> Correct, a good SHORT discussion on this is ASD 9th Edition page 2-310
> at the bottom "General Rules for Simple Span Beams Carrying Moving
> Concentrated Loads"... This theory may have to be expanded to true
> influence lines upon multiple uneven spans. But it works good for
> simple span beams.
> Greg Effland, P.E.
> KC MO
> -----Original Message-----
> From: Cain, William [mailto:bcain(--nospam--at)ebmud.com]
> Sent: Tuesday, June 05, 2001 12:36 PM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: RE: Golf Course Bridge
> Actually finding the maximum moment without a computer is
> not all that difficult if one uses influence lines. If you
> place the midpoint between your heaviest load and the center
> of gravity of all the loads that will be on the bridge at
> the maximum point on the moment influence line, that will
> produce the maximum moment in the girder. Of course, since
> the EIT after your signature on a prior posts indicates that
> you have probably been educated since advent of the frequent
> use of the computer for structural analysis, you may not
> have learned influence lines. Refer to most any text on
> indeterminate analysis such as Norris and Wilbur or Kinney
> for a discussion of this technique. It will give you a much
> better feel for the structure than reams of computer
> Bill Cain, SE
> Oakland CA
> -----Original Message-----
> From: Brian M. McMahon
> Sent: Tuesday, June 05, 2001 9:43 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Golf Course Bridge
> Finding the maximum moment for the girder(s) with
> the vehicle load is somewhat tricky, especially by
> hand (without computer software). If you use a
> 10K vehicle you can check me with the follow
> Assumption: Back wheel = 4K and front wheel = 1K
> (Spacing between wheels is 5'-6" and wheel span is
> Hint: The CG of the vehicle is 1.1 ft left of the
> center line of the span, L/2 (that would be the
> rear wheel)
> M = 1.25*L + 6.05/L - 5.5 K*lbs
> R (left support) = 5 - 5/X - 11/L
> X is the distance from the left support to the
> center of the back wheel.
> Make sure you prove these formulas before using
> them. It's been a while since I derived them.
> But, I had them written down.
> Thanks to Bill he knew the word Bollards for those
> metal posts at the end of the bridge. Space them
> as required.
> Don't forget to buy your AASHTO manual. You'll
> pay for it with your first bridge.
> Good luck!
> Brian McMahon
> Timber Design
> Universal Building Specialties, Inc.
> Auburndale, Florida 33823
> (863) 967-1131
> ----- Original Message -----
> From: T. Eric Gillham PE
> To: seaoc list
> 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
> 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
> 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
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