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Homework Help: Statics Project help

  1. Nov 26, 2007 #1
    I am working on a statics project and need a little help on what to do next. A link to the project diagram and description is below:


    I've simplified the distributed load on top of the bridge to: 2400 lbs above point A, 4000 lbs above point B, 3200 lbs above points C, D, and E, 4000 lbs above point F, and 2400 lbs above point G. The tip says to distribute the weight of the members at the nodes. I'm not sure what exactly that means. Also, I'm unsure of what I should use to start out with for the weight. I know obviously that the stronger the member the greater the weight, but I'm not sure how to start. Should I just use the 1" diameter pipe for each member and use that as a baraomter to go higher or lower? Once I figure out how to use the draw the weight, what would be the easiest way to find the external forces with so many known forces? Maybe moments about point G? Thanks for any help!
  2. jcsd
  3. Nov 26, 2007 #2
    Sorry I forgot to add the new one with all the measurements on it. From A to B is 15', B to C, C to D, D to E, and E to F are all 10', and F to G is 15'.
  4. Nov 28, 2007 #3


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    Your distribution of the roof loads is very good. The members weight can be distributed as 2 equal loads, one at the top and one at the bottom of each member, but they are so small compared to the roof load that I wouldn't worry about them initially. You can calculate reactions by summing moments at about any one support, but since the truss is symmetrical in geometry and load, the vertical reactions at each support are equal, and I don't see any primary horizonal reactions at either support.
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