1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple truss question driving me crazy =/

  1. May 8, 2009 #1

    hachi_roku

    User Avatar

    simple truss question....driving me crazy!! =/

    1. The problem statement, all variables and given/known data
    the question wants the forces in all the members of the truss. i have found that members bc and ef are zero force members...i cannot find the others. I am at a loss because ive tried all the methods i have been taught and the answers are not right. I NEED HELP!!!


    2. Relevant equations



    3. The attempt at a solution
    i have tried to take sum of forces in x prime (the AD axis), for members tbd and tcd....and also have tried doing tab and tda.
     

    Attached Files:

    hachi_roku, May 8, 2009
  2. jcsd
    Phys.org - latest science and technology news stories on Phys.org
  3. May 8, 2009 #2

    hachi_roku

    User Avatar

    Re: simple truss question....driving me crazy!! =/

    just in case you can't see the pic....the lengths from the pin to d is 16 ft, while the horizontal distance from the pin to d is 12 ft. the load at b is 2000 and the load at d is 3000. i have found a_y to be 3500 lbs
     
    hachi_roku, May 8, 2009
  4. May 8, 2009 #3

    hachi_roku

    User Avatar

    Re: simple truss question....driving me crazy!! =/

    the angles between ab and ac is 30, while the angles between db and dc is 30
     
    hachi_roku, May 8, 2009
  5. May 8, 2009 #4

    mathmate

    User Avatar

    Re: simple truss question....driving me crazy!! =/

    If you want to show the picture fast, you can upload it to picture-servers and post the link. Sometimes the approval can take a day.
     
    mathmate, May 8, 2009
  6. May 9, 2009 #5

    mathmate

    User Avatar

    Re: simple truss question....driving me crazy!! =/

    > i have found that members bc and ef are zero force members
    Very good!

    > i have found a_y to be 3500 lbs
    Very good. (note: in engineering/mechanics terms, the reaction at A is usually shown as Ra) Ay is understandable, you are probably doing a physics course.

    > ive tried all the methods i have been taught and the answers are not right.
    What methods have you been taught? Does 'triangle of forces' mean anything to you? How about 'summing forces in x and y'?
    Can you post the calculations and the answer you've got using your method, and the answers given. Sometimes the answers are misprinted or mis-transcribed by the teacher or the student.

    Hope to hear from you soon.
     
    mathmate, May 9, 2009
  7. May 10, 2009 #6

    djeitnstine

    User Avatar
    Gold Member

    Re: simple truss question....driving me crazy!! =/

    Hachi_roku, I have an idea. If the question really wants ALL of the forces in each member, start out by finding the reaction forces -of course. Then start by resolving the unknown forces in the pins A, B C, D... in that order. Surely every force in each member will become apparent.
     
    Last edited: May 10, 2009
    djeitnstine, May 10, 2009
  8. May 10, 2009 #7

    mathmate

    User Avatar

    Re: simple truss question....driving me crazy!! =/

    Hint:
    with perfect symmetry of loading and geometry, you only have to work out half of the structure, for example ABCD. The other half (DEFG) can be replaced by a single horizontal reaction. Note, however, that the reaction at A has a vertical and horizontal component.
    The horizontal reaction at D can easily be obtained by taking moments about A.
     
    mathmate, May 10, 2009
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Simple truss question driving me crazy =/

  1. Another simple truss problem (Replies: 9)

  2. Truss Question (Replies: 2)

  3. Simple truss nodal forces (Replies: 2)

  4. Truss problem (simple question) (Replies: 5)

  5. Simple Statics Question: Truss Structure (Replies: 1)

Loading...