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Truss Analysis

  1. Feb 14, 2010 #1
    Truss Analysis :(

    1. The problem statement, all variables and given/known data


    Find the force on each of the members and tell if it is tension of compression.

    2. Relevant equations

    M = fd [tex]\sum[/tex]Fx and Fy = 0

    3. The attempt at a solution

    Well, my professor said to us that the first thing to do is to compute for the reactions on the pin. After that, start using Free body diagram on one of the pin, and continue to complete the truss.

    Here's what I did...

    I set point D as pivot... then
    [tex]\sum[/tex]M = 8A - 16cos55 - 12cos55 = 0
    A = 2.0075 N upward

    But shouldn't the summation of all forces be zero? By having A = 2.0075 and an unknown Rxn on D (which obviously will point upward), the system won't be in equilibrium because cos35 + 1.5cos35 = 2.0479 N.

    Just help me getting the correct Reactions on point A and D and i'll be able to solve this problem.. thanks..

  2. jcsd
  3. Feb 14, 2010 #2
    Re: Truss Analysis :(

    How many reaction components are there at A?
  4. Feb 14, 2010 #3


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    Gold Member

    Re: Truss Analysis :(

    that should be M = 16A - ......etc
    if you sum forces in y direction, A_y -1(sin35) -1.5(sin35) +D_y =0, plug in value for A_y and solve for D_y.
    looks like you had a math typo, some trig errors,and you missed a variable when summing y forces = 0. You can check your work by summing moments about A to solve for D_y.
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