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Homework Help: Truss Analysis

  1. Feb 4, 2010 #1
    1. The problem statement, all variables and given/known data

    I have a simple truss to analyze using excel. I have done this and know how to do it on pen and paper using one equation to eliminate variables in another until down the line an answer pops out and I go back in and solve for all the other variables.

    However, this time we have to use excel and it involves creating a matrix of the forces and computing its inverse. But the matrix I have as of now is not singular as the 3 columns for the support forces are all at zero. When I input the forces from the external analysis I get a bunch of #####. My instructor gave us the spreadsheet to use and this is the only section which we has any forumla put in so I do not want to mess with it. The formula he put in is a summation of the components in x and y for each member at each joint. They should add up to zero, and they do. THe problem is when I get to the external forces as I am unclear how to include them in this table.

    I tried to insert a table showing the numbers but it just comes up as the code I put it in. So I attached it as a text file. Hopefully it works.

    Hmm, I am sure I have left a lot of unanswered questions about what exactly I am trying to do. Please let me know how I can help to make this more understandable.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Feb 4, 2010 #2
    Either you must include the reaction components in the set of applied loads by calculating them by hand and inserting them in matrix B, or you could include 3 additional members representing the reaction components at A and at E. The working you give doesn't seem to 'know' where the reaction forces are, as an input, although it is looking for an output.
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