Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to calculate equation system in Matlab, with some knowns

  1. Apr 12, 2015 #1
    It's part of finite elements analysis.
    All I need is to solve F=Ku,K is [12x12] matrix .
    Some of the members of u are zeros ,some members of F are known forces . K is all known .
    How do I solve F=Ku in that way ??

    Thanks in advance.
  2. jcsd
  3. Apr 12, 2015 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    It's not clear if your K matrix is for a single structure or is the stiffness matrix for one element.

    In any event, if you haven't studied linear algebra, particularly things like Gaussian elimination or Cholesky decomposition, now will be a good time.

    If you are studying finite element analysis, there is usually part of the course which is devoted to solving the system of equations and understanding the various methods.
  4. Apr 13, 2015 #3
    If this is just a Matlab question, then use u = K \ F. If it's a finite element question, you need to consult a few textbooks first.
  5. Apr 13, 2015 #4
    I studied Linear Algebra ,and that's overcomplicating things .
    All I am asking : How do I solve in Matlab something like this :
    [A] [1 0 1 0][M]
    [V] [0 1 2 0][N]
    [0]=EA/L [0 1 2 0][Q]
    [D] [0 4 5 4][L]

    Where I know some of the variables in the first matrix ,and I know some variables in the last matrix (in a form of parameter,lets say Q is known and given) .
    I need to find A,B,C,D,M,N and L .
    How do I do this in Matlab ?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook