How to calculate equation system in Matlab, with some knowns

Click For Summary

Discussion Overview

The discussion revolves around solving a system of equations represented by the equation F=Ku in the context of finite element analysis using Matlab. Participants explore methods for handling known and unknown variables within the stiffness matrix and the force vector.

Discussion Character

  • Technical explanation
  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on solving the equation F=Ku, where K is a known 12x12 matrix, and some members of u and F are known or zero.
  • Another participant questions whether the K matrix pertains to a single structure or an element, suggesting familiarity with linear algebra concepts like Gaussian elimination or Cholesky decomposition may be beneficial.
  • A different participant suggests using the Matlab syntax u = K \ F for solving the equation, indicating a straightforward approach if the question is purely about Matlab.
  • One participant expresses that the previous suggestions may overcomplicate the issue, providing a specific matrix equation and asking how to solve for multiple variables in Matlab, given some known parameters.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to solve the equation system in Matlab, with differing opinions on the complexity of the problem and the necessary mathematical background.

Contextual Notes

There are unresolved aspects regarding the definitions of the matrices involved and the specific conditions under which the variables are known or unknown. The discussion does not clarify the dependencies or assumptions related to the finite element analysis context.

berdan
Messages
31
Reaction score
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.
 
Physics news on Phys.org
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.
 
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.
 
SteamKing said:
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.

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 ?
 

Similar threads

  • · Replies 32 ·
2
Replies
32
Views
4K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
6K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 14 ·
Replies
14
Views
4K
  • · Replies 1 ·
Replies
1
Views
4K