finite element method

[pragya garg]

How to combine 3 stiffness element matrices(6X6) into a
single global stiffness matrix??(in my prog d size of
global stiffness matrix is 10X10). There are in all 3
elements and total no. of nodes is 5 with each node
havinhg 2 dof. the dof mapping is in the form- [u1 v1 u2
v2....u5 v5] for the global stiffness matrix. Is there any
way to this?? please help it's very urgent

[Nasser Abbasi]

"pragya garg" <pragy...@gmail.com> wrote in message
news:fbvtgd$43o$1...@fred.mathworks.com...

Building global stiffness matrix from element stiffness matrices is
something that should be explained in number of textbooks. Maybe your
textbook does not show this? There are number of places on the net that show
how to do this as well.

google "assembly of global stiffness matrix" , I get 423,000 hits.

This site below seems to have a nice demo how to do this
http://www.u-aizu.ac.jp/~niki/javaappl/jassem/jassem.html

For a class I took, I wrote a small report on FEM, and at the end of it I
have an example for a 2D assembly of global stiffness matrix, see end of
this:
http://www.12000.org/my_courses/UCI_COURSES/CREDIT_COURSES/spring_2006/spring_MAE_207/other_class_documents/Nasser_Abbasi/lecture_notes_nov_27_2006/HTML/report_fixed.htm

If you are looking for a function as part of standard matlab to do this, I
am not sure there is one, but may be in some toolbox, You can Google around
and search.

Nasser

[Praveen kumar N]

"pragya garg" wrote in message <fbvtgd$43o$1...@fred.mathworks.com>...

N =input('Number of elements N=');%enter the number of elements
n=4+(2*(N-1));% Number of variables
KK =zeros(n) ; % Initialize global stiffness matrix to zero
%Elemental stiffness matrix
k=[_, _, _, _;...
_, _, _, _;...
_, _, _, _;...
_, _, _, _];...%write elemental stiffness matrix
%
%Global Stiffness Matrix Assembly
%
for ii=1:N
KK(2*ii-1:2*(ii+1),2*ii-1:2*(ii+1))=...
KK(2*ii-1:2*(ii+1),2*ii-1:2*(ii+1))+k;
end
%
%Imposing Boundary Condition