User:Eml4500.f08.FEABBQ.koby/HW4

Notes for Oct. 6, 2008
Connectivity Array "conn"

Consider the two bar truss system:

In this diagram the relationship between the local and global nodes can be seen. These relations are stored in the "connectivity array" in our Matlab Code:

$$ conn = \begin{bmatrix} 1 & 2 \\ 2 & 3 \\ \end{bmatrix} $$

$$conn(e,j)=$$ global node number of local node $$j$$ at element $$e$$

Location Matrix Master Array "lmm"

The Location Matrix Master Array stores the equation number for the element stiffness coefficient at each local degree of freedom

$$ lmm = \begin{bmatrix} 1 & 2 & 3 & 4 \\ 3 & 4 & 5 & 6 \\ \end{bmatrix} $$

$$lmm(i,j)=$$ equation number (global degree of freedom #) for element stiffness coefficient to the $$j$$th local degree of freedom number $$i$$

HW: Modify the Matlab code for the two bar truss to solve the 3 bar truss system:



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Back to pg 12: Method 2 to derive k(e)

-transform a system with 4 degrees of freedom into a system also with 4 degrees of freedom (as opposed to 2) so that the transform matrix is now 4x4 and hopefully invertible.