University of Florida/Eml4500/f08.qwiki/Lecture 11

For a more thorough understanding of the Finite Element Method, it is wise to derive the element force displacement with respect to the global coordinate system.

Meeting 12

Recall from Page 6-1, $k^{(e)}{d}^{(e)}=f^{(e)}$ (Equation 1) Note to self; make sure these are 4x4, 4x1, 4x1

Note to self: insert diagrams (2) and the matrices for kq=P

$q_i^{(e)}$=axial displacement of element e at local node $i$ $P_i^{(e)}$=axial force of element e at local node $i$

The overall goal is to derive equation 1 from equation 2(already derived in Meeting 4) We want to find the relationship between:

• $q_{2x1}^{(e)}$ and $d_{4x1}^{(e)}$
• $P_{2x1}^{(e)}$ and $f_{4x1}^{(e)}$

The relationships can be expressed in the form: $q_{2x1}^{(e)}=T_{2x4}^{(e)}{d}_{4x1}^{(e)}$

Consider the displacement of local node i, denoted by $d_i^{(e)}$: Note to self: make sure the i is enclosed by a square

Insert figure 12-3

$d_{[i]}^{(e)}=d_1^{(e)}i+d_2^{(e)}j$