University of Florida/Eml4500/f08.qwiki/Lecture 5
Read: Chapter 4 Chapter 1: Big Picture
- 1.1 Discritization (1.1.1 Plane truss elem)
- 1.2 Assembly of elem. eqs. Ex. 1.4: Five-bar truss
- 1.4 Elem Soln and model validity (1.4.1 Plane truss elem)
Steps to solve simple truss system described on 9/3
1.Global: The displacement dofs are partitioned into: 1)a known part,e.g.(fixed dofs, constraints) 2)an unknown part: solve using FEA
The same for global forces: 1) known part 2) unknown part
2.Element picture:
- Element dofs
- Element forces
3.Global FD relation:
- Element stiffness matrices in global coordinates
- Element force matrices in global coordinates
- Assembly of element stiffness matrix and element force matrix into global FD relation knxndnx1=Fnx1
4.Elimination: The elimination of known dofs to reduce the global FD rel. (stiffness matrix non-singular => invertible)
m = number of unknown displacement dofs
n = number of all displacement dofs
- m < n
d=k-1F
5. Compute Element Forces
6. Compute Reactions
Example:
- L(1)=4 L(2)=2 (Length)
- E(1)=3 E(2)=5 (Young's Modulus)
- A(1)=1 A(2)=2 (Area)