Page 547 - Aircraft Stuctures for Engineering Student

528 Matrix methods of structural analysis

-a+c b+c -a+c b-c -2c -2b
b+c a+c -b+c a-c -2c -2a
1 -a+c -b+c a+c -b-c -2c 2b
[4T[wl - a-c -b-c a+c 2c -2a
16
=
-2c -2c -2c 2c 4c 0
- -2b -2a 2b -2a 0 4a

1 -a+c -b+c a+c -b-c -2c 2b
[Ke] =-
4 b-c a-c -b-c a+c 2c -2a
-2c -2c -2c 2c 4c 0
-2b -2a 2b -2a 0 4a

12.8.3 Stiffness matrix for a quadrilateral element

Quadrilateral elements are frequently used in combination with triangular elements to
build up particular geometrical shapes.
Figure 12.14 shows a quadrilateral element referred to axes Oxy and having corner
nodes, i, j, k and I; the nodal forces and displacements are also shown and the

YA
Fy,Il v, t

F., i* ui
i

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