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Solution of Equilibrium Equations in Static Analysis: LDLT Solution ...

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LDL T <strong>Solution</strong><br />

Now, get the solution U <strong>of</strong> KU=R with R=[0 1 0 0 0] T<br />

V 1 = R 1 = 0<br />

i<br />

V 2 = R 2 – l 12 V 1 = 1 –0 = 1<br />

∑ − 1<br />

Vi<br />

= Ri<br />

− l<br />

r=<br />

mi<br />

V 3 = R 3 – l 23 V 2 = 0 –(‐2)(1) = 2<br />

V 4 = R 4 – l 34 V 3 = 0 –(‐3)(2) = 6<br />

V 5 = R 5 – l 15 V 1 – l 25 V 2 – l 35 V 3 – l 45 V 4 = 0 – 0 – (‐1)(1) – (‐2)(2) – (‐2) (6) = 17<br />

ri<br />

V<br />

r<br />

forward<br />

reduction<br />

Hence: V=[0 1 2 6 17] T and<br />

V<br />

− 1<br />

= D V =<br />

[0 1 2 6 34] T<br />

V<br />

(5) =<br />

i = 5<br />

V<br />

→ U = =<br />

5<br />

V5 34<br />

V V l U<br />

V2 = V2 − l25U5 = 1 −( − 1)(34) = 35<br />

(4) (5)<br />

V3 = V3 − l35U5 = 2 −( − 2)(34) = 70<br />

(4) (5)<br />

V 4<br />

= V 4<br />

− l 45U<br />

5<br />

= 6 −( − 2)(34) = 74<br />

U<br />

(4) (5)<br />

1<br />

=<br />

1 −<br />

15 5 = 0 − ( − 1/ 2)(34) =<br />

17<br />

(4) (5)<br />

(4)<br />

4<br />

V4 74<br />

backsubstitution<br />

b i<br />

V = V − l U<br />

r<br />

( i−1) ( i)<br />

r r ri i<br />

= m ,..., i − 1<br />

= = R = [ 17 35 292 70 74 4]<br />

i<br />

3 T<br />

15-Jun-07<br />

Method <strong>of</strong> F<strong>in</strong>ite Elements I<br />

24

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