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64
Chapter 3. Examples
PLBEAM 1 1 2 3 4
PLBEAM 2 3 4 5 6
PLTRUSS 3 1 5
X 1 0.
0.
X 3 0.1 0.
X 5 0.25 0.
FIX 1
INPUTX 2 1
DYNE
1 1
DYNE
3 1
RLSE 2 1
END
HALT
XM 2 1.
XM 3 0.8
XM 5 0.5
ESTIFF 1 130.
ESTIFF 2 105.
INPUTX 2 1 0.0 10.0
END
END
In a MATLAB session we find for the stationary configuration (r01 ) and (r02 ) in agreement with
Eqs. (3.9) and (3.10):
>> spacar(7,’massspring’)
>> x(lnp(3,1))
ans =
0.1184
>> x(lnp(5,1))
ans =
0.2891
The linearized equations of motion in terms of the dynamic degrees of freedom are:
"
m1 0
0 m2
#"
#
"
k + k2 − m1 φ̇2
−k2
δr̈1
+ 1
δr̈2
−k2
k2 − m2 φ̇2
#"
#
" #
0
δr1
=
0
δr2
(3.11)