Page 1
The load vector corresponding to unconstrained degrees of freedom is (vide
30.4d),
{}
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=
6
24
12
6
5
4
p
p
p
p
k
(4)
In the given frame constraint degrees of freedom are .
Eliminating rows and columns corresponding to constrained degrees of freedom
from global stiffness matrix and writing load-displacement relationship for only
unconstrained degree of freedom,
9 8 7 3 2 1
, , , , , u u u u u u
Page 2
The load vector corresponding to unconstrained degrees of freedom is (vide
30.4d),
{}
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-
- =
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=
6
24
12
6
5
4
p
p
p
p
k
(4)
In the given frame constraint degrees of freedom are .
Eliminating rows and columns corresponding to constrained degrees of freedom
from global stiffness matrix and writing load-displacement relationship for only
unconstrained degree of freedom,
9 8 7 3 2 1
, , , , , u u u u u u
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-
-
6
5
4
3
44 . 44 10 44 . 4
10 3 . 1338 0
44 . 4 0 5 . 2001
10
6
24
12
u
u
u
(5)
Solving we get,
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×
×
×
=
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3 -
5 -
-6
6
5
4
10 0.13 -
10 1.695 -
10 6.28
u
u
u
(6)
65
45
6.28 10 m., 1.695 10 uu
--
=× =- ×
Let be the support reactions along degrees of freedom
respectively (vide Fig. 30.4e). Support reactions are calculated by
9 8 7 3 2 1
, , , , , R R R R R R
9 , 8 , 7 , 3 , 2 , 1
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6
5
4
3
9
8
7
3
2
1
9
8
7
3
2
1
33 . 13 10 0
10 5 0
0 0 2000
88 . 8 0 44 . 4
0 3 . 1333
44 . 4 0 48 . 1
10
6 5 4
u
u
u
p
p
p
p
p
p
R
R
R
R
R
R
F
F
F
F
F
F
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92 . 25
40 . 25
57 . 12
85 . 16
59 . 22
42 . 11
92 . 1
40 . 1
57 . 12
14 . 1
59 . 22
57 . 0
24
24
0
18
0
12
9
8
7
3
2
1
R
R
R
R
R
R
(7)
Page 3
The load vector corresponding to unconstrained degrees of freedom is (vide
30.4d),
{}
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-
- =
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?
?
?
?
?
?
=
6
24
12
6
5
4
p
p
p
p
k
(4)
In the given frame constraint degrees of freedom are .
Eliminating rows and columns corresponding to constrained degrees of freedom
from global stiffness matrix and writing load-displacement relationship for only
unconstrained degree of freedom,
9 8 7 3 2 1
, , , , , u u u u u u
?
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-
-
6
5
4
3
44 . 44 10 44 . 4
10 3 . 1338 0
44 . 4 0 5 . 2001
10
6
24
12
u
u
u
(5)
Solving we get,
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×
×
×
=
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?
?
3 -
5 -
-6
6
5
4
10 0.13 -
10 1.695 -
10 6.28
u
u
u
(6)
65
45
6.28 10 m., 1.695 10 uu
--
=× =- ×
Let be the support reactions along degrees of freedom
respectively (vide Fig. 30.4e). Support reactions are calculated by
9 8 7 3 2 1
, , , , , R R R R R R
9 , 8 , 7 , 3 , 2 , 1
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6
5
4
3
9
8
7
3
2
1
9
8
7
3
2
1
33 . 13 10 0
10 5 0
0 0 2000
88 . 8 0 44 . 4
0 3 . 1333
44 . 4 0 48 . 1
10
6 5 4
u
u
u
p
p
p
p
p
p
R
R
R
R
R
R
F
F
F
F
F
F
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92 . 25
40 . 25
57 . 12
85 . 16
59 . 22
42 . 11
92 . 1
40 . 1
57 . 12
14 . 1
59 . 22
57 . 0
24
24
0
18
0
12
9
8
7
3
2
1
R
R
R
R
R
R
(7)
Example 30.2
Analyse the rigid frame shown in Fig 30.5a by direct stiffness matrix method.
Assume and . The flexural
rigidity
54
200 GPa ; 1.33 10 m
ZZ
EI
-
==×
2
01 . 0 m A =
EI and axial rigidity EA are the same for all beams.
Solution:
The plane frame is divided in to three beam elements as shown in Fig. 30.5b.
The numbering of joints and members are also shown in Fig. 30.5b. The possible
degrees of freedom at nodes are also shown in the figure. The origin of the
global co- ordinate system is taken at A (node 1).
Page 4
The load vector corresponding to unconstrained degrees of freedom is (vide
30.4d),
{}
?
?
?
?
?
?
?
?
?
?
?
?
?
?
-
- =
?
?
?
?
?
?
?
?
?
?
?
?
?
?
=
6
24
12
6
5
4
p
p
p
p
k
(4)
In the given frame constraint degrees of freedom are .
Eliminating rows and columns corresponding to constrained degrees of freedom
from global stiffness matrix and writing load-displacement relationship for only
unconstrained degree of freedom,
9 8 7 3 2 1
, , , , , u u u u u u
?
?
?
?
?
?
?
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=
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?
?
-
-
6
5
4
3
44 . 44 10 44 . 4
10 3 . 1338 0
44 . 4 0 5 . 2001
10
6
24
12
u
u
u
(5)
Solving we get,
?
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?
?
?
?
?
?
?
?
?
?
?
?
×
×
×
=
?
?
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?
?
?
?
?
?
?
?
?
?
?
3 -
5 -
-6
6
5
4
10 0.13 -
10 1.695 -
10 6.28
u
u
u
(6)
65
45
6.28 10 m., 1.695 10 uu
--
=× =- ×
Let be the support reactions along degrees of freedom
respectively (vide Fig. 30.4e). Support reactions are calculated by
9 8 7 3 2 1
, , , , , R R R R R R
9 , 8 , 7 , 3 , 2 , 1
?
?
?
?
?
?
?
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- -
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+
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6
5
4
3
9
8
7
3
2
1
9
8
7
3
2
1
33 . 13 10 0
10 5 0
0 0 2000
88 . 8 0 44 . 4
0 3 . 1333
44 . 4 0 48 . 1
10
6 5 4
u
u
u
p
p
p
p
p
p
R
R
R
R
R
R
F
F
F
F
F
F
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=
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+
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=
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92 . 25
40 . 25
57 . 12
85 . 16
59 . 22
42 . 11
92 . 1
40 . 1
57 . 12
14 . 1
59 . 22
57 . 0
24
24
0
18
0
12
9
8
7
3
2
1
R
R
R
R
R
R
(7)
Example 30.2
Analyse the rigid frame shown in Fig 30.5a by direct stiffness matrix method.
Assume and . The flexural
rigidity
54
200 GPa ; 1.33 10 m
ZZ
EI
-
==×
2
01 . 0 m A =
EI and axial rigidity EA are the same for all beams.
Solution:
The plane frame is divided in to three beam elements as shown in Fig. 30.5b.
The numbering of joints and members are also shown in Fig. 30.5b. The possible
degrees of freedom at nodes are also shown in the figure. The origin of the
global co- ordinate system is taken at A (node 1).
Now formulate the element stiffness matrix in local co-ordinate system and then
transform it to global co-ordinate system. In the present case three degrees of
freedom are considered at each node.
Member 1: ° = = 90 ; 4 ? m L ; node points 1-2 ;
21
0
xx
l
L
-
== and
21
1
yy
m
L
-
== .
The following terms are common for all elements.
52
2
6
5 10 kN/m; 9.998 10 kN
AE EI
L L
=× = ×
23
3
12 4
4.999 10 kN/m; 2.666 10 kN.m
EI EI
L L
=× =×
Page 5
The load vector corresponding to unconstrained degrees of freedom is (vide
30.4d),
{}
?
?
?
?
?
?
?
?
?
?
?
?
?
?
-
- =
?
?
?
?
?
?
?
?
?
?
?
?
?
?
=
6
24
12
6
5
4
p
p
p
p
k
(4)
In the given frame constraint degrees of freedom are .
Eliminating rows and columns corresponding to constrained degrees of freedom
from global stiffness matrix and writing load-displacement relationship for only
unconstrained degree of freedom,
9 8 7 3 2 1
, , , , , u u u u u u
?
?
?
?
?
?
?
?
?
?
?
?
?
?
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?
?
=
?
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?
?
?
?
?
?
?
?
?
?
-
-
6
5
4
3
44 . 44 10 44 . 4
10 3 . 1338 0
44 . 4 0 5 . 2001
10
6
24
12
u
u
u
(5)
Solving we get,
?
?
?
?
?
?
?
?
?
?
?
?
?
?
×
×
×
=
?
?
?
?
?
?
?
?
?
?
?
?
?
?
3 -
5 -
-6
6
5
4
10 0.13 -
10 1.695 -
10 6.28
u
u
u
(6)
65
45
6.28 10 m., 1.695 10 uu
--
=× =- ×
Let be the support reactions along degrees of freedom
respectively (vide Fig. 30.4e). Support reactions are calculated by
9 8 7 3 2 1
, , , , , R R R R R R
9 , 8 , 7 , 3 , 2 , 1
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
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?
?
?
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?
?
- -
-
- -
- -
+
?
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=
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?
?
?
?
?
?
?
6
5
4
3
9
8
7
3
2
1
9
8
7
3
2
1
33 . 13 10 0
10 5 0
0 0 2000
88 . 8 0 44 . 4
0 3 . 1333
44 . 4 0 48 . 1
10
6 5 4
u
u
u
p
p
p
p
p
p
R
R
R
R
R
R
F
F
F
F
F
F
?
?
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?
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?
?
?
?
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-
-
-
=
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-
-
-
+
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-
-
=
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?
?
92 . 25
40 . 25
57 . 12
85 . 16
59 . 22
42 . 11
92 . 1
40 . 1
57 . 12
14 . 1
59 . 22
57 . 0
24
24
0
18
0
12
9
8
7
3
2
1
R
R
R
R
R
R
(7)
Example 30.2
Analyse the rigid frame shown in Fig 30.5a by direct stiffness matrix method.
Assume and . The flexural
rigidity
54
200 GPa ; 1.33 10 m
ZZ
EI
-
==×
2
01 . 0 m A =
EI and axial rigidity EA are the same for all beams.
Solution:
The plane frame is divided in to three beam elements as shown in Fig. 30.5b.
The numbering of joints and members are also shown in Fig. 30.5b. The possible
degrees of freedom at nodes are also shown in the figure. The origin of the
global co- ordinate system is taken at A (node 1).
Now formulate the element stiffness matrix in local co-ordinate system and then
transform it to global co-ordinate system. In the present case three degrees of
freedom are considered at each node.
Member 1: ° = = 90 ; 4 ? m L ; node points 1-2 ;
21
0
xx
l
L
-
== and
21
1
yy
m
L
-
== .
The following terms are common for all elements.
52
2
6
5 10 kN/m; 9.998 10 kN
AE EI
L L
=× = ×
23
3
12 4
4.999 10 kN/m; 2.666 10 kN.m
EI EI
L L
=× =×
[] [] [ ][]
6
5
4
3
2
1
10 66 . 2 0 10 1 10 33 . 1 0 10 1
0 10 5 0 0 10 5 0
10 1 0 10 50 . 0 10 1 0 10 50 . 0
10 33 . 1 0 10 1 10 66 . 2 0 10 1
0 10 5 0 0 10 5 0
10 1 0 10 50 . 0 10 1 0 10 50 . 0
6 5 4 3 2 1
'
3 3 3 3
5 5
3 3 3 3
3 3 3 3
5 5
3 3 3 3
1
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
× × × × -
× × -
× × × × -
× × × × -
× - ×
× - × - × - ×
=
= T k T k
T
(1)
Member 2: ° = = 0 ; 4 ? m L node points 2-3; 1 = l and 0 = m .
[] [] [ ][ ]
9
8
7
6
5
4
10 666 . 2 10 1 0 10 33 . 1 10 1 0
10 1 10 5 . 0 0 10 1 10 5 . 0 0
0 0 10 0 . 5 0 0 10 0 . 5
10 33 . 1 10 1 0 10 666 . 2 10 1 0
10 1 10 5 . 0 0 10 1 10 5 . 0 0
0 0 10 0 . 5 0 0 10 0 . 5
9 8 7 6 5 4
'
3 3 3 3
3 3 3 3
6 6
3 3 3 3
3 3 3 3
6 5
2
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
× × - × ×
× - × × - × -
× × -
× × - × ×
× × - × ×
× - ×
=
= T k T k
T
(2)
Member 3: ° = = 270 ; 4 ? m L ; node points 3-4 ;
21
0
xx
l
L
-
== and
21
1
yy
m
L
-
==- .
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