MS lect6 mo id 309495 Nieznany

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Computational Methods

1D Examples

Małgorzata Stojek

Cracow University of Technology

March 2012

MS

(L-53 CUT)

FEM

03/2012

1 / 44

Beam Example

M = qL

2

2L

L

P = qL

q

e1

e2

θ

1

w

1

θ

θ

w

w

2

2

3

3

d

1

d

2

d

3

d

4

d

5

d

6

=

w

1

θ

1

w

2

θ

2

w

3

θ

3

MS

(L-53 CUT)

FEM

03/2012

2 / 44

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Beam Element Library

Prismatic Beam

Stiffness Matrix

:

K

e

=

EI
h

3

12

6h

12

6h

4h

2

6h

2h

2

12

6h

symm

4h

2

Consistent Nodal Forces:

constant

distributed load

concentrated

force

q

(

x

) =

q

q

(

x

) =

P

δ

x

(

x

h
2

)

F

e

q

=

q

h

1
2

1

12

h

1
2

1

12

h

F

e

q

=

P

1
2

1
8

h

1
2

1
8

h

MS

(L-53 CUT)

FEM

03/2012

3 / 44

First Element

Stiffness Matrix

DOFs: 1, 2, 3, 4; h

=

2L

K

e

1

4

×

4

=

EI

(

2L

)

3

12

6

(

2L

)

12

6

(

2L

)

6

(

2L

)

4

(

2L

)

2

6

(

2L

)

2

(

2L

)

2

12

6

(

2L

)

12

6

(

2L

)

6

(

2L

)

2

(

2L

)

2

6

(

2L

)

4

(

2L

)

2

=

EI

2L

3

3

3L

3

3L

3L

4L

2

3L

2L

2

3

3L

3

3L

3L

2L

2

3L

4L

2

MS

(L-53 CUT)

FEM

03/2012

4 / 44

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First Element

Consistent Nodal Forces

F

e

1

q

=

q

(

2L

)

1
2

1

12

(

2L

)

1
2

1

12

(

2L

)

=

qL

1

1
3

L

1

1
3

L

y

1
3

qL

2

x

1
3

qL

2

[

element 1

]

qL

qL

MS

(L-53 CUT)

FEM

03/2012

5 / 44

Second Element

DOFs: 3, 4, 5, 6; h

=

L

Stiffness Matrix

K

e

2

4

×

4

=

EI

(

L

)

3

12

6

(

L

)

12

6L

6

(

L

)

4

(

L

)

2

6

(

L

)

2

(

L

)

2

12

6

(

L

)

12

6

(

L

)

6

(

L

)

2

(

L

)

2

6

(

L

)

4

(

L

)

2

Consistent Nodal Forces

P

=

qL

F

e

2

q

=

P

1
2

1
8

L

1
2

1
8

L

y

1
8

qL

2

x

1
8

qL

2

[

element 2

]

1
2

qL

1
2

qL

MS

(L-53 CUT)

FEM

03/2012

6 / 44

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Assembly

Global Stiffness Matrix

K

=

0

6

×

6

(+)

K

e

1

4

×

4

(+)

K

e

2

4

×

4

K

=

EI

(

L

)

3

3
2

3
2

L

3
2

3
2

L

0

0

3
2

L

2L

2

3
2

L

L

2

0

0

3
2

3
2

L

3
2

+

12

3
2

L

+

6L

12

6L

3
2

L

L

2

3
2

L

+

6L

2L

2

+

4L

2

6L

2L

2

0

0

12

6L

12

6L

0

0

6L

2L

2

6L

4L

2

K

=

EI

(

L

)

3

3
2

3
2

L

3
2

3
2

L

0

0

3
2

L

2L

2

3
2

L

L

2

0

0

3
2

3
2

L

27

2

9
2

L

12

6L

3
2

L

L

2

9
2

L

6L

2

6L

2L

2

0

0

12

6L

12

6L

0

0

6L

2L

2

6L

4L

2

MS

(L-53 CUT)

FEM

03/2012

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Assembly

Global Load Vector

F

q

=

0

6

×

1

(+)

F

e

1

q

4

×

1

(+)

F

e

2

P

4

×

1

0

0

0

0

0

0

qL

1
3

qL

2

qL

1
3

qL

2

0

0

qL

1
3

qL

2

qL

+

1
2

qL

1
3

qL

2

+

1
8

qL

2

1
2

qL

1
8

qL

2

=

qL

1
3

qL

2

3
2

qL

5

24

qL

2

1
2

qL

1
8

qL

2

MS

(L-53 CUT)

FEM

03/2012

8 / 44

background image

Assembly

Generic System of Linear Equations

Kd

=

F

q

EI

(

L

)

3

3
2

3
2

L

3
2

3
2

L

0

0

3
2

L

2L

2

3
2

L

L

2

0

0

3
2

3
2

L

27

2

9
2

L

12

6L

3
2

L

L

2

9
2

L

6L

2

6L

2L

2

0

0

12

6L

12

6L

0

0

6L

2L

2

6L

4L

2

w

1

θ

1

w

2

θ

2

w

3

θ

3

=

qL

1
3

qL

2

3
2

qL

5

24

qL

2

1
2

qL

1
8

qL

2

NOTE:

det K

=

0,

rank

(

K

) =

4

.

MS

(L-53 CUT)

FEM

03/2012

9 / 44

Boundary Conditions

kinematic constraints

natural

BCs

(essential "BCs")

(nonhomogeneous)

w

1

=

0,

θ

1

=

0,

w

2

=

0

at x

=

3L,

M

=

qL

2

w

1

θ

1

w

2

θ

2

w

3

θ

3

0
0
0

θ

2

w

3

θ

3

qL

1
3

qL

2

3
2

qL

5

24

qL

2

1
2

qL

1
8

qL

2

qL

1
3

qL

2

3
2

qL

5

24

qL

2

1
2

qL

1
8

qL

2

+

qL

2

NOTE:
rank

(

K

) =

4

&

3

support constraints

←→

beam is

statically indeterminate

.

MS

(L-53 CUT)

FEM

03/2012

10 / 44

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Solution I

EI

(

L

)

3

3
2

3
2

L

3
2

3
2

L

0

0

3
2

L

2L

2

3
2

L

L

2

0

0

3
2

3
2

L

27

2

9
2

L

12

6L

3
2

L

L

2

9
2

L

6L

2

6L

2L

2

0

0

12

6L

12

6L

0

0

6L

2L

2

6L

4L

2

0

0

0

θ

2

w

3

θ

3

=

qL

1
3

qL

2

3
2

qL

5

24

qL

2

1
2

qL

7
8

qL

2

EI

(

L

)

3

6L

2

6L

2L

2

6L

12

6L

2L

2

6L

4L

2

θ

2

w

3

θ

3

=

5

24

qL

2

1
2

qL

7
8

qL

2

+

EI

(

L

)

3

3
2

L L

2

9
2

L

0

0

12

0

0

6L

0

0

0

MS

(L-53 CUT)

FEM

03/2012

11 / 44

Solution II

RECALL:

EI

(

L

)

3

6L

2

6L

2L

2

6L

12

6L

2L

2

6L

4L

2

θ

2

w

3

θ

3

=

5

24

qL

2

1
2

qL

7
8

qL

2

Solution is:

θ

2

w

3

θ

3

=

7

12

qL

3

EI

19
16

qL

4

EI

41
24

qL

3

EI

d

=

0

0

0

θ

2

w

3

θ

3

=

0

0

0

7

12

qL

3

EI

19
16

qL

4

EI

41
24

qL

3

EI

MS

(L-53 CUT)

FEM

03/2012

12 / 44

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Postprocessing

Siły Przyw ˛ezłowe

RECALL:

K

e

d

e

=

F

e

=

F

e

q

+

W

e

W

e

=

Q

1

M

1

Q

2

M

2

=

K

e

d

e

F

e

q

y

M

1

Q

1

[

beam element

]

Q

2

y

M

2

MS

(L-53 CUT)

FEM

03/2012

13 / 44

Siły Przyw ˛ezłowe

Element 1

y

M

1

Q

1

[

beam element

]

Q

2

y

M

2

W

e

1

=

K

e

1

d

e

1

F

e

1

q

W

e

1

=

EI

2L

3

3

3L

3

3L

3L

4L

2

3L

2L

2

3

3L

3

3L

3L

2L

2

3L

4L

2

0

0

0

7

12

qL

3

EI

qL

1

1
3

L

1

1
3

L

Q

e

1

1

M

e

1

1

Q

e

1

2

M

e

1

2

=

1
8

qL

1
4

qL

2

15

8

qL

3
2

qL

2

y

1
4

qL

2

y

3
2

qL

2

[

element 1

]

1
8

qL

15

8

qL

MS

(L-53 CUT)

FEM

03/2012

14 / 44

background image

Siły Przyw ˛ezłowe

Element 2

y

M

1

Q

1

[

beam element

]

Q

2

y

M

2

W

e

2

=

K

e

2

d

e

2

F

e

2

q

W

e

2

=

EI
L

3

12

6L

12

6L

6L

4L

2

6L

2L

2

12

6L

12

6L

6L

2L

2

6L

4L

2

0

7

24

qL

3

EI

43
48

qL

4

EI

17
12

qL

3

EI

qL

1
2

1
8

L

1
2

1
8

L

Q

e

2

1

M

e

2

1

Q

e

2

2

M

e

2

2

=

qL

3
2

qL

2

0

qL

2

x

3
2

qL

2

y

qL

2

[

element 2

]

qL

0

MS

(L-53 CUT)

FEM

03/2012

15 / 44

Reactions at Supports I

1
4

qL

2

y

y

3
2

qL

2

[

element 1

]

1
8

qL

15

8

qL

3
2

qL

2

x

y

qL

2

[

element 2

]

qL

0

15

8

qL

+

R

2

=

ql

R

2

=

ql

+

15

8

qL

=

23

8

qL

8

1

1
4

2

qL

23
8

P = qL

q

2L

L

qL

qL

M = qL

2

MS

(L-53 CUT)

FEM

03/2012

16 / 44

background image

Reactions at Supports II

8

1

1
4

2

qL

23
8

P = qL

q

2L

L

qL

qL

M = qL

2

W

=

Kd

F

q

=

K

0

0

0

7

12

qL

3

EI

19
16

qL

4

EI

41
24

qL

3

EI

qL

1
3

qL

2

3
2

qL

5

24

qL

2

1
2

qL

1
8

qL

2

=

1
8

qL

1
4

qL

2

23

8

qL

0
0

qL

2

MS

(L-53 CUT)

FEM

03/2012

17 / 44

Equations of Equilibrium

8

1

1
4

2

qL

23
8

P = qL

q

2L

L

qL

qL

M = qL

2

i

P

i

y

?

=

0

1
8

qL

q

·

2L

+

23

8

qL

qL

=

0

i

M

i

x

=

0

?

=

0

1
4

qL

2

+

q

·

2L

·

L

23

8

qL

·

2L

+

qL

·



2L

+

L
2



+

qL

2

=

0

MS

(L-53 CUT)

FEM

03/2012

18 / 44

background image

Wykresy Sił Przekrojowych

8

1

1
4

2

qL

23
8

8

1

8

15

qL

2

qL

1
4

2

3

qL

2

P = qL

q

2L

L

qL

qL

M = qL

2

Q(x)

qL

qL

M(x)

2

qL

MS

(L-53 CUT)

FEM

03/2012

19 / 44

Truss Example

3

2

5

1

4

EA

EA

y

x

1

1

1

2EA

2EA

EA

1

2

3

4

P

MS

(L-53 CUT)

FEM

03/2012

20 / 44

background image

Truss Discretization

3

2

5

1

4

EA

EA

1

1

1

2 EA

2 EA

EA

x

y

1

2

4

3

u

u

u

u

u

u

u

u

1

2

3

4

5

6

7

8

no elem.

nodes

global DOFs

length

α

c

=

cos α

s

=

sin α

1

1, 3

1, 2, 5, 6

2

π

/

4

2/2

2/2

2

1, 2

1, 2, 3, 4

1

0

1

0

3

3, 2

5, 6, 3, 4

1

π

2

0

1

4

2, 4

3, 4, 7, 8

2

π

/

4

2/2

2/2

5

3, 4

5, 6, 7, 8

1

0

1

0

MS

(L-53 CUT)

FEM

03/2012

21 / 44

Truss Element Library

Prismatic Bar

Stiffness Matrix

:

K

e

=

EA

L

c

2

cs

c

2

cs

cs

s

2

cs

s

2

c

2

cs

c

2

cs

cs

s

2

cs

s

2

=

EA

L

c

2

cs

c

2

cs

s

2

cs

s

2

c

2

cs

symm

s

2

Consistent Nodal Forces:

constant

distributed load

q

(

x

) =

q

F

e

q

=

qL

2

c

s

c

s

MS

(L-53 CUT)

FEM

03/2012

22 / 44

background image

Element Stiffness Matrix

K

e

1

4

×

4

=

K

e

4

4

×

4

=

EA

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

K

e

2

4

×

4

=

K

e

5

4

×

4

=

EA

1

0

1 0

0

0

0

0

1 0

1

0

0

0

0

0

K

e

3

4

×

4

=

EA

0

0

0

0

0

1

0

1

0

0

0

0

0

1 0

1

MS

(L-53 CUT)

FEM

03/2012

23 / 44

Assembly

Global Stiffness Matrix

K

=

0

8

×

8

(+)

K

e

1

4

×

4

(+)

K

e

2

4

×

4

(+)

K

e

3

4

×

4

(+)

K

e

4

4

×

4

(+)

K

e

5

4

×

4

F

q

=

0

8

×

1

(no distributed loads)

Before assembly

K

=

0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0

MS

(L-53 CUT)

FEM

03/2012

24 / 44

background image

no elem.

global DOFs

1

1, 2, 5, 6

K

e

1

4

×

4

=

EA

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

K

=

EA

2

2

2

2

0 0

2

2

2

2

0 0

2

2

2

2

0 0

2

2

2

2

0 0

0

0

0 0

0

0

0 0

0

0

0 0

0

0

0 0

2

2

2

2

0 0

2

2

2

2

0 0

2

2

2

2

0 0

2

2

2

2

0 0

0

0

0 0

0

0

0 0

0

0

0 0

0

0

0 0

MS

(L-53 CUT)

FEM

03/2012

25 / 44

no elem.

global DOFs

2

1, 2, 3, 4

K

e

2

4

×

4

=

EA

1

0

1 0

0

0

0

0

1 0

1

0

0

0

0

0

K

=

EA

2

2

+

1

2

2

+

0

1 0

2

2

2

2

0 0

2

2

+

0

2

2

+

0

0 0

2

2

2

2

0 0

1

0

1 0

0

0 0 0

0

0

0 0

0

0 0 0

2

2

2

2

0 0

2

2

2

2

0 0

2

2

2

2

0 0

2

2

2

2

0 0

0

0

0 0

0

0 0 0

0

0

0 0

0

0 0 0

MS

(L-53 CUT)

FEM

03/2012

26 / 44

background image

no elem.

global DOFs

3

5, 6, 3, 4

K

e

3

4

×

4

=

EA

0

0

0

0

0

1

0

1

0

0

0

0

0

1 0

1

K

=

EA

2

2

+

1

2

2

1

0

2

2

2

2

0 0

2

2

2

2

0

0

2

2

2

2

0 0

1

0 1

+

0

0

0

0

0 0

0

0

0

1

0

1

0 0

2

2

2

2

0

0

2

2

+

0

2

2

+

0

0 0

2

2

2

2

0

1

2

2

+

0

2

2

+

1

0 0

0

0

0

0

0

0 0 0

0

0

0

0

0

0 0 0

MS

(L-53 CUT)

FEM

03/2012

27 / 44

no elem.

global DOFs

4

3, 4, 7, 8

K

e

4

4

×

4

=

EA

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

K

=

EA

2

2

+

1

2

2

1

0

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

0

1

0 1

+

2

2

2

2

0

0

2

2

2

2

0

0

2

2

1

+

2

2

0

1

2

2

2

2

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

1

2

2

2

2

+

1

0

0

0

0

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

MS

(L-53 CUT)

FEM

03/2012

28 / 44

background image

no elem.

global DOFs

5

5, 6, 7, 8

K

e

5

4

×

4

=

EA

1

0

1 0

0

0

0

0

1 0

1

0

0

0

0

0

K

=

EA

2

2

+

1

2

2

1

0

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

0

1

0 1

+

2

2

2

2

0

0

2

2

2

2

0

0

2

2

1

+

2

2

0

1

2

2

2

2

2

2

2

2

0

0

2

2

+

1

2

2

+

0

1

0

2

2

2

2

0

1

2

2

+

0

2

2

+

1

+

0

0

0

0

0

2

2

2

2

1

0

2

2

+

1

2

2

+

0

0

0

2

2

2

2

0

0

2

2

+

0

2

2

+

0

MS

(L-53 CUT)

FEM

03/2012

29 / 44

Assembly

Generic System of Linear Equations

Kd

=

F

q

=

0

K

=

EA

2

2

+

1

2

2

1

0

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

0

1

0 1

+

2

2

2

2

0

0

2

2

2

2

0

0

2

2

1

+

2

2

0

1

2

2

2

2

2

2

2

2

0

0

2

2

+

1

2

2

1

0

2

2

2

2

0

1

2

2

2

2

+

1

0

0

0

0

2

2

2

2

1

0

2

2

+

1

2

2

0

0

2

2

2

2

0

0

2

2

2

2

det K

=

0,

rank

(

K

) =

5

MS

(L-53 CUT)

FEM

03/2012

30 / 44

background image

Boundary Conditions

kinematic constraints

external nodal forces

(essential "BCs")

(natural "BCs")

u

1

=

0,

u

2

=

0,

u

4

=

0

at node no 4,

P

=

10

u

1

u

2

u

3

u

4

u

5

u

6

u

7

u

8

0
0

u

3

0

u

5

u

6

u

7

u

8

0
0
0
0
0
0
0
0

0
0
0
0
0
0
0

P

MS

(L-53 CUT)

FEM

03/2012

31 / 44

Solution I

EA

2

2

+

1

2

2

1

0

2

2

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

0

1

0

1

+

2

2

2

2

0

0

2

2

2

2

0

0

2

2

1

+

2

2

0

1

2

2

2

2

2

2

2

2

0

0

2

2

+

1

2

2

1

0

2

2

2

2

0

1

2

2

2

2

+

1

0

0

0

0

2

2

2

2

1

0

2

2

+

1

2

2

0

0

2

2

2

2

0

0

2

2

2

2

0

0

u

3

0

u

5

u

6

u

7

u

8

=

0

0

0

0

0

0

0

P

MS

(L-53 CUT)

FEM

03/2012

32 / 44

background image

Solution II

EA

1

+

2

2

0

0

2

2

2

2

0

2

2

+

1

2

2

1

0

0

2

2

2

2

+

1

0

0

2

2

1

0

2

2

+

1

2

2

2

2

0

0

2

2

2

2

u

3

u

5

u

6

u

7

u

8

=

0

0

0

0

P

+

EA

1

0

2

2

2

2

2

2

0

2

2

2

2

1

0

0

2

2

0

0

2

2

0
0
0

MS

(L-53 CUT)

FEM

03/2012

33 / 44

Solution III

Solution is:

u

3

u

5

u

6

u

7

u

8

=

1

EA

P

P



2

+

1



P

P



2

+

2



P



2

2

+

3



d

=

0

0

u

3

0

u

5

u

6

u

7

u

8

=

1

EA

0

0

P

0

P



2

+

1



P

P



2

+

2



P



2

2

+

3



MS

(L-53 CUT)

FEM

03/2012

34 / 44

background image

Reactions at Supports

W

=

Kd

F

q

=

K

1

EA

0

0

P

0

P



2

+

1



P

P



2

+

2



P



2

2

+

3



0

=

0

P

0

2P

0

0

0

P

MS

(L-53 CUT)

FEM

03/2012

35 / 44

Equations of Equilibrium

2

3

4

P

1

1

1

x

y

1

0

P

2P

i

P

i

y

?

=

0

P

+

2P

P

=

0

i

M

i

1

?

=

0

2P

·

1

P

·

2

=

0

i

M

i

4

?

=

0

P

·

2

2P

·

1

=

0

MS

(L-53 CUT)

FEM

03/2012

36 / 44

background image

Postprocessing in Global Coordinate System

Siły przyw ˛ezłowe W

−→

W

e

x

1

,

W

e

y

1

α

−→

W

e

x

2

,

W

e

y

2

W

e

=

W

e

x

1

W

e

y

1

W

e

x

2

W

e

y

2

=

K

e

d

e

F

e

q

=

K

e

d

e

MS

(L-53 CUT)

FEM

03/2012

37 / 44

u

1

u

2

u

3

u

4

u

5

u

6

u

7

u

8

0

0

P

EA

0

P

(

2

+

1

)

EA

P

EA

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

no elem.

nodes

global DOFs

1

1

,

3

1, 2

,

5, 6

EA

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

0
0

P

(

2

+

1

)

EA

P

EA

=

P

P

P
P

x

y

1

3

1

P

P

P

P

pr ˛et rozci ˛agany

P

2

MS

(L-53 CUT)

FEM

03/2012

38 / 44

background image

u

1

u

2

u

3

u

4

u

5

u

6

u

7

u

8

0

0

P

EA

0

P

(

2

+

1

)

EA

P

EA

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

no elem.

nodes

global DOFs

2

1

,

2

1, 2

,

3, 4

EA

1

0

1 0

0

0

0

0

1 0

1

0

0

0

0

0

0
0

P

EA

0

=

P

0

P

0

2

2

1

P

P

x

y

pr ˛et ´sciskany

P

MS

(L-53 CUT)

FEM

03/2012

39 / 44

u

1

u

2

u

3

u

4

u

5

u

6

u

7

u

8

0

0

P

EA

0

P

(

2

+

1

)

EA

P

EA

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

no elem.

nodes

global DOFs

3

3

,

2

5, 6

,

3, 4

EA

0

0

0

0

0

1

0

1

0

0

0

0

0

1 0

1

P

(

2

+

1

)

EA

P

EA

P

EA

0

=

0

P

0

P

3

3

2

P

P

x

y

pr ˛et ´sciskany

P

MS

(L-53 CUT)

FEM

03/2012

40 / 44

background image

u

1

u

2

u

3

u

4

u

5

u

6

u

7

u

8

0

0

P

EA

0

P

(

2

+

1

)

EA

P

EA

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

no elem.

nodes

global DOFs

4

2

,

4

3, 4

,

7, 8

EA

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

1
2

2

P

EA

0

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

=

P
P

P

P

x

y

4

4

2

P

P

P

P

pr ˛et ´sciskany

P

2

MS

(L-53 CUT)

FEM

03/2012

41 / 44

u

1

u

2

u

3

u

4

u

5

u

6

u

7

u

8

0

0

P

EA

0

P

(

2

+

1

)

EA

P

EA

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

no elem.

nodes

global DOFs

5

3

,

4

5, 6

,

7, 8

EA

1

0

1 0

0

0

0

0

1 0

1

0

0

0

0

0

P

(

2

+

1

)

EA

P

EA

P

(

2

+

2

)

EA

P

(

2

2

+

3

)

EA

=

P

0

P

0

5

3

4

P

P

x

y

pr ˛et rozci ˛agany

P

MS

(L-53 CUT)

FEM

03/2012

42 / 44

background image

Sprawdzenie

Siły przyw ˛ezłowe w pr ˛etach.

Reakcje wi ˛ezów, obci ˛a˙zenia w ˛ezłów.

3

3

2

P

P

2

2

1

P

P

4

4

2

P

P

P

P

5

3

4

P

P

1

3

1

P

P

P

P

x

y

x

y

2

3

4

P

1

0

P

2P

Równowaga w ˛ezłów:

P

1

P

1

P

2

1

P

1

P

2

P

3

4

P

2

2P

4

P

P

1

P

1

P

3

P

5

3

P

4

P

4

P

5

4

P

MS

(L-53 CUT)

FEM

03/2012

43 / 44

Axial Forces

G l o ba l i z a ti o n : Fo rce Tra n s fo rm a ti o n

x

y

i

j

f

xi

f

yi

f

xj

f

yj

f

yi

f

xi

f

xj

f

yj

α

_

_

_

_

T

=

c

s

0

0

s

c

0

0

0

0

c

s

0

0

s

c

f

x

i

f

y

i

f

x

j

f

y

j

=

c

s

0

0

s

c

0

0

0

0

c

s

0

0

s

c

f

x

i

f

y

i

f

x

j

f

y

j

W

e

=

T

W

e

MS

(L-53 CUT)

FEM

03/2012

44 / 44


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