The Problem. sin 1 = (-12 - 0) / (20) = -0.6 cos 1 = (16 - 0) / (20) = 0.8 sin 2 = (12 - 0) /...
-
date post
21-Dec-2015 -
Category
Documents
-
view
229 -
download
3
Transcript of The Problem. sin 1 = (-12 - 0) / (20) = -0.6 cos 1 = (16 - 0) / (20) = 0.8 sin 2 = (12 - 0) /...
The Problem
Elements and Nodes
144 in 3
4
5
3
45
192 in 108 in
Plane Truss
2
1
3
1
2
10 kips
100 kips
(AE/L) = (AE/L) = AE/L1 2
Global System Degrees of Freedom
4P , X 4
3P , X 3 5P , X 5
6P , X 6
2P , X 2
1P ,
1 u1
Local Element Degrees of Freedom
X 1
f , u 4 u4f , u
3 u3f , u2 u2f , u
sin1 = (-12 - 0) / (20) = -0.6cos1 = (16 - 0) / (20) = 0.8sin2 = (12 - 0) / (15) = 0.8cos2 = (9 - 0) / (15) = 0.6
Sines and Cosines
3 4 1 2
S1 AEL
1
0.64 0.48 0.64 0.48
0.48 0.36 0.48 0.36
0.64 0.48 0.64 0.48
0.48 0.36 0. 48 0.36
3
4
1
2
S2 AEL
2
0.36 0.48 0.36 0.48
0. 48 0.64 0.48 0.64
0.36 0.48 0.36 0.48
0.48 0.64 0.48 0.64
1
2
5
6
1 2 5 6
Element Matrices [S]
K Sii1
NM
System Stiffness Matrix
3 4 1 2
S1 AEL
1
0.64 0.48 0.64 0.48
0.48 0.36 0.48 0.36
0.64 0.48 0.64 0.48
0.48 0.36 0. 48 0.36
3
4
1
2
S2 AEL
2
0.36 0.48 0.36 0.48
0. 48 0.64 0.48 0.64
0.36 0.48 0.36 0.48
0.48 0.64 0.48 0.64
1
2
5
6
1 2 5 6
Element Matrices [S]
Summing Element Stiffnesses
.64 -.48 -.64 .48
-.48 .36 .48 -.36
-.64 .48 .64 -.48
.48 -.36 -.48 .36
Summing Element Stiffnesses
.64+.36 -.48+.48 -.64 .48 -.36 -.48
-.48+.48 .36+.64 .48 -.36 -.48 -.64
-.64 .48 .64 -.48
.48 -.36 -.48 .36
-.36 -.48 .36 .48
-.48 -.64 .48 .64
KAEL
0.64 0.36 0.48 0.48 0.64 0.48 0.36 0.48
0.48 0.48 0.36 0.48 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0.48 0 0 0.36 0.48
0.48 0.64 0 0 0.48 0.64
1
2
3
4
5
6
1 2 3 4 5 6
Two Matrix Contributions
1 2 3 4 5 6
K AEL
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0. 48 0 0 0.36 0.48
0.48 0.64 0 0 0.48 0.64
1
2
3
4
5
6
Final [K]
P1
P2
P3
P4
P5
P6
AE
L
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0.48 0 0 0.36 0.48
0.48 0.64 0 0 0.48 0.64
X1
X2
X3
X4
X5
X6
Final Equation P=KX
System Stiffness Matrices
1
2 4
53
6
7 1
7 6
32
5
4
Node Numbering Scheme 1 Node Numbering Scheme 2
KScheme 1
X X X X X X 0 0 0 0 0 0 0 0
X X X X X X 0 0 0 0 0 0 0 0
X X X X X X X X 0 0 0 0 0 0
X X X X X X X X 0 0 0 0 0 0
X X X X X X X X X X 0 0 0 0
X X X X X X X X X X 0 0 0 0
0 0 X X X X X X X X X X 0 0
0 0 X X X X X X X X X X 0 0
0 0 0 0 X X X X X X X X X X
0 0 0 0 X X X X X X X X X X
0 0 0 0 0 0 X X X X X X X X
0 0 0 0 0 0 X X X X X X X X
0 0 0 0 0 0 0 0 X X X X X X
0 0 0 0 0 0 0 0 X X X X X X
KScheme 2
X X X X 0 0 0 0 0 0 0 0 X X
X X X X 0 0 0 0 0 0 0 0 X X
X X X X X X 0 0 0 0 X X X X
X X X X X X 0 0 0 0 X X X X
0 0 X X X X X X X X 0 0 0 0
0 0 X X X X X X X X 0 0 0 0
0 0 0 0 X X X X X X X X 0 0
0 0 0 0 X X X X X X X X 0 0
0 0 0 0 X X X X X X X X X X
0 0 0 0 X X X X X X X X X X
0 0 X X X X 0 0 X X X X X X
0 0 X X X X 0 0 X X X X X X
X X X X 0 0 0 0 0 0 X X X X
X X X X 0 0 0 0 0 0 X X X X
Solving the System of Equations
Modify for Known Loads
Elements and Nodes
144 in 3
4
5
3
45
192 in 108 in
Plane Truss
2
1
3
1
2
10 kips
100 kips
(AE/L) = (AE/L) = AE/L1 2
Global System Degrees of Freedom
4P , X
4
3P , X3 5P , X5
6P , X
6
2P , X2
1P ,
1 u1
Local Element Degrees of Freedom
X 1
f , u 4 u4f , u
3 u3f , u2 u2f , u
10
100
P3
P4
P5
P6
AE
L
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0.48 0 0 0.36 0.48
0. 48 0.64 0 0 0.48 0.64
X1
X2
X3
X4
X5
X6
Modify for Boundary Conditions
Elements and Nodes
144 in 3
4
5
3
45
192 in 108 in
Plane Truss
2
1
3
1
2
10 kips
100 kips
(AE/L) = (AE/L) = AE/L1 2
Global System Degrees of Freedom
4P , X4
3P , X3 5P , X5
6P , X 6
2P , X2
1P ,
1 u1
Local Element Degrees of Freedom
X 1
f , u 4 u4f , u
3 u3f , u2 u2f , u
10
100
P3
P 4
P5
P6
AE
L
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0.48 0 0 0.36 0.48
0. 48 0.64 0 0 0.48 0.64
X1
X 2
0
0
0
0
Modify to Ease Solution
10
100
0
0
0
0
AE
L
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0 0 L / AE 0 0 0
0 0 0 L / AE 0 0
0 0 0 0 L / AE 0
0 0 0 0 0 L / AE
X1
X2
X3
X4
X5
X6
Return Symmetry
10 ( 0.64AE / L)(X3) (0.48AE / L)(X4) ( 0.36AE / L)(X5 ) ( 0.48AE / L)(X6 )
100 (0.48AE / L)(X3) ( 0.36AE / L)(X4 ) ( 0.48AE / L)(X5 ) ( 0.64AE / L)(X6 )
0
0
0
0
AE
L
1.00 0.00 0 0 0 0
0.00 1.00 0 0 0 0
0 0 L / AE 0 0 0
0 0 0 L / AE 0 0
0 0 0 0 L / AE 0
0 0 0 0 0 L / AE
X1
X2
X3
X4
X5
X6
Modified Equations
10
100
0
0
0
0
AE
L
1.00 0.00 0 0 0 0
0.00 1.00 0 0 0 0
0 0 L / AE 0 0 0
0 0 0 L / AE 0 0
0 0 0 0 L / AE 0
0 0 0 0 0 L / AE
X1
X2
X3
X4
X5
X6
Recap
Initial Matrix
0
0
0
0
0
0
AE
L
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0.48 0 0 0.36 0.48
0. 48 0.64 0 0 0.48 0.64
X1
X2
X3
X4
X5
X6
Loads
10
100
0
0
0
0
AE
L
1.00 0.00 0.64 0.48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0.64 0.48 0.64 0.48 0 0
0.48 0.36 0.48 0.36 0 0
0.36 0.48 0 0 0.36 0.48
0.48 0.64 0 0 0. 48 0.64
X1
X2
X3
X4
X5
X6
Boundary Conditions
10
100
0
0
0
0
AE
L
1.00 0.00 0.64 0. 48 0.36 0.48
0.00 1.00 0.48 0.36 0.48 0.64
0 0 L / AE 0 0 0
0 0 0 L / AE 0 0
0 0 0 0 L /AE 0
0 0 0 0 0 L / AE
X1
X2
X3
X4
X5
X6
Symmetry
10
100
0
0
0
0
AE
L
1.00 0.00 0 0 0 0
0.00 1.00 0 0 0 0
0 0 L / AE 0 0 0
0 0 0 L / AE 0 0
0 0 0 0 L / AE 0
0 0 0 0 0 L / AE
X1
X2
X3
X4
X5
X6
Solution
10 = AE/L X1100 = AE/L X2 0 = AE/L X3 0 = AE/L X4 0 = AE/L X5 0 = AE/L X6
X
10LAE
100LAE
0
0
0
0
Force Calculation (f=sbX)
f i (EAT) i
1
1
AE
L i
1 1
1 1
cosi sin i 0 0
0 0 cosi sini
X1i
X2i
X3i
X4i
t i AEL
iX3i X1i cosi X4i X2i sin i (EA)iT
{(X3i-X1i) cosi + (X4v-X2v) sini} is simply the change in length
t1 = AE/L {(10L/AE - 0)(0.8) + (100L/AE - 0)(-0.6)} + (0)t2 = AE/L {(0 - 10L/AE - 0)(0.6) + (0 - 100L/AE - 0)(0.8)} + (0)
t1 = f2 = -f1 = -52 kipst2 = f4 = -f3 = -86 kips