Optimal Design of Power Transmission Towers Project Description

Optimize design of a latticed power transmission tower and poles to withstand transient dynamic loads due to a severe earthquake. Members of the structure should be selected directly from the commercially available ones.

Analysis Model for Tower

# of members: 316 (angle sections modeled as 3D beam elements) # of joints: 111 (666 degrees of freedom) Loading: Static loads: normal conductor loads, wind loads,

broken conductor loads Dynamic load: El Centro earthquake record

Analysis: Nonlinear transient dynamic analysis using ANSR program

a. Front View b. Side View

FIG. 110 kV Tangent-Type Tower (not to scale, units are in m., number in the parenthesis are nodal coordinates, member numbers are in italics)

63 (1.76, 0., 1.76).

14

151

198

71

.

259

42 .

244

135 .55 (1.48, 4.25, 1.48)

G

F

A

B

C

E

D

3.52

y x z

y

x

z 1.125

1.36

1.10

1.05

1.05

2.29

2.00

1.85

1.70

1.40

2.15

2.10

1.75

1.05

1.05

1.10

H

I

I I

1.125

A A

Cross-Section A-A

1.30 1.30

0.80

1

78 79

80 81 (3.35, 18.44, 0.)

82 83

39 (1.04, 10.95, 1.04)

66

1

3 2

2

Design Variables

Member sizes available in a vendor catalog. Members are grouped into 9 sections. Thus there are 9 discrete design variables.

Cost Function Minimize total cost of the structure; taken as proportional to mass of the structure.

Constraints Based on ANSI/ASCE Manual, Design of Latticed Steel Transmission Structures. Time dependent constraints are imposed on combined axial compression and bending, combined axial tension and bending, and shear stress. In addition constraints on slenderness ratio and member sizes are imposed.

Results Several discrete variable optimization methods are developed and evaluated. Each optimization run took about two weeks on a medium level HP desktop workstation.