transmission line design structures &...
TRANSCRIPT
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Transmission & Distribution Program
Transmission Line Design Structures & Foundations
TADP 549
Steel Poles -
Pier Foundations -
Software
Presentation 6.6
Dr. Prasad Yenumula
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Commercial Software
MFAD
CAISSON
LPILE
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Rigid Pile Theories
Several rigid pile theories
– Broms method, 1964
– Brinch Hansen, 1961
– Parker and Reese, 1970
– Petrasovits and Award,1972
– Meyerhof et al., 1981
– Prasad and Chari, 1999
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Comparison Between Rigid Pile Theories
Different theories assume different soil pressure distributions and shape factors, so these methods yield different results
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MFAD (Moment Foundation Analysis and Design)
MFAD
– EPRI Software
– MFAD predict both ultimate moment capacity
and deflections/rotations
– Uses Brinch-Hanson theory to predict ultimate
moment capacity
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MFAD (Moment Foundation Analysis and Design)
•MFAD software uses
“Four-spring” nonlinear
subgrade modulus model
•In the subgrade reaction
approach, continuous
nature of the soil medium
is ignored and is idealized
by four different types of
non-linear springs
Source: IEEE 691-2001
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MFAD (Moment Foundation Analysis and Design)
•To characterize the
springs, deformation
modulus of soil is required
•FAD suggests to use
pressuremeter modulus
value
•Pressuremeter modulus
values shall be obtained
from empirical correlations
or through actual
pressuremeter test
Source: IEEE 691-2001
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CAISSON
CAISSON
– Product of Power Line Systems
– Predict ultimate moment capacity
– Uses modified Broms’ theory
– No features to predict deflections/rotations
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Illustrated Example-1
For a self-supported deadend steel pole,
design a pier foundation using the following
data:
Loadings on the pier (extreme wind load
case)
Lateral load = 171.0 kips
Moment = 11193.0 kips-ft
Axial load = 78.0 kips
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Illustrated Example-1 (Cont.)
Design pier foundation for following conditions:
Part A – Factor of safety against lateral soil failure = 1.0, no limitations
on deflections/rotations
Part B – What will happen if the following limitations on rotations and
deflections are applied:
• Total ground line rotation limit: 2 deg
• Non-recoverable ground line rotation limit: 0.5 deg
• Total ground line deflection: 2 inches
• Non-recoverable ground line deflection: 1 inch
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Illustrated Example-1 (Cont.)
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Illustrated Example-1 (Cont.)
Solution (Part A)
– Factor of safety against lateral soil failure = 1.0
– No limitations on deflections/rotations
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Illustrated Example-1 (Cont.)
Solution (Part B)
– What will happen if the limitations on rotations and
deflections are applied:(* Note: Caisson does not
have capabilities to predict deflections/rotations)
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Illustrated Example-1 (Cont.)
Remarks
– In part A, FAD and CAISSON software provided
different embedment depths because they use
different theoretical models
– In part B, the deflection/rotation criteria
governed over the ultimate lateral soil failure
– Do not generalize these sample results
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Illustrated Example-1 (Cont.)
Structural design of concrete Pier (Part A)-MFAD
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Illustrated Example-1 (Cont.)
Structural design of concrete Pier (Part A)-MFAD
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Illustrated Example-1 (Cont.)
Structural design of concrete Pier (Part A)-MFAD
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Illustrated Example-1 (Cont.)
Structural design of concrete Pier (Part A) - MAD
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Illustrated Example-1 (Cont.)
Structural design of concrete Pier (Part A) - MFAD