gtw tower crossing
TRANSCRIPT
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DESIGNING A 332 CROSSING TOWERUsing PLS-TOWER 11.16
By: George Watson, Consulting Engineer
CenterPoint Energyformerly Reliant Energy
formerly Houston Industries Inc.
formerly Houston Lighting & Power
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Small Service Area (2.5%)Big Electrical Load (25%)
Texas Peak Load for2010 was 66,000mw
CNP Peak Load for2010 was 16,100mw
(25% of Texas Total)
233 Substations
3800 Miles of T-Lines
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Typical Houston housewith 11 Car Garage
61,000 Square Feet on an 11 Acre Lot
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Ancient Tower Design Tools
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Early Stress Analysis
Graphical Method ofJoints
Many Assumptions toAllow Analysis
Multiple Load Cases
Very Time Consuming
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Calculator from 1973 ($2,000)
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1976 Tower Design on CDC 6600
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Tower hit by a barge of scrap
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PLS-TOWER Face Designation
The windward transverse face is that on which apositive transverse wind (in the positive Y-direction)would blow.
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Adjust Drag Factors
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Start with a basic geometry
Tower Baseis 27 x 18
All Redundants mustbe accounted for in
the Drag AreaCalculations, eitherby adding to themodel or adjusting
the factors
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Start with a basic geometry
Tower Baseis 27 x 18
Redundants addedand Leg Members
split
Crossing Diagonalsjoint added
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Start with a basic geometry
The 7 Joints shownare the Primary Joints
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Start with a basic geometry
The CrossingDiagonal Joints must
be re-calculated if theleg slope is changed
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Add Some Extensions
Add a 40 footExtension
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Add Some Extensions
Add a 20 footExtension
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Add Some Extensions
Add a 32 footExtension
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Add Some Extensions
Add 3 more32 foot
Extensions
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Add Some Extensions
Add another32 foot
Extension
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Add Some Extensions
Add a 48 footExtension
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The Final Starting Geometry
332-0 Tall
109.6 Wide
73.1 Deep
7 Primary Joints
214 Secondary Joints
384 Member Groups
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Evaluate Different Base Spreads
Change OneJoint
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Make the Base Wider
332-0 Tall
124.4 Wide
92.8 Deep
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Make the Base Narrower
332-0 Tall
75.1 Wide
53.3 Deep
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Use PLS-CADD Lite
Max Line Angle
Max Span
Min Line Angle
Min Span
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Generate Design Load Cases
Max Line Angle
Max Span
Min Line Angle
Min Span
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New Tower Version 11.16
Redundant Check and Design
Included Angle Check
Climbing Load Check and Design
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Evaluate the Best Leg Slope
The CrossingDiagonal Joints must
be re-calculated if theleg slope is changed
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Evaluate the Best Leg Slope
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Evaluate the Best Leg Slope
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Evaluate the Best Leg Slope
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Crossing Tower Statistics
Crossing Span is 1700
Anchor Span is 1200
Line Angle is 20
Wind Speed is 120 MPH
Wind on Structure accounts for 77% of FoundationLoad
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Observation
In the days prior to PLS-CADD and Tower, theseWhat-If permutations were not possible withoutmassive manpower and many weeks or months ofEngineering calculations.
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Questions?