RSA Presentation

June 9-12, 2004 GTSUG Boston, MA 1

CASE Center’s Antenna Tower Program

Program AbstractThe CASE Center is developing a program for the design of steel antenna towers and supporting structures based on the TAI/EFA-22-F Standard, as reaffirmed March 27, 2003. This new program is designed to give the steel antenna tower and supporting structure design engineer and easy-to-use program to construct a tower and appurtenance model, analyze the model, review the results and code check the structural components. The model is constructed by entering data into spreadsheet-like tables. Models may be saved into neutral files and retrieved at a later date for adjustment or further refinement. Supported towers include monopoles, 3- or 4-sided latticed towers, with or without guys.



Program Goals

• Simplified modeling of tower and monopole geometry

• Simplified appurtenance input

• Automatic ice and wind load calculations

• Nonlinear analysis for guyed towers and monopoles



Program Goals (cont)

• Concise result reporting including twist, sway and displacement for antennas

• Code check by ASD9 along with TIA/EFA-222-F adjustments



Program Limitations

• No light gauge or cold-formed components (AISI) are code checked or have tables provided.

• Connections (bolts or welds) are not checked or designed.



Program Layout- Tabbed spreadsheet-like input

- Graphical display of current model

- Menu selections for- File input- GTSTRUDL processing- Results review



Program Usage

• Modeling

• Input file creation

• Results



Usage: Modeling

• Basic Geometry– Tower type: Monopole, 3- ro 4- sided– Tower height– Base and top widths– Additional inflection (slope change) points



Usage: Modeling

Basic geometry data entry



Usage: Modeling

• Constants– Wind speed

• Section 16, County listings of wind speeds available as drop-down lists

– Ice thickness– Ice density– Wind + ice reduction factor



Usage: Modeling

Constants entry sheet



Usage: ModelingState and county drop-downs for wind speed



Usage: Modeling

• Section data– Length of section– Number of panels– Bracing type (X, C or K)– Existence of girts– Properties



Usage: ModelingData entry sheet for Section Geometry



Usage: ModelingData entry sheet for Section properties



Usage: Modeling

• Appurtenances– Type

• Flat• Round• Dish

– Properties• Width / Diameter• Height• Weight



Usage: Modeling

• Appurtenances (cont)– Elevation– Mount

• Number of mounts• Weight of single mount• Equivalent projected area of single mount• Legs (1 or more)



• Appurtenances (cont)– Feed line(s)

• Number of feed lines• Feed line diameter• Face(s) feed lines are attached to

– Description• 128 character description/note about appurtenance

Usage: Modeling



Usage: Modeling

• Guys– Tower attachment location– Anchor– Torque arms



Usage: Input File

• Job name and description

• Geometry

• Loads

• Code check

• Analysis

• Additional GTSTRUDL commands

• Notes and comments



Usage: Input FileA GTSTRUDL input file is created upon request once the model data is entered or read from a neutral file. This file is used to get analysis results and code check information from GTSTRUDL and is not deleted. You can use this file to go beyond the limits of the Antenna Tower program and add your own GTSTRUDL commands to do dynamic analysis, support pad modeling, etc. Note that you can add these extra commands to the .gta file (Antenna Tower program neutral file) so they will be automatically be added to the generated GTSTRUDL input file the next time you use the .gta file. You can also add comments that will be added to the GTSTRUDL input file as NOTES.



Usage: Input File

• Job name and description– STRUDL ‘name’ ‘description’

• Geometry– JOINT COORD, MEM INC, MEM PROP, etc.– DEFINE GROUP (by types: legs, braces, girts

and by section)



Usage: Input File

• Loads– Wind and ice loads are generated on a panel-

by-panel basis to take advantage of feed line termination within a section

– Self weight– Ice (if specified) applied as joint loads at the

top of each panel.



• Loads (cont)– Wind loads are applied as joint loads at the

top of each panel.– As many wind directions as are needed

created.– Design loads are created by FORM LOAD to

allow nonlinear analysis.

Usage: Input File



Usage: Input File

• Paramters– CODE: ASD9, maybe TOWER for single

angles to do a second code check.– ALSTRINC: to account for increased

allowable stress for towers under 1200’.– KY, KZ, LY, LZ as needed to satisfy Section

3.1.14 for single angles in compression.



Usage: Input File

• Parameters (cont)– Possible new parameter ‘TIA’ to keep code

check complete in GTSTRUDL.

• Analysis– Static for self supporting towers– Nonlinear for monopoles and guyed towers.



Usage: Input File

• Additional GTSTRUDL commands– You can add extra commands to adjust the

generated input file or add loads that the Tower program doesn’t support. Once the additional commands are created, they can be added to the neutral file so they will be automatically appended each time an input file is created.



Usage: Input File

• Notes and comments– You can also add non-executable information

which will be added to the input file as NOTES. This data could include file names, explanations for unusual values such as extra high wind speeds, etc.



Usage: Results

• Base reactions

• Displacement of tower joints

• Twist, sway and displacement of antennas

• Member end forces

• Code check results

• Printed reports



Neutral File

• .gta extension

• Text file – human readable and editable

• Easy to manage

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