TV and Radio Tower Broadcast Structures May 2012
Madison J. Batt, SE, PEDirector of Tower EngineeringMay 18, 2012
About MeAbout Me
TV and Radio Towers 2 5/18/2012
Madison J. Batt, PE, SE
•35 years of experience in the field of structural engineering, y p g g,specifically focused on tower engineering for the last 26 years in the examination, evaluation, analysis, and design of towers and communication sites. I have managed over 1,000 tower projects g jand have climbed and observed the condition of over 500 towers, ranging in height from 50 to 2,000 feet.
•Licensed in 49 States, Washington D.C., Guam, and Puerto Rico.
TV and Radio Towers 3 5/18/2012
A Brief History
TV and Radio Towers 4 5/18/2012
Towers For TV and Radio
•First broadcast towers were built for AM radio
•No specific design standard for towers before 1949
•First Standard – RETMA (TR-116) 1949 – Wind Pressure 20/13.3 and 30/20( )
•EIA/TIA 222 – First issued in 1959 – Wind Pressure varied based on map (30-70)
•EIA/TIA 222-A, B, and C in 1966 to 1976 – Wind Pressure Map (30-85)
•EIA/TIA 222-D, E, and F in 1986 to 1996 – Wind Speed Fastest Mile County listings for wind (70 110) Ice (Major change to standard)listings for wind (70-110) Ice (Major change to standard)
•TIA 222-G 2005 to Present- Wind speed 3 Second Gust (Major change to standard)
TV and Radio Towers 5 5/18/2012
G Standard and impact on Industry
•Mandated by Building Officials (IBC) - Not by industry
•3 Second gust versus Fastest Mile
•Updated Ice loadingp g
•Exposure categories
•Topographic categoriesTopographic categories
•Earthquake design
Importance classification•Importance classification
•Serviceability requirements
TV and Radio Towers 6 5/18/2012
•Ref: http://www.stainlessllc.com/Resources/NAB2007Paper.pdf
Results of Analysis to G Standard
•TIA-222-G adopted by 2007 amendments of IBCp y
•Most Municipalities will accept TIA-222-G
•Ice Loading is more realistic
•Topographic has large impact on towers on elevated locations
•Towers designed to older standards benefit
TV and Radio Towers 7 5/18/2012
TIA-222-G
TV and Radio Towers 8 5/18/2012
EIA/TIA-222-C
TV and Radio Towers 9 5/18/2012
Tower Engineering is a Specialization of Structural Work
TV and Radio Towers 10 5/18/2012
Engineering
• Electrical Engineers, Communication Engineers, Radio/TV g , g ,Engineers
• Mechanical Engineers, HVAC, Mechanical Equipmentg
• Civil Engineers, Structural Engineers, Soils Engineers
• Lots of others Engineer types Chemical, Aeronautical etc.
TV and Radio Towers 11 5/18/2012
Tower Engineering (Subset of Structural and Civil)
• Wind and Ice (Seismic too)• Pure structure• Field Inspections• Analysis• Retrofit Design• Reports• Reports• New Towers• Construction
TV and Radio Towers 12 5/18/2012
Guyed Towers Inspections
TV and Radio Towers 13 5/18/2012
Guyed Towers
• Tallest Structures Globally
• Exception: Burj Khalifa, Exception: Burj Khalifa, Dubai - Tallest Building (tallest structure in the world)
TV and Radio Towers 14 5/18/2012
Guyed Towers
TV and Radio Towers 15 5/18/2012
Guyed Anchors
• Requires expansive areas of land to secure tower
• Guyed towers commonly located in remote fields, farmland, or mountain tops
• Structural properties demand specialized design and knowledgeg
TV and Radio Towers 16 5/18/2012
Self-Support Towers
TV and Radio Towers 17 5/18/2012
Self-Support Towers
Examples of TV and FM Antennas
TV and Radio Towers 18 5/18/2012
FM Towers
TV and Radio Towers 19 5/18/2012
TV Tower (with FM antenna)
Multiple Antenna Mounted Tower
• Top Antenna serves TV
• Side Mounted Antennas serve FMand DTV
TV and Radio Towers 20 5/18/2012
TV Tower (with FM antenna)
New Antenna Installation
TV and Radio Towers 21 5/18/2012
AM Towers
TV and Radio Towers 22 5/18/2012
AM Towers
Example of a “Hot” Tower – Entire tower radiates active waves
TV and Radio Towers 23 5/18/2012
AM Towers
•Oldest Towers in ServiceOldest Towers in Service
•Narrowest Face Widths
•Commonly designed and constructed as a guyed structure
• Design patterns vary
TV and Radio Towers 24 5/18/2012
AM Towers
• Isolated Tower Base
• Tower is unsafe to touch
TV and Radio Towers 25 5/18/2012
Antenna Installation
ENG AntennaENG AntennaInstallation
TV and Radio Towers 26 5/18/2012
Antenna Installations
TV and Radio Towers 27 5/18/2012
New Towers
TV and Radio Towers 28 5/18/2012
KRKO - Foundation Construction - Everett
TV and Radio Towers 29 5/18/2012
Tower Inspections
TV and Radio Towers 30 5/18/2012
Tower Inspections
Tower inspections are laborious and dangerous:
• Engineers are required to complete extensive safety training• Engineers must be in very good physical condition
TV and Radio Towers 31 5/18/2012
• Engineers must be in very good physical condition
Tower Inspections
TV and Radio Towers 32 5/18/2012
Tower Inspections
• Adverse Conditions
• Ice Loads
TV and Radio Towers 33 5/18/2012
Inspections - After Disasters
Ten days after Hurricane Katrina Ten days after Hurricane Katrina – New Orleans, Louisiana
TV and Radio Towers 34 5/18/2012
Tower Inspections – After Disasters
•View from tower showing •View from tower showing water around building
• Water had been 8 feet higher swamping equipment in transmitter building
TV and Radio Towers 35 5/18/2012
Failed Towers
TV and Radio Towers 36 5/18/2012
Failed Towers - Collapse
• Experience leads to other areas
• Expert on failure investigationinvestigation
• Expert witness
TV and Radio Towers 37 5/18/2012
Tower Failures
F il d h d t d t • Failed anchor rods at rod to plate forging
• Fatigue failureFatigue failure
TV and Radio Towers 38 5/18/2012
Tower Failures
Magnetic particle testing of rods
TV and Radio Towers 39 5/18/2012
Failed Towers - Collapse
TV and Radio Towers 40 5/18/2012
Failed Towers - Collapse
TV and Radio Towers 41 5/18/2012
Failed Towers - Collapse
TV and Radio Towers 42 5/18/2012
Failed Towers - Collapse
Guyed Tower failure
TV and Radio Towers 43 5/18/2012
Tower Failures
It appears poor welding of antenna to base of antenna caused failureantenna caused failure
TV and Radio Towers 44 5/18/2012
Digital TV Trends
•In Most Markets, Broadcasters are adding one or more secondary channels
•Majority of Stations have finalized DTV transition
•There are however numerous Stations with Analog antennas still onThere are, however, numerous Stations with Analog antennas still on the tower
•When antennas are removed, a tower study should be done to make sure tower is not overstressed by the removal of antenna (Especially on Guyed towers)
•A good reference
TV and Radio Towers 45 5/18/2012
•A good reference http://www.stainlessllc.com/Resources/Tower_Effects_Presentation.pdf
Guyed Tower with Large Antennas to be Removed
•Removal of large side-mounted or top-mounted antenna has impact on adjacent span(s)j ( )
•Guy wires sized for large wind loads from antennas will overstress legs and bracing and cause an imbalance in the guy system
•Transmission line loading can cause greater stress on tower than antenna
TV and Radio Towers 46 5/18/2012
Tower Mast Moment Curve With Antenna removed
5/18/201247 TV and Radio Towers
Mast Moment with Guy wire Modifications
5/18/201248 TV and Radio Towers
Whats Next
•Is Mobile TV the next big move?
•Antennas are being installed on towers with big V-polarization for Mobile TV reception
•Will consumers go to this?
•Is there a trend for consumers to drop cable and satellite for over-the-air broadcast, Netflix and Internet TV?
•Are consumers buying FM Digital Radios for their homes and ?
TV and Radio Towers 49 5/18/2012
cars?
QUESTIONS?
THANK YOU!
TV and Radio Towers 50 5/18/2012