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John Corini - PE

This presentation by J. F. Corini, a professional engineer, explores computer modeling and engineering aspects of amateur radio towers, including wind loading, guy wire tension, and mast length. Learn about the extreme design and structural considerations needed for ham radio towers, with detailed analyses and comparisons of various tower sections. Discover the importance of pretension in guy wires and mast length for optimal tower performance and stability. Gain valuable insights into tower construction and design practices for safe and effective installations.

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John Corini - PE

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  1. John Corini - PE Key To Successful Tower Installations: Under Stack And Over Guy Tom Wagner N1MM J. F. Corini KE1IH-YCCC

  2. KE1IH BACKGROUND • First Licensed as KA1MDG in 1983 • One of The YCCC “Smaller” Guns • Practicing Design/Structure Engineer of 25 years • Currently an Aerospace Composite Structures Engineer for Pratt and Whitney • Registered Professional Engineer in Mass. • Have Design and “Stamped” Towers in Ma., Ct and NY. J. F. Corini KE1IH-YCCC

  3. A Look At Computer Modeling Amateur Radio Towers - KE1IH • Topics of Discussion: • Free Standing Tower • Wind Loading Calculations • Guy Wire Tension • Importance of Mast Length • Guyed Tower – Beam Properties Method • Guyed Tower – Beam Element method • Questions J. F. Corini KE1IH-YCCC

  4. Free Standing Tower Free Body Diagram Loads in Blue, are Known Loads in Green need to be determined Antenna and Mast Forces Wind Load Tower Base Reaction Shear Force Tower Base Reaction Axial Force Tower Base Moment Reaction J. F. Corini KE1IH-YCCC

  5. An Extreme Ham Tower This 70 foot tower was originally to be 100 feet – designed to withstand 110 MPH The Tower Steel is over 6 1/2 feet wide at the base Typical Bolted Brace J. F. Corini KE1IH-YCCC

  6. An Extreme Ham Tower The Concrete Base is 8’ 6” wide on each side and over 7 feet deep. There is over 18 Yards of Concrete in the base and it weighs over 70,000# ( 35 tons). J. F. Corini KE1IH-YCCC

  7. This tower model has 400 nodes and 992 elements Welded Section The deflection at the top to the tower is 28”, the deflection at the top of the mast is 48” Bolted Sections J. F. Corini KE1IH-YCCC

  8. EIA 110 MPH WIND – NO ICE EIA 100 MPH WIND – NO ICE EIA 82.5 MPH WIND – ¼” Radial ICE MASS CODE 90 MPH WIND NO ICE Tower Section MEDIAN HEIGHT Max Pressure Max Force Max Pressure Max Force Max Pressure Max Force Max Pressure Max Force 10 31 973 26 804 17 673 21 588 30 31 804 26 664 17 576 21 476 50 35 550 29 434 20 480 31 430 70 38 535 32 443 22 510 31 380 90 41 421 34 348 24 425 31 280 Wind Loading Comparison J. F. Corini KE1IH-YCCC

  9. Tower Section Tower Section Element Tower Section Element 110 MPH Wind Load NOICE 82.5 MPH Wind Load - 1/4 “ Radial Ice AISC Maximum Allowable Load or Stress AISC Maximum Allowable Load or Stress Maximum Tower Leg Load Maximum Tower Leg Load Maximum Tower Leg Stress Maximum Tower Leg Stress Max Allowable Tower Leg Load Tower Section Max. Allowable Tower Leg Stress Max. Allowable Tower Leg Stress 7N 7N 12 12 43,977 pounds 34,530 pounds 23,378 psi 29,775 psi 50,685 pounds 50,685 pounds 34,310 psi 34,310 psi 6N 6N 31 31 35,950 pounds 46,980 pounds 31,808 psi 24,340 psi 50,686 pounds 50,686 pounds 34,310 psi 34,310 psi 5N 5N 62 62 37,390 pounds 49,030 pounds 22,086 psi 28,962 psi 55,624 pounds 55,624 pounds 34,150 psi 34,150 psi 4N 4N 102 102 22,780 pounds 31,270 pounds 18,566 psi 25,485 psi 40,389 pounds 40,389 pounds 32,910 psi 32,910 psi 3WN 3WN 163 163 11,430 pounds 17,029 pounds 16,565 psi 24,680 psi 22,423 pounds 22,423 pounds 32,480 psi 32,480 psi 100 Foot Free Standing Tower Results Max Stress J. F. Corini KE1IH-YCCC

  10. Guyed Tower Free Body Diagram Loads in Blue, are Known Loads in Red are unknown Loads in Green need to be determined Antenna and Mast Forces Upper Guy Wire Reaction Force Wind Load Lower Guy Wire Reaction Force Tower Base Reaction Axial Force Tower Base Reaction Shear Force J. F. Corini KE1IH-YCCC

  11. Tower Section Nodal Loadings Wind Force Applied to Nodes – Intersection of Tower Tubes and Braces J. F. Corini KE1IH-YCCC

  12. Wind Loading ASCE/EIA RS-222 J. F. Corini KE1IH-YCCC

  13. Antenna Drag Force Calculations J. F. Corini KE1IH-YCCC

  14. Antenna Wind Loading – Cont. D1 R10 Dr D10 D15 D1010 J. F. Corini KE1IH-YCCC

  15. Antenna Drag Force CalculationsContinued TH6DXX – CW LOW D1010 8.09 square feet per hy-gain J. F. Corini KE1IH-YCCC

  16. Importance of Pretension in Guy Wires Guy Wire Stiffness verses Buckling Load - Single Guy Guy Wire Stiffness verses Buckling Load - 2 Guys This Information Was Published By the CSME in 1997 Minimum Practical Guy Wire Stiffness J. F. Corini KE1IH-YCCC

  17. Importance of Pretension in Guy WiresContinued Stiffness of ¼” EHS Guy Wire J. F. Corini KE1IH-YCCC

  18. Importance of Pretension in Guy WiresContinued Using The Same Methodology: • The Stiffness of 3/16” Guy Wires: • 537 #/in or a Decrease of ~ 360 #/in • The Stiffness of 5/16” Guy Wires: • 1512 #/in or an Increase of ~ 610 #/in J. F. Corini KE1IH-YCCC

  19. Importance of Mast Length F1 L1 F2 R1 L2 Mast Length L3 R2 J. F. Corini KE1IH-YCCC

  20. Importance of Mast Length Using The Same Methodology: • For a 16’ Mast With 6’ in the Tower: • Radial Load At The Thrust Bearing, R1 = 900#, an Increase of 350# • Radial Load At The Rotator, R2 = 500#, an increase of 350# • For a 14’ Mast With 4’ in the Tower: • Radial Load At The Thrust Bearing, R1 = 1600# , an Increase of 1050# • Radial Load At The Rotator, R2 = 1200#, an increase of 1050# Conclusion: Longer Length of Mast in The Tower a Major Benefit J. F. Corini KE1IH-YCCC

  21. Computer Model of Rohn 25 TowerBeam Method Tower modeled using 3D beams with “equivalent” Rohn 25 properties Results: Max Tower Moment = 2800 ft/# Allowable Moment = 6720 ft/# Margin of Safety = 2800/6720 = .42 Max Mast Moment = 28800 in/# Mast Bending Stress = Mmax/S =84,850 #/in^2 Max Guy Wire Force= 430# Max Deflection (mast) = 30.3” Guy Wires Modeled as Compression Only Elements J. F. Corini KE1IH-YCCC

  22. Tower Deflection FEM Results 20 foot mast- loose guys, fixed at base 20 foot mast- tight guys, fixed at base 20 foot mast –2 guys 14 foot mast, free at base 16 foot mast-free at base 20 foot mast-free at base J. F. Corini KE1IH-YCCC

  23. Tower Bending Moments 80’ Tower Fixed at Base 80’ Tower 2 Guys Free to Rotate at Base J. F. Corini KE1IH-YCCC

  24. 80’ Rohn 25 at KE1IH QTH J. F. Corini KE1IH-YCCC

  25. NASTRAN FEM MODEL of TOWER and ANTENAS 40-2CD 40 meter beam TH6DXX Rohn 25 Tower Tower has 590 Elements and 226 Nodes Guy Anchors fixed in all directions Tower Base – fixed in all directions – case 1 Tower Base –free to rotate– case 2 J. F. Corini KE1IH-YCCC

  26. Tower Model Details Rotor & Bearing Plates Modeled as Rigid Regions Tower Tubes and Mast Modeled as 3D Beam Guy Wires Modeled as Rods, with Springs as Anchors Tower Braces Modeled as 3D Beams J. F. Corini KE1IH-YCCC

  27. Tower Wind Load Distribution 100 MPH Wind Speed Max Wind Load 12 pounds per node J. F. Corini KE1IH-YCCC

  28. Tower Deflections Due To Wind Max Deflection at Mast = 61” Max Tower Deflection = 12” J. F. Corini KE1IH-YCCC

  29. Tower Deflections – Second TH6DXX Max Tower Deflection = 12” Second TH6DXX Location J. F. Corini KE1IH-YCCC

  30. Tower Bending Stress Due to Wind Max Stress is 69,800 psi in Mast J. F. Corini KE1IH-YCCC

  31. Bending Stress at Tower Top Max Mast Stress Un-deformed tower 10,400 psi stress in tower due to mast bending J. F. Corini KE1IH-YCCC

  32. Tower Base Bending Stress – Single TH6DXX Max Tower Bending Stress is at the Base = 11,800 psi Base Fixed J. F. Corini KE1IH-YCCC

  33. Tower Base Bending Stress – 2 TH6DXX Max Tower Bending Stress is at the Base = 11,800 psi Base Fixed J. F. Corini KE1IH-YCCC

  34. Tower Axial Stress J. F. Corini KE1IH-YCCC

  35. Tower Base Stress- Single TH6DXX Max Tower Axial Stress is at the Base = 23,200 psi Max allowable stress per AISC = 23,400 Base Fixed J. F. Corini KE1IH-YCCC

  36. Tower Base Stress- Single TH6DXX2 Guys Max Tower Axial Stress is at the Base = 27,500 psi Max allowable stress per AISC = 23,400 Base Fixed J. F. Corini KE1IH-YCCC

  37. Tower Base Stress- 2 TH6DXX Max Tower Axial Stress is at the Base = 17,800 psi Rigid Region used to Model Pier and Plate Base Free to Rotate – Pier Pin J. F. Corini KE1IH-YCCC

  38. Tower Base Axial Stress – 2 TH6DXX Max Tower Axial Stress is at the Base = 27,500 psi Max allowable stress per AISC = 23,400 Base Fixed J. F. Corini KE1IH-YCCC

  39. Tower Axial Stress at Tower Top Max Axial Stress – 23,000 psi Due to mast and bearing plate J. F. Corini KE1IH-YCCC

  40. Antenna and Mast Rotations Due to Torque 24,000 in-pound Torque applied to mast J. F. Corini KE1IH-YCCC

  41. Tower Base Stress Due to Self Weight J. F. Corini KE1IH-YCCC

  42. K1ZM’s Cape Cod QTH J. F. Corini KE1IH-YCCC

  43. “Star” Guys at K1IR’s QTH Star Guy Bracket J. F. Corini KE1IH-YCCC

  44. J. F. Corini KE1IH-YCCC

  45. J. F. Corini KE1IH-YCCC

  46. Elevated Guy Anchor Guy Wire Force = F F = 3600# 34 degrees Guy Anchor Height = h = 6’ M = h *12*3600(cos 34) ~ 432k-in/# Srequired = M/(36000*.6) = 20 in3 Or 2 - 8” deep channels J. F. Corini KE1IH-YCCC

  47. F = 3600# Elevated Guy Anchor W = Anchor Weight M = 432k-in/# Guy Wire Force = F R1 =12000# H = 36” J. F. Corini KE1IH-YCCC

  48. Summary of Tower Base Axial Stress J. F. Corini KE1IH-YCCC

  49. Contact Information – KE1IH • KE1IH@ARRL.net • This Presentation is available at: • http://www.yccc.org/Articles/articles.htm J. F. Corini KE1IH-YCCC

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