Monopoles - Current Design Issues
Monopoles - Current Design Issues
Monopoles - Current Design Issues
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2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresDiscussion of <strong>Current</strong> <strong>Issues</strong>Related toSteel TelecommunicationsMonopole StructuresDavid W. Hawkins, P.E., M.ASCE 11Department Manager, Paul J. Ford and Company, Structural Engineers,250 East Broad Street, Suite 1500, Columbus, OH 43215PH (614) 221-6679; email: dhawkins@pjfweb.com© Copyright 2010 by Paul J. Ford and Company, all rights reserved.1 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresAbout Paul J. Ford and Company• Founded in 1965 by Paul J. Ford• Employee-Owned (ESOP) Since 1994• Since 1976; <strong>Design</strong> of Self-Support and GuyedTowers for Cable TV and Long-Distance Telephone• Since 1985; <strong>Design</strong> of Telecom/Cellular Towers• Mid-1990‟s; Telecom Act of „96; Boom in <strong>Design</strong> ofTelecom Towers and <strong>Monopoles</strong>• Yearly Average of 2,000 Analyses, <strong>Design</strong>s and/orReinforcement of Towers and <strong>Monopoles</strong>© Copyright 2010 by Paul J. Ford and Company, all rights reserved.2 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresAbout the AuthorDavid W. Hawkins, P.E., M.ASCE▪ Education: BS („83), MS („89), The Ohio State University▪ Experience: 25 years with Paul J. Ford and Company,Structural Engineers▪ Member, TIA TR-14.7 Engineering Subcommittee▪ Member, TIA TR-14.7 Structural Reliability Task Group▪ Chair, TIA TR-14.7 Monopole <strong>Design</strong> Sub-Task Group© Copyright 2010 by Paul J. Ford and Company, all rights reserved.3 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresOverview -- Types of Tubular Steel Poles:▪ Flagpoles▪ Electric Utility Poles▪ Traffic Signal Poles▪ Highway Light and Sign Poles▪ Commercial Sign Poles▪ Telecommunications AntennaSupport Poles (<strong>Monopoles</strong>)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.4 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresTelecommunications <strong>Monopoles</strong>Generally categorized into two main types:(1.) Tubular Round Shaftswith bolted flange splices(2.) Polygonal Tapered Shaftswith slip-joint splices andbolted base plate connections.(12 and 18-sided are common)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.5 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresTelecommunications<strong>Monopoles</strong>PolygonalPoleFabrication© Copyright 2010 by Paul J. Ford and Company, all rights reserved.6 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresTelecommunications<strong>Monopoles</strong>PolygonalPoleComponents© Copyright 2010 by Paul J. Ford and Company, all rights reserved.7 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresTelecommunications <strong>Design</strong> Reference StandardsTIA/EIA-222-F-96 (1996)▪ Referenced by IBC 2006 (Ch. 35)▪ Sections 1609.1.1, 3108.4TIA-222-G-2005 (2005)▪ Referenced by 2007 Supplementto the IBC (Ch. 35; Sect. 1609.1.1)▪ Referenced by IBC 2009 (Ch. 35)Sections 1609.1.1, 3108.4© Copyright 2010 by Paul J. Ford and Company, all rights reserved.8 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresTelecommunications <strong>Design</strong> Reference StandardsTIA-222-F (1996)▪ ASCE 7-88 Fastest Mile Winds▪ AISC ASD (elastic; 1/3 stress increase)TIA-222-G (2005)▪ ASCE 7-02 3-sec Gust Winds▪ AISC LRFD (elastic limit states)TIA-222-G-2 (2009)▪ AISC LRFD (plastic limit states)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.9 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresCompare TIA-222-G with G-2TIA-222-G and G-1 (Addendum 1):Factored Loads withElastic Limit StatesTIA-222-G-2 (Addendum 2):Factored Loads withPlastic Limit States© Copyright 2010 by Paul J. Ford and Company, all rights reserved.10 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresCompare TIA-222-G with G-2Table 4-8: Effective Yield Stress for Polygonal Tubular MembersTIA-222-G and G-1 (Addendum 1) Upper Limits:Effective Yield Stress, F‟y = FyMoment Capacity, Mn = F‟y S (Elastic)TIA-222-G-2 (Addendum 2) Upper Limits:Effective Yield Stress, F‟y = 1.27 FyMoment Capacity, Mn = F‟y S= (1.27 Fy) S(where Z ≈ 1.27 S for 18-sided polygon)= Fy Z (Plastic)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.11 of 37
F'y / FyCompact Limit0.759Compact Limit1.17TIA-222-G Table 4-81.31.21.11.00.90.80.71.27 1.27 1.27 1.251.221.182010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole Structures1.141.101.00 1.00 1.00 1.00 1.00 1.00 1.00 1.001.060.96(18-sided Polygon)1.020.92TIA-222-G-2 (Addendum 2)TIA-222-G and G-10.990.890.950.850.910.820.870.780.830.750.800.720.76 0.740.60.68 0.67© Copyright 2010 by Paul J. Ford and Company, all rights reserved.(Fy/E) 1/2 (w/t)12 of 37
Factored Flexural Strength: Shaft Moment Capacity,Φ f Mn (ft-kips)Table 4-8: Effective Yield Stress, ø f F‟y2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresFactored Flexural Strength (Shaft Moment Capacity) ChartComparison of TIA-222-G and G-1 (Addendum 1) with TIA-222-G-2 (Addendum 2)9,000 Example: Shaft 48” Diam; 18-Sided Polygon; Fy=65 ksi 808,000707,0006,0005,0004,0003,0002,0001,000TIA-222-G Factored Flexural Strength, ΦMnTIA-222-G-2 Factored Flexural Strength, ΦMnTIA-222-G Table 4-8: Effective Yield Stress, Φf F'y60504030201000.125 0.188 0.250 0.313 0.375 0.438 0.500 0.563 0.625 0.688 0.750Shaft Wall Thickness, t (inches)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.TIA-222-G-2 Table 4-8: Effective Yield Stress, Φf F'y013 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresCompare TIA-222-G with G-2Summary:Effective Shaft FlexuralStrength for Polygonal PolesCan be 10% to 27% HigherWith TIA-222-G-2(Addendum 2)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.14 of 37
© Copyright 2010 by Paul J. Ford and Company, all rights reserved.2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresFatigue and Vortex Shedding <strong>Issues</strong>• Criteria for fatigue and dynamic effects from vortexshedding are not currently addressed in TIA-222-G.• AASHTO has fatigue criteria for highway structures, butmay not be appropriate for telecommunications poles.• ASCE Manual 72 (1990) and ASCE 48-05 Standard(2006) mention vortex shedding and fatigue but do notprovide specific criteria.• TIA TR-14.7 Subcommittee intends to address fatigueand vortex shedding criteria in future revisions of theTIA-222 Standard.• Additional research and testing is needed to developfatigue design criteria for poles.15 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresShaft Upgrades and ReinforcingMain Types:1. Field WeldedRisks: Fire, Corrosion2. Field BoltedCons: Larger connectionsthan welded© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Polygonal pole shaft with field bolted channelreinforcements. (Courtesy B. Reese) 16of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresDiscussion of Monopole FailuresMan-Caused:▪Monopole Fires▪Vandalism▪Cracks in Poor Welds in Base PlatesEnvironmental Influence:▪Extreme Wind with Debris▪ Vortex Shedding Fatigue© Copyright 2010 by Paul J. Ford and Company, all rights reserved.17 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresMonopole Fires(Courtesy B. Reese)(Courtesy B. Reese)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.(Courtesy B. Reese)Most fires are caused by field activities such as flame torching holesin the shaft and field welding. Heat from careless burning andwelding ignites debris, such as bird nests, in the pole which thenignites the plastic coated coaxial cables.18 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresMonopole Flange Connection Failures(Courtesy B. Reese)(D. Hawkins)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Collapse of pipe poleswith bolted flange splices19 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresMonopole Flange Connection Failures(D. Hawkins)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Collapse of pipe poleswith bolted flange splices(D. Hawkins)20 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresMonopole Flange Connection Failures(D. Hawkins)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Collapse of pipe poleswith bolted flange splices(D. Hawkins)21 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresMonopole Flange Connection FailuresToe crack at top of weld at vertex inshaft to base plate connection.(Courtesy B. Reese)Toe crack at vertex in shaft.(Courtesy B. Reese)“Toe Cracks” in Base Plate Welds at ShaftVertex in Polygonal Poles© Copyright 2010 by Paul J. Ford and Company, all rights reserved.22 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresMonopole Flange Connection FailuresMagnetic Particle (MT)(Courtesy B. Reese)(Courtesy B. Reese)Ultrasonic (UT) Testing© Copyright 2010 by Paul J. Ford and Company, all rights reserved.NDT Testing for “Toe Cracks”in Base Plate Welds23 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresBase Plate and Flange Plate Connections▪ Base Plates Without Stiffeners▪ Base Plates With Gusset Plate Stiffeners▪ Flange to Shaft Connection Types:(a) “Socket” Type with fillet welds(b) “Tee” Joint Type with CJP Welds© Copyright 2010 by Paul J. Ford and Company, all rights reserved.24 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresBase Plates Without Stiffeners<strong>Current</strong> design methodologies assume linear elastic bending of the baseplate. Typically used with AISC-ASD with TIA-222-F working loads.TIA TR-14.7 Subcommittee researching new base plate design criteria:• Plastic yield line methods at limit states. Analogous to yield lines inconcrete slabs, uses balanced energy approach.• Uses AISC-LRFD with TIA-222-G factored loads.• Base plate is proportioned for minimum thickness to eliminate pryingforces on the bolts.• Plate ultimate capacity determined by plastic bending limits (FyZ).• Results indicate plate thickness should be at least equal to anchor roddiameter.• Preliminary FEA studies of unstiffened base plates show yield linedistribution of stress.© Copyright 2010 by Paul J. Ford and Company, all rights reserved.25 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresBase Plates Without StiffenersFEA model results for six bolt double flangeconnection on round pole shaft.© Copyright 2010 by Paul J. Ford and Company, all rights reserved.26 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresBase Plates Without StiffenersFEA model results for six bolt flange connection.Round pole shaft elements hidden.© Copyright 2010 by Paul J. Ford and Company, all rights reserved.27 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresBase Plates Without StiffenersFEA model results for six bolt flange connection.© Copyright 2010 by Paul J. Ford and Company, all rights reserved.28 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresBase Plates Reinforced WithGusset Plate StiffenersBase plate reinforcement with „Tall‟gusset plate stiffeners. (Courtesy B.Reese)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Base plate reinforcement with „Tall‟gusset plate stiffeners, new anchorrods and brackets. (Courtesy B.Reese)29 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresGusset Plate Stiffener ProportionsTaper(typ.)h18”Taper(typ.)h 6”w6”„Short‟ Stiffener withh:w = 1:1 aspect ratio(Not recommended)© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Chamfer(typ.)w6”Chamfer(typ.)„Tall‟ Stiffener withh:w = 3:1 aspect ratio(Recommended)30 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresFEA of Stiffened Base PlatesNo Stiffeners3x3Stiffeners6x6Stiffeners© Copyright 2010 by Paul J. Ford and Company, all rights reserved.6x18StiffenersDbl 6x18Stiffeners31 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresFEA of Stiffened Base PlatesNo Stiffeners 3x3 Stiffeners 6x6 Stiffeners6x18Stiffeners© Copyright 2010 by Paul J. Ford and Company, all rights reserved.Dbl 6x18Stiffeners32 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresFurther Research Needed<strong>Issues</strong>:TIA TR-14.7 Subcommittee has voluntarymembers from engineering firms, towerowners, fabricators and contractors.There has been no significant fundingavailable for research. Each groupcontributes their own time and resourcesfor any research work done.© Copyright 2010 by Paul J. Ford and Company, all rights reserved.33 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresFurther Research NeededOpportunities for Additional Research:• Develop base plate design methods using limitstates and reliability based approaches.• FEA studies of unstiffened and stiffened baseplates using non linear methods.• Full scale physical testing of unstiffened andstiffened base plates to correlate with FEA.• Fatigue research for base plate connections,with and without stiffeners.© Copyright 2010 by Paul J. Ford and Company, all rights reserved.34 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresAdditional Research NeededFEA Simulations:• „Non-Rigid‟ Base Plates with Bolt Prying• Square Base Plates (bolts in quadrants)• Base Plates with Stiffeners (incl. fatigue)• Using Nonlinear Material (Plastic) Methods• Parametric studies (plate thickness, bolt size,shaft type, bolt circle, flange diameter, etc.) todetermine empirical relationships© Copyright 2010 by Paul J. Ford and Company, all rights reserved.35 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresAdditional Research Needed(continued)Physical Testing:• Full scale physical testing of baseplates• Full scale physical testing of baseplates with stiffeners© Copyright 2010 by Paul J. Ford and Company, all rights reserved.36 of 37
2010 ASCE / SEI Structures Congress | Orlando, FLNon-Building Structures | May 15, 2010 | D. HawkinsDiscussion of <strong>Current</strong> <strong>Issues</strong> Related to Steel Telecommunications Monopole StructuresTHANK YOU© Copyright 2010 by Paul J. Ford and Company, all rights reserved.37 of 37
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