31 brinker proposed design standard for towers

7/30/2019 31 Brinker Proposed Design Standard for Towers

1/21

ANSI/TIA-222-G-DS1-2011DRAFT 3-29-2011 Rev 0

ANSI/TIA STANDARDDESIGN SUPPLEMENT

Design Supplement for Small Wind TurbineSupport Structures

TIA-222-G-DS1 Draft 3-29-2011 Rev 0

TELECOMMUNICATIONSINDUSTRY ASSOCIATION

TR14.7 Sub-committee

tiaonline.org


2/21


NOTICE OF COPYRIGHT

This document is copyrighted by the TIA.

Reproduction of these documents either in hard copy or soft copy (including posting on theweb) is prohibited without copyright permission. For copyright permission to reproduce

portions of this document, please contact TIA Standards Department or go to the TIA website(www.tiaonline.org) for details on how to request permission. Details are located at:

http://www.tiaonline.org/standards/catalog/info.cfm#copyright

OR

Telecommunications Industry AssociationStandards & Technology Department

2500 Wilson Boulevard, Suite 300

Arlington, VA 22201 USA

+1(703)907-7700

Organizations may obtain permission to reproduce a limited number of copies by entering into a

license agreement. For information, contact:

IHS15 Inverness Way

East Englewood, CO 80112-5704 or call

U.S.A. and Canada (1-800-525-7052)

International (303-790-0600)


3/21


NOTICE OF DISCLAIMER AND LIMITATION OF LIABILITY

The document to which this Notice is affixed (the Document) has been prepared by one

or more Engineering Committees or Formulating Groups of the Telecommunications

Industry Association (TIA). TIA is not the author of the Document contents, but

publishes and claims copyright to the Document pursuant to licenses and permission

granted by the authors of the contents.

TIA Engineering Committees and Formulating Groups are expected to conduct their

affairs in accordance with the TIA Engineering Manual (Manual), the current and

predecessor versions of which are available at http://www.tiaonline.org/standards/procedures/manuals/

TIAs function is to administer the process, but not the content, of document preparation

in accordance with the Manual and, when appropriate, the policies and procedures of theAmerican National Standards Institute (ANSI). TIA does not evaluate, test, verify or

investigate the information, accuracy, soundness, or credibility of the contents of the

Document. In publishing the Document, TIA disclaims any undertaking to perform anyduty owed to or for anyone.

If the Document is identified or marked as a project number (PN) document, or as a

standards proposal (SP) document, persons or parties reading or in any way interested in

the Document are cautioned that: (a) the Document is a proposal; (b) there is no

assurance that the Document will be approved by any Committee of TIA or any other

body in its present or any other form; (c) the Document may be amended, modified or

changed in the standards development or any editing process.

The use or practice of contents of this Document may involve the use of intellectual

property rights (IPR), including pending or issued patents, or copyrights, owned by one

or more parties. TIA makes no search or investigation for IPR. When IPR consisting of

patents and published pending patent applications are claimed and called to TIAs

attention, a statement from the holder thereof is requested, all in accordance with the

Manual. TIA takes no position with reference to, and disclaims any obligation toinvestigate or inquire into, the scope or validity of any claims of IPR. TIA will neither be

a party to discussions of any licensing terms or conditions, which are instead left to theparties involved, nor will TIA opine or judge whether proposed licensing terms or

conditions are reasonable or non-discriminatory. TIA does not warrant or represent that

procedures or practices suggested or provided in the Manual have been complied with as

respects the Document or its contents.

If the Document contains one or more Normative References to a document published by

another organization (other SSO) engaged in the formulation, development or

publication of standards (whether designated as a standard, specification,recommendation or otherwise), whether such reference consists of mandatory, alternate

or optional elements (as defined in the TIA Engineering Manual, 4th edition) then (i) TIA

disclaims any duty or obligation to search or investigate the records of any other SSO for

IPR or letters of assurance relating to any such Normative Reference; (ii) TIAs policy of


4/21


encouragement of voluntary disclosure (see Engineering Manual Section 6.5.1) of

Essential Patent(s) and published pending patent applications shall apply; and (iii)Information as to claims of IPR in the records or publications of the other SSO shall not

constitute identification to TIA of a claim of Essential Patent(s) or published pendingpatent applications.

TIA does not enforce or monitor compliance with the contents of the Document. TIA

does not certify, inspect, test or otherwise investigate products, designs or services or any

claims of compliance with the contents of the Document.

ALL WARRANTIES, EXPRESS OR IMPLIED, ARE DISCLAIMED, INCLUDING

WITHOUT LIMITATION, ANY AND ALL WARRANTIES CONCERNING THEACCURACY OF THE CONTENTS, ITS FITNESS OR APPROPRIATENESS FOR A

PARTICULAR PURPOSE OR USE, ITS MERCHANTABILITY AND ITS

NONINFRINGEMENT OF ANY THIRD PARTYS INTELLECTUAL PROPERTYRIGHTS. TIA EXPRESSLY DISCLAIMS ANY AND ALL RESPONSIBILITIES FOR

THE ACCURACY OF THE CONTENTS AND MAKES NO REPRESENTATIONS ORWARRANTIES REGARDING THE CONTENTS COMPLIANCE WITH ANY

APPLICABLE STATUTE, RULE OR REGULATION, OR THE SAFETY OR

HEALTH EFFECTS OF THE CONTENTS OR ANY PRODUCT OR SERVICE

REFERRED TO IN THE DOCUMENT OR PRODUCED OR RENDERED TOCOMPLY WITH THE CONTENTS.

TIA SHALL NOT BE LIABLE FOR ANY AND ALL DAMAGES, DIRECT OR

INDIRECT, ARISING FROM OR RELATING TO ANY USE OF THE CONTENTS

CONTAINED HEREIN, INCLUDING WITHOUT LIMITATION ANY AND ALLINDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES

(INCLUDING DAMAGES FOR LOSS OF BUSINESS, LOSS OF PROFITS,

LITIGATION, OR THE LIKE), WHETHER BASED UPON BREACH OFCONTRACT, BREACH OF WARRANTY, TORT (INCLUDING NEGLIGENCE),

PRODUCT LIABILITY OR OTHERWISE, EVEN IF ADVISED OF THE

POSSIBILITY OF SUCH DAMAGES. THE FOREGOING NEGATION OFDAMAGES IS A FUNDAMENTAL ELEMENT OF THE USE OF THE CONTENTS

HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA

WITHOUT SUCH LIMITATIONS.


5/21


1

SMALL WIND TURBINE SUPPORT STRUCTURES

TABLE OF CONTENTSOBJECTIVE 2

SCOPE 2

1.0 GENERAL 2

2.0 TURBINE MANUFACTURER DATA 4

3.0 EFFECTIVE PROJECTED AREA 4

4.0 DRAG FACTORS FOR POLE STRUCTURES 5

5.0 EXTREME WIND CONDITION 5

6.0 EXTREME ICE CONDITION 5

7.0 EXTREME EARTHQUAKE CONDITION 5

8.0 CRITICAL TURBINE MOMENTS 6

9.0 SERVICEABILITY REQUIREMENT 6

10.0 DYNAMIC REQUIREMENTS 6

11.0 FATIGUE STRENGTH 7

12.0 OTHER STRUCTURAL MATERIAL 12

13.0 FOUNDATIONS 12

14.0 MAINTENANCE AND MATERIAL ASSESSMENT 13

REFERENCE TABLES 14

ANNEX A: REFERENCES (INFORMATIVE) 17

Note: Informative annexes contain additional information that are not consideredpart of the standard.


6/21


2

Small Wind Turbine Support Structures

OBJECTIVE

The objective of this Design Supplement is to provide recognized literature intended tobe used in conjunction with the ANSI/TIA-222-G Standard, Structural Standard forAntenna Supporting Structures and Antennas (TIA) for the design and analysis ofstructures supporting Small Wind Turbines (SWTs) defined as wind turbines with rotorswept areas less than 2,200 sq. ft. [200 sq. m].

This Design Supplement defines how specific portions of the TIA Standard shall beapplied to SWT supporting structures and provides supplementary requirements thatpertain specifically to the unique characteristics of SWT supporting structures.

The provisions of this Design Supplement are intended to be used for the developmentof standard designs for SWT supporting structures and for the design and analysis ofsite-specific structures.

SCOPE

This Design Supplement is intended to apply to self-supporting or bracketed latticedtowers, guyed masts and pole structures that support single or multiple SWTs that mayalso support antennas and other appurtenances.

The design and analysis of turbine components are not included within the scope of thisDesign Supplement.

1.0 GENERAL

1.1 Design Criteria

SWT supporting structures shall be in conformance with the requirements of TIA andthe additional supplementary requirements of this Design Supplement.

The design parameters used for standard designs for SWT supporting structuresdeveloped in accordance with this Design Supplement shall be verified prior toinstallation.

Conformance to this Design Supplement is not required for structures supporting windturbines with rotor swept areas less than 22 sq. ft. [2 sq. m]. Structures supportingturbines with rotor swept areas less than 22 sq. ft. [2 sq. m] may be designed and/oranalyzed in accordance with the TIA Standard with each turbine considered as anappurtenance. The effective projected area of each turbine shall be determined inaccordance with TIA Section 3.0. The effective projected area shall be considered to beconstant for all wind directions. The wind force based on the effective projected area ofeach turbine shall be considered as a wind load using a load factor equal to 1.6 and awake interference factor, Ka, equal to 1.0.


7/21


3

1.2 Turbine Model

For all loading conditions with the exception of fatigue, a turbine shall be modeled as a

mass and an effective projected area.

Unless otherwise specified, the center of mass and the centroid of the effectiveprojected area shall be considered to be at the hub height of the turbine and assumedto be distributed symmetrically about the vertical centerline of the turbine base.

When a horizontal offset of the center of mass from the vertical centerline of the turbinebase is specified by the turbine manufacturer, the additional overturning moment on thesupporting structure due to turbine weight shall be considered to occur in the directionwhich adds to the overturning moment from the horizontal turbine thrust.

For fatigue loading, unless otherwise specified, the turbine effective projected area shallbe replaced with the equivalent constant range fatigue loads determined in accordancewith Section 11.0.

For the purpose of determining factored extreme loading conditions, turbine weight shallbe considered a dead load and turbine forces and moments shall be considered as windloads.

1.3 Definitions

Equivalent constant range load: a constant amplitude load range intended to

represent the fatigue effects of actual variable amplitude loading events.

Flange plate: a base, top or intermediate flange welded to a latticed tower leg or polestructure.

Hub height above turbine base: the height of the center of the wind turbine rotorabove the turbine base.

Initial tension condition: the equilibrium position of a guyed mast (with correspondingforces in the components of the mast) with guys at their specified installation tension.

Turbine base: the base of the turbine that interfaces with the supporting structure.

1.4 Abbreviations

AISC American Institute of Steel Construction Manual, 13th EditionAWEA American Wind Energy Association Standard AWEA 9.1-2009AWS American Welding Society Standard AWS D1.1/D1.1M:2010SWT Small Wind TurbineTIA Telecommunications Industry Association Standard ANSI/TIA-222-G


8/21


4

2.0 TURBINE MANUFACTURER DATA

The following turbine data shall be provided by the turbine manufacturer:

1. Type of turbine: horizontal or vertical axis machine2. Rotor diameter, ft [m]3. Rotational Rotor Speed at electrical power rating of turbine, RPM4. Hub height above turbine base, ft [m]5. Maximum turbine horizontal thrust (unfactored), Lb [N]6. Wind speed at hub height associated with the specified maximum turbine horizontal

thrust, mph [m/s]7. Weight of turbine, Lb [N]8. Horizontal offset of turbine weight from vertical centerline of turbine base, ft [m]9. Weight of rotor (blades and hub), Lb [N]

10. Distance from center of rotor mass to vertical centerline of turbine base, ft [m]11. Clearance requirements of turbine blades to the supporting structure (considering

deflected shape of blades under wind loading)12. Connection details for the turbine base13. Natural frequency limitations of the supporting structure, Hertz

3.0 EFFECTIVE PROJECTED AREA

The effective projected area of a turbine shall be calculated in accordance with thisSection unless the effective projected area of the turbine is specified by the turbinemanufacturer. The effective projected area of a turbine shall be considered to be

constant for all wind directions with a wake interference factor, Ka, equal to 1.0.

Unless otherwise specified by the turbine manufacturer, the effective projected area ofthe turbine, (EPA)T, shall be calculated in accordance with the following equation n:

(EPA)T = Fmaxt (ft)2

0.00256(Vmax)2

(EPA)T = Fmaxt (m)2

0.613(Vmax)2

where:

Fmaxt = maximum unfactored horizontal turbine thrust, lbs [N]Vht = wind speed at hub height associated with the specified maximum turbine

horizontal thrust, mph [m/s]


9/21


5

4.0 DRAG FACTORS FOR POLE STRUCUTRES

The TIA drag factors for pole structures consider a minimum level of roughness due toattachments common to communication structures. For SWT supporting pole structureswithout appurtenances attached along their height, the drag factors specified in Table2.0 may be used in place of the TIA drag factors.

5.0 EXTREME WIND CONDITION

The TIA basic wind speed (50-year return, 3-second gust at 10 m height) used forinvestigating the TIA extreme wind condition shall be the larger of the basic wind speedspecified by the turbine manufacture, the basic wind speed for the site and 110 mph [50m/s].

Note: The fatigue investigation criteria specified in Section 11.0 is based on thesupporting structure satisfying a minimum strength requirements equivalent to a 110mph [50 m/s] design basic wind speed, exposure category C. Lower strengthrequirements would require extensive fatigue investigations of the supporting structurethat are not within the scope of this Design Supplement.

6.0 EXTREME ICE CONDITION

The design ice thickness and corresponding basic wind speed shall be determined fromthe TIA Standard when a specific site location is specified. The default design icethickness for standard designs shall be 1 inch [25 mm] occurring simultaneously with a

40 mph [18 m/s] basic wind speed. Unless more accurate data is provided for theturbine, the weight of the turbine shall be increased 25% and the calculated (EPA) T ofthe turbine shall be increased 15% from the no-ice condition.

7.0 EXTREME EARTHQUAKE CONDITION

The operational loads of the turbine shall be considered insignificant compared toearthquake loading due to the mass of the turbine and the supporting structure.Operational loading need not be considered to occur simultaneously with earthquakeloading. The masses of the turbine, the structure and all appurtenances shall beincluded in the determination of earthquake loading. The default spectral response at

short periods (Ss) shall be considered as 0.60. Earthquake analysis in accordance withTIA shall be required for SWT supporting structures located in areas with Ss valuesgreater than 0.60.

Note: SWT supporting structures have a lower Ss threshold value compared to antennasupporting structures.


10/21


6

8.0 CRITICAL TURBINE MOMENTS

Unless otherwise specified by the turbine manufacturer, the extreme wind conditionshall be assumed to govern over other turbine operational loading conditions thatsubject the supporting structure to an overturning or twisting moment. These conditionsinclude braking, shorts, shut down, maximum rotational speed condition, extremeyawing, etc.

When a critical turbine moment is specified by the turbine manufacturer, the momentshall be investigated by considering an additional extreme wind loading conditionwithout ice. Unless otherwise specified, the specified moment shall be considered tooccur simultaneously with a 25 mph [11 m/s] basic wind speed with the calculatedeffective projected area of the turbine (EPA)T and the TIA importance factor, I, for windload without ice, based on the structure classification. Unless otherwise specified, a

load factor of 1.6 shall be applied to the specified moment. A specified overturningmoment shall be considered to occur at the top of the structure in the same direction asthe wind. A specified twisting (yaw) moment shall be considered to act about thevertical centerline of the turbine base in a counterclockwise direction in the plan view.

9.0 SERVICEABILITY REQUIREMENT

Unless otherwise specified, the stiffness of the supporting structure shall result in a tipdeflection no greater than 1% of the structure height for the TIA service loadingcondition (60 mph [27 m/s] basic wind speed without ice) with the calculated effectiveprojected area of the turbine (EPA)T.

10.0 DYNAMIC REQUIREMENTS

The natural frequency modes involving single, double and triple curvature of thesupporting structure shall be determined for a no-ice condition when natural frequenciesof the support structure to be avoided are specified by the turbine manufacturer. One ofthe elastic three-dimensional models specified in TIA shall be used to determine thefundamental frequency modes. The simplified TIA fundamental frequency equationsshall not be used for SWT supporting structures. The masses of the turbine, thestructure and all appurtenances shall be included in the structural model at the properlocations.

Unless a detailed analysis is undertaken to determine an appropriate foundation springconstant to be used in the determination of natural frequencies, the calculated naturalfrequencies of the structure shall be adjusted +/- 10% for comparison to the turbinemanufacturers specified natural frequencies. When frequency ranges or min/maxfrequencies are provided by the turbine manufacturer, no adjustments to the calculatednatural frequencies of the supporting structure are required.Note: Natural frequency modes involving torsion may require investigation for verticalaxis turbines when specified by the turbine manufacturer.


11/21


7

11.0 FATIGUE STRENGTH

11.1 Equivalent Constant Range Wind Loading on Supporting Structure

Unless otherwise specified, fatigue wind loading on the supporting structure andsupported appurtenances (excluding the turbine) shall be considered as an additionalservice loading combination (Kfd = 0.85 for all structures) using a 30 mph [13 m/s]uniform wind speed (Kz, Kzt and Gh equal to 1.0) and the importance factor for fatigueloading specified in Table 11-1 based on the TIA structure classification for thesupporting structure. The fatigue loading on the supporting structure shall beconsidered to occur simultaneously with the equivalent constant range turbine loadsspecified in Section 11.2.

11.2 Equivalent Constant Range Turbine Loads

Equivalent constant range fatigue loads for horizontal axis turbines shall be calculatedfrom the following equations:

Fxt = equivalent constant range turbine horizontal force, lbs [N]= (Kfd)(If)(Cfxt)(Dr)

2

Mty = equivalent constant range turbine overturning moment, ft-lbs [N-m]= (Kfd)[2(Wtr)(Lrc) + (Dr)(Fxt) / 12]

Mtx = equivalent constant range turbine shaft torsion, ft-lbs, [N-m]

= (Kfd)[(If)(Cmtx)(Dr)

2

/ Nr + 0.005(Wtr)(Dr)]

where:

Kfd = 0.85If = importance factor for fatigue from Table 11-1Cfxt = 1.0 [48]Dr = rotor diameter, ft [m]Wtr = weight of rotor (hub and blades), lbs [N]Lrc = distance between center of gravity of rotor and centerline of the supporting

structure, ft [m]

Cmtx = 275 [4000]Nr = rotor rotational speed, rpm

Note: Kfd accounts for the probability of the applied load range occurring form adirection that creates a response in any one given support structure component.

The horizontal force, Fxt, shall be applied concentrically in the direction of the wind atthe hub height of the turbine. The overturning moment, Mty, shall be applied at the topof the supporting structure in a vertical plane in the direction which adds to theoverturning moment resulting from Fxt. The moment, Mtx, shall be applied at the top ofthe supporting structure in a vertical plane normal to the wind direction (shaft torsion).


12/21


8

The unit direction vector for Mtx shall be in the direction of the wind. Alternately, themoments Mty and Mtx may be combined into a resultant overturning moment andapplied in the direction which adds to the overturning moment resulting from Fxt.

Note: Turbine weight shall be included in the fatigue investigation analysis. Theequivalent constant range fatigue load Fxt includes wind loading on the turbine;therefore, the effective projected area of the turbine is not included in the fatigueinvestigation analysis.

Equivalent constant range fatigue loads for vertical axis turbines shall be provided bythe turbine manufacturer. The equivalent constant range fatigue loads shall be basedon the turbine cycling between 50% and 150% of the rated power at a 30 mph windspeed. Fatigue loads shall include the effects of eccentric wind loading on the turbineand the effects of eccentric rotor mass.

11.3 Fatigue Analysis

An analysis of the supporting structure shall be performed using the equivalent constantrange loads from Sections 11.1 and 11.2. The resulting member stresses shall beconsidered as equivalent fatigue damage stress ranges. Equivalent fatigue damagestress ranges shall not exceed the design stress ranges specified in Section 11.4 for theindentified components. Other components of SWT supporting structures shall beconsidered to have adequate fatigue strength when properly sized for the extreme windloading condition specified in Section 5.0.

Note: The design stress ranges specified in Section 11.4 are considered as thresholdfatigue stress ranges (indefinite number of cycles); therefore, the number of cyclesbased on the design life of the structure is not required for a fatigue analysis performedin accordance with this Design Supplement.

11.3.1 Self-Supporting or Bracketed Structures

Analysis of pole and latticed self-supporting or bracketed structures shall be performedusing a load factor of zero for dead load and a load factor of 1.0 for all other loads. Thestress range in each component shall be considered to equal the absolute value of thestress in the component.

11.3.2 Cantilever Portions of Guyed Masts

The cantilever portion of a guyed mast shall be modeled as a self-supporting structurein accordance with Section 11.3.1.

11.3.3 Guyed Masts below the Cantilever

11.3.3.1 Latticed Masts


13/21


9

The full height of the mast with the cantilever shall be analyzed using a load factor equalto 1.0 for all loads. The results of the initial tension condition and the results of thefatigue analysis shall be used to determine the stress ranges in the mast.

Leg members below the cantilever that are subjected solely to axial compression fromthe fatigue analysis need not be investigated for fatigue.

The stress range in leg members below the cantilever subjected to axial tension fromthe fatigue analysis shall be considered equal to the sum of the leg tension stress fromthe fatigue loading condition and the absolute value of the leg stress from the initialtension condition.

The stress range in bracing members shall be equal to the absolute value of the stressform the fatigue analysis.

11.3.3.2 Tubular Pole Masts

The full height of the mast with the cantilever shall be analyzed using a load factor equalto 1.0 for all loads. The results of the initial tension condition and the results of thefatigue analysis shall be used to determine the stress ranges in the mast.

Tubular mast components below the cantilever with cross sections that are subjectedsolely to compression stresses (due to combined axial load and bending) from thefatigue analysis need not be investigated for fatigue.

The stress ranges in a tubular mast component below the cantilever subjected totension stresses from the fatigue analysis shall be considered equal to the sum of themaximum tensile stress in the component from the fatigue analysis and the absolutevalue of the maximum stress in the component from the initial tension condition.

11.4 Design Stress Ranges

The stresses calculated form the fatigue analysis shall be considered as equivalentfatigue damage stress ranges and shall not exceed the values specified in Sections11.4.1 and 11.4.2 unless otherwise specified.

11.4.1 Category A Components (limited to a stress range of 4.5 ksi [31 MPa]):

1. Pole structures at ports or welded attachments.2. Pole flanges connected with a full penetration weld without a backer3. Pole flanges connected with a full penetration weld with a backer connected to the

flange with a full penetration or continuous fillet weld.4. Pole flanges or latticed tower legs, with stiffeners connected to a continuous top

annular ring plate.5. Legs in latticed structures with welded connection plates, flanges or other welded

attachments.


14/21


10

11.4.2 Category B Components (limited to a stress range of 2.6 ksi [18 MPa]):

1. Pole flanges connected with a full penetration weld with a backer connected to the

flange without a full penetration or continuous fillet weld.2. Pole socketed flanges connected with double fillet welds.3. Latticed structure legs and pole flanges with stiffeners.4. Main load carrying bracing members in latticed structures with effective

slenderness ratios less than 60 that have welded end connections or weldedgusset plates for use with a bolted connection.

5. Tension only bracing members with welded end connections or welded gussetplates

11.4.3 Anchor Rods (limited to a combined stress range of 7.0 ksi [48 MPa]

The stress range shall be calculated by combining stresses due to axial loads and

bending on the individual anchor rods regardless of whether grout is utilized andregardless of the distance between the bottom of the leveling nut and top of concrete.Axial anchor rod forces from a moment reaction shall be determined from an elasticdistribution of anchor rod forces. The distance between the top of concrete and thebottom of the leveling nut shall be used to determine anchor rod bending momentsbased on assuming an inflection point equal to 0.65 times the gap dimension. Anchorrod bending stresses shall be determined using the anchor rod elastic section modulus.

For anchor rods arranged in a round pattern, the following equations apply (otherarrangements shall follow an equivalent methodology):

dn = d - 0.9743 / nt inches= d - 0.9382(p) mm

S = [(dn)3] / 32

Fa1 = anchor rod axial load due to an applied vertical reaction= Pa / nar

Fa2 = anchor rod axial load due to an applied resultant overturning moment reaction= 4(Ma) / [nar(Dp)]

Va1 = anchor rod shear load due to an applied resultant shear reaction= 2(Va) / nar

Va2 = anchor rod shear force due to an applied torsional moment reaction= 2(Ta) / [nar(Dp)]

Mb = anchor rod bending due to an applied shear reaction= (Va1 + Va2)(0.65)(Iar)

Ffar = stress range in anchor rod= (Fa1 + Fa2) / (An) + Mb / S


15/21


11

where:

dn = tensile root diameter of anchor rodd = nominal diameter of anchor rodnt = number of threads per inchp = pitch of threads, mmS = section modulus of anchor rodPa = applied vertical reaction (larger of tension or compression reaction) on anchor

rod groupnar = number of anchor rodsMa = applied resultant overturning moment reaction on anchor rod groupDp = anchor rod bolt circleVa = applied resultant shear reaction on anchor rod groupTa = applied torsional moment reaction on anchor rod group

Iar = length form top of concrete to bottom of leveling nutAn = net area of anchor rod through the treaded portion

11.5 Miscellaneous Requirements for Fatigue Strength

11.5.1 Latticed Structures

The maximum effective slenderness ratios for members and the minimum gusset platethicknesses for member connections shall be determined form Table 11-2 unlessotherwise specified.

11.5.2 Guy Anchorages

Guy connection plates for guyed mast anchor rods shall be limited to designs usingpinned connection plates.

11.5.3 Connection Bolts for Turbine Bases

Bolted connections shall be fully tensioned in accordance with the AISC Standard. Thenumber, size, arrangement and grade of turbine base connection bolts shall bespecified by the turbine manufacturer.

11.5.4 Complete Penetration Flange Plate Welds for Pole Structures

A reinforcing outer fillet weld shall be provided for all complete penetration welds. Thesize of the weld reinforcement shall be no smaller than 25% of the pole wall but neednot be greater than 0.375 inches [10 mm].

Complete penetration welds made without backers shall have an inner fillet weld sizeequal to the size of the reinforcing outer fillet weld.

Backer bars, when used in complete penetration welds, shall be continuous for their fulllength with all backer bar joints made with complete penetration groove weld butt joints


16/21


12

in accordance with AWS. Backer bars shall not exceed 0.375 inches [10 mm] when afillet weld is used to attach the backer bar to the flange plate.

11.5.5 Socketed Flange Plate Welds for Pole Structures

The inner fillet weld shall be an equal leg fillet weld with the weld size not less than thepole wall thickness minus 1/16 inch [2 mm]. The outer fillet weld shall be an unequalleg fillet weld with the long leg of the fillet weld along the pole wall with an approximately30 degree angle between the fillet weld and the pole wall.

12.0 OTHER STRUCTURAL MATERIALS

This Design Supplement has been developed primarily for steel SWT supportingstructures but may also be applied to other materials using appropriate resistance

factors to result in an equivalent level of reliability.

12.1 Extreme Loading Conditions

The nominal strengths for extreme loading conditions for material other than steel shallbe based on the minimum strengths guaranteed by the manufacturer of the material oralternately, based on tests to determine strengths of 95% survival probability with a 95%confidence limit. Resistance factors applied to nominal strengths shall be in accordancewith Table 12-1.

12.2 Fatigue Loading Condition

The design stress range values indicted in Section 11.4 include appropriate resistancefactors applied to the nominal stress ranges for steel components manufactured inaccordance with TIA. Appropriate resistance factors for other materials shall be appliedto the nominal fatigue stress ranges in accordance with the Table 12-2.

For materials that do not display a fatigue threshold limit, the number of cycles used todetermine the nominal stress range for use with this Design Supplement shall be basedon 5 million cycles.

13.0 FOUNDATIONS

Mat foundations for self-supporting structures shall be sized so that the reactions formthe serviceability loading combination result in compressive soil bearing stress over thefull plan dimension of the mat.

Drilled shaft or pile foundations subjected to lateral load shall be designed consideringrepetitive loading soil conditions.


17/21


13

14.0 MAINTENANCE AND CONDITION ASSESMENT

The maintenance and condition assessment of SWT supporting structure shall be inaccordance with TIA except the recommended interval period is 6 months for allsupporting structure types.


18/21


14

REFERENCE TABLES

Table 4-1Force Coefficients (CF) for Pole Structures without Attachments

(Refer to TIA for Pole Structures with Attachments)

C

Mph-ft

[m/s-m]

Round 18-Sided 16-Sided 12-Sided 8-Sided

< 32 [4.4](Subcritical)

1.2 1.2 1.2 1.2 1.2

32 to 64 162/(C)1.42 59.3/(C)1.13 25.7/(C)0.884 5.06/(C)0.415 1.2

[4.4 to 8.7]

(Transitional)

[9.64/(C)1.42] [6.29/(C)1.13] [4.41/(C)0.884] [2.21/(C)0.415] [1.2]

> 64 [8.7]

(Supercritical)

0.45 0.55 0.65 0.90 1.2

C = (I Kzt Kz)0.5 (V)(D) for D in ft [m], V in mph [m/s]

I = TIA importance factor for wind loading

Kzt = TIA topographic factorKz = TIA velocity pressure coefficient

V is the 50-year, 3-second gust basic wind speed for the loading condition underinvestigation.

D is the pole outside diameter for rounds or the outside point-to-point diameter forpolygons.


19/21


15

REFERENCE TABLES

Table 11-1Fatigue Importance Factors, If

Table 11-2Latticed Structure Limitations

AWEA TurbinePower Rating

MaximumEffective

Slendernessof Members

MinimumGussetPlate

ThicknessUp to 10 kW 200 3/16 [5 mm]Over 10 kW to 25 kW 185 1/4 [6 mm]Over 25 kW 175 3/8 [10 mm]

TIA StructureClassification

FatigueImportance

Factor, IfI 0.70II 1.00III 1.35


20/21


16

REFERENCE TABLES

Table 12-1Resistance Factors for Extreme Loadings

(Other Structural Materials)

Type of Failure Resistance FactorYielding of ductile material 0.90Local or global buckling 0.85Fracture of brittle or ductile material 0.75

Table 12-2Resistance Factors for Fatigue Loading

(Other Structural Materials)

Basis of Nominal Stress Range ResistanceFactor

50% survival probability with coefficientof variation 15%

0.60

50% survival probability with coefficientof variation < 15%

0.67

Test data with basis of 95% survivalprobability with a 95% confidence level

0.85


21/21


17

ANNEX A: REFERENCES (Informative)

AASHTO, Standard Specifications for Structural Supports for Highway Signs,Luminaires, and Traffic Signals, 5th Edition, American Association of State Highwayand Transportation Officials, 2009.

AISC, Steel Construction Manual, 13th Edition, American Institute of SteelConstruction, Inc., 2005.

ASCE, Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-05,American Society of Civil Engineers, 2005.

AWEA, AWEA Small Wind Turbine Performance and Safety Standard, AWEA 9.1-2009, American Wind Energy Association, 2009

AWS, Structural Welding Code - Steel, AWS D1.1/D1.1M:2010, American WeldingSociety, 2010.

IEC, Wind Turbine-Part 1: Design Requirements, IEC 61400-1, InternationalElectrotechnical Commission, Third Edition 2005-08.

IEC, Wind Turbine-Part 2: Design Requirements for Small Wind Turbines, IEC 61400-2, International Electrotechnical Commission, Second Edition 2006-03.

TIA, Structural Standard for Antenna Supporting Structures and Antennas, ANSI/TIA-222-G, Telecommunications Industry Association, 2005.

31 brinker proposed design standard for towers

Documents