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### Records in this category

- 2.6.9.1.1 For square towers: How can we calculate the DF and DR factors for other wind directions?
- 2.6.8 and Figure 2‐1 While considering the appurtenance load including ice in Rev G, should we consider thedefault ice thickness or the escalated design ice thickness calculated per Section 2.6.8 of TIA‐222‐G?
- Section 2.6.9.2What does the term “In the absence of more accurate data” mean?
- Section 2.6.9.2Is it acceptable to use the results of Computational Fluid Dynamics (CFD) testing as a substitute to the requirements outlined in section 2.6.9.2? If so, what conditions must be meet? If so, can we claim the tower is compliant with TIA-222-G if the wind tunnel data is used?
- Section 2.6.9.2Can I use loading that is less than the values prescribed by the written TIA-222-G and claim compliance with the standard? If so, under what conditions?
- Section 2.6.9.2Is it acceptable to use the results of wind tunnel testing as an acceptable substitute to the requirements outlined in section 2.6.9.2? If so, what conditions must be meet? If so, can we claim the tower is compliant with TIA-222-G if the wind tunnel data is used?
- 2.6.7.4 Gust Effect Factor for Structures Mounted on Other Structures
- Is there reciprocity between ANSI/TIA-222-G and CSA S37-01? In other words, if a tower is designed to CSA S37-01, does it also meet ANSI/TIA-222-G Standard? And vice versa?
- Section 2.6.6 Calculating the topographic factors
- As everyone is aware, many jurisdictions are now adopting the IBC 2012, which has updated wind speed maps. Regarding TIA-222-G, can the converted (Vasd) wind speeds from the IBC 2012 be used instead of the wind speeds listed in TIA-222-G, or do we need to take the more stringent of the two? I know this gets a little tricky when the risk category/structure class is something other than II, since the importance factors in TIA are more elaborate (wind speed with no ice, with ice, ice weight) than those in the IBC (who simply provide a number for the wind speed with no ice). We do a lot of work on the Atlantic coastline, and these changes would be most beneficial to our clients. Any interpretation of this would be greatly appreciated.
- Section 2.7.3 states “Further, …earthquake effects may be ignored when the total seismic shear is less than 50% of the total horizontal wind load without ice.” Does ignoring earthquake effects include the seismic considerations of Section 9.6, since the tower structure itself would be capable of satisfying that requirement?
- I am currently working a telecommunications tower project where dead weight of concrete blockswill be used to resist uplift and sliding forces at the base of a truss tower. These blocks of concretemust be placed above the soil.Provision 2.3.2 of TIA‐222‐G, Equation 2 shows the load combination of .9D + 1.0 Dg + 1.6 W. Sincethe dead load contributed by the concrete foundation and the steel tower above is the actualweight of concrete (not some assumed dead load used for the design of superstructure), is itnecessary to reduce the dead load of the concrete footing by 10%? Is there an ASD loadcombination (where wind load is not multiplied by 1.6) that can be used to calculate the requiredcounter weight?
- in case of telecommunication tower to be built on an isolated hill where category 2 applies and no dwellings exist around or roads, can we take importance factor of class I or in between class I and class II
- in case of telecommunication tower to be built on an isolated hill where category 2 applies and no dwellings exist around or roads, can we take importance factor of class I or in between class I and class II
- The definition of Z in sections 2.6.5.2, 2.6.6.4, and 2.6.8 is incorrect and completely different fromthe definition on Page 11. Please provide clarification.
- If Ca=1.5 is used for a rectangular cluster of round lines, can that be considered a "sub-critical" coefficient, so that Ka can be equal to 1-epsilon, with the 0.6 cap, provided the lines are all in the face zone? The term “sub-critical” only applies to round objects, not square or rectangular, and Ca=1.5 does not seem to be sub-critical coefficient nor a “flat” coefficient. But the edges of the cluster are round, after all.
- Section 2.6.5.2 “Velocity Pressure Coefficient”Question: Shall “z” in the equation be based on mid-height of panels of lattice structures or is it a centroid location of lattice structures panel? For example if the length of panel (Bracing type = X-Brace) is 10 ft then z should be = 5 ft or based on the centroid location.
- Section 2.6.6.4 - Rev-G provides a simplified method of calculating Kzt that differs from the method provided in Figure 6-4 of ASCE7. The resulting wind pressures when using the Rev-G method are often significantly higher than those calculated using the ASCE7 method. Is it acceptable to use ASCE7 wind pressures instead of defaulting to Rev-G wind pressures when Kzt>1?
- Does section 2.8.2 Limit State Deformations of ANSI/TIA 222-G apply to the tower structures, or does it apply to appurtenances only? If this displacement limit applies to tower sections, in the case of a stealth monopole tower would the 3% limit be applied over the whole height of the tower (tower+stealth section) or should it be applied over just the stealth section?Can section 2.8.2 also be applied to a TIA-222-F structural analysis since currently this code does not include any displacement limits?Thanks,
- Where it has been suggested in previous posts that topography factors shall be determined in the worst case wind direction. Can the combination of topography factors and exposure factors in specific wind directions be looked at differently for each wind direction or must the worst case topography and worst case exposure apply in all wind directions?
- We understand section 2.6.4.1 to apply only to areas that are not listed in App. B or to areas that may have special wind or ice loading that generate higher loads than those specified in App. B. Would it be possible to use section 2.6.4.1 to justify wind or ice loads that are less than those prescribed in App. B?
- Waveguides, downleads, and other cables are frequently strapped to tower legs. Sometimes there is just one, sometimes there are many. Sometimes they're just on one leg, sometimes on all. TIA-222-G section 2.6.9.1.1 note 5 provides guidance for attachments such as step bolts and "similar linear irregularities" on round structural members. Is "similar linear irregularities" intended to cover linear cylindrical objects strapped to tower legs, even though (it seems to me) that they are not at all similar to step bolts and that they will affect wind drag on a tower in a different way than step bolts? If the answer is no, then what section of 222-G deals with this? If this is not in 222-G, then how are one or more linear cylindrical objects strapped to one or more legs supposed to be treated?
- Should step pegs and safety climb be included in the Ra calculations for determining the appropriate Cf and additional linear appurtenance wind area calculated for TIA-G? It appears that in the transition from TIA-E to F to G the additional drag to the structure from step pegs and safety climb have already been accounted for.In TIA-E the force coefficients for tubular pole structures were less than those in TIA-F and TIA-G.In TIA-E, foot note 3 states that when step bolts… are attached to the outside of a tubular pole structure the Cf factor must be multiplied by 1.3.TIA-F removed this footnote but increased the force coefficients by 1.3 (except for the subcritical cases for which the force coefficient is 1.2). Presumably the footnote was removed and the values and formulas in the force coefficient table were revised so that the drag of step pegs and safety climb would be considered in the table rather than by footnote. TIA-G is using similar force coefficients as TIA-F (about 1.3 times that of TIA-E and presumably accounting for the drag increase due to step pegs and safety climb) but then state to include linear appurtenances such as ladders… or other similar projections in the Ra calculation. Step pegs and safety climb are not specifically mentioned but would be “similar projections”. If step pegs and safety climb are included in the Ra factor it seems that these linear appurtenances are being double counted when determining the additional drag on the structure.Based on the above discussion, in the calculation of Ra can the area of step bolts and safety cable be ignored?
- Approximately when will the next revision or amendment to 222 be? What are the top two or three major changes being contemplated? Will 222 be aligned with ASCE 7-2010 (yes, I'm aware of the FAQ related to this)? Has there been any discussion of aligning 222 wind pattern provisions with those of EN 1993-3-1 and C37?
- Section 3108.1 of the 2012 IBC eliminates the 222-G exceptions related to seismic design and it changes the horizontal extent of escarpments. Did the 222-G committee submit comments on those two proposed provisions during the development of 2012? If so, what were the comments? If not, does the committee agree with those provisions?
- Regarding recent FAQ 1128: would it be possible to add the committee's reasoning for requiring the worst-case exposure category for all directions, even though ASCE 7-2010 allows exposure category to vary, based on a rational analysis of upwind roughness? Likewise, regarding recent FAQ 1129, since ASCE 7-2010 specifically allows reductions below its own mapped values (last sentence of 1st paragraph of 26.5.3), it would be helpful to understand why the committee feels that basic wind speeds less than those in ASCE 7-2010 should not be permitted, even if they could be rationally justified using ASCE 7-2010 procedures.
- Section 2.6.5: Addendum 2 defines Exposure Category C as "Sites located in Exposure B terrain that are located further than two miles but less than twenty times the height of the structure from an Exposure D terrain." That region is only possible for towers more than 528 feet tall. Did the authors mean "...less than two miles but more than twenty times the height..." That would make more sense and coordinate with the definition of Exposure D.
- Shall “z” in the equation be based on mid-height of panels of lattice structures or is it a centroid location of lattice structures panel? For example if the length of panel (Bracing type = X-Brace) is 10 ft then z should be = 5 ft or based on the centroi
- Section 2.6.6.4 - Rev-G provides a simplified method of calculating Kzt that differs from the method provided in Figure 6-4 of ASCE7. The resulting wind pressures when using the Rev-G method are often significantly higher than those calculated using the A
- Does section 2.8.2 Limit State Deformations of ANSI/TIA 222-G apply to the tower structures, or does it apply to appurtenances only?
- Can section 2.8.2 also be applied to a TIA-222-F structural analysis since currently this code does not include any displacement limits?
- Where it has been suggested in previous posts that topography factors shall be determined in the worst case wind direction. Can the combination of topography factors and exposure factors in specific wind directions be looked at differently for each wind d
- Is it acceptable to use Ka = 0.6 for feedlines and also consider the feedline ladder (consisting of angle rails and rungs) to be shielded?
- For double angles, are the modified (KL/r)m equations shall be considered along y-y axis only?
- Referencing Section 2.3.2, Exception 4 and Note 3; for a guyed mast anchor foundation design, is it the intent of the Standard to consider the weight of the concrete anchor foundation and soil directly over the foundation as dead load with the load factor of 1.2 specified in Load Cases 1, 3 and 4, even though the weight of the concrete and soil counteracts the guy anchor uplift reaction?In addition, is it the intent of the Standard that all soil strengths that are a function of the density of the soil be calculated with a factor of 1.0 applied to the density of soil for calculating nominal soil strengths with the resistance factors of Section 9.4.1 applied to the nominal strengths?
- Is there any back up material for the usage of Ka=0.6 for feedlines?The formula to subtract the solidity ratio appears to indicate that Ka=0.8 might be more likely for open structures without many feedlines. So it appears that the value of 0.6 is not conservative. The text reads:"Ka need not exceed 0.6"Should the text instead read:"Ka shall not be less than 0.6" ?
- I am a structural engineer in Oregon, and I have a question concerning the interplay between the requirements for wind loading from the 2012 IBC, and designs based upon the TIA-222-G standard. We have a tower that supports 911 services and therefore is considered a category IV structure. Using the 2012 IBC Section 1609.1.1, Exception 5 allows for designs using the TIA-222-G standard. Language at the end of this section notes that for designs using the TIA the ultimate design wind speeds determined from the Figures should be converted to nominal wind speeds, following Section 1609.3.1. With this tower being an essential facility, the Figure for Category III and IV structures would be used to determine the wind speed, and then converted to ASD following the Code’s provisions.From this point forward the design would be per the TIA-222-G (with Addendum 2 updates). It is our understanding that the VASD determined in the IBC serves as the basic speed to be used for the TIA analysis. Our question concerns where the importance factor comes into effect. Following the TIA as it is currently written, an analysis using this standard would apply an Iw value of 1.15 for wind without ice conditions, as required from Table 2-3, regardless of how the basic wind speed was determined. We want to validate that this is correct, as following 2012 IBC, based upon the ASCE 7-10, wind design has been revised to include the importance factor in the wind charts and removes this factor from the equations. We would appreciate direction on if the importance factor should now be considered included in the wind speed provided by the 2012 IBC and not applied when designing per the TIA, or the changes to the IBC do not affect the TIA, and the Iw values should be applied as written in the current TIA standard.
- Section 2.6.1: In the definitions section of 2.6.1, a 50-year mean recurrence interval is specified for wind on ice loading. However, in 2.6.8 a limit state factor of 2.0 is used. Per ASCEC10.4.6 paragraph 2, this factor of 2 is for a 500-year mean recurrence interval, not a 50-year mean recurrence interval. Therefore, if we are to design for a 50-year interval we must use a factor of 1.0, not 2.0. Will TIA acknowledge this fact and allow our company to use a factor of less than 2.0?If not, please explain your reasoning for using this 500-year storm event factor. Also, if TIA is unwilling to change said equation, is it acceptable to ask the jurisdiction to wave this factor in favor of the 50-year factor of 1.0?
- Does TIA-222-G include any consideration of loads other than wind, ice, and seismic? I am looking at a situation in a coastal floodplain which is subject to flooding, with the possibility of impact loads from loose boats. How should these loads be taken into consideration?
- Hello,The effective projected area of transmission lines mounted in a cluster is based on the appropriate out-to-out dimension of the cluster (Fig. 2-12 on Rev. G). In other words, (12) 2" lines stacked 6-on-6 with clear spacing of 1" and Ca= 1.5 will have an (EPA) N = [2x6+5x1)] x 1.5 for ice loading, assuming ice will fill in all spaces. Does this mean, for no ice loading, space between the stacked lines can be neglected? Ex. (EPA) N = [2x6]x1.5, assuming lines are perfectly stacked and ice does not control.RegardsShan
- Section 2.6.9My question is regarding how to determine the wind loading on a triangular shroud that is surrounding all equipment on a monopole. This question encompass all shrouds of this nature, but the shroud in question for this particular case was 6’ tall by 13’ wide on a 48” diameter round pole. There were a few methods discussed based on our interpretation of the code. These interpretations are presented below. Please advise if which method(s) are recommended by the TIA.For the first case we considered the shroud as a truss type mount with a solidity ratio of 1.0. The code specifies to determine the wind area as though the platform were a section of a latticed structure in accordance with section 2.6.9.1. Since we have a solid face, using this equation with a solidity ratio of 1.0 will give us a Cf of 2.1. There was an argument that this section was for lattice tower and would not apply to monopoles, but we do not believe this is the intent of the code. Section 2.6.9.2.3 mentions no shielding shall be considered for the supporting structure, but we neglected the EPA of the pole structure shielded by the shrouds based on the limit stated in 2.6.9/2.6.9.1. For the second case we considered the shrouds as appurtenances. Using a Ca = 1.2 and Ka = 1.0 (per section 2.6.9.4 we cannot use a Ka less than 1.0) we came up with front and side EPA for the shrouds and modeled one off each face. We did not consider the shrouds to shield each other and although there are is not a reference for shielding the pole for appurtenances, we considered both methods above to shield the pole section within the shrouded region.The last method, which we did not agree with, proposed to treat the shroud as an appurtenance, but to allow shielding to the appurtenances (shrouds) on the other faces along with using a Ka=1.0. This gives an EPA of 94 sf. We believe this to be very aggressive and would recommend using one of the methods described above. Example calculations for this particular shroud are shown below. The shroud is 6’ tall by 13’ wide on a 48” diameter round pole.Pole EPA: 0.6x4’x6’ = 14.4 sfShroud as Mount:Cf: 3.4(1.0)^2 – 4.7(1.0) + 3.4 = 2.1EPA: 2.1x6x13 = 163.8 sfEPA minus pole = 149.4 sf Shroud as Appurtenances (did not consider side area):Ca: 1.2EPAn: 1.2x6x13 = 93.6 sfETAt: 0Ka= 1.0EPA = 1.0 [93.6 + 2 x 93.6 x Cos(60)^2] = 140.4 sfEPA minus pole = 126 sfShroud as Appurtenances (shielding allowed):EPAn: 1.2x6x13 = 93.6 sf
- Hello. A question was asked about the validity of using IBC 2012 in lieu of TIA-222_G for wind loads. Your response was that ASCE 7-10 may be used as an alternate, but the response did not specifically address the IBC. Is it to be understood that the IBC is not acceptable whereas the ASCE 7-10 is?Thank you!
- Section A.2.2 and Table 2-1 establish the classification of structures based on reliability (I, II and III). What would be the classification of a communication tower installed inside of an electrical substation facility? What does the default structure classification means?
- Section A.2.2 and Table 2-1 establish the classification of structures based on reliability (I, II and III). What would be the classification of a communication tower installed inside of an electrical substation facility? What does the default structure classification means?

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## Section 2.0 - Loads

ID #1176

## Section 2.6.9My question is regarding how to determine the wind loading on a triangular shroud that is surrounding all equipment on a monopole. This question encompass all shrouds of this nature, but the shroud in question for this particular case was 6’ tall by 13’ wide on a 48” diameter round pole. There were a few methods discussed based on our interpretation of the code. These interpretations are presented below. Please advise if which method(s) are recommended by the TIA.For the first case we considered the shroud as a truss type mount with a solidity ratio of 1.0. The code specifies to determine the wind area as though the platform were a section of a latticed structure in accordance with section 2.6.9.1. Since we have a solid face, using this equation with a solidity ratio of 1.0 will give us a Cf of 2.1. There was an argument that this section was for lattice tower and would not apply to monopoles, but we do not believe this is the intent of the code. Section 2.6.9.2.3 mentions no shielding shall be considered for the supporting structure, but we neglected the EPA of the pole structure shielded by the shrouds based on the limit stated in 2.6.9/2.6.9.1. For the second case we considered the shrouds as appurtenances. Using a Ca = 1.2 and Ka = 1.0 (per section 2.6.9.4 we cannot use a Ka less than 1.0) we came up with front and side EPA for the shrouds and modeled one off each face. We did not consider the shrouds to shield each other and although there are is not a reference for shielding the pole for appurtenances, we considered both methods above to shield the pole section within the shrouded region.The last method, which we did not agree with, proposed to treat the shroud as an appurtenance, but to allow shielding to the appurtenances (shrouds) on the other faces along with using a Ka=1.0. This gives an EPA of 94 sf. We believe this to be very aggressive and would recommend using one of the methods described above. Example calculations for this particular shroud are shown below. The shroud is 6’ tall by 13’ wide on a 48” diameter round pole.Pole EPA: 0.6x4’x6’ = 14.4 sfShroud as Mount:Cf: 3.4(1.0)^2 – 4.7(1.0) + 3.4 = 2.1EPA: 2.1x6x13 = 163.8 sfEPA minus pole = 149.4 sf Shroud as Appurtenances (did not consider side area):Ca: 1.2EPAn: 1.2x6x13 = 93.6 sfETAt: 0Ka= 1.0EPA = 1.0 [93.6 + 2 x 93.6 x Cos(60)^2] = 140.4 sfEPA minus pole = 126 sfShroud as Appurtenances (shielding allowed):EPAn: 1.2x6x13 = 93.6 sf

The intent of the Standard is to calculate the effective projected area of a discrete appurtenance in accordance with Section 2.9.6.2. The effective projected area for both the normal and transverse directions are intended to be calculated in accordance with Table 2-8 based on the aspect ratio of the projected area of the discrete appurtenance for each direction. The leeward faces of the appurtenance under each wind direction may be considered shielded in accordance with Section 2.6.9.4. For a triangular discrete appurtenance as described in the question, the back faces may be considered to be 100% shielded when determining the EPA for the normal and transverse directions.

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- Section 2.6.9.2What does the term “In the absence of more accurate data” mean?
- Section 2.6.9.2Is it acceptable to use the results of Computational Fluid Dynamics (CFD) testing as a substitute to the requirements outlined in section 2.6.9.2? If so, what conditions must be meet? If so, can we claim the tower is compliant with TIA-222-G if the wind tunnel data is used?
- Section 2.6.9.2Can I use loading that is less than the values prescribed by the written TIA-222-G and claim compliance with the standard? If so, under what conditions?

Author: John Erichsen

Revision: 1.0

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