Structure Specifications

COMMUNICATION STRUCTURES SPECIFICATIONS Steve Krohn, P.E. © 2010 Valmont Industries, Inc. All rights reserved.

Make Sure You Get What You Order…Today and in the Future •

Explain the implications of good specifications • •

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Short term and long term financial impacts Are you getting everything you are asking for?

Comparison of Specification Interpretations Examples of specifications based on our experience Question and Answer session

© 2010 Valmont Industries, Inc. All rights reserved.

Structure Specifications 

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Are you meeting your future requirements? Is your 4 carrier structure really a 4 carrier structure? Are you really saving money?  Is

today’s choice affecting tomorrow’s reinforcement budget?


Structure Specifications “The Playbook”   

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Basic Requirements Details your design expectations Provides the loading requirements that you have specified for current and future use Provide the same specifications to all manufacturers so you receive comparable bids  Ensures

all manufacturers are designing based on the same requirements


Important Specification Information • • • •

Structure Height Design Code Mount Options Antenna/Microwave Mount Locations •

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Antenna Sizes Dish Specifications Site Location •

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Design purposes only?

Longitude and Latitude • Exposure Category • Topography Category

Structure Classification Cable/Waveguide Size and Quantity Additional Load Clarification


Design Code Options • •

TIA/EIA-222-Rev F vs. TIA-222-Rev G Rev F • •

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Rev G • • • •

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Allowable Design Fastest Mile wind speed Limit State Design 3-sec gust wind speed Site Characteristics included when considering wind loading Includes Seismic and Ice Loading consideration

90 mph Rev G is approximately 75 mph Rev F


Mount Options •

Platforms • •

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Extensions Arms •

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13’ Low Profile Platform without handrails 13’ Low Profile Platform with handrails

T-Arms

Significant EPA differences


Antenna Size

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Effective Projected Area typically accounts for more than 50% of the forces on the pole

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(48)- 6’ x 1’ x 4” antennas: EPA= 390.2 ft2

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(48)- 8’ x 1’ x 4” antennas: EPA= 550.5 ft2


Site Characteristics and Structure Classification •

Exposure Category •

Variations in ground surface roughness that arise from topography and vegetation as well as from constructed features. (TIA-222-G)

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Exposure B: Structures in Urban or Suburban areas.

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Exposure C (default): Structures located in open terrain scattered with obstructions that are less than 30’ tall.

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Exposure D: Structure is in flat, unobstructed shoreline exposed to wind flowing over open water.


Site Characteristics and Structure Classification

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Topography Category •

Location of structure to hills, ridges, and escarpments that constitute abrupt changes in geography will result in wind speed-up effects. (TIA-222-G)

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Category 1 (default)- No abrupt changes in general topography.

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Category 2- Structures located at or near the crest of an escarpment.

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Category 3- Structures located in the upper half of a hill.

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Category 4- Structures located in the upper half of a ridge or mountain.

Flat


Escarpment

Hill

Mountain

Site Characteristics and Structure Classification

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Structure Classification •

Importance factor based on classification of human hazard/property damage if structure was out of service for an extended period of time (TIA-222-G)

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Class 1 (I=0.87): Structures that due to height, use or location represent a low hazard to human life and damage to property in the event of a failure and/or used for services that are optional. I.E. Ham Radio Tower

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Class 2 (I=1.0) (default): Structures that due to height, use or location represent a substantial hazard to human life and damage to property in the event of a failure and/or used for services that may be provided by other means. I.E. Typical Cell Tower

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Class 3 (I=1.15): Structures that due to height, use or location represent a high hazard to human life and damage to property in the event of a failure and/or used for primary communication. I.E. Emergency Response Tower


Dish Specifications •

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Sway Requirements based on dish frequency and dish size The higher the frequency the stricter the twist and sway requirements


Steps to competitive and proper designs 

Well written specifications  Contact

Valmont Industries for all your specification questions and concerns.

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Provide any clarification to all manufacturers Review designs  Ensure

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that specifications are adhered to

If base reactions are significantly different there is a difference in specification interpretation


Steps to competitive and proper designs 14

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The lowest price doesn’t always meet your needs.

Did you get what you wanted?


Questions 15


Site Characteristics and Structure Classification •

Exposure Category •

Variations in ground surface roughness that arise from topography and vegetation as well as from constructed features. (TIA-222-G)

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Exposure B: Urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger. Use of this exposure shall be limited to those areas for which terrain representative of Exposure B surrounds the structure in a ll directions for a distance of at least 2,630 ft (800m) or ten times the height of the structure, whichever is greater.

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Exposure C: Structures located in open terrain scattered with obstructions that are less than 30’ tall (9.1m). This category includes flat, open country, grasslands and shorelines in hurricane prone regions.

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Exposure D: Structure is in flat, unobstructed shoreline exposed to wind flowing over open water (excluding hurricane prone regions) for a distance of at least 1 mile (1.61 km). Shorelines in Exposure D include inland waterways, lakes and non-hurricane coastal areas. Exposure D extends inland a distance of 660 ft (200 m) or ten times the height of the structure, whichever is greater. Smooth mud flats, salt flats and other similar terrain shall be considered as Exposure D.
