# TIA 222 G.pdf: How to Design and Fabricate Antenna Supporting Structures and Antennas According to the Standard

## What is TIA 222 G.pdf and why is it important?

## Introduction

TIA 222 G.pdf is a structural standard for antenna supporting structures, antennas, and small wind turbine support structures. It was published by the Telecommunications Industry Association (TIA) in 2005, with two addenda in 2006 and 2008. It is also known as ANSI/TIA-222-G or simply TIA-222-G.

## TIA 222 G.pdf

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TIA 222 G.pdf provides the requirements for the structural design and fabrication of new and the modification of existing antenna supporting structures, antennas, small wind turbine supporting structures, appurtenances attached to such structures. It also provides requirements for maintenance, inspection, use of existing structures.

TIA 222 G.pdf represents a significant change from previous versions of the standard. Some of the main changes and updates include:

The adoption of limit states design philosophy based on load and resistance factor design (LRFD) method

The introduction of structure classes based on use and risk

The revision of wind speed maps based on 3-second gust measurements

The incorporation of national ice loads based on ASCE 7

The inclusion of seismic loads based on site class and seismic design category

The revision of load combinations and strength design criteria

The update of fabrication and construction requirements

The purpose of TIA 222 G.pdf is to ensure that antenna supporting structures are designed and constructed to withstand the environmental loads and operational loads without compromising their safety and reliability. The benefits of the standard include:

The improvement of buyer/user confidence in the quality and performance of antenna supporting structures

The simplification of building permit process nationally by unifying the application of the standard

The enhancement of the reliability of wireless networks during emergency situations by increasing the resilience of antenna supporting structures

The creation of an international standard that is compatible with other codes and standards

## Structure classification

TIA 222 G.pdf classifies structures according to their use and risk. The structure class determines the return period of the design wind speed, which is the average time interval between occurrences of a wind speed equal to or greater than a specified value.

The standard defines three structure classes: I, II, and III. The definitions and return periods of each class are as follows:

Structure ClassDefinitionReturn Period (years)

IStructures that due to height, use or location represent a low hazard to human life and damage to property in the event of failure and/or used for services that are optional and/or where a delay in returning the services would be acceptable.25

IIStructures that due to height, use or location represent a significant hazard to human life and/or damage to property in the event of failure and/or used for services that may be provided by other means.50

IIIStructures that due to height, use or location represent a substantial hazard to human life and damage to property in the event of failure and/or used for essential services that must be maintained during an emergency situation.100

Some examples of structures that belong to each class are:

Class I: residential wireless and conventional 2-way radio communications; television, radio and scanner reception; wireless cable; amateur and CB radio communications.

Class II: commercial wireless communications; broadcast radio and television; microwave relay; cellular telephone; public safety communications.

Class III: emergency response communications; 911 dispatch centers; police, fire and ambulance communications; homeland security communications; military communications.

## Exposure categories and topographic categories

TIA 222 G.pdf defines exposure categories based on the surface roughness and wind speed at a site. The exposure category reflects the effect of the terrain on the wind as it approaches a structure. The standard defines three exposure categories: B, C, and D. The definitions and wind coefficients of each category are as follows:

Exposure CategoryDefinitionWind Coefficient (KZ)

BUrban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger.KZ=0.9 for zKZ=1.0 for 10 mz15 mKZ=1.05 for z>15 m

COpen terrain with scattered obstructions having heights generally less than 9 m.KZ=0.85 for zKZ=1.0 for 9 mz15 mKZ=1.14 for z>15 m

DFlat, unobstructed areas exposed to wind flowing over open water (excluding shorelines in hurricane prone regions) for a distance of at least 1 mile. Shorelines in Exposure D include inland waterways, the Great Lakes and coastal areas of California, Oregon, Washington and Alaska.KZ=0.85 for zKZ=1.0 for 4.6 mz15 mKZ=1.20 for z>15 m

## Wind load calculation

TIA 222 G.pdf provides a method for calculating wind loads on antenna supporting structures and antennas. The wind load is the force exerted by the wind on a structure or its components. The wind load depends on the wind pressure, which is the force per unit area exerted by the wind on a surface.

The basic formula for wind pressure is:

P = qzGhCf

where:

P is the wind pressure (N/m)

qz is the velocity pressure at height z (N/m)

Gh is the gust effect factor

Cf is the force coefficient

The velocity pressure at height z is calculated as:

qz = 0.613 KZKZTKDV

where:

KZ is the exposure coefficient for height z

KZT is the topographic factor for height z

KD is the directionality factor

V is the basic wind speed (m/s)

The gust effect factor accounts for the dynamic response of the structure to wind gusts. It is calculated as:

Gh = 0.925 + 0.34/(B/Cd)

where:

B is the gust response factor (dimensionless)

Cd is the damping ratio (dimensionless)

The force coefficient depends on the shape and orientation of the structure or its components. It is determined from tables or figures provided in the standard.

An example of wind load calculation for a structure is:

The structure is a Class II self-supporting tower with a height of 50 m and a base width of 5 m.

The structure is located in an Exposure C site with a basic wind speed of 40 m/s and a Topographic Category 1.

The structure has a triangular cross-section with three legs and nine panels of solid face antenna.

The structure has a damping ratio of 0.02 and a directionality factor of 0.85.

The wind load on the structure is calculated as follows:

The velocity pressure at height z is calculated as:qz=0.613 KZKZTKDV=0.6131.1410.8540=1064 N/m

The gust effect factor is calculated as:Gh=0.925 + 0.34/(B/Cd)=0.925 + 0.34/(1/0.02)=1.06

The force coefficient for the tower legs is taken as 1.2 and for the antenna panels as 1.8.

The wind load on each tower leg at height z is calculated as:P = qzGhCf=10641.061.2=1350 N/m

The wind load on each antenna panel at height z is calculated as:P = qzGhCf=10641.061.8=2027 N/m

The total wind load on the structure at height z is calculated as the sum of the wind loads on the tower legs and the antenna panels:P = 31350 + 92027=22851 N/m

## Seismic load calculation

TIA 222 G.pdf provides a method for calculating seismic loads on antenna supporting structures and antennas. The seismic load is the force exerted by the ground motion on a structure or its components. The seismic load depends on the seismic base shear, which is the total horizontal force acting on the base of a structure.

The basic formula for seismic base shear is:

V = CsW

where:

V is the seismic base shear (N)

Cs is the seismic response coefficient (dimensionless)

W is the total dead load of the structure and its attachments (N)

The seismic response coefficient is calculated as:

Cs=I/R(SDS/g)

where:

I is the importance factor (dimensionless)

R is the response modification factor (dimensionless)

SDS is the design spectral response acceleration at short periods (m/s)

g is the acceleration due to gravity (9.81 m/s)

The importance factor depends on the structure class and is taken as 0.87 for Class I, 1.00 for Class II, and 1.15 for Class III.

The response modification factor depends on the type of structure and its ductility and redundancy. It is determined from tables provided in the standard.

The design spectral response acceleration at short periods depends on the site class and the seismic design category of the site. It is determined from maps or tables provided in the standard or by geotechnical investigation.

An example of seismic load calculation for a structure is:

The structure is a Class II guyed mast with a height of 100 m and a base diameter of 1 m.

The structure is located in a Site Class D site with a Seismic Design Category C and a design spectral response acceleration at short periods of 0.6 g.

The structure has a triangular cross-section with three legs and six panels of wire mesh antenna.

The structure has a response modification factor of 3.5 and a total dead load of 100 kN.

The seismic load on the structure is calculated as follows:

The importance factor is taken as 1.00 for Class II.

The seismic response coefficient is calculated as:Cs=I/R(SDS/g)=1/3.5(0.6/9.81)=0.017

The seismic base shear is calculated as:V = CsW=0.017100000=1700 N

## Ice load calculation

TIA 222 G.pdf provides a method for calculating ice loads on antenna supporting structures and antennas. The ice load is the force exerted by the ice accumulation on a structure or its components. The ice load depends on the ice thickness, which is the maximum radial distance from the surface of a structure or its component to the outer surface of the ice.

The basic formula for ice thickness is:

t = 0.0254 KIRI

where:

t is the ice thickness (m)

KI is the ice mapping factor (dimensionless)

RI is the radial ice thickness (mm)

The ice mapping factor depends on the geographic location and elevation of the site. It is determined from maps provided in the standard.

The radial ice thickness depends on the exposure category and structure type of the site. It is determined from tables provided in the standard.

An example of ice load calculation for a structure is:

The structure is a Class II monopole with a height of 30 m and a base diameter of 0.5 m.

The structure is located in an Exposure B site with an ice mapping factor of 1.0 and a radial ice thickness of 12.7 mm.

The structure has a circular cross-section with no appurtenances.

The ice load on the structure is calculated as follows:

The ice thickness is calculated as:t = 0.0254 KIRI=0.0254112.7=0.32 m

The ice load on the structure is calculated as the product of the ice density, the ice thickness, and the gravity:P = ρit g=9000.329.81=2827 N/m

## Load combinations and strength design

TIA 222 G.pdf provides a method for combining different types of loads to determine the maximum load effects on a structure or its components. The load effects are the internal forces and moments induced by the external loads. The load combinations are sets of load factors that multiply the nominal loads to account for their variability and uncertainty.

The standard defines seven types of load combinations: Strength I, II, III, IV; Service I; Extreme Event I, II. The definitions and load factors of each type are as follows:

Load CombinationDefinitionLoad Factors

Strength IBasic combination for strength design1.4D + 1.6L + 1.6W + 0.5E + 1.6I + 0.5T

Strength IIAlternative combination for strength design when wind or seismic governs1.2D + 1.6L + (1.3W or 1.0E) + 1.6I + 0.5T

Strength IIIAlternative combination for strength design when wind or seismic governs and dead load is small compared to live load0.9D + 1.6L + (1.3W or 1.0E) + 1.6I + 0.5T

Strength IVAlternative combination for strength design when wind or seismic governs and dead load is large compared to live load1.6D + (1.3W or 1.0E) + 1.6I + 0.5T

Service IBasic combination for serviceability limit states such as deflection and vibrationD + L + W + E + I + T

Extreme Event IBasic combination for extreme wind events such as hurricanes and tornadoes1.1D + 1.1WE + 0.5L + 0.5I + 0.5T

Extreme Event IIBasic combination for extreme ice events such as ice storms1.1D + 1.1IE + 0.5L + 0.5W + 0.5T

where:

D is the dead load

L is the live load

W is the wind load

E is the seismic load

I is the ice load

T is the temperature load

WE is the extreme wind load

IE is the extreme ice load

TIA 222 G.pdf also provides a method for strength design of a structure or its components. Strength design is a method that ensures that a structure or its component can resist the load effects without exceeding its capacity. The capacity is the maximum internal force or moment that a structure or its component can sustain without failure.

The basic formula for strength design is:

φPnPe

where:

φ is the resistance factor (dimensionless)

Pn is the nominal capacity (N or Nm)

Pe is the factored load effect (N or Nm)

The resistance factor depends on the type of material and failure mode and is determined from tables provided in the standard.

The nominal capacity depends on the geometry and properties of the structure or its component and is calculated using formulas provided in the standard.

The factored load effect depends on the type of load combination and is calculated using formulas provided in the standard.

An example of strength design for a structure component is:

The structure component is a steel angle leg of a self-supporting tower with a cross-sectional area of 0.01 m, a yield strength of 250 MPa, and an ultimate strength of 400 MPa.

The structure component is subjected to a factored axial load effect of 200 kN under Strength I load combination.

The strength design of the structure component is performed as follows:

The resistance factor for steel angle leg under axial tension is taken as 0.9.

The nominal capacity for steel angle leg under axial tension is calculated as:Pn=FyA=2500.01=2500 kN

## Fabrication and construction requirements

TIA 222 G.pdf provides requirements for fabrication and construction of antenna supporting structures and antennas. Fabrication is the process of manufacturing structural components and connections from raw materials. Construction is the process of assembling and erecting structural components and connections on site.

The standard specifies quality assurance and quality control measures for materials, welding, bolting, galvanizing, etc. Quality assurance is the process of ensuring that the materials and processes used in fabrication and construction meet the specified standards and codes. Quality control is the process of verifying that the materials and processes used in fabrication and construction comply with the specified standards and codes.

The standard also specifies inspection and testing procedures for structural components and connections. Inspection is the process of examining the structural components and connections for defects, damages, or deviations from the design specifications. Testing is the process of applying loads or stresses to the structural components and connections to evaluate their performance or behavior.

An example of fabrication and construction requirements for a structure component is:

The structure component is a steel angle leg of a self-supporting tower with a cross-sectional area of 0.01 m, a yield strength of 250 MPa, and an ultimate strength of 400 MPa.

The structure component is fabricated from ASTM A36 steel and welded to other components using E70XX electrodes.

The structure component is galvanized after fabrication to provide corrosion protection.

The structure component is constructed on site using high-strength bolts with a minimum tensile strength of 830 MPa.

The fabrication and construction requirements for the structure component are as follows:

The steel angle leg must conform to ASTM A36 specifications for chemical composition, mechanical properties, dimensional tolerances, etc.

The welding must conform to AWS D1.1 specifications for welding procedure, welder qualification, inspection, etc.

The galvanizing must conform to ASTM A123 specifications for coating thickness, adhesion, appearance, etc.

The bolting must conform to ASTM A325 specifications for bolt type, grade, size, installation, inspection, etc.

## Conclusion

TIA 222 G.pdf is a structural standard for antenna supporting structures, antennas, and small wind turbine support structures. It provides requirements for structural design and fabricatio