Technical Specifications for the Installation of Telecoms Mast and Towers-NCC

TECHNICAL SPECIFICATIONS

FOR THE

INSTALLATION OF

TELECOMMUNICATIONS MASTS AND TOWERS

1

Table of Contents Page Chapter One – General Principles of Practice 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Preamble Types of Structures General Guidelines Certification - Company and Employees Siting Environmental Requirements Structural Certification The Terrain Basic Wind Speed

Chapter Two – Design and Construction 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

Service Life Superstructure Structural Types for Self-Support Lattice Painting Obstruction Lighting Substructure Earthing and Lightning Protection Safety Devices

Chapter Three – Material Specifications 3.1 3.2 3.3 3.4 3.5 3.6 3.7

The Superstructure Concrete Earthing and Lightning Protection Metals and Galvanizing Earthing Clamps U-Bolts Connector Clamps

3 4 5 5 7 8 9 14 14 16

20 21 21 26 55 55 56 75 81 85 86 87 88 88 89 89 91 2

3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15

Screw Down Clamps Earth Bars and Disconnecting Clamps Lightning Arrestor Copper Tapes Connectors Bi-metallic Connectors Guy System Materials Antenna Mounting Frames

Chapter Four – Maintenance and Testing 4.0 4.1 4.2 4.3 4.4 4.5 4.6

First Line Maintenance Hot Dip Galvanization Tower Maintenance Maintenance Philosophy Routine Checks Annual Maintenance Checks Testing

92 93 95 96 97 98 99 101

108 109 109 109 110 111 113 115

Glossary

121

Index

124

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CHAPTER ONE

GENERAL PRINCIPLES OF PRACTICE

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1.1

Preamble

This document is intended to be a general, simple to read guide for telecommunications services operators, fabricators and installers of telecommunications towers and masts in the environmental, safety and engineering practice that must be adhered to. It is intended to be a handbook to be used by all who shall have anything to do with telecommunications towers and masts whether as owners, fabricator, installers and local authorities. We have also provided comprehensive data on wind speeds for the entire country that will form an easy reference material for engineers that are in the business of designing masts and towers. Responsibilities of telecommunications tower owners, users, builders are set out in easy to read format, devoid of technical jargons. These regulations consider towers from the different standard structures, the perspective of their being made up of substructures and the superstructures, public safety, safety of personnel and safety of equipment. Compliance to the standards set out herein is mandatory.

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1.2

Types of Structures

Telecommunication towers may be of several types and range in height from 30 to 300 meters or more. Three general forms of telecommunication towers are • Monopoles that consist of tapered steel tubes that fit over each other to form a stable pole, • Guyed towers that are stabilized by tethered wires • Self-supporting towers that are free-standing lattice structures. These are illustrated in Figure 1 below.

.

Monopole

Guyed

Self-supporting

Figure 1 - Tower Types

1.3 General Guidelines This specification applies to communication lattice towers and masts constructed and installed in Nigeria. (a) It is assumed that the predominant load on these structures is wind load. 6

(b)Each structure shall be made of hot dip galvanized steel sections. (c) Masts could be guyed or free standing (d)Free standing masts should not exceed 150 meters in height. (e) Masts and towers may be installed on a property with the written permission of the property owner and the approval of the Nigerian Communications Commission. (f) Structures above 30 meters in height may only be installed with a clearance certificate issued by the Nigeria Airspace Management Authority (NAMA). (g) No masts or towers (irrespective of the height) may be installed within 15 kilometers of any airport without prior approval and a permit from the Nigeria Airspace Management Authority (NAMA). This requirement also applies to such structures within the proximity of helicopter pads and their approaches. (h) The armed forces are exempted from this regulation in times of war only. At the cessation of hostilities any structures erected under this waiver must be submitted for reassessment and approval. (i) The open space available at the site of a proposed mast or tower installation must be at least three times the space required by the base of the structure. (j) A permit must be obtained from the Nigerian Communications Commission for the erection of any Masts or Towers whose height exceeds 20 meters and such structures shall be registered with the NCC on completion. The following documents will be submitted to the NCC as part of the application for a permit.

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I. Site plan showing the proposed structure location in relation to adjoining structures. II. Evidence of ownership of the property on which the structure is to be installed or a written consent of the landlord. III. Geographical coordinates of the proposed location of the structure and that of the nearest airport, heliport or helipad. In the alternative, a permit issued by the Nigeria Airspace Management Authority (NAMA) for the erection of the structure in the proposed location. IV. Design of the structure showing its effective height, foundation, guys (where used), members, ladders, rest and work platforms, earthing, lightning protection and aviation lighting. V. Detailed information on the software package used in the design to enable easy verification of the fidelity of the design of the structure. VI. Certification of the proposed installer issued by the Nigerian Communications Commission (NCC). The following guide-lines should be adhered to: Each completed mast or tower must have a name plate bolted to each of its legs on which the following particulars of the fabricator, operator and installer are detailed • • • •

Name of owner address of owner telephone numbers of owner Permit Number issued by the NCC for erection of the Mast at the location and in addition the following particulars pertaining to the antenna.

• • • •

date of erection height number of antenna Operating Frequencies

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• Location address • Geographical coordinates • a log book showing inspection dates and types of inspections performed A tower or mast erecting crew must have a current Workmen’s Compensation policy from a 1st Class insurance company to a minimum value of five million naira or any such amount as may from time to time be specified by the Nigerian Communications Commission, for any one claim for third party claims. Responsibility for accidents during the installation period shall be that of the installer and it shall revert to the owner of the masts or towers on completion and handover. All masts and towers must be insured by their owners against third party claims in the event of collapse. 1.4

Certification - Company and Employees

The minimum basic educational qualification for employees in the fabrication, erection and maintenance of towers and masts shall be a four year training programme in welding and machining from an accredited Technical College and a City and Guilds Final Certificate. Installers who meet the basic qualifications shall be licensed by the NCC. No installers shall operate without the NCC license. All checking visits and maintenance interventions have to be done by employees with special qualification in telecom tower manufacture or maintenance. A tower fabricating company shall be licensed by the NCC upon satisfaction that • She has acquired enough capital equipment to enable her deliver safe and quality installation. • She has in her employ, qualified and licensed fabricators. • She has a good Workmen’s compensation insurance policy from a reputable insurance company • She also has a good third party accident insurance policy • She has a viable Health, Safety and Environment policy

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Tower and mast installation is an equipment based procedure. A company applying to the NCC for an installation permit shall possess or demonstrate easy access to the following capital equipment: • • • • • •

1.5

Packer Excavators Bull Dozer Forklift Long Boom Arm Crane Concrete Vibrator and Poker Siting

This Section establishes siting the location of telecommunication towers and masts with the objective of minimizing their number, protecting and promoting public safety, and mitigating the adverse visual impacts on the community whilst promoting the provision of telecommunications service to the public. Cities may not refuse the placement, construction and modification of tower facilities on the basis of environmental or radio frequency emissions as long as such facilities comply with the Nigerian Communications Commission’s regulations concerning such emissions. Telecommunications towers and masts, when permitted by the Nigerian Communication Commission and the local authority, shall be regulated and governed by the following use regulations and requirements. 1.6

Environmental Requirements

Height The maximum height that may be approved for a telecommunication tower in Nigeria is 150 meters. A tower, more than 50 meters in height, may be approved by the National Communications Commission if the Commission is satisfied that the increased height of the tower: (1) Will not be detrimental to the public health, safety or general welfare. (2) Will not have a substantial negative effect upon neighbourhood. (3) Is in conformity with the intent and purpose of the planning of the area and the general plan of the community. 10

(4) Will not impair the obligation to comply with any other applicable laws or regulations. 1.6.1 Space requirements. a. One parking/loading space shall be required to serve a telecommunication tower site. b. Any tower site lying 50 meters or less from a paved road shall be paved c. If the site is more than 50 meters from a paved road, hard-surfacing of parking / loading spaces and driveways shall not be required for those portions of the site lying more than 50 meters from any paved road. d. Stealth and/or camouflage design of towers and antennas are encouraged to reduce the visual impact of the structure. 1.6.2 Screening An opaque screen at least 2.5 meters in height must surround the base of a telecommunication tower. The screening shall also include landscaping provisions for any portions of the development visible f rom adjacent residential or used property or right-of-way. The use of barbed wire or other security fencing material shall be allowed. Screening requirements may be waived if the design of the tower is found to be compatible with the adjacent land uses. 1.6.3 Removal of abandoned towers A tower that has not been maintained for a continuous period of three years shall be considered abandoned. The NCC will determine the date of abandonment and may request documentation from the owner/operator regarding the issue of usage. Upon the determination of abandonment, the NCC will issue a removal notice to the owner. The owner shall dismantle and remove the tower from the property within 90 days of receipt of notice from the Nigerian Communications Commission. An abandoned tower that is not removed within the 90 day

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period shall be removed by the NCC and removal costs plus a penalty shall be paid by the owner. 1.6.4 Inspections Telecommunication towers shall be inspected by a qualified tower inspection service employed by the NCC once every six months to assess the structural condition of the tower and support equipment. Owners of towers which fail to meet the required standards will be notified to remedy the situation within 30 days. Failure to remedy notified lapses shall attract stiff penalties. 1.6.5 Authorization All telecommunications towers and masts shall be erected and operated in compliance with Nigerian Communications Commission and Nigeria Airspace Management Authority regulations. 1.6.6 Structure Towers and masts shall be designed and located such that should any structure fall, it will avoid habitable structures and public streets. This shall be the major determinant factor in the issue of setbacks from adjacent existing structures. 1.6.7 Co-location Towers shall be designed and built to accommodate a minimum of three service providers on the same structure, if over 25 meters in height. The owner of the tower must certify to the NCC that the tower is available for use by other telecommunications service providers on a reasonable cost and nondiscriminatory basis. The Nigerian Communications Commission will have the final authority for arbitration where any serious disagreement that threatens collocation arises. 1.6.8 Fencing Security fencing, if installed, shall be by a wrought iron, barbed wire, steel chain link fence with evergreen hedge or a masonry wall not less than 1.8 meters in height. The exterior of equipment buildings and/or metal equipment cabinets visible from residential areas or public rights-of-way

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shall be painted to reflect the color and character of adjoining structures or blend with adjacent landscaping and other surroundings. 1.6.9 Setbacks All telecommunication towers as well as guys and guy anchors shall be located within the buildable area of the property and not within the front, rear, or side building setbacks. Telecommunication towers in excess of 150 meters in height shall be set back a minimum of 50 meters from the rightof-way of all controlled access, federal and state roadways designated as freeways, to provide unobstructed flight paths for helicopters. Towers shall be set back the greater distance of: (a) 10 meters from any residential or used property; (b) 25 percent of the height of the tower (c) The distance specified as a potential hazard area by the designer of the structure. Guy wire anchors and accessory structures shall not encroach into the mandatory setbacks listed above. 1.6.10

Signage

No signage, lettering, symbols, images, or trademarks in excess of 1200 cm2 shall be placed on or affixed to any part of a telecommunications tower, mast, antenna or antenna array fencing other than as required by NCC for the purposes of Telco identification. No adverts will be allowed on these structures. 1.6.11

Lighting

Telecommunication towers shall only be illuminated as required by NAMA and/or ICAO. No signals, lights or illumination of any kind shall be permitted on or directed towards any tower unless as required by the NAMA or any other appropriate public authority. Security lighting around the base of a tower must be shielded so that no light is directed towards adjacent properties or rights-of-way.

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The purpose of obstruction lighting and marking is to ensure that an obstruction to air navigation remains visible at a range sufficient to permit a pilot to take appropriate action in order to avoid the obstruction by not less than 305m vertically within a horizontal radius of 610 meters from the obstruction. A typical obstruction lighting kit shall include the following: • • • • •

Light with bulbs of a minimum of 10,000hrs service life Junction box Photo sensor Power cable (in conduit and armoured) Weather proof Light flasher. Flash rates of 40/min are allowable typical values. • Assembly hardware such as U-bolts and connection bolts Design of a lighting kit is regulated by governmental organizations. One factor in determining lighting requirement is the height of the structures. ICAO regulates the international industry whilst NAMA is regulator of the Nigerian industry in line with ICAO recommendations. Aviation lighting gear should be designed to have minimal serviceable components so as to reduce the p roblems of regular ascent of towers to service lamps. 1.6.12

Residential Areas

Telecommunications towers above 25 meters in height are, as a general rule, not permitted within districts delineated as residential. Where they are by exception allowed, they must be placed a minimum ratio of 3 to 1 distance to height to the nearest residential property. Towers or masts or monopoles in excess of 25 meters in height are permitted in the non-residential districts. 1.6.13

Tower to Tower Spacing

Any new telecommunications tower in excess of 55 meters in height must be located a minimum of one kilometer from any other existing tower in excess of 55 meters in height.

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1.6.14

Nearness to Power Lines

No tower or mast shall be installed in close proximity to High Voltage electrical power transmission lines. The closest distance shall be that equivalent to 120% of the height of the mast. In other words, the minimum separation shall be the height of the mast plus 20% of the same height as a safe margin. 1.6.15

Alternative Mounting Structures

Alternative Mounting Structures 30 meters or less in height shall be permitted in residential areas. Alternative Mounting Structures in excess of 30 meters in height are permitted in the non-residential areas. Alternative Mounting Structures must be similar in color, scale and character to adjoining buildings or structures or blend with the landscaping and other surroundings immediately adjacent to them so as to generally avoid the creation of unique visual objects that stand out in the environment. 1.6.16

Antenna Mounts

Antenna mounts must have structural integrity so as to guarantee public safety. (i)

Whip and Panel Antenna Mounts a.

b. c. (ii)

Individual telecommunications antennas are allowed on existing low tension electric utility poles, light standards, and telecommunication towers in excess of 12 meters in height, provided that the total length of any antenna does not exceed 15 percent of the height of the existing structure. Telecommunications antennas and arrays are not allowed on existing high tension electric transmission towers. Panel and whip antennas are permitted on billboard structures.

Dish Antenna Mounting Standards 15

a.

Ground mounted dish antennas in excess of five feet (1.5 meters) height shall be screened from roadways and adjacent property by a minimum 1.8 meter high screening fence.

b.

Building and roof mounted dish antennas of one (1) meter or less in diameter, are permitted in all areas. No permits are required for this category

c.

1.7

Building/roof mounted dish antennas in excess of 1 meter in diameter, may be permitted on buildings on the condition that a structural engineer’s certification that the building will withstand the additional load is provided to the Nigerian Communications Commission.

Structural Certification

Prior to the installation of a telecommunications tower, mast and antenna support structure on any building or roof the NCC shall be provided with a structural engineer's certification that the structure will support and not be adversely affected by the proposed mast, tower, antenna and associated equipment. 1.8

The Terrain

The terrain for purposes of this specification is Nigeria and includes its territorial waters and the continental shelf. In making designs for masts and tower structures, this terrain is classified into three broad geographical zones based on measured worst case wind speeds measured over a period of 30 years . 1) Exposed smooth terrain with virtually no obstructions and in which the height of any obstructions is less than 1.5m. This category includes open sea coasts, lake shores and flat, treeless plains with little vegetation other than short grass. 2) Open terrain with widely spaced obstructions (100m apart) having heights and plan dimensions generally between 1.5m and 10m. This category includes large airfields, open parklands or farmlands and undeveloped outskirts of towns and suburbs with few trees.

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3) Terrain having numerous closely spaced obstructions generally the size of domestic and high rise buildings. This category includes wooded areas and suburbs, towns and industrial areas, fully or substantially developed. Wind loading shall be the predominant dynamic loading to be considered outside dead weights since severe environmental conditions that lead to additional seasonally variable loads are non-existent. Wind load rating is based on the height of the tower and where it is located.

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Figure 1.1 Figure 1.1 above is a map of Nigeria showing the average wind speeds as measured by the Nigerian Meteorological Agency. Wind loading for a structure is to be considered over the full length of the structure and is to be measured in Newtons per square meter (N/m2). The basic wind speeds depicted in this map are measured at 10 meters above the ground. These values increase with height and need to be so corrected when making computations.

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Engineers are encouraged to consider and design for specific conditions that might exceed these given standard values. Design philosophy shall be based on two limiting states - strength and serviceability. The strength limit considers the loading of a tower under extreme conditions; the serviceability limit ensures the tower will provide the proper service under normal conditions. Towers shall be analyzed under three specific types of loading: (a) (b) (c)

wind environmental seismic

Wind effect on a tower must take cognisance of a number of external conditions that might change the dynamics of the wind, such as terrain, gusts, the method of wind-speed determination and the value of safety factors needed for a specific tower type. The safety factor defines the impact a failure of the tower would have to its operational integrity, human life and property. A proportionate amount of over design must be applied to take care of these. 1.9

Basic Wind Speed

The superstructure is really being designed to resist various pressures, wind load, being the major one for Nigeria. Wind velocities constitute the measured data generally available. A conversion has to be made from wind velocity to wind pressure. Various existing standards define and measure wind velocity in different ways and therefore the formulas used to convert these velocities to pressure produce results that can vary as much as 25%. That translates into a 25% difference in design loads that will produce different foundation sizes all of which mean a totally different installed cost. Engineers are therefore encouraged to use basic wind speeds in design of wind loading. Basic wind speed approach assumes wind given winds speeds from meteorological measurement to be at 10m above ground level. Basic wind speed design escalates the wind load from 10 meters above ground to the top of the structure. For example, for a 90 meter tower with a basic wind speed design of 115 km hr-1, the wind load design at the top of the tower is 160 km hr-1. Structures shall be designed to withstand forceful wind speeds that occur 19

on the average of once every 30 to 50 years. This wind speed is then escalated, with height, to a much higher wind speed at the top of the structure. A gust factor to account for the varying nature of wind shall also be incorporated into the design of the structure. The wind speeds shown in figure 1.1 above were measured from the stations listed in Table 1.1. Engineers who desire greater accuracy in their wind speed calculations are encouraged to use figure 1 in conjunction with Table 1.1. Table 1.1 STATION NAME S/N 1 YELWA 2

BIRNI KEBBI

3

SOKOTO

4

GUSAU

5

KADUNA

6

KATSINA

7

ZARIA

8

KANO

9

BAUCHI

10

NGURU

11

POTISKUM

12

MAIDUGURI

13

ILORIN

LAT. 10.53’ N 12.28’ N 13.01’ N 12.10’ N 10.36’ N 13.01’ N 11.06’ N 12.03’ N 10.17’ N 12.53’ N 11.42’ N 11.51’ N 08.29’ N

LONG . 04.45’ E 04.13’ E 05.15’ E 06.42’ E 07.27’ E 07.41’ E 07.41’ E 08.12’ E 09.49’ E 10.28’ E 11.02’ E 13.05’ E 04.35’ E

STATE KEBBI KEBBI SOKOTO ZAMFARA KADUNA

ELEV. 244.0 220.0 350.8 463.9 645.4

KATSINA

517.6

KADUNA

110.9

KANO

472.5

BAUCHI

609.7

YOBE

343.1

BORNO

414.8

BORNO

353.8

KWARA

307.4

20

14

SHAKI

15

BIDA

16

MINNA

17

ABUJA

18

JOS

19

IBI

20

YOLA

21

ISEYIN

22

IKEJA

23

26

OSHODI MET.AGRO LAGOS (HQ) ROOF LAGOS (MARINE) IBADAN

27

IJEBU-ODE

28

ABEOKUTA

29

OSHOGBO

30

ONDO

31

BENIN

32

AKURE

33

WARRI

24 25

08.40’ N 09.06’ N 09.37’ N 09.15’ N 09.52’ N 08.11’ N 09.14’ N 07.58’ N 06.35’ N 06.30’ N 06.27’ N 06.26’ N 07.26’ N 06.50’ N 07.10’ N 07.47’ N 07.06’ N 06.19’ N 07.17’ N 05.31’ N

03.23’ E 06.01’ E 06.32’ E 07.00’ E 08.54’ E 09.45’ E 12.28’ E 03.36’ E 03.20’ E 03.23’ E 03.24’ E 03.25’ E 03.54’ E 03.56’ E 03.20’ E 04.29’ E 04.50’ E 05.06’ E 05.18’ E 05.44’ E

OYO NIGER

144.3

NIGER

256.4 343.1

FCT PLATEAU

1780.0

TARABA

110.7

ADAMAWA

186.1

OYO

330.0

LAGOS

39.4

LAGOS

19.0

LAGOS

14.0

LAGOS

2.0

OYO

227.2

OGUN

77.0

OGUN

104.0

OSUN

302.0

ONDO

287.3

EDO

77.8

ONDO

375.0

DELTA

6.1

21

34

LOKOJA

35

ONITSHA

36 37

PORT HARCOURT OWERRI

38

ENUGU

39

UYO

40

CALABAR

41

MAKURDI

42

IKOM

43

OGOJA

07.47’ N 06.09’ N 04.51’ N 05.29’ N 06.28’ N 05.30’ N 04.58’ N 07.44’ N 05.58’ N 06.40’ N

06.44’ E 06.47’ E 07.01’ E 07.00’ E 07.33’ E 07.55’ E 08.21’ E 08.32’ E 08.42’ E 08.48’ E

KOGI

62.5

ANAMBRA

67.0

RIVERS

19.5

IMO

91.0

ENUGU

141.8

AKWA IBOM

38.0

CROSS RIVER BENUE

61.9

CROSS RIVER CROSS RIVER

112.9 119.0 117.0

Table 1.1 – Meteorological Stations in Nigeria

The above data obtained from the National Meteorological Services indicate that the highest recorded wind speed over a period of 20 years is 7 ms-1, which translates to a mere 420 mhr-1. However, wind gusts of the order of 55 km hr-1 have been recorded infrequently. Since these data form our worst case scenario, masts and towers in Nigeria shall be designed to withstand a minimum ground wind speed of 70 km hr-1.

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CHAPTER TWO

DESIGN AND CONSTRUCTION

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2.1 SERVICE LIFE The expected service life of a tower shall be 25 years. The design, choice of f abrication materials, fabrication methods, installation accessories, all safety factors and tower loadings shall all be made to conform to standards for this to be achieved. Qualified professional engineers shall design and specify materials that meet the requirements to give a minimum service life of 25 years in the working environment. Qualified welders and skilled welding supervision shall be deployed to give positive effect on the finished product. The highest quality of welding must be built in. Poor quality welding will be apparent shortly after installation by which time repairs will be very expensive and time consuming. Proper welding means good quality finishes and thus minimizes long term maintenance costs. 2.2 SUPERSTUCTURE 2.2.1 Finishes All steel materials that are to be used in the superstructure shall as a standard be hot-dip galvanized and later painted according to NAMA paint schedule for obstructions. All aluminum materials shall have aluminum finish and will be equally painted according to NAMA paint schedule for obstructions. 2.2.2 Self-Support towers Self support design is often the solution of choice when land availability is limited. The tower uses tapered sections, and face widths will vary according to height and load capacity required. They are recommended for most applications in Nigeria anywhere it is technically feasible to install them. They are designed and constructed in: 1) Lattice structure • • • • • •

Triangular or square structure With tube legs, angle legs, lattice legs or solid round legs Sections in steel angle steel or steel tubes Steel angle cross bracing. Tapered sections Face widths vary according to height and load capacity.

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• Rest platforms provided every 20 meters of height • Work platforms provided at all height where antennas are to be installed • Fitted with climbing ladder Standard support forms for lattice structures are specified as follows: a) Lattice Leg • cost-efficient, high-capacity design • ideally suited for multi-carrier applications • fast and easy assembly • Bracings shall be of angle steel

b) Angle Leg • bolt-up construction • constructed from steel angle steel • Bracings shall be of angle steel

c) Tube Leg / Solid Round Leg • time-proven strong structural shape • constructed from schedule 80 pipes • Bracings shall be of angle steel • bolt-up construction

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Towers legs shall be constructed from schedule 80 pipes or angle steel. Hollow aluminum pipes shall be used for short towers. Bracings shall be of angle steel construction or aluminum in case of aluminum towers. Mast sections, when made from steel pipes, shall be joined to each other through joint plates welded to the base of each section. The width of the mast section joint plates should be double the width of the wall of the pipe they are supporting. Gussets shall be used in the strengthening of the weld joint between the base plate and the tower section. Each plate shall have four 20mm diameter holes drilled to accommodate four 18mm bolts, nuts and washers. When bolting sections together, bolts shall be placed upside down with washers and nuts on topside of plates, the connecting face of plates shall not be painted. Lock nuts must be used but nuts on bolts may be clinched if lock nut is not utilized. Lock washers and lock nuts shall on no account be omitted on antenna support steel work and dish panning arms as that will directly result in loss of signals. When a tower is made from angle steel, sections shall be joined to each other through appropriately sized flanges, bolts, washers and lock nuts. Bracing inhibits torque on a tower and its non adequate application exposes towers to torque. This in turn results in loss of signal during strong winds speeds. 2.2.3 Monopole Towers Monopole or Post Masts are to be made from galvanised hollow steel pipes or high strength steel. They shall be designed for a variety of multi-user configurations and finishes to meet local aesthetic requirements. The pipes are to be constructed tapered so that one pipe base fits into the top of another until the desired height is achieved. A joint in the arrangement has an overlay between the two adjacent pipes. The depth of the overlay, the base width and the number of pipes in a particular monopole shall be determined by height desired of the tower, the

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thickness of the pipe walls, the base diameter and whether the tower shall be guyed or not. For a monopole, • Sections shall be made from hollow, heavy duty, thick steel tubes, flanged steel tubes or low-alloy, high-strength steel. • Each shaft section shall be a constant-tapered hollow steel section • Slip joints are designed with a minimum of 1 1/2 times the pole diameter at the splice. • Sections shall fit into each other with overlap • Pipe diameter shall decrease from bottom to top • Shall be guyed or self supported • Shall be fitted with climbing rugs • Usually not very tall structure in the self support design Tapered steel and flanged steel poles feature designs that blend well into the environment and require minimum space for installation. Flanged steel poles are easy to handle and install. Connections shall be precision fitted to allow quick assembly of modular sections and the top platform, side arms or mounting frame. Pole sections shall be made with identical base flange plates to permit simplified modifications of mounting heights and antenna reconfigurations. Tapered steel poles have comparatively smaller base diameters and so demand minimal land space. Tapered poles can be installed quickly do offer extremely efficient strength-to-cost ratio. 2.2.4 Guyed Towers Guyed masts do also come in lattice, triangular or square, tapered or straight, as well as monopole structural forms. Guyed masts are supported and held in position by guy wires or ropes. Mast Guy Ropes shall be made from pre-stretched steel only. For every mast, the specified minimum strength of the guy wire shall be the maximum tension likely to occur in the worst loading condition. Guy wires must not be over tightened. Excessive tension may cause alignment problems and even a cable rupture. It may cause permanent wrapping of tower structural parts. Extreme precaution must be taken while tightening because just 3 turns of a tightening device would increase the tension of a 45m long guy wire by about 250kg.

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All sections must be straight square sections and eliminate any potential problems with twisting or the need to shim the legs. Typical tower sections shall have a brace configuration with horizontals (z, x or k) and pivot base sections. These tower-structures are wholly of steel, modular and hot-dip galvanized. Sections can be of the same face width but should the tapered type be contemplated, it shall be designed with junction flanges. Tube or solid legs with solid bracing increases the tower rigidity to allow for the twist and sway. In the guyed mode all the forces on a tower are supported by the guy wires. Everything about the guy wire has to be engineered with precision and a minimum safety factor of 2.0 applied to the design. The design, based on the load calculations shall determine working load and the break strength required of the guy wire and subsequently the choice of the size and grade of the wire. The choice of each guy earth screw anchor shall be dependent on its holding power in the soil, which is a function of its diameter and length. This is used to compute the minimum number of guys required. As a general rule guys are planted in three directions at 120 o apart from each other. The distance from the base of the tower to the guy anchor base shall be one quarter of the height of the tower. 2.2.5 Roof Mounts Roof mounting is an inexpensive way of elevating signals above roof interference or any other obstruction. Structural checks must be made to ascertain the capability of a chosen roof to withstand the additional load being imposed on it by the structure and the entire antenna array it will support. All roof mounted masts or towers must be certified by the building’s structural engineer before installation. As a general regulation roof mounts shall be limited to light weight structures of low heights and support minimal dead and dynamic loads. Roof mounts can be installed in the penetrating or non-penetrating modes. They can be self support or guyed.

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2.3 Structural types for Self Support Lattice Single Bracing

Panel Height

Face width Type

S1

S2

Redundant diagonal

S3 Redundant Horizontal

X - Bracing Panel Height

Type

X1

X2

X3

X4

X5

X6

K4

K5

K6

K - Bracing

Panel Height

Type

K1

K2

K3

Figure 2.1 – Bracing Types Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles. Lattice Mast Bracing Types

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Diagonal Spacing

Double K2 Down Double K3, K3A, K4

Double K 1 Down

K – Brace Down

K – Brace Up

Figure 2.2 Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

30

Horizontal

Secondary Horizontal

Diamond

Z bracing

Double K

M - Bracing

Figure 2.3 Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

31

K-Brace End Panel K-Brace End panel

K-Brace End Panel

Face A Double Slope-Bracing

Diagonal Up Z-Brace

Diagonal Down Z-Brace Figure 2.4

Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

32

Horizontal

X-Brace CX-Brace

TX-Brace

Secondary Horizontal

Horizontal

CX, TX-Brace with Secondary Horizontal

K-Brace

Left

Redundant Vertical

Redundant Sub-Horizontal

K1 Down K1 Up (Opposite)

K2 Down K 2 Up (Opposite)

Figure 2.5 Members shall be made from solid rod, pipe or angles.

33

Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

Redundant Sub Horizontal

K 3 Down K 3 Up (opposite)

K 3A Down K 4 Up

(Opposite)

Redundant Sub-Horizontal Redundant Diagonal

Redundant Sub-Diagonal

K 1B Down

Figure 2.6 34

Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

Sub Diagonal Working Point Sub Diagonal Redundant Sub Horizontal

Optional Vertical

Red Diagonal 3

Horizontal 3

Diagonal 2 Horizontal 2 Diagonal 1

Horizontal 1

Diagonal

Figure 2.7 Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

35

Sub Diagonal Redundant Sub Horizontal

Optional Vertical

Diagonal 3

Horizontal 3

Diagonal 2

Horizontal 2 Diagonal 1

Horizontal 1

Diagonal

Figure 2.8 Portal Bracing Members shall be made from solid rod, pipe or angles. Engineer must specify wall thickness if design is of pipes and sizes and thickness of legs if of angles.

36

Face width

Section height Slopechange

Height

Face width

Fig. 2.9 X-braced, self supporting, lattice design showing face width, slope change and tower height

37

Face width 0.16

Section 15 Section 14 Section 13 Section 12 Section 11 Section10

This represents a generalized design of a 15 section, 6m length per section tower.

Section 9 Section 8 300'

Section 7 275.6'

Section 6 Section 5 Section 4 Section 3 Section 2 Section 1

Loading considerations to be taken into account in the specification of bracing sizes, bracing configuration (double or single), bracing bolt sizes, leg size and type, face widths at top and base, etc are: • Wind speed to include gust factor if applicable • Total anticipated antenna load • Maximum Shear per leg • Maximum uplift reaction • Maximum compression

34'

Face width

Figure 2.10 Superstructure of a 15 section X - Braced Steel Tower showing antenna mounts. Tower can be designed and fabricated as a three or four legged self support structure. New sections that are intended to result in higher towers shall be added below section 1 with the design philosophy as to face widths being maintained. 38

Face width 4

Section 13 Section 12 Section 11 Section 10 Section 9

Generalized prototype design of a 13 section, 6m length per section tower.

Section 8 Section 7

H

Section 6

23623'

Section 5 Section 4

Section 3 Section 2 Section 1

Loading considerations to be taken into account in the specification of bracing sizes, bracing configuration (double or single), bracing bolt sizes, leg size and type, face widths at top and base, etc are: • Wind speed to include gust factor if applicable • Total anticipated antenna load • Maximum Shear per leg • Maximum uplift reaction • Maximum compression

Face width

Figure 2.11 Superstructure of a 13 section X - Braced Steel Tower Tower can be designed and fabricated as a three or four legged self support structure. New sections that are intended to result in higher towers shall be added below section 1 and the design philosophy as to face widths maintained. 39

78 metre Tower

100 meter Tower 1.6m

section 13

section 16

section 12

section 15

section 11

section 14

section 10

section 13

section 9

section 12

section 8

section 11

section 7

section 10

section 6

section 9

section 5

section 8

section 4

section 7

section 3

section 6

section 2

section 5

section 1

section 4

Face Width 8.4metres section 3

section 2

Two towers of different heights illustrating the general relationships between lattice tower heights, number of sections and the face widths at the top and bottom. Both towers are of identical design but have different heights.

section 1

Face width 10.4 meters

Figure 2.12 - Self Support Lattice Towers of different heights 40

Structural Design of a 12-section self support tower in single or Z bracing. Face width decreases from base to top of the tower

9"

12"

15"

18"

21"

24"

27"

13

19

25

31

37

43

26

32

38

44

33

39

45

21

27

16

22

17

23

18

24

18"

40

46

35

41

47

30

36

42

48

21"

24"

28

34

LEG # 7

15

H

10

20

LEG # 5

Lower Frame

LEG # 2

9

L e g #1

14

LEG # 4

X

LEG # 3

8

LEG # 6

Top Frame 7

6" 11

29

24" 12

W

15"

Section 3

Section 2

Section 1

27"

Section 5

Section 4

39"

Section 7

Section 6

42"

30"

33"

49

55

61

67

73

50

56

62

68

74

57

63

69

75

36"

30"

58

53

54

LEG # 12

52

LEG # 11

LEG # 9

LEG # 8

51

LEG # 10

25 1-/X''

X'

64

70

76

59

65

71

77

60

66

72

H

24"

36"

Section 8

Section 9

38"

Section 10

42"

Section 11

78

45"

Section 12

Figure 2.13 A 12-section, single braced, lattice tower. Each section is tapered to produce an overall tapered structure. Additional sections, if the tower has to be higher shall be of greater face width than section 12 until the tower reaches required height.

41

Design Data of a Ten Section Light Duty Self-Supporting Tower Table 2.1

TOWER SCHEDULE Section Number

Spread Dimension Upper Lower

1 (Top)

30 cm 30 cm

30 cm 30 cm

30 cm 50 cm 72 cm

50 cm 72 cm 94 cm

5.0 cm 2 5.0 cm 2 5.0 cm

94 cm 114 cm

114 cm 135 cm

135 cm 156 cm 176 cm

156 cm 176 cm 198 cm

5.75 cm 2 5.75 cm 2 5.75 cm

2 3 4 5 6 7 8 9

10(Grnd) **Cross-sectional area

Tower Legs** 36 KSI Yield STR

Tower Braces 36 KSI YIELD STR

Bolts A 325 GRADE

5.0 cm 2 5.0 cm

2

2.5cm x 2.5cm x 0.32cm 2.5cm x 2.5cm x 0.32cm

8mm 8mm

2

2.5cm x 2.5cm x 0.32cm 3.2cm x 3.2cm x 0.5cm 3.2cm x 3.2cm x 0.5cm

8mm 10mm 10mm

5.0 cm 2 5.75 cm

2

3.2cm x 3.2cm x 0.5cm 3.2cm x 3.2cm x 0.5cm

10mm 10mm

2

3.2cm x 3.2cm x 0.5cm 3.2cm x 3.2cm x 0.5cm 3.2cm x 3.2cm x 0.5cm

10mm 10mm 10mm

Table 2.2

SECTION HEIGHTS AND WEIGHTSD WEIGHTS Section Number 1

Height

Legs

Braces

Lap Links

Total

3.0 m

36 Kg

8.5 Kg

4.5 Kg

65 Kg

2

3.0 m

36 Kg

8.5 Kg

4.5 Kg

65 Kg

3

3.0 m

36 Kg

10 Kg

4.5 Kg

70 Kg

4

3.0 m

36 Kg

17.7 Kg

4.5 Kg

101 Kg

5

3.0 m

36 Kg

27.5 Kg

4.5 Kg

111 Kg

6

3.0 m

36 Kg

29 Kg

4.5 Kg

127 Kg

7

3.0 m

40 Kg

30 Kg

4.5 Kg

153 Kg

8

3.0 m

40 Kg

33 Kg

4.5 Kg

162 Kg

9

3.0 m

40 Kg

34 Kg

4.5 Kg

171 Kg

10

3.0 m

40 Kg

37 Kg

N/A

216 Kg

42

Table 2.3 SUPERSTRUCTURE DESIGN AND LOADING HEIGHT ABOVE WIND SPEED GROUND Km/ hr

30 m

24 m

18 m

12 m

ALLOWABLE DEAD WEIGHT PER SECTION

MAX COAX QTY/SIZE

MAX COAX 9m BELOW QTY/SIZE

Kg.

WIND LOAD TOP (M2)

WIND LOAD 9m BELOW TOP (M2)

FLAT

ROUND

FLAT

ROUND

0.9

1.4

1.1

1.7

0.46

0.7

1.86

2.79

110

90

3 / 25mm

3 / 25mm

125

90

3 / 25mm

110

135

3 / 25mm

6 / 25m

1.67

2.51

125

135

3 / 25mm

6 / 25mm

0.70

1.05

145

135

3 / 25mm

?

0.74

1.11

110

180

6 / 25mm

6 / 25mm

2.14

125

180

6 / 25mm

6 / 25mm

1.11

145

180

3 / 25mm

6 / 25mm

0.64

110

360

12 / 25mm

?

4.83

125

360

12 / 25mm

?

3.35

145

360

9 / 25mm

?

2.69

0.88

1.32

?

?

2.32

3.48

1.67

1.25

1.88

0.95

0.85

1.13

?

?

5.30

?

?

4.04

?

?

3.21

7.25

Table 2.4 FOUNDATION DESIGN AND LOADING HEIGHT ABOVE GROUND

WIND SPEED Km / hr

MAX VERTICAL (KIPS)

MAX UPLIFT (KIPS)

MAX SHEAR/LEG (KIPS)

TOTAL SHEAR (KIPS)

AXIAL (KIPS)

30 m

145

23.0

19.0

2.12

3.50

2.34

24 m

145

22.0

18.2

1.92

3.42

2.09

18 m

145

17.0

14.7

1.40

2.50

1.82

12 m

145

24.1

22.4

1.73

3.30

1.52

Below 145 ms -1 wind speed; shear, vertical and uplift forces are negligible. All foundation designs shall be in accordance with maximum reaction loads indicated above. Modification of loading locations and equipment can be made provided reaction loads do not exceed indicated values. 43

Design Data of a Fifteen Section Medium Duty Self-Supporting Tower Table 2.5 SELF-SUPPORTING TOWER SCHEDULE Section Number 1

Spread Dimension Upper Lower 46 cm 46 cm

Tower Legs**

Tower Braces

Bolts

36 KSI Yield STR

36 KSI YIELD STR

A 325 GRADE

5.0 cm2

3.2cm x 3.2cm x 0.5cm

10 mm

2

3.2cm x 3.2cm x 0.5cm 3.2cm x 3.2cm x 0.5cm 3.8cm x 3.8cm x 0.5cm

10 mm 10 mm 10 mm

3.8cm 3.8cm 4.4cm 4.4cm 4.4cm

10 10 12 12 12

2 3 4

46 cm 46 cm 76 cm

46 cm 76 cm 1.04 m

5.0 cm 2 5.0 cm 5.75 cm2

5 6 7 8 9

1.04 m 1.32 m 1.6 m 1.88 m 2.16 m

1.32 m 1.6 m 1.88 m 2.16 m 2.43 m

5.75 cm 5.75 cm2 9.30 cm2 9.30 cm2 9.30 cm2

10 11 12

2.43 m 2.72 m 3.0 m

2.72 m 3.0 m 3.27 m

10.8 cm2 10.8 cm2 10.8 cm2

5cm x 5cm x 0.5cm 5cm x 5cm x 0.5cm 5cm x 5cm x 0.5cm

12 mm 12 mm 12 mm

13 14 15

3.27 m 3.56 m 3.84 m

3.56 m 3.84 m 4.11 m

16 cm2 16 cm2 16 cm2

6.4cm x 6.4cm x 0.5cm 6.4cm x 6.4cm x 0.5cm 6.4cm x 6.4cm x 0.5cm

16 mm 16 mm 16 mm

2

x x x x x

3.8cm 3.8cm 4.4cm 4.4cm 4.4cm

x x x x x

0.5cm 0.5cm 0.5cm 0.5cm 0.5cm

mm mm mm mm mm

Table 2.6 SECTION HEIGHTS AND WEIGHTS Section Number 1

Height

Legs

Braces

Brace Plates

Total

3.0 m

36 Kg

25 Kg

N/A

65 Kg

2

3.0 m

36 Kg

25 Kg

N/A

65 Kg

3

3.0 m

36 Kg

29 Kg

N/A

70 Kg

4

3.0 m

40 Kg

57 Kg

N/A

102 Kg

5

3.0 m

40 Kg

67 Kg

N/A

112 Kg

6

3.0 m

40 Kg

78 Kg

N/A

127 Kg

7

3.0 m

65 Kg

79 Kg

N/A

153 Kg

8

3.0 m

65 Kg

88 Kg

N/A

162 Kg

9

3.0 m

65 Kg

98 kg

N/A

171 Kg

10

3.0 m

76 Kg

123 Kg

8.0 Kg

216 Kg

11

3.0 m

76 Kg

134 Kg

8.0 Kg

227 Kg

12

3.0 m

76 Kg

145 Kg

8.0 Kg

246 Kg

13

3.0 m

111 Kg

148 Kg

12.7 Kg

288 Kg

14

3.0 m

111 Kg

156 Kg

12.7 Kg

296 Kg

15

3.0 m

111 Kg

166 Kg

12.7 Kg

306 Kg 44

Table 2.7 SUPERSTRUCTURE DESIGN AND LOADING HEIGHT

45 m

39 m

33 m

27 m

21 m

15 m

ALLOWABLE DEAD WIND SPEED WEIGHT PER LEVEL

MAX COAX QTY/SIZE

KPH

KGS.

110

135

3 / 22 mm

125

135

145

MAX COAX 9m BELOW QTY/SIZE

WIND LOAD TOP (SQ. M)

WIND LOAD 9m BELOW TOP (SQ. M)

FLAT

ROUND

FLAT

ROUND

3 / 22 mm

2.09

3.14

3.07

4.60

3 / 22 mm

3 / 22 mm

1.40

2.09

2.42

3.62

135

3 / 22 mm

3 / 22 mm

0.37

0.56

0.56

0.84

110

205

3 / 22 mm

3 / 22 mm

2.14

3.21

3.16

4.74

125

205

3 / 22 mm

3 / 22 mm

1.58

2.37

2.60

3.90

145

205

3 / 22 mm

3 / 22 mm

1.02

1.53

1.30

1.95

110

270

6 / 22 mm

6 / 22 mm

2.23

3.34

4.09

6.13

125

270

6 / 22 mm

6 / 22 mm

1.58

2.37

3.25

4.88

145

270

6 / 22 mm

6 / 22 mm

1.20

1.81

2.32

3.48

110

360

6 / 22 mm

6 / 22 mm

2.23

3.34

4.09

6.13

125

360

6 / 22 mm

6 / 22 mm

1.53

2.30

3.25

4.88

145

360

6 / 22 mm

6 / 22 mm

1.02

1.53

2.32

3.48

110

400

9 / 22 mm

?

2.14

3.21

?

?

125

400

9 / 22 mm

?

1.95

2.93

?

?

145

400

9 / 22 mm

?

1.72

2.58

?

?

110

400

9 / 22 mm

?

2.14

3.21

?

?

125

400

9 / 22 mm

?

1.49

2.23

?

?

145

400

9 / 22 mm

?

1.11

1.62

?

?

45

Table 2.8 TOWER FOUNDATION DESIGN & LOADING

TOWER HEIGHT

WIND SPEED

MAX VERTICAL

MAX UPLIFT

MAX SHEAR/LEG

TOTAL SHEAR

AXIAL

KPH

(KIPS)

(KIPS)

(KIPS)

(KIPS)

(KIPS)

145

63.13

48.14

6.9

13.54

7.5

40 m

145

51

40

5.1

10

5.39

35 m

145

40

33

4.45

7

4.27

30 m

145

29.21

24.21

2.92

4.68

3.97

25 m

145

17.29

14.02

1.79

2.65

2.53

145

15.94

12.9

1.73

2.6

2.14

45 m

20 m

Below 145 ms -1 wind speed; shear, vertical and uplift forces are negligible. All foundation designs shall be in accordance with maximum reaction loads indicated above. Modification of loading locations and equipment can be made provided reaction loads do not exceed indicated values. Table 2.9 Footing Assembly Weight Table Weight (Kg/m)

Weight x 12 (Kg/m)

43

17.16

1.43 1.43

17.16 17.16

2.23

26.76

2.40 2.40 1.61

28.8 28.8 19.32

3.06 3.02

36.72 36.24

46

Table 2.10 Lap Link Weight Table Weight (Kg/m)

Weight x 3 (Kg/m)

55.63

166.89

58.01

174.03

62.63

187.89

65.55

196.65

Table 2.11 STRUCTURAL DESIGN DATA FOR A TYPICAL LATTICE TOWER Section 1 2 3 4 5 6 7 8 9 10 11 12 13

• • • • • • •

80 meter Tower (Pipe) Configuration Height Leg Size (cm) Brace m Grade A500 steel Configuration Size (mm) 6 20 Schedule 80 Double Angle A 90 x 80 12 20 Schedule 80 Double Angle A 90 x 80 18 20 Schedule 80 Single 2x 100 x 100 x 4 24 20 Schedule 80 Single 2x 100 x 100 x 4 30 15 Schedule 80 Single 2x 100 x 100 x 4 36 15 Schedule 80 Single 2x 100 x 100 x 4 42 13 Schedule 80 Single 3x 75 x 75 x 1.5 48 13 Schedule 80 Single 3x 75 x 75 x 1.5 54 13 Schedule 80 Single 3x 60 x 60 x 6 60 8 Schedule 80 Single 3x 60 x 60 x 6 66 8 Schedule 80 Single 4x 60 x 60 x 6 72 6.5 Schedule 80 Single 4x 50 x 50 x 5 80 6.5 Schedule 80 Single 3x 50 x 50 x 5

All brace connections shall be bolted and provided with locking pal nuts. Sections are in typical 6 meter lengths Leg strength minimum 46 KSI yield. Max Share/Leg: 40.11 KIPS Max Uplift: 288.26 KIPS Max Compression: 345.76 KIPS Design Wind Speed is 120 Km hr-1

47

Table 2.12 STRUCTURAL DESIGN DATA FOR A TYPICAL LATTICE TOWER 100 metre Configuration Lattice Tower Section

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Height ( m)

Leg Thickness (cm) 50 KSI

6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96

16 16 16 16 13 13 13 13 10 10 9 7.5 7.5 5 5 5

Brace Bolt Size Diag. Config. (2) 20mm Double A (2) 20mm Double A (2) 20mm Double A (2) 20mm Double A 22mm Single 2A 22mm Single 2A 22mm Single 2A 22mm Single 2A 22mm Single 2A 20mm Single 2A 20mm Single 3A 20mm Single 3A 20mm Single 3A 16mm Single 4X 16mm Single 5X 16mm Single 1X

Redundant Size (mm) Size (cm) 90 x 75 x 6 6 x 6 x 60 90 x 75 x 6 6 x 6 x 60 90 x 75 x 6 6 x 6 x 60 90 x 75 x 6 6 x 6 x 60 10 x 10 x 6 6 x 6 x 60 10 x 10 x 6 6 x 6 x 60 10 x 10 x 6 6 x 6 x 60 75 x 75 x 8 6 x 6 x 60 75 x 75 x 8 6 x 6 x 60 75 x 75 x 8 6 x 6 x 60 75 x 75 x 8 6 x 6 x 60 60 x 60 x 600 6 x 6 x 60 60 x 60 x 600 6 x 6 x 60 50 x 50 x 6 25 SOLID 25 SOLID -

BRACE

1 2 3 4

• • • • • • • • •

6 12 18 24

Internal Traingle 75 x 75 x 6 75 x 75 x 6 75 x 75 x 6 75 x 75 x 6

Sections are in typical 6 metre lengths All brace connections shall be bolted and provided with locking pal nuts. All X-Braces shall be center bolted. Structure is designed for a maximum wind speed of 160 Km hr-1 Total structure design weight (unloaded) is 38,000 Kgs Maximum design shear / Leg is 80 KIPS Total shear at the Base is 155 KIPS Maximum design uplift is 627 KIPS Maximum design Compression is 733 KIPS

48

Monopole Tower – Structural Form Platform

Platform Height Section 1

d

d

Section 2

d

d – section overlap

d

Section 3

Height

d

d

Section 4

d

d Section Height

Section 5

Base Plate Figure 2.14 Sections fit into each other with an overlap (d). Base diameter, section height, depth of overlap between sections and total mast height are all structural stability issues determined by the structural design engineer. For higher towers, additional sections are added below section 5 until the required height is reached but there must be corresponding increases in base width as the number of sections and consequently the height increases.

49

Table 2.13

Design details of a four section, 45 meter Monopole (Typical) Section

Length (m) Number of Sides Thickness (mm) Lap splice / section overlap (m) Top Dia (cm) Bottom Dia (cm) Grade of Steel Weight (Kg) Material Strength

4 13.7 18 10 106 130 8.4 80 ksi

3 2 12 12 18 18 8 6.5 1.7 1.45 80 75 110 93 A572-65 5.3 3.5 80 ksi 65 ksi

1 11.2 18 5.5 1.14 56 75 2.3 65 ksi

Tower above is designed for a 100 Km hr-1 basic wind

50

Antenna carrying Monopole (Self Supporting)

Figure 2.15 Pictorial of a self-supporting monopole tower fully fitted with antenna support bracket and carrying antennas

51

Section of a Typical Guyed three-legged Mast (Single or Z-bracing)

A – Face Width (uniform throughout the mast) B – Vertical brace height C - Bolt spacing D – Steel member width E – Section height

The design of a guyed mast must be such that it is very straight, easily connected and erector-friendly. Figure 2.16

52

N-section Guyed Pole Mast Triangular guy wire support

Antenna support and outrigger

1

2H

Turn buckles for Guy wire tension fine tuning

1

4

H

Base Plate

Base Plate

Figure 2.17 A four section guyed monopole illustrating the relationship between tower height (H) and the horizontal distance from tower base to the guy anchor (1/4 H). Tower can be installed in many sections. This design of masts is ideal for the installation of HF-SSB dipole antennas.

53

Triangular Guy Wire support Fits into the top portion of the Mast

Galvanised stake for attachment of buckles Used for Guy tension fine tuning

Figure 2.18 Details of parts of the guyed pole mast in figure 2.17 above

54

Figure 2.19 Shows in detail, the antenna support outrigger shown in figure 2.17 above.

55

Roof Mounts - Pictorial

Figure 2.20 Different ways of implementing roof mounts showing acceptable installation standards that guarantee safety. 56

Figure 2.21 Examples of Non-Penetrating Roof Mounts These can be implemented where possible with mass or reinforced concrete bases.

Figure 2.22 Penetrating Roof Mounts showing acceptable craftsmanship

57

2.4 Painting All skeleton type structures must be painted to ICAO stipulations on obstruction painting. ICAO stipulates that • For structures up to 212 meters, the structure shall be given seven equal bands of red and white paint or orange and white paint. • For structures above 212 metres nine bands of paint in alternating red and white or red and orange. • In all cases the top and bottom of mast or tower must be painted red or orange. • Paint shall be non gloss finish (matt). In addition mast and towers shall be painted with base primer paint, one suitable under coat of red and white or orange and white followed by two coats of non gloss (matt) paint. 2.5 Obstruction Lighting All mast and tower structures in Nigeria must conform strictly to ICAO / NAMA regulations with respect to obstruction lighting of tall structures as follows: • For every fifty meters of height above ground level, a tower shall have installed on it, one lamp on top and two lamps at the sides. • Obstruction lamps shall be fitted and shall be maintained in a working condition at all times on all structures within 15 kilometers of an airport or helipad. • Light intensity and colour as follows: Tower Height

Light Intensity

Light Colour

Below 45 m

not below 10 candelas

Red and fixed

Betw 45 and 150m

not below 1600 candelas

Red and flashing

Greater than 150m

4,000 to 20,000 candelas

White Flashing

58

NAMA / ICAO Lighting Regulation 105 - 150 m

Single light

45 - 107 m

Double lights 0 - 45 m

Figure 2.23 Schamatic representation of the ICAO / NAMA obstruction lighting regulations. 2.6 Substructure Foundations for the tower and mast structures shall be designed to withstand the full expected dynamic loads - antennae, feeders, wind loading, etc. It shall take cognisance of the complete findings of the site conditions (geotechnical investigation of soils and wind conditions). This may call for different types of foundation which may take the form of reinforced concrete blocks, standard pad and column, raft, preset rock anchors or piles. Engineers must compute the weight of tower structure, weight of antenna feeders and all associated steel work then calculate effects of wind loads on total surface.

59

Constructional materials and installation methods must conform to the conditions prevalent at the site. Worst case load design condition shall always constitute the initial factor of safety against overturning for complete foundations or any part thereof. Standard foundation designs are to be made for normal soils. They may be modified to suit the soil conditions at the installation site. Soil investigations must be carried out at each site to determine the bearing pressures (vertical and horizontal) and other subsurface conditions. The final foundation design shall be made to suit the soil conditions at the site. Normal soils are defined as dry cohesive soils having a) an allowable net vertical bearing capacity 192kPa b) an allowable net horizontal pressure 63kPa per linear meter of depth to a maximum of 192kPa. c) unit weight of compacted soil greater than 16kNm -3 d) water table is at a depth greater than 2.5m below the surface e) f) g) h)

coefficient of passive earth pressure greater than 3.2 coefficient of active earth pressure of approximately 0.3 non acidic properties no organic materials are present in the soil

Three basic physical forces shall be taken into consideration whilst designing tower and masts foundations. They are: a. Vertical down load b. Base shear c. Uplift load Proper soil borings shall be made by competent soil testing specialists and they must go deeper than the probable depth of the foundation to make sure of soil type consistency a little deeper.

60

For guyed towers, borings are also to be taken at all guy locations and at the base pier location. Conditions can vary widely on the site. Watch out that the concrete mix specified by engineer is adhered to. 2.6.1 Foundations and Anchors Foundations and Anchors shall be designed to support the structures and specified loads for specific soil conditions. Pile, raft or specially designed foundations or anchors are to be considered in submerged, marshy or peat soil conditions. Foundation designs shall be made and certified by qualified and registered professional engineers. 2.6.2 Standard Foundation Standard foundations and anchors may be used for construction when actual soil parameters equal or exceed normal soft parameters. Geotechnical investigation to verify that actual site soil parameters equal or exceed normal soil parameters must be made before standard foundations and anchors are utilized in final designs. Foundations and anchors shall be designed for the maximum structure reactions resulting from the anticipated worst loading conditions. When nonstandard foundations and anchors are to be used for construction, the soil parameters recommended by the geotechnical engineer should incorporate a minimum safety factor of 2.0 against ultimate soil strength. 2.6.3 Rock Anchors Rock anchors shall be of type to permit long life and shall be treated against corrosion to last over the design life of the tower. Pre-stressed rock anchors are to have their upper terminating steel work in such a way as to have a steel-tosteel connection between the structure footing and the rock anchor tendon. The upper end termination of rock anchors shall not be encased in concrete but shall be protected against corrosion so as to allow any subsequent checking of the tension in the tendons during the life of the structure. 2.6.4 Anchor Bolts Template Templates provide proper anchor bolt orientation at the time of foundation forming. Templates shall be precisely fabricate and used in constructing tower foundations to design specifications. Use of templates eliminates problems associated with misalignment. A minimum of two anchor stirrups shall be 61

provided around each leg of a tower. Each stripe shall have a safe working load (SWL) of 100KN. 2.6.5 Uplift Anchors are to be dimensioned to provide sufficient safety against overturning. A qualified geotechnical engineer shall design foundations especially when they are to be sited in non-standard soils and the application of prototype designs for normal soils becomes undesirable. Standard foundations, anchors, or drilled and buried piers shall be assumed to resist uplift forces by their own weight plus the weight of earth enclosed within an inverted pyramid or cone whose sides form an angle of 300 with the vertical. The base of the cone shall be the base of the foundation if an undercut or toe is present or the top of the foundation base in the absence of the foundation undercut. Earth shall be considered to weigh 16kN/m3 and concrete 24kN/m3. Straight shaft drilled piers for standard foundations shall have an ultimate skin friction of 31 kPa per linear meter of depth to a maximum of 48kPa of shaft surface area for uplift or download resistance. Nonstandard foundations, anchors, and drilled piers shall be designed in accordance with the recommendations of a geotechnical report. A mat or slab foundation for a self-supporting structure shall have a minimum safety factor against overturning of 1.5. The effects of the presence of water shall be taken into account in the design of nonstandard foundations. Reduction in the weight of materials due to buoyancy and the effect on soil properties under submerged conditions shall be considered. 2.6.6 Concreting Loose material shall be removed from bottom of excavation and the sides of excavation shall be rough and free of loose cuttings before concrete placement. Concrete shall be placed in such a way that will prevent segregation of concrete material and any occurrence that may decrease the strength or durability of the foundation. Concrete placement shall be continuous. No construction joints shall be allowed. Weight of concrete mixture shall be 24kNm -3. Concrete mixture must be such as to enable the concrete develop a minimum compressive strength of 30Nm-2 in 28 days. Reinforcement steel shall be grade 50 deformed bars and shall be covered with concrete overlay of a minimum thickness of 75mm. Spacers shall be used to achieve this minimum cover on 62

reinforcement. Concrete should always be thoroughly mixed prior to putting in place, and any water which, seeps into excavation should be removed prior to placing concrete. A concrete vibration machine must be used until all concrete is in place. The concrete column of foundation must always be installed inside wood or steel formwork and left in place for 24 hours before removing. When the formwork is removed concrete must be kept wet for first seven days of drying in the south of the country whilst a ten-day period is recommended for the north. Aggregate size shall be 20mm. Mechanical vibration shall be used in making concrete so as to eliminate honeycombs and voids. Welding and splicing is prohibited on reinforcement steel and embodiments. Concrete curing time should be 28 days. The surface level of mast foundation, guy anchor and tower foundation blocks shall be between 150mm and 300mm above the highest point of the existing ground level. When separate blocks of foundation for each leg of tower are employed, the upper surface of each must be at the same level. The upper surfaces of all foundations are to be given a gentle slope to ensure water run off. They are to be painted further with bituminous paint to avoid dampness around the foundation bolts, sole plates and guy attachment steel works. All loose materials are to be removed from the excavation before placement of concrete. A curing time of four weeks (28 days) is to be allowed before erection of steel on the concrete base. Structural backfill shall be compacted in 225mm maximum layers to 95% of maximum dry density at optimum moisture content. It must have a minimum compacted weight of 1.6kNm -3. Top of the foundation shall be sloped to drain with a floated finish. Exposed edges of the concrete shall be chamfered. If power cables, feeders, grounding tape must pass through concrete base, appropriately sized diameter plastic or asbestos pipe shall be imbedded in concrete works. Where land for structure is limited, grounding tapes and rods may be placed below or to the side of foundation.

63

2.6.7 Raft Foundation The dimensions of the raft are to be chosen so that the pressure distribution under maximum design loads will be such that tensile forces will not develop under a significant part of the raft area. Raft foundations shall be designed by certified foundation engineers using geotechnical data for the site. A name plate giving details of the designer and the builder shall be placed in conspicuous location at the tower base. 2.6.8 Piles In swamps and peat soils, pile foundations are recommended in order to overcome catastrophic effects of uneven settlement in other types of foundation. Pile foundations shall be designed by certified foundation engineers using geotechnical data for the site. A name plate giving details of the designer and the builder shall be placed in conspicuous location at the tower base. 2.6.9 Drilled foundations Foundations can be drilled in any type of soil formation. In normal soils it is a straightforward and easy task. Drill the hole. Drop in a pre-wired rebar cage. Place the concrete with a pump tube. The roughness of the sides of the hole provides the necessary resistance against pullout. For sandy soils, it is a little more tricky. The hole will usually cave in as its being drilled. A casing can be used and pulled out as the concrete is placed so the concrete is in contact with the sides of the hole. Or drilling slurry could be used. The hole is kept filled with "mud". As the concrete is pumped into the bottom of the hole, the mud is pumped out at the top. The concrete likewise makes intimate contact with the soil and the foundation provides the support that the engineering calls for. 2.6.10 Reinforcement Main reinforcement bars shall have a minimum concrete cover of 75mm. Sufficient auxiliary reinforcement shall be included to minimize the occurrence of cracking whilst the integrity of the foundation remains intact. Reinforcement in block type foundations shall be such as to ensure that the total weight of concrete can be fully utilized to give the specified resistance to uplift forces. 64

2.6.11 Factors of safety The factors of safety of the complete foundations and any component thereof against overturning shall be made for the worst design load condition. In the case of guy anchor blocks, a safety factor of 2 shall be applied to the maximum design guy tension. In calculating the resistance to shear (for the foundation only) the friction between the bottom face of the concrete and the soil shall be taken into account. In the case of guy anchor blocks, the earth resistance in the direction of the horizontal force may be assumed to be utilized, in which case the soil shall be checked against the possibility of shear-friction failure. The soil surrounding the foundation shall not be included in the calculation of resistance to uplift and overturning. 2.6.12 Foundation Drawings Foundation drawings shall indicate structure reactions, material strengths, dimensions, reinforcing steel and embedded anchorage material type, size and location. Foundations designed for normal soil conditions shall be so noted. Every foundation design shall include site soil data as a footnote.

Typical Guy Anchor footing

Typical footing of self support Tower (K – Bracing)

Figure 2.24 65

Foundation design for Self- Supporting Post Mast Infill between base and plate (concrete or epoxy)

Base Plate Studding

4 no. studding assembly are used on a post mast

Levelling nut Retaining plate

Y

X

Dimensions of X and Y are dependent on soil conditions, dead weight of mast and wind loading .Square and level shuttering .Template laid across shuttering .Studding fitted .Infill of concrete

Figure 2.25

66

SECTION VIEWS – SHOWING SUBSTRUCTURE ARRANGEMENT (Raft Foundation) X1 X

A

Horizontal Ties X4

X3

Vertical Bars A

FOUNDATION PLAN

D2

Ground Level

D1

Horizontal Ties Vertical Bars Foundation stub leg

D

L

Tower Base

1"-3"

SECTION THROUGH FOUNDATION

Figure 2.26 This foundation type can be used for all types of towers. It is applied for individual legs for a three or four legged structure. Type of soil and the overall dynamic loading determine the dimensions. These shall be determined for each particular site by the geotechnical engineer. 67

BASIC RAFT FOUNDATION DESIGN FOR TOWERS

X

Center of pad and Tower

A

A

½X X

Plan View 19mm chamfer on 4 sides

Horizontal Levelling Brace Short Base Section

Adequate projection of leg above concrete top to enusre good clearance for bottom Y tower brace attachment

Bar Clearance

Y-z

Horizontal bars, spaced according to engineer's design

Section AA

Figure 2.27 All dimensions, reinforcement steel sizes and quantities shall be according to the engineer’s design which will be dependent on the soil characteristics, dead loading of mast, its height and worst case calculated wind loading

68

Traditionally reinforced concrete is the choice option for tower guy anchors. A concrete block, in the size determined by the design engineer, is placed against undisturbed earth to hold the guys. Construction involves digging, forming and pouring the concrete, then backfilling and tamping. The equipment required includes backhoes, forming equipment and concrete mixers, etc. Floor mat

Steel reinforcement for Tower leg Completed tower footing showing leveling bolts

Figure 2.28A

Figure 2.28B

Construction of raft foundation for a Tower in a sandy soil

69

Basic Foundation Design - Four Legged Tower Projection above concrete base Levelling nuts Lock nuts Studding (4 No. on each leg) Y

Z

X

SECTION Stud holes

Anchor Plates

X2(All sides)

Studding Details

X1 (All sides)

Mild Steel Base Plate

Figure 2.29 Design for light weight mast in normal soil Foundation design for one leg in a three or four legged tower configuration. This is a galvanised steel tower socket base for installation on a concrete foundation. Each corner of the base is provided with a clearance hole for studs that provide a leveling method. Typical values for a lightweight tower in a normal soil are as follows: Concrete Depth

1.2 meter

Concrete Width

1.8 meter

Face Width

0.65 meter

Base Width

1. meter

70

Drilled Pier Foundation Design for Towers in Swamps (Three Legged)

32' - 6"

Braced anchor bolts

A

16'-3"

A

A 9' - 4 9/16"

A

60o 60o 60°

60°

Tower Center 18' - 9 1/18"

120°

120o Tower Leg Base Plate A

Double Nut

Drilled Pier Form Top. Drilled Pier with galvanised sheet metal

Non shrink grout

Anchor bolt projection 135

Drain plate

33" - 0"MINIMUM

A

BASE DETAIL

FOUNDATION PLAN

SECTION A - A .

Figure 2.30 Plan of a typical foundation type for unconsolidated soils. All dimensions are to be specified by a geotechnical engineer and are strictly dependent on the site soil characteristics, expected maximum dynamic loads, shear stress, uplift and compression.

71

Typical Micropile in an unconsolidated Formation

Helical screw pile Helical pier extension shaft

Single or multi helix Lead section with bearing plates

Figure 2.31 Section of drilled Pier Foundation 72

Typical Anchor Assembly This is easily deployed in unconsolidated formations for guy anchors, in drilled pier and micro-pile foundations. They exist in a lot of configurations. Lengths can be varied according to the soil characteristics. Lengths are increased by the use of extensions.

Extension

Forged Couplings

Helical Extension

Lead Section

Figure 2.32: TYPICAL ANCHOR ASSEMBLY

73

Figure 2.33 Typical Pier and Pad foundation construction

Tower Base

Guy stay blocks Figure 2.34 Completed Guyed Tower foundation site 74

Basic Foundation Design for a Three legged slim lattice Mast Ground Level

W

Y

Expansion fillet A393 wire mesh to side faces Nominal Cover to all faces

X

Section View X X/2

X/2

W – Lattice face width at the base X – Foundation dimension (square)

X/2 X X/2

Plan View Figure 2.35 All dimensions are to be specified by a geotechnical engineer and are strictly dependent on the site soil characteristics, expected maximum dynamic loads, shear stress, uplift and compression.

75

C

L

Tower axis and centre pad

L

C

A

A

Square (W)

PLAN VIEW Tower section Grade

Y

d1

d

#7 Steel bars

Drainage bed of compacted gravel and sand ELEVATION VIEW - section AA

Figure 2.36 Tower Foundation using micropiles

All dimensions are to be specified by a geotechnical engineer and are strictly dependent on the site soil characteristics, expected maximum dynamic loads, shear stress, uplift and compression. Typical values in normal soil for a 45 meter light weight steel tower are: Concrete Depth Concrete Width Face Width Base Width

1.2 meters 1.8 meters 0.57 meters 1.0 meters

This design does not give room for leveling after concrete has been poured

76

Foundation Design for a Self –Support Monopole Tower Section

Plan

Design basic wind speed is 100 Km hr -1 Plate thickness is 6 Plate grade is A36. Anchor Bolt Grade is A325 X. Yield Strength is 4 ksi. Bolt Length is a minimum of 1meter. Base Plate outer diam is 1.5 m Base plate inner diam is 1.1 m

Figure 2.37 Dimensions given above vary with the peculiarities of the monopole and the soil

77

2.6.13 Foundation in Swamps Guyed tower erection in swamps can be performed more quickly, more efficiently and less expensively with modified construction techniques and an alternative method for anchoring. One alternative method is the ‘simple marsh anchor’ method. This technology uses square rods with screw helices at one meter intervals on the initial three to six meter length. These rods are then screwed into the ground with one, two, or three meter extensions being added until the proper depth and torque are reached. This method is analogous to driving in earth rods into the earth except that here, hydraulic screwing is used. The torque and final depth are determined by the soil and by the pulling strength required. Each anchor is then topped with an eye to attach one guy wire. Using screw anchors requires only the availability of an auger machine to screw the anchors into the ground. No digging of holes, forming, and pouring concrete for the guy anchor is required. With this method, just one anchor per guy wire would do. The anchors are simply screwed into the ground until a layer of earth is encountered that is resistant enough to achieve the required installation torque. Anchors could be screwed into the ground for a few hundred meters. The depth could be shortened considerably by using multiple anchors with load-distributing linkages. This method has unique advantage of ease of adding extensions or additional anchors at a later date, should guy wire capacity need to be increased for additional load requirements or for the addition of torque arms. The only concrete needed is for the tower base foundation. 2.7 Earthing and Lightning Protection All masts shall be grounded. The earth resistance measured at the earth terminal block shall be less than 2 ohms. A lightning air terminal (Faraday Rod) shall be mounted on mast top and a vertical copper earth wire or tape run down the side of one mast leg to ground and connected to the earth at the terminal box. The most important in getting a good earth is the use of right and good quality materials for installation. 78

Tapered Base, Guyed Tower - Grounding

Twin Lightning rod connection

Guyed Tower Leg Grounding

Leg grounding for self-support Tower

ALTERNATE WAYS OF GROUNDING AT GUY - ANCHORS

79

Figure 2.38 Earthing and lightning protection methods

Tower Leg Earth

TOWER FOUNDATION AND LEGS

Equipment Room

2

1

1

Antenna Cable Bulkhead separately earthed to Tower

2

Other Equipment Earth bonded to Tower

Earth Bar Earth Tape - Copper Buried Earth Rods

TOWER EARTHING DESIGN - TYPICAL 80

Figure 2.39

2.7.1 Earthing Earthing and Lightning protection shall be provided in all completed towers sites to protect equipment from damage and personnel from harm which may result from excessive voltages during a lighting strike. The arrangement shall be such that lightning discharge current must be prevented from entering equipment rooms. Equipotential conditions shall be maintained throughout the site by bonding. The resistance achievable in an earth installation is directly proportional to the resistivity of the soil at the depth to which the earth rod has been driven. When the soil resistivity of a site is not known it can be measured without excavation, by using a direct reading meter and earth spikes. It can also be read out from tables, such as Table 2.1 below, if soil type is accurately known. Resistivity at any depth is related to the diameter of the earth rod, the target resistance and the depth to which the earth electrode is driven into the soil by: R = (p / 275L) ×log 10 (400L / d) Where

R p L d

is the target resistance is the resistivity of the soil is the length of electrode in meters is the diameter of electrode in cm

An accurate assessment of the soil resistivity should be made around the tower base using a direct reading resistance meter to determine the appropriate depth to drive in the copper earth rods, the number of rods, the need for an earth mat, etc. Table 2.1 gives typical values which can be used for computation but shall not serve as a substitute for actual measured values.

81

Table 2.14 – Resistivity Values for different Soil Types Soil

Resistivity, ohm, cm

Marshy Ground Loam and Clay Chalk Sand Peat Sandy Gravel Rock

200 – 270 400 – 15,000 6,000 – 40,000 9,000 – 800,000 20,000 30,000 – 50,000 100,000

2.7.2 Construction of an Earth Lightning rod is clamped to the highest point on the mast. Ground wire is connected to the lightning rod and shall, most desirably, be one continuous piece all the way to the earth ground rod. Sometimes, the antenna type may not permit the use of a lightning rod point. In such cases, the ground wire shall be taped or wire-tied to the mast as far up as practical. Ground wire shall run from the tip of the mast, be connected to the tower, and then run all the way to the ground. Copper bond earth rods made up of copper electrolytically bonded onto a high tensile steel core shall be driven into the ground at varying depths dictated by earth resistivity measurements. Several lengths of the rod may have to be so driven in. Each length is coupled to the next through coupling threads. The rod is driven in by hammering on the driving high tensile steel head. Each leg of a mast or tower shall have at least one earth rod driven into the ground beside it. The leg of the mast is tied to the earth rod through a flat copper tape. The number of earth rods to be driven into the ground at the optimum depth shall be such that is necessary to achieve a suitably low resistance. Where a good grounding cannot be obtained at a reasonable depth, a three meter pit should be dug and partly filled with layers of carbon, salt and manure and backfilled firmly. The maximum permissible resistance to earth is 2 ohms. 82

2.7.3 Protective Grounding Structures shall be directly grounded to a primary ground. A minimum ground shall consist of two, 1.2 meter long, 16 mm diameter galvanized steel ground rods driven not less than 2.4 meters into the ground, 180° apart, adjacent to the structure base. The ground rods shall be bonded with a lead of not smaller than 5 mm tinned bare copper connected to the metal base of the structure of each leg of a tower. A similar ground rod shall be installed at each guy anchor and connected to each guy at the anchor in case of guyed towers. Self-supporting towers exceeding 1.5 m in base width shall have one ground rod per tower leg. All the earth rods shall be tied together to maintain an equipotential all over the structure. Top ground strap are to be bonded at both ends. Bottom ground strap are also to be bonded at both ends. All equipment on a structure (antennas, antenna supports, warning safety lights, etc) shall be connected by a secondary ground. The earth of the tower shall be bonded to the general earth of any adjoining equipment room and all shall form a single earth. The maximum permissible resistance to earth is 2 ohms. 2.7.4 Lightning Protection Separate down conductors shall be installed from each air terminal (lightning spike). In addition, the structure shall also be a return path to the earth. These two systems shall to be bonded together. Lightning spikes should be long enough to give 45 0 cone of protection over all aerials. Air terminations are to be copper rod, hard or medium – hard drawn, Air Terminal – Lightning Spike 12mm in diameter. Down conductors shall be Figure 2.40 made from 25mm by 3mm soft annealed copper strip. The earth termination shall be independent of the foundation reinforcement. When rods are used as earth electrodes these should be driven into the ground 83

to a depth of at least 2.4m in normal soil or the depth predetermined for the site from measurements. Longer lengths should, when necessary, be built up of 1.2m lengths screwed onto each other with internal screw and socket joints. If one earth electrode cannot obtain the specified resistance, additional electrodes should be connected in parallel. Such additional electrodes may be those provided for other down conductors. The distance between any two driven electrodes should be about equal to their driven length. All connections between earth conductors and steelwork shall be via sacrificial legs or brackets where copper would be in contact with concrete. It shall be painted with bitumen or separated from the concrete with itemized paper. Earth conductor runs shall be straight as far as is practicable. Any bends that may be unavoidable shall be smooth and of maximum radius. The resistance to ground of the earth system shall be below 2 ohms. 2.8 Safety Devices Safety devices shall be installed on every tower above 45 meters high. Of importance are the fall arrest systems, climbing ladders or step bolts, guard rails, work / test platforms, rest platforms and anti-climb systems. Fall Arrest Safety System

Figure 2.41 84

A complete fall arrest system consists of the rail and the trolley.

2.7.1 Trolley • • •

Locking brake pawl attaches to climber’s harness Moves freely along the Safety Rail with climber in normal climbing position In case of a slip trolley brakes remain locked until the force is removed

Falls are instantly arrested when a sudden downward motion is applied to the Trolley. Trolley remains stationary once disconnected from the harness.

Installed anywhere on the tower leg, and adaptable to most structures. It is to be fabricated from lightweight high tensile Aluminum Safety Rail 2.7.2 Anti Climb Shields Anti Climbs consist of metal sheets bolted to tower legs. They are constructed to prevent unauthorized persons from climbing a tower. It is ideal for tower sites around schools and public areas where public safety is a concern.

85

2.7.3 Climbing Facilities (a)

Access Ladders To be made from hot dip galvanized steel or aluminum sections. Mountable on all tower types and monopoles. Amenable to inside or outside mounting. Climbing Ladders shall be of steel or aluminum depending on tower material and shall be provided with the following: (a) (b) (c)

Safety cages Landing places – rest and work platforms Protective finishes

Ladders are to be attached to the tower structure. The lowest point on the ladder shall be at a height of 3m to 4.5m above ground level and it shall run all through to the top of the structure. The ladder shall be so located that a clearance of at least 150mm at the rear of the ladders exists between the ladder and the structure. Anti climbing devices shall be provided on the structure to prevent access except from the climbing ladder. The vertical separation between rest platforms shall be 20m. Work and test platforms shall be located at those points where antennas are to be installed. Platforms – Work / Rest / Test All platforms shall be readily accessible from the climbing ladder. The access to all platforms and walkways from the vertical climbing ladder shall be from one direction only. Platforms and walkways shall be designed to carry a point load of 150kg at any point without a deflection exceeding 6.0mm. Guard-rails These shall be of height between 0.9m and 1.1m and shall be provided on all platforms, stairways and horizontal members used as walkways. They shall have an intermediate rail at half this height and a toe board not less than 150mm high. The distance between any toe-board and the lowest guard – rail 86

above it shall not exceed 750mm. Widths of walk-ways and platforms should not be less than 650mm. Walk-ways and surface used as working platforms or traversed to gain access to platforms or traversed to gain access to working positions are to be provided with anti-slip surface. Guard rails and toe boards shall be attached at each vertical stanchion. They shall be secured to prevent rotation. Step Bolt They are climbing facilities ideally suited to fixing on monopoles.

Safety Enhancement Safety in the installation and use in service of masts and towers are enhance by the following practices which shall be mandatory on all tower owners and installers (1) (2) 3) (4) (5)

Tower assembly parts shall be standardized e.g. fasteners for the main structure should ideally be of only one size, length and material. Manually handing over of parts or tools between installers during tower erection is totally forbidden. All parts must be fully labeled especially where the method of assembling is not obvious. Towers must be structurally designed for simple assembly - ease of fit, elimination of small loose parts, etc. On-site welding and riveting is prohibited. All site connections shall be by bolt and nut with a means provided for locking the nut against loosening by vibration. All nuts bolts and washers shall be galvanized. Such galvanizing shall be done so as to permit the ready assembly of nuts and bolts after galvanizing. Taper washers shall be used whenever the steel section shape requires their use. Bolt lengths shall be such that with the locking device in place a 87

minimum of one complete thread shall protrude beyond the nut. Bolt threads shall protrude inside the structure only.

88

CHAPTER THREE

MATERIALS SPECIFICATIONS

89

3.1 The Superstructure 3.1.1 Members’ Sizes The sizes of members in compression shall be such that the maximum slenderness ratios are: Ladder Bracing members Subsiding members

120 150 180

No load-carrying angle shall be smaller than 50 x 50 x 6mm. The minimum thickness of gussets and similar plates on the main structure shall be 8mm. 3.1.2 Intersecting Bracings Where a gusset plate connects bracings that cross, at least one of the bracings shall be continuous between the main members to which it connects. Towers and Masts shall be manufactured from the following materials a) Steel with hot dip galvanized finish b) Stainless Steel with # 4 or # 7 finish c) Aluminum - polished, anodized and painted finish 3.1.3 Lattice Structures 1. Legs

- Tubular - Angular - Solid Round Leg 2. Members - Tubular pipes - Angles 3. Bracing - Angles - Tubular pipes - Steel rods 3.1.4 Monopole Structures 1. Sections - hollow, heavy duty, thick steel pipes 90

- hollow, heavy duty, flanged steel pipes 3.1.5 Guys 1. Wires 2. 3. 4. 5.

- Extra High Strength stainless steel or galvanised steel cable. Earth Screw Anchor – Galvanised steel or stainless steel. Thimble -- Galvanised steel or stainless steel. U-Bolt - Galvanised steel or stainless steel. Turnbuckle - Galvanised steel or stainless steel.

Both lattice and monopole structures shall be made from steel for tall, heavy load bearing towers or aluminum for lightweight light duty towers. Tower components shall be of the following classification: • All steel members shall be fabricated from Grade 50 or 42, A36 or A 57250. • All steel tubes shall be fabricated from Grade 43C. • All structural pipes shall be fabricated from Grade 42 or Grade C steel. • Anchor rods shall be fabricated from Grade B7 steel. • Rebar shall be fabricated from Grade 400 steel. • Diagonals shall be fabricated from Grade 43A steel. • Structural Bolts fabricated from Grade A325 steel. • Steel angles shall have a minimum strength of 56ksi for tower legs and 36ksi for tower members. • Round legs shall be fabricated from schedule 40 pipes. • Braces shall be fabricated from Grade A36 or A 572-50 steel 3.2 Concrete Ordinary cement shall be used. Cement of different types may not be mixed. High Alumina (HA) cement may not be used for concrete mixing. Additives that hasten the setting of cement or give a denser concrete shall not be used. All sand shall be clean, sharp, gritty, and free from loam earth, salt and other impurities like humic acids. Sand shall not contain more than 15% clay or silt. The sand shall contain grains from the finest sizes up to 4.75 mm. Grains smaller than 0.25 mm in size shall not constitute more than 15% of the total weight of the sand to be used.

91

Aggregate shall be clean screened river ballast gravel, graded in size and free from dirt, floury stone dust, loam or earth or any other impurities. The maximum size of aggregate to be used shall be 19 mm. Water to be used for concrete mixing shall be free from oil, salt, and organic substances. It shall be clear. Cement shall have a mixture of 1:2:4. The concrete shall be thoroughly mixed by machine. 3.3 Earthing and Lightning Protection Installation Materials Air Terminals shall be made from copper. Saddles (ridges, flat, light duty or heavy duty) shall be made from gunmetal or aluminum. Clamps shall be made from gunmetal or aluminum. Bi-metallic clamps shall be employed when joining aluminum earth rods to copper earth conductors. Earth bars shall be made from high conductivity copper. Copper Earth rods shall be made from: • High tensile steel core with copper film electrolytically bonded to it to a minimum thickness of 0.25mm. • Solid copper earth rods for extremely high corrosive environments U-bolts could be of copper but with gunmetal back plates. 3.4 Metals and Galvanising The following metals and alloys shall be used in tower fabrication, construction and for foundation reinforcement: • • • • • • •

Magnesium Zinc Aluminum Lead / Tin Brass / Copper / Bronze Silver Graphite

92

3.5 Earthing Clamps

Figure 3.1 Typical clamps for installation of earth tapes

3.6 U-Bolts

93

Multi-Point Air terminal

Elevation Rods

Mounting Brackets

Figure 3.2 Earth and lightning protection materials Rod to Tape Coupling

Building in Rod Holdfasts

94

3.7 Connector Clamps

Square Tape Clamp

Oblong Box Clamp/7

Figure 3.2 Installation Materials – Earthing and lightning protection

95

3.8 Screw down Clamp

Plate Type Clamp

Figure 3.3 Installation Materials – Earthing and lightning protection 96

3.9 Earth Bars and Disconnecting Links

Insulator

6-way disconnecting link

Wooden base disconnecting link

Disconnecting link channel Iron base

Inspection Housing

Figure 3.4 These materials are used for earthing installation to make testing easy 97

Figure 3.5 These materials are used for earthing installation to make testing easy Conductor inspection housing shall be installed at test points to protect the earth rod and earth connections and make them available for testing. It shall be made from high grade, heavy duty polypropylene and ultra violet stabilized to prevent degradation by sunlight. It shall be non-brittle.

98

3.10 Lightning Arrestor Installation Materials

Pointed Air Rod

Flat Saddle

Light Duty Saddle

Figure 3.6 Pointed Air rod and installation saddle 99

3.11 Copper Tapes – Can be Tin or lead covered Copper Tape

Flexible Copper braid

Figure 3.7 Flat Copper Tape and Flexible Copper Braid

100

3.12

Connectors Circular cable connector

Cable to Tape Junction Clamp

Cable To Cable Test Clamp

Figure 3.8 Cable connectors 101

3.13

Bi-Metallic Connectors

Metal Tape Clip

Non-Metallic Clips

Figure 3.9 Cable and Tape clips 102

3.14

Guy System Materials

Earth Screw Anchor

Turnbuckle

Guy Wire

Figure 3.10 Guy materials Guying materials shall conform to the sizes, mechanical strengths and capacities shown below in Tables 3.1 (1-4)

103

Table 3.1.1 Guying Cable Size & Grade Working Load Break Strength Wt. / 100 strands 3.5mm x 7 x 7 Galvanised Steel 154 Kg 771 Kg 1.27 Kg 10mm x 7 x 19 Galvanised Steel 1306 Kg 6532 Kg 1.10 Kg 8mm x 7 x 19 Stainless Steel(304) 245 Kg 1089 Kg 2.27 Kg 5mm x 7 x 19 304 Stainless Steel(304) 336 Kg 1678 Kg 4.10 Kg 6.5mm x 7 x 19 Stainless Steel(304) 581 Kg 2903 Kg 5.00 Kg

Table 3.1.2 Turnbuckles Working Load (Kg) Diameter & Take Up Unit Wt. (Kg) 750 10mm X 15cm 0.45 1,000 12.5mm X 22cm 0.9 1,500 15mm X 30cm 1.8 Turnbuckles shall be made from drop forged steel, be of hot dip galvanized Finish and have Eye and eye construction

Table 3.1.3 Earth Screw Anchors Helix Holding Power Unit Wt(Kg) Diameter in Normal Soil 75 cm 12.5 mm 10 cm 1,135 Kg. 3.2 120 cm 16 mm 15 cm 1,815 Kg. 5.5 173 cm 17.5 mm 20 cm 5,000 Kg. 12 12.5mm Link from earth anchor to turnbuckle. Hot dip galvanized finish.

Overall Length Rod Dial. In.

Table 3.1,4 U-Bolt Clips and Thimbles Description 3mm Galvanized Steel U-Bolt Clip 8mm Galvanized Steel U-Bolt Clip 6.5mm Galvanized Steel U-Bolt Clip 8mm Galvanized Steel U-Bolt Clip 10mm Galvanized Steel U-Bolt Clip 6.5mm Galvanized Heavy Duty Thimble 8mm Galvanized Heavy Duty Thimble 10mm Galvanized Heavy Duty Thimble

Kgs. Per 100 4.54 8.16 8.16 13.6 21.8 4.54 6.35 11.34

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3.2

Antenna Mounting Frames

Frames for mounting antennas on towers or masts shall be designed in sympathy with the type of tower structure, the type and weight and size of the antenna. They shall be made from galvanised steel, stainless steel or aluminum. There shall be no welded parts. All joints shall be implemented with bolts and nuts. Some basic designs exist for certain tower structural forms. A few are shown below.

Tower structure

Antenna Mount on Self-Support Tower

DETAIL B

A

A

Plan View Section View

Side Antenna Mount

105

Side Antenna Mount

SADDLE- BRACKET

106

Side Mount

Plan View Section View

Antenna Mount on Self-Support Tower

107

108

Antenna Mount on Self-Support Tower

Plan View Section View

109

metal clip

110

metal clip

metal clip

metal bracket

111

CHAPTER FOUR

MAINTENANCE AND TESTING

112

4.0

First Line Maintenance

In tower design, it is assumed that the worst case scenario is a total mechanical failure. This can be caused by stress, extreme overload, use of defective and poor quality materials, fatigue, corrosion, poor workmanship, insufficient maintenance, sabotage, as well as any combination of these factors. Every design must attempt to foresee all possible combinations of these that can occur in the installation environment and incorporate protective answers to them in the design. This is the first line of maintenance. 4.1

Hot Dip Galvanization

Unprotected steel can be seriously damaged due to environmental factors as rain, salty humid air and extremes of temperature. Corrosion transforms steel back to its natural state of iron, which is very fragile and can prove to be deadly in structures like towers which support heavy pressures. The best way to avoid this phenomenon is through a process called "hot dip galvanization". This process consists of dipping steel in melted zinc at 450°C. At this temperature iron and zinc share great affinity, and allow an alloy to form where pure zinc prevails to the outside. The final product is a steel surface protected with a zinc coating. Due to the difference of electrochemical potential between zinc and steel (cathodic protection), a zinc coating protects steel in such a way that slightly exposed surfaces due to cutting, scratching or piercing are equally protected against corrosion. What considerably affects the appearance and gauge of galvanization is the contents of alloy elements that are present in steel: carbon, magnesium, and silicon. The greatest effect is produced by silicon in concentrations higher than 0.12%. Most steels can be galvanized: high-strength steel, low-carbon steel, low-alloy steel, and steels with as much as 0.20% copper content; the most appropriate being low-carbon steels. 4.2

Tower Maintenance

Towers require regular maintenance. Regular maintenance is especially important for the purposes of public safety, network availability, environmental aesthetics and life time quality of the structures. Maintenance is as important to self supporting masts and towers as it is to 113

guyed masts. For masts and towers, maintenance is mandatorily preventive as any breakdown comes usually with catastrophic consequences. Maintenance and inspection of steel antenna towers and antenna supporting structures should be performed by the owner on a routine basis. Major inspections shall be performed, at a minimum, every 3 years for guyed towers and every 5 years for self-supporting towers. Ground and aerial procedures should be performed only by authorized personnel, experienced in climbing and tower adjustments. All structures shall be inspected after severe winds or other extreme loading conditions. Shorter inspection intervals of 2 years for guyed towers and three years for self supporting towers shall be obligatory for structures in coastal salt water environments, in corrosive atmospheres, and in areas subject to frequent vandalisation. At every tower site, the owner shall keep a maintenance log book in a thick cellophane folder. This folder shall be readily accessible to the regulators inspectors. It shall have the following information: • • • • • •

Installation Date Inspection due dates Painting due dates Minor Maintenance due dates Major Maintenance due dates Name and address of Inspector

For each of the due dates, the log must show whether the inspection or the maintenance was carried out and by whom. 4.3

Maintenance Philosophy

The external condition of Towers and Masts must be regularly inspected with intent to detect deterioration. Necessary maintenance works must be carried out timely. Periodic checks and inspection of the structure must be carried out: At regular intervals of time during the service life of the structure After the installation of an additional load like antennas on the structure After each serious climatic event like tempest, hurricane, tornado 114

The first thorough check of the structure should be carried out 6 months after its installation and erection. Maintenance checks should be carried out yearly henceforth 4.4

Routine Checks

4.4.1 Main structure Check that there are no structure components missing Check that bars are neither warped, holed nor spitted. Replace all defective parts. Check structure components for corrosion Check that draining holes on pipe leg members, pipe lattice parts are not blocked. Check the climbing facilities, platforms, catwalks for integrity 4.4.2 Tower Base Foundation Check for settlements or movements Check for erosion Site condition (standing water, drainage, trees, etc.) Check bolts, nuts and lock nuts for tightness Grout condition 4.4.3 Guy wires Check that each cable that is part of the guy wire is neither broken nor warped Measure the tension of each guy wire using a strand dynamometer and compare result with the installer's stated values. Check guy wires condition (corrosion, breaks, nicks, kinks, etc) Check that the guy wire tightening system is properly greased. Check for loose or missing fasteners Check base for settlement, movement or earth cracks 115

Check backfill heaped over concrete for water shedding Check anchor rod condition below earth Check for signs of corrosion and take remedial timely steps Ensure anchor head is clear of earth 4.4.4 Bolting parts Check that no bolts or nuts or any bolting part like washers, pins, etc is missing. Replace these immediately. Check bolts tightening. Check bolts, nuts and bolting parts for corrosion. Check anchorage rod in the concrete. 4.4.5 Verticality Check with the appropriate devices such as theodolite that the structure stands vertical. There shall be no tilts. Take two measurements in two different planes with a 90' angle difference. 4.4.6 Antennas and Accessories Check antennas and antenna supports good condition Check coaxial cables good condition Check fixing clamps good condition. 4.4.7 Safety components Check that access ladder is in good condition Check rest and work platforms for defects, wear and tear Check that all safety components are existing and complete Check the correct functioning of the fall arrestor system For a fall arrestor system with cable, check that the cable has not been over tightened. Check that the anti climbing door is functioning. 4.4.8 Lightning and Earthing system Check that all lightning and Earthing components are existing and complete including lightning arrestor, copper strip, connection plate, 116

Check the Earthing connection of coaxial cables, Measure the resistivity of the Earth and confirm conformity to expected values. 4.4.9 Aviation Safety Lights Check that all components are in place, Check condition and well functioning of components (Light bulb, energy cables, fixing parts, photoelectric cell, connections) Check earthing of the light wiring. 4.4.10

Anti corrosion protection

Check all galvanised members for integrity Check paint condition. Check for signs of corrosion on the structure, of the bolts, bolting accessories, harnesses, antenna supports, etc For guyed masts, check for corrosion on the entire guy assembly.

4.4.11

Salty environment

Wash the structure and accessories with clean water once every six months to eliminate residue salt particles which may not be washed away by rain. 4.4.12

Concrete blocks

Check the good condition of above ground concrete block parts. There must not be any water collection, cracking or splitting, chipped or broken concrete. Check the condition of anchor setting in the concrete block. Check anchor-bolt corrosion. 4.4.13

Tower loading

Check types, numbers and installed heights of all antennas currently on the structure and confirm that the loading does not exceed structure design load.

117

4.5

Annual Preventive Maintenance Checks

4.5.1 Structure Tension of Guy wires using a dynamometer. Geometry of the structure. Re-tighten main structure and accessories bolted parts (10%) Geometry of the Bars. Rigidity of Antennas and Accessories. 4.5.2 Safety Ensure anti climb door can open and close. Clean and grease all hinges. Ensure the work platform's trap can open and close. Clean and grease all door hinges. Fixing of the fall arrestor system Check tower ladder for any signs of weakness, re-tighten all bolts Check the riggers’ safety gear, take inventory and record it Right placing and right installation of safety components. Test of the fall arrestor system with individual equipment. 4.5.3 Earthing Physical condition of the lightning rod Physical condition of the lightning arrestor Physical condition and installation of the copper strip Connection of the concrete block copper belting onto the copper strip Connection of coaxial cables earthing onto the copper strip Connection between the bottom coaxial cable earthing and the collection Copper bar fixed on the concrete block Tightening of the brass bolts of the lightning protection electrodes Resistivity the lightning protection electrodes 118

Earth resistance 4.5.4 Aviation Safety Lights Functionality of controllers, flashers, alarms and photo control Condition of electrical wires, connectors and earthing Condition and fixing of energy cables Conduit, junction boxes, and fasteners weather tight and secure Bulb condition - change all bulbs at one time immediately before the rated service hours is achieved. Condition and fidelity of the power supply systems 4.5.5 Coating Discrepancies in galvanization Paint coating. Repaint every three years Rust and/or corrosion conditions ICAO / NAMA Color marking conditions Water collection in members - unplug drain holes, etc.

4.6

TESTING

Measurement of Guy Tension Tension should be measured when wind is relatively still. Measurements in wind velocity above 25 m/s (90km/h) will yield misleading results. Tension results can be considered satisfactory if they fall within 15% of the tension value stated by the manufacturer and/or installer. Excessive tension may cause alignment problems and even a cable rupture. It may even cause permanent wrapping of tower structural parts. There are two basic methods of measuring guy tensions in the field: 1. the direct method 2. the indirect method. 119

4.6.1 The Direct Method (see Figure 4.1) A dynamometer (load cell) with a come-along (length adjustment device), is attached to the guy system by clamping onto the guy just above the turnbuckle and onto the anchor shaft below the turnbuckle, thus making the turnbuckle redundant. The come-along is then tightened until original turnbuckle begins to slacken. At this point the dynamometer carries the entire guy load to the anchor, and the guy tension may be read directly off the dynamometer dial. This method is used to set the correct tension by adjusting the come-along until the proper tension is read on the dynamometer. Two control points are marked, one above the clamping point on the guy and one on the anchor shaft, and the control length is measured. The dynamometer and come-along are then removed, and the original turnbuckle is adjusted to maintain the control length previously measured.

Dyanamometer Come - Along

Turnbuckle (1) Dynamometer Method As come-along is tightened, dynamometer carries all the load

a

120

(3) Pulse Method

(2) Swing Method

Pulse travels up and down the guy N times In p seconds

Guy swings from a to b and back N times in p seconds

Figure 4.1 Measurement of Tension of Guy

4.6.2 The Indirect Method There are two common techniques for the indirect measurement of guy initial tension - the pulse or swing method (vibration) (Figure 4.2) and the tangent intercept method (Figure 4.3). (a) The Pulse Method

L

V

V

TM

L

W 2L H

M

TA

T

TA

WV 2L

W

H

121

H Figure 4.2 Relationship between Guy Tension at Anchor and at Mid-Guy One sharp jerk is applied to the guy cable near its connection to the anchor causing a pulse or wave to travel up and down the cable. On the first return of the pulse to the lower end of the guy cable, a stop watch is started. A number of returns of the pulse to the anchor are then timed, and the guy tension is calculated from the following equations:

where TA = Guy tension at anchor TM = Guy tension at mid-guy W = Total weight of guy, including insulators, etc. L = Guy chord length N = Number of pulses or swings counted in P seconds

V = Vertical distance from guy attachment on tower to guy attachment at anchor H = Horizontal distance from guy attachment on tower to guy attachment at anchor N = Number of pulses or swings counted in P seconds P = Period of time measured for N pulses or swings (s) Instead of creating a pulse that travels up and down the guy, one may achieve the same result by causing the guy cable to swing freely from side to side while timing N complete swings. The formulas given above will also apply for this approach. 122

(b) The Tangent Intercept Method C

I I

V

V

ht f sig o Line

W

a TA H H

Figure 4.3 A line of sight is established which is tangential to the guy cable near the anchor end and which intersects the tower leg a distance (tangent intercept) below the guy attachment point on the mast. This tangent intercept distance is either measured or estimated and the tension is calculated from the following equation:

where C = Distance from guy attachment on tower to the center of gravity of the weight W 123

I = The tangent intercept If the weight is uniformly distributed along the guy cable, C will be approximately equal to 1-I/2. If the weight is not uniformly distributed, the guy may be subdivided into n segments and the following equation may be used:

where

Wi = Weight of segment i Ci = Distance from the guy attachment on the tower to the center of gravity of segment i If the intercept is difficult to establish, one may use the guy slope at the anchor end with the following equation:

where cz = Guy angle at the anchor Note that

and that

and that WC in equation (7) may be replaced with S, as was done in equation (5). 124

Glossary of Terms Plumb -- The horizontal distance between the vertical centerlines at any two elevations shall not exceed .25 percent of the vertical distance between the two elevations. Twist -- The twist (angular rotation in the horizontal plane) between any two elevations shall not exceed 0.5 degrees in 3 m and the total twist in the structure shall not exceed 5". Length -- For tubular steel pole structures with telescoping joint, butt welded or flanged shaft connections, the overall length of the assembled structure shall be within plus 1 percent or minus 1/2 percent of the specified height. Normal Soil -- A cohesive soil with an allowable net vertical bearing capacity of 192 kPa and an allowable net horizontal pressure of 63 kPa per linear meter of depth to a maximum of 192 kPa. Twist -- The angular rotation of the antenna beam path in a horizontal plane from the no-wind load position at a specified elevation. Sway -- The angular rotation of the antenna beam path in a vertical plane from the no-wind load position at a specified elevation. Displacement -- The horizontal translation of a point relative to the no-wind load position of the same point at a specified elevation. Grounding is the means of establishing an electrical connection between the structure and the earth, adequate for lightning, high voltage, or static discharges. Primary Ground is the conducting connection between the structure and earth or some conducting body, which serves in place of the earth. Secondary Ground is the conducting connection between an appurtenance and the structure. Climbing Facilities -- Components specifically designed or provided to permit access, such as fixed ladders, step bolts, or structural members. 125

Climbing Safety Devices -- Equipment devices other than cages, designed to minimize accidental falls, or to limit the distance of such falls. The devices permit the person to ascend or descend the structure without having to continually manipulate the device or any part of the device. The climbing safety device usually consists of a carrier, safety sleeves, and safety belts. Working Facilities -- Work platforms and access runways. Guy Connection - the hardware or mechanism by which a length of guy strand is connected to the tower, or guy anchor. Lux is lumens/sq m Candela is light intensity. Its unit is the lumen Alternative Mounting Structure - man made tree, clock tower, church steeple, bell tower, utility pole, light standard, identification pylon, flagpole, or similar structure, designed to support and camouflage or conceal the presence of telecommunications antennas. Antenna - structure or device used to collect or radiate electromagnetic waves, including directional antennas, such as panels, wireless cable and satellite dishes, and omni-directional antennas, such as whips, but not including satellite earth stations. Antenna Array - An arrangement of antennas on their supporting structure. Dish Antenna - A parabolic or bowl shaped device that receives and/or transmits signals in a specific directional pattern. Panel Antenna - An antenna which receives and/or transmits signals in a directional pattern. Antenna, Stealth - A telecommunications antenna that is effectively camouflaged or concealed from view. Telecommunications Antenna - An antenna used to provide a telecommunications service. Whip Antenna - An omni-directional dipole antenna of cylindrical shape which is no more than 15 cm in diameter. Co-location - single telecommunications tower and/or site used by more than one telecommunications service provider. 126

Identification Pylon - A permanent ground mounted sign consisting solely of a single monolithic structure used to identify a development. Guyed Tower - Any telecommunications tower supported in whole or in part by cables anchored to the ground. Tower Height - The distance measured from ground level to the highest point of any and all components of the structure, including antennas, hazard lighting, and other appurtenances. Monopole - A self-supporting telecommunications tower which consists of a single vertical pole fixed into the ground and/or attached to a foundation. Self-supporting Lattice - A telecommunications support structure which consists of an open network of metal braces forming a tower which is usually triangular or square in plan. Telecommunications Tower - A self-supporting or guyed structure more than 5 meters in height, built to support one or more telecommunications antennas .

127

Index A • • • • • • • • • • • • • • • •

Access Ladders Accidents during the installation period Aggregate Air Terminal Airport Alternative Mounting Structure Aluminum – polished, anodized and painted finish Anchor Bolts Template Angle leg Annual preventive maintenance checks Antenna Mounting Frames Anti Climb Shields Anti Corrosion protection Authorization Aviation Lighting Aviation safety lights

83, 112 7 59, 87 75, 80, 88,90 6, 55 13, 122 86 58 21, 22 113 101 82 112 10 6, 12 112, 114

B • • • • • • • • •

Base Plate 23, 74 Basic Foundation Design for Slim lattice mast 72 Basic wind speed 15, 16, 74 Bi-metallic 88, 98 Bolting 23, 111, 112, 124 Bolt-up construction 22 Bracing 21, 25, 26, 27, 28 29, 33, 35, 49, 62, 86 Building and roof mounted dish antennas 13 Bull Dozer 8 C

• • • • •

Cable and Tape clips Cable Connectors Certification City and Guilds Clamp

98 97 6, 7, 13, 14 7 88, 89, 91, 92, 97, 112 128

• • • • • •

Clearance certificate Climbing Coating Co-location Concreting Copper-Tapes

6 24, 81, 82, 83, 84, 110, 111, 112, 121, 122 109, 114 10, 122 59 79, 96

D • Dish Antenna Mounting Standards • Drilled pier Foundation design • Dynamometer

13 67 111, 113, 115, 116

E • • • • •

Earthing 75,76, 78, 88, 89, 91, 92, 93, 94, 112, 114 Effective height 6 Elevation Rods 90 Environmental requirements 9 Excavators 8 F

• • • • • • • • • • • • • •

Fabricators and Installers 4 Face width 21, 34, 35, 36, 37, 38, 49, 67, 72. 73 Factors of safety 61 Fall Arrest Safety System 81 Faraday Rod 75 Finishes 21, 23, 83 Flat saddle 96 Flexible copper braid 96 Footing Assembly 43 Foundation Design and Loading 40 Foundation Design 40, 43, 57, 58, 67, 72, 74 Foundation Engineers 60, 61 Foundation in swamps 75 Free standing masts 5

129

G • • • • • • • • • •

Geographical coordinates 6, 7 Graphite 88 Ground mounted dish antennas 13 Guard-rails 81, 84 Gust factor 16, 35, 36, 126 Guy Anchor 11, 25, 50, 60, 61, 6, 66, 70, 75, 80,122 Guy materials 99 Guy wires 24,25, 111, 113 Guyed Towers 5, 24, 57, 80, 110 Guys 6, 11, 25, 66, 87 H

• • • • •

Height of Towers HF-SSB dipole antennas High Alumina (HA) Hot Dip Galvanization Humic Acid

8 50 87 109 87

I • • • • •

ICAO Inspections Installation permit Insulator Intersecting bracings

11, 12, 55, 56, 114 7, 10, 110 8 93, 118 86

J • Junction box K • K-bracing • KNm -3 • Kpa

12, 114

26, 27, 28, 29, 30. 31 57, 59, 60 57, 59, 121

L 130

• • • • • • • • •

Lap Link Weight Table 44 Lattice 5, 21, 22, 24, 26, 27, 34, 37, 38, 44, 45, 73. 86, 67, 111, 123 Saddle 86, 95 Lighting 6, 11, 12, 55, 56, 78, 123 Lightning and Earthing system 112 Lightning Arrestor 95, 112, 114 Lightning protection 6, 75, 76, 78, 80, 88, 90, 91, 92, 114 Log book 7, 110 Long Boom Arm Crane 8 M

• • • • • • • •

Magnesium Maintenance Maximum compression Maximum shear Measurement of Guy Tension Monopole structures Monopole Towers Multi-Point Air Terminal

88, 109 7, 8, 21, 108, 109, 110, 113 35, 36 35, 36 115 86, 87 23 90

N • • • • • • • • •

Name plate Nearness to power lines Nigeria Airspace Management Authority NAMA Nigerian Communications Commission NCC Nigerian Meteorological Agency Non-Metallic clips N-Section Guyed Pole Mast

7, 60, 61 12 6,10 11, 12, 21, 55, 56, 114 6, 7, 8, 10, 13 6, 7, 8, 9, 10, 11, 14 15 98 50

O • • • • •

Oblong Box Clamp Obstruction lamps Obstruction lighting Open terrain Operating Frequencies

91 55 12, 55, 56 14 7 131

• Out rigger

50, 52

P • • • • • • • • • • • • • • • •

Packer Painting Panel Height Permit Number Photo sensor Pier and Pad foundation construction Piles Plate Type clamp Platform height Platforms Pointed Air Rod Post Masts Property Owner Protective Grounding Public Health Public Safety

8 55, 110 26 7 12 71 56, 61 92 45 6, 21, 81, 111, 112, 122 95 23 6 80 9 4, 8, 13, 82, 109

R • • • • • • • • • • • •

Radio frequency emissions 8 Raft Foundation 60, 64, 66 Redundant Diagonal 31 Reinforcement 59, 60, 61, 65, 66, 80, 88 Removal of abandoned towers 9 Residential Areas (towers in) 11, 12, 13 Resistivity values for different soil types 79 Resistivity 78, 79, 112, 114 Rest platforms 21, 81, 83 Rock Anchors 56, 58 Roof Mounts 25, 53, 54 Routine checks 111 S

• Safe Working Load (SWL) • Safety components

58 112,113 132

• • • • • • • • • • • • • • • • • • • • • • • • • • •

Safety Devices Safety Enhancement Safety of equipment Safety of personnel Salty environment Screening Security Fencing Self Support Lattice Service Life of Towers Setbacks of Towers Side Antenna Mount Signage Silver Site Plan Siting Slip Joints Slope change Solid Round Leg Space requirements Square structure Standard foundation Steel member width Step Bolt Structural certification Substructure Superstructure Superstructure Design and Loading

81, 122 84 4 4 113 9, 13 9, 11 26, 37 12, 21, 110 10, 11 103 11 88 6 8 24 34 21, 22, 86 9 21 58, 59 49 64,121 14 4, 56, 64 4, 16, 21, 35, 36, 40, 42, 86 40, 42

T • • • • • • • • • •

Tapered sections Technical College Terrain Thimble Total anticipated antenna load Tower Base Foundation Tower loading Tower maintenance Tower schedule Tower to Tower Spacing

21 7 14, 16, 128 87, 100 35, 36 75, 111 21, 113 109 39, 41 12 133

• Tube leg • Turnbuckle

21, 22 87, 99,100, 115

U, V • • • •

U-Bolt clip U-Bolts Uplift Verticality

99, 100 12, 68, 89 35, 36, 40, 43, 45, 57, 59, 61, 62, 68, 72, 73 112

W • • • • • • •

Weather proof light flasher 12 Wind flow map 15 Wind Load 16, 40, 121, 14 Wind loading 14 Wind Speeds 15, 16, 17, 19, 35, 36, 40, 42, 43, 44, 45, 74 Work platforms 21 Workmen’s compensation 6, 21, 83, 112 X, Y, Z

• X-braced, self supporting, lattice design • Z bracing • Zinc

34, 45 38 88, 109

134