This specification document covers the projecting principles of monopole towers that will be used antenna installations in the GSM base station installation projects
In case there are conflicts between various standards and codes or engineering design data, the most rigid standard and code will be taken as a basis after seeking the approval
In case the revisions of the related standards will be published, following the new standards and renewing the production according to these standards is the contractor’s responsibility after seeking the approval
Metrical system will be used in the measurements.
3. DESIGN PRICIPLES
Towers will be designed according to the following heights unless otherwise requested by Client.
Towers will be designed according to the following heights unless otherwise requested by client.
The monopole could be polygonal slip joint or flanged type manufactured ·
All monopoles shall be complete with the accessories for antenna installation, cables fixing, access ladder up to the top of the structure along with a safety rail & safety hanger, grounding, lightning conductor system & aircraft warning light system ·
The contractor shall design calculations, outline drawings,fabrication and assembly drawings, fabrication charts, and bill of materials prior to delivery.
Design must be done to allow operations and maintenance works to be performed easily.
Dimensioning of the construction and connection elements will be done in accordance with the latest issue of Guide for Design of Steel Transmission Towers-ASCE published by American Society of Civil Engineers – ASCE.
A climbing ladder will be built on the monopole in order to provide the maintenance and operations personnel to climb on the tower. Ladder step spacings will be maximum 30 cm. A safety rail & fall arrestor shall be provided attached to the access ladder.
Tower will be designed to allow the installation of aircraft warning light and a copper lightning arrestor at the highest point with a minimum length of 1.2 meters. Easy access to the aircraft warning lamp shall be available.
The contractor is responsible to obtain results from tower designs, acceptance tests & quality assurance, such that compliance with all conditions prescribed in these specifications is evidenced.
The contractor is not allowed to use the designed monopoles for any other application without the prior consent of Client.
Each monopole shall be designed to be at optimum dodecagonal horizontal cross section (as swaying and vibration should be held at minimum) and self supportive and be calculated as per tensile-compressive forces system.
Life time of the monopoles shall be minimum 30 years.
Monopoles can be supplied with or without top platform according to the request and/or approval of Oman Mobile.
· The top platform shall have 3,0 m diameter, for the monopole without a top platform a small light circular area shall be provided for access to the antennas.
· Platform shall be furnished with non-slip floor appropriately fixed with a suitable bearing structure with bolted joints. Moreover the platform floor shall not allow tools, and objects to fall.
· Top platform shall be provided with foot stop plate (h=15cm) and protective railings (made with two currents) not less than 110 cm in height, in accordance with regulations in force on the subject.
· Working Platform shall be accessed via a hatch complete with opening and closing system.
It shall be possible for hatches to remain open if necessary.
All the underground connections of the earthing system shall be made with Cadweld method.
7. STEEL ELEMENTS
If the connection elements are designed with flanges, number of attachments and eccentricity of the attachments will be kept in minimum as much as possible.
· Dimensioning of the elements and connection elements will be done in accordance with the latest issue of Guide for Design of Steel Transmission Towers-ASCE published by American Society of Civil Engineers – ASCE.
· The necessary holes needed for the ground connection must be designed.
· Monopole Connection and Fixation: The monopole base plate will be attached on the concrete base via achorage bolts and proper grouting shall be applied
· Contractor shall make his own survey to the sites if required and shall be responsible for obtaining all dimensions and level necessary for the proper fabrication of the steelworks.
· The Contractor shall be responsible for every piece being made to the correct form and size.
· The Contractor shall inform the Engineer of the date on which fabrication will commence, shall keep the Engineer informed of the fabrication programme and shall permit the Engineer or his representative full access to his factory at all reasonable hours for the purpose of inspecting the steelwork at any stage of its manufacture. Contractor must clearly understand that any material and workmanship not complying with this specification shall upon inspection whether at his works, the site or in erected position be rejected and replaced to the entire satisfaction of the Engineer.
8. MONOPOLE LOAD ASSUMPTIONS
The following loads have to be considered for the monopole design: Antenna Load:
· N°6 mobile antennas with weight of 15 Kg each and dimensions of 2.58 x 0.3 x 0.15 m.
· N° 2 solid parabolic antennas with average weight of 25 Kg and diameter of 0,6 m.
· N° 2 solid parabolic antennas with average weight of 45 Kg and diameter of 1,2 m.
Dead load for auxiliary equipment such as feeder, feeder joints, antenna structure and other installation equipments.
· Design wind speed shall be 160 Km/h (45 m/s).
· Operational wind speed (maximum twist and tilt shall be ±0.5 degree at this speed) shall be 120 Km/h (34 m/s).
10. CABLE LADDERS & SUPPORTS
Vertical Cable Ladders
The vertical cable ladder could be either external supports running next to the access ladder on the monopole or could be internal J-Hooks for hanging the cables inside the
11. ACCESS LADDER & FALL ARREST SYSTEM
The Monopoles are to be equipped with hot dip galvanized climbing ladders with approved safety system. Safety system shall consist of a fall arrestor (mouse) that can freely move on a steel cable or a perfectly continuous rail and in case of fall it will lock itself protect the individual from falling down. The width of the climbing ladder shall be at least 400 mm. The spacing of the step rungs (thickness minimum 16 mm) shall be 250 mm maximum and they shall be capable to carry 1 kN concentrated load (gM = 1.5). There shall be no obstruction behind the climbing ladder for the foot.
Bolts, nuts and washers
The connection bolts, nuts and washers will be according to any of the following standards (or equivalent):
Dimensional standards for fasteners