The telecom network service works mainly execute by the following way
1. Network Planning
2. Site Acquisition
3. Site Designing & construction
4. Networking
In the previous Section we have discussed about Site Acquisition works & this section we will discuss about Site Designing, Drawing & Calculation considering warid telecom tower project executed by Motorola in Bangladesh especially in Chittagong, Comilla & Sylhet region.
3.1 General
This discussion focuses generally on typical BTS sites.
3.2 Site Design
3.2.1 Standards and Codes of Practice
The design and construction of the Permanent Works shall comply with Bangladesh National Building Code (BNBC) and for items outside of this code appropriate British Standards shall be adopted. Regulations made and requirements issued by the Bangladeshi Government and by Relevant Authorities shall also be followed as specified herein.
3.2.2 Design Life and Serviceability
The design life of a structure or piece of equipment is that period for which it is designed to fulfill its intended function when inspected and maintained in accordance with standard procedures. The assumption of a design life for a structure or component does not necessarily mean that the structure will no longer be fit for its purpose at the end of that period. Neither will it necessarily continue to be serviceable for the length of time without adequate and regular inspection and routine maintenance.
Paint systems for steelwork shall ensure a minimum life of 15 years before full maintenance painting is required. The corrosion protection of non-structural steel items shall be appropriate to the accessibility of the item for inspection and maintenance.
The design life for the complete GSM network and all its physical components, other than for the structural and civil components mentioned above, shall be 15 years.
3.2.3 Site Layout
All sites (including Rooftop sites) shall a provision for a generator to be installed on site. The space to be allocated for this provision shall be 3m x 4m x 2.8m High.
Rooftop Site The design of a rooftop installation requires the simultaneous consideration of a number of factors. The GSM and microwave antenna locations, the cable routes and the equipment room location are all interrelated with each other. An efficient design shall address all of these factors and arrive at a workable and sensible solution. Generally were possible the Antenna Support Structure shall be placed on top of the Equipment Room.
Prior to commencing design of a rooftop site, a very thorough investigation of the host building shall take place at the time of the TSV. A rooftop can be structurally sensitive to the positioning of heavy loads.
Greenfield Site The positioning of both the tower and equipment room are interrelated. It is not possible to set out one without due consideration for the other. With this in mind, each element of a ground Site should be examined separately.
Greenfield Sites shall be enclosed in a standard compound. Vehicle access to the site area shall be possible. All services shall be installed in a way that prevents the necessity of further civil and underground works inside the site compound.
A geotechnical report is required to establish foundation types and sizes for the tower, cable ladder, equipment room etc.
The tower shall be positioned such that its foundation is within the site boundary. It is also preferable to have a 500 to 1000mm gap between the tower foundation edge and the compound wall/fence to accommodate the earthing ring.
The preferable orientation is such that the feeder cables pass straight from tower to equipment room with no bends.
On every ground site the perimeter shall be indicated and protected by the means of a wall/fence. The area inside the wall/fence, the compound, shall accommodate the footprint of the tower, the equipment room and shall allow space for manipulation and possible later upgrades. The compound shall be cleared from any vegetation surface.
The typical compound sizes adopted for the project shall be as follows:
· 42m High Tower – 15m x 11m
· 50m High Tower – 18m x 13m
· 60m High Tower – 19.5m x 14.5m Note in occurences where the site compound may need to be elevated, these sizes may need to be increased to account for the earth batters around the site.
The equipment room shall be sufficiently protected from flooding. The room shall be raised from the existing surface in accordance with the maximum of the following requirements:
· Maximum Local flood level (as indicated by owner or neighbors of the property) + 500 mm or Top of major road/highway drainage pipe (within 300 m of the site) + 500 mm. or
· Top of paddy/rice field wall height (within 300 m of the site) + 500 mm. or
· Top of major road/highway or
· 500 mm
3.3 Site Calculations
The Contractors Engineer (Civil/Structural or Electrical) shall undertake all the necessary calculations to design and construct a site. All works associated with a site shall be designed, fabricated, galvanized, handled, erected and installed to meet the Bangladesh National Building Code (BNBC) and for items outside of this code appropriate British Standards shall be adopted.
3.3.1 Rooftop Sites
Some of the calculations that shall be undertaken as a minimum for Rooftop Sites include Structural Adequacy of the existing building to take the Antenna Support Structure, Equipment Room and Generator Room. Also Structural design of the Equipment and Generator Room such as columns, walls, roof slab and beams.
Load and fixing connections shall also be designed for items such as: -
Antenna Support Structures
· Poles
· Equipment Rooms
· Cable Ladder Systems
· KWH Meter Support Poles
The connections may consist of the appropriate grillages, spreader beams, ring beams and pads that transmit the loads to the structural elements of the building to ensure that it has sufficient load capacity. Structural calculations shall be carried out to demonstrate that the designs are suitable for all critical loads.The supports may be constructed from reinforced concrete or galvanised steel sections.
3.3.2 Greenfield Sites
Some of the calculations that shall be undertaken as a minumum for Greenfield Sites are:
· Antenna Support Structure Foundation.
· Structural design of the Equipment Room and Generator Room such as columns, walls, roof slab and beams.
· Structural Design of Equipment Room and/or Generator Room Foundations .
· Structural Design of Fence/Wall and Gate including Foundations.
3.3.3 Existings Drawings
When “Existing” Drawings are provided by an owner for a building or an existing Antenna Support Structure it is the Contractors responsibility to verify whether the drawings are correct or not.
3.3.4 Existing Structure Investigation Certificate (ESIC)
The Existing Structure Investigation Certificate (ESIC) is a single page certificate used for Existing Structures (typically Rooftops but also for existing towers for co-located sites). The purpose of the certificate is to approve the structure for use as a telecommunication site.
3.3.5 General Arrangement Drawings (GAD)
The basic function of the General Arrangement Drawings is to firstly show to the owner what is proposed in regard to construction of the site on their property or building. Also within the project team the drawings are used to confirm the Technical Site Visit. It is important that the size and location of the lease area/s are clearly and accurately indicated in the GAD’s.
The minimum information is as follows:
· Cover Page & Index
· Location Map
· Plan (Shall include Generator Room/provision)
· Elevation
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Fig: Sample GF Plan
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3.3.6 Detailed Design Drawings (DD)
The “Detailed Design” Drawings shall contain all the information found on the General Arrangement Drawings and in addition the following:
· Equipment Room Structural Details
· Equipment Room Layout Plan
· Site Earthing, Lightning and Electrical Plan
· Antenna Support Structure Foundation
· Generator Room Structural Details
· Generator Room Layout Plan
· Any other Site Specific works needs to be shown in detail.
3.3.7 “As-Built” Drawings
Any information, which has changed on the “Detailed Design” drawings that occurred during the construction phase of the site, shall be shown on the “As-Built” drawings. Items that typically require adjustment are:
· Final Site Levels
· Power Run and Cable Sizes
· Final Antenna Heights/Sizes and Orientation.
3.4 Geotechnical Investigations
A geotechnical investigation shall be carried out for all Greenfield sites to determine Antenna Support Structure and Equipment Housing foundation types and sizes. A professionally qualified geotechnical engineer shall supervise the investigation.
3.4.1 Boreholes/Borelogs
The Contractor should allow for drilling two boreholes per site to a depth to be determined by the Geotechnical engineer on site, depending on soil conditions. Boreholes shall be separated by a distance of more than 10 m to obtain a better understanding as to the variability of the soil conditions. The minimum depth of bore shall be 30m. Boreholes shall be performed within the proposed lease boundary. Standard Penetration Test (SPT) values are to be obtained at intervals of 1.5m for the full length of the bore.
After completing the borehole the Contractor shall ensure the following:
· GPS coordinates of the boreholes are recorded
· Soil removed to be put back into the borehole and the site is left in an acceptable condition to the owner’s satisfaction.
· Any damage to the site due to the boring machine shall be repaired at the expense of the Contractor.
3.4.2 Standard Penetration Tests for High Level Foundations
High level foundations which do not require piles (also known as “Pad Foundations”) shall have a “Standard Penetration Test” performed after the excavation is complete on site. This foundation type could be for an Equipment room or Antenna Support Structure. This test shall be performed and the result verified by a Geotechnical Engineer before installing the foundation.
Should the excavation be subjected to wet weather between the time of the original test and installing the foundation, then the test shall be performed again. This is to avoid settlement due to high level softening of the soil beneath the foundation.
3.5 Foundations
3.5.1 General
The foundations shall be designed to carry all the design loads for the related structural elements. Foundations shall be designed and constructed to meet the Bangladesh National Building Code (BNBC) and for items outside of this code appropriate British Standards shall be adopted.
The foundation shall be based upon the tower type and the soil investigation report. The Contractor retains responsibility for the foundation design and shall produce calculations to demonstrate that the design is suitable for the site specific conditions encountered. The design shall be made and endorsed by an appropriately qualified Certified Bangladeshi Civil/Structural Engineer. Design parameters regarding the ground/soil conditions are to be obtained from the Geotechnical Investigation Report for the site.
3.5.2 Pad/Spread Foundations
For all Pad or Spread foundations including Antenna Support Structures, Equipment Rooms, Cable ladder Supports, Perimeter Brick Wall etc. the Geotechnical Report and consistent with the assumptions made in the design. For pad or spread foundations a “Standard Penetration Test” shall be undertaken and approval obtained from a Certified Bangladeshi Geotechnical Engineer prior to placement of reinforcement and pouring of concrete.
Under no circumstances shall the founding material for a tower, equipment or generator room be on direct fill.
3.6 Piling
3.6.1 General
All piling shall be designed and constructed to meet the Bangladesh National Building Code (BNBC) and for items outside of this code appropriate British Standards shall be adopted.
3.6.2Bored Piles
The Contractor shall accept full responsibility for the method of working, for the sinking and sealing of the casing against the entry of water and the positioning of the completed pile within the required tolerances and to the anticipated founding depth indicated on the drawings. If materials and/or obstacles are encountered during driving the Geotechnical Engineer is to be consulted and provide re-design the foundation to suit.
Founding level
Founding levels shall be established by “down the hole” inspections and proof drilling at each main pile location.
Excavation
A “Bentonite” slurry shall be used where required to prevent collapse of the bore hole.
3.7 Concrete Works
All concrete works shall be designed and constructed to meet the Bangladesh National Building Code (BNBC) and for items outside of this code appropriate British Standards shall be adopted.
3.7.1 Concrete Material
Concrete shall consist of a mixture of cement, fine and coarse aggregate and water. The proportions of the constituents shall be used in accordance with the design and specifications relative to the specified strength.
The proportions of aggregates to cement shall be such as to produce a mixture which will work readily into the corners of forms and around reinforcement but without permitting the materials to segregate or excess water collect on the surface.
Cement shall be Portland cement Type-I ASTMC-150.
Fine Aggregate shall consist of well-graded, clean natural sand (Sylhet or local as per the Concrete Strength Table) free from organic impurities and deleterious substances and shall have fineness modules of not less than 2.5 for Sylhet sand & 1 for local sand.
Coarse Aggregate shall have a maximum size of 20mm, well graded and not larger than ¾ of the minimum clear spacing between reinforcing bars.
Water shall be fresh, clean, free of salt and chemically neutral.
The minimum compressive strength of concrete shall be as per the Concrete Strength Table below.
Concrete Strength Table
Item
Minimum Compressive Strength (28 Day)
Aggregate Types
Minimum Ratio’s*
Major Structural
Items such as
Piles, Foundations,
Equipment Housing
=3,000 psi
Fine Aggregate - Sylhet sand
Coarse Aggregate - ¾”
Crushed stone chips
1: 1.5: 3
Minor Structural Items eg. Boundary walls, stairs etc.
=2,500 psi
Fine Aggregate - Local sand. Coarse Aggregate - 1st class clay brick ¾” chips
1:2:4
* Cement: Fine Aggregate: Coarse Aggregate
The consistency of concrete shall be determined following evaluation of the placement conditions for each individual section of the work. Maximum Slump:
· Piles – 150 mm
· All other Structures - 75mm (includes pile caps, equipment rooms etc).
3.7.2 Reinforcement Steel in Concrete
All Deformed bars shall be a minimum of Grade 40 (fy = 40,000 psi), Grade 60 (fy = 60,000) shall be used where deemed necessary by the Civil/Structural Engineer.
3.7.3 Curing
Concrete shall be adequately protected against the effects of inclement weather. Measures shall be taken to avoid loss of water from the concrete surface during curing. These measures can be continuous watering, covering with wet mats, Hessian, sealing with polythene or use of spray on membrane. The curing period shall be assumed to be a minimum of 14 days.
3.7.4 Repair of Concrete
Following striking of formwork, any repairs necessary shall be completed within 24 hours.
3.8 Brickwork
3.8.1General
This section consists of the supply and laying of all Brickwork required for the satisfactory completion of the Works. All brickwork shall be designed, manufactured, handled and constructed to meet the Bangladesh National Building Code (BNBC) and for items outside of this code appropriate British Standards shall be adopted.
Two types of brickwork shall be used on the project. They are:
· 16”x4”x8” sized “Conpac” Hollow Block (or approved equivalent)
· Clay Bricks which shall be “1st class” (as commonly referred to in Bangladesh)
Both types of brickwork shall be from an approved manufacturer.
No brick/blocks shall be used until they have been thoroughly soaked in clean water for at least eight hours. Soaking shall be discontinued one hour before use. Care shall be taken that the brick/blocks are clean and free from slime or dirt of any kind. If necessary, brick/blocks shall be scrubbed clean. The height of day’s work shall be limited to 1.5m unless otherwise permitted. All brickwork shall be thoroughly cured for a period of at least 7 days.
3.8.2Joints and Mortar
Joint thickness shall be minimum ¼” and shall in no case exceed 3/8”. Construct vertical control joints where shown on the drawings and at not more than 8m spacing along all walls where not specifically shown. The Mason shall discuss in advance with the Subcontractor the location of all control joints when they are not shown on the drawings. Control joints shall be continuous vertical joints. Reinforcement and filling grout shall be continuous through the joint unless shown otherwise.
· Mortar of unless otherwise required, shall consists of 1 part of cement and 4 parts of sand.
· Cement shall be Portland cement Type-I ASTMC-150.
· Water shall then be added in a controlled manner, only the minimum necessary being used to produce a workable mixture of normal consistency. Water shall be same as required for concrete.
· Sand shall be clean well-graded natural sand having a minimum F.M.1.5. The water cement ratio in no case shall exceed 0.50 by weight, or as directed by the Civil/Structural Engineer.
3.8.3 Plastering
Two types of Plaster shall be used for the project:
· Ceilings – shall consist of plaster mixed as 1 part of cement to 3 parts of sand and have a nominal thickness of ½”.
· All other - shall consist of plaster mixed as 1 part of cement to 4 parts of sand and have a nominal thickness of ½”to ¾”. Only enough water shall be added to provide plasticity. Plaster shall be mixed only in quantities for immediately use. Plaster, which has taken initial set, shall not be used on the work with or without addition of fresh material. Before application of plaster the joints in brick wall shall be adequately raked out where necessary and smooth concrete surface shall be roughened to provide key.
Materials shall meet requirements specified below and in the relevant section of materials specifications.
· Cement shall be Portland cement Type-I ASTMC-150.
· Water shall be same as required for concrete.
· Sand shall be clean well grade natural sand having F.M. of 0.8
The thickness of plastering shall vary dependant upon the surface being plastered. For a “flush” brick surface ½” shall be used for a rough or uneven brick face ¾” shall be used.
Plaster shall be kept moist and protected from weather for 10 days immediately following completion.
3.9 Equipment Room Design & Construction
3.9.1 General
Where the requirement is to utilize Indoor Equipment, the equipment shall be housed in an equipment room. The type of room is dependent upon the site being Greenfield or Rooftop as to whether a new equipment room or modification of existing room is required.
The minimum internal floor space requirements of an equipment room to house the BTS are 4000mm x 3000mm x 2800mm height.
The walls, floor and ceiling shall provide a minimum fire resistance of 60 minutes and shall have a heat transmission coefficient that is no higher than 0.45 W/m2K. The room shall be watertight.
The completed installation shall be finished in accordance with the technical specifications and suitable for the housing and operation of the equipment to be installed.
For BTS sites the floor slabs shall be able to carry the following:-
· Live Point load - Limited to an area of 50 x 50 mm shall be possible up to 2.5 kN.
· Live Local load - Shall be possible up to 6.5 kN/m2. Local load means, that any single square meter within the room shall be capable to be loaded with the stipulated Live Load weight, but not that the total load within the perimeters or the rooms is to be calculated as the total of the room area, multiplied by this value.
· Total Room Area Uniform Live Load – The uniform live load used to check the slab (applied over the whole floor area) shall be 3 kN/m2.
On “Transmission Hub” sites, “SDH” sites and “BSC” sites a generator room shall also be required in addition to the equipment room. The typical floor space requirement of an equipment room to house the generator and fuel tank is 4000mm x 3000mm x 2800mm height.
3.9.2 Walls
The walls between the columns shall be made a minimum of 250mm thick. The interior walls shall be covered with ceramic tiles or plastered the exterior walls shall be plastered.
Any openings shall be sealed to ensure fire resistance and insulation. The inside surfaces should be flat and shall be of sufficient strength to support the equipment to be contained therein. Any entry plate should be properly fixed into the wall and sealed using a fire resistant non-shrinking sealant/grout. The entry plate and other wall penetrations shall be waterproofed.
The door shall be a 2m high by 1m wide. The door frame shall be of steel construction with industrial heavy duty stainless steel type hinges – non removable. The door and frame shall have an anti-corrosive finish. The lock mechanism shall be one embedded lock, a handle on both sides with a padlock on the external face.
3.9.3 Roof/Ceiling
The roof shall be RC slab and overhang the wall by a minimum of 600mm. The top of the slab is to be graded to minimise the run-off of water towards the feeder cable entry plate. The Contractor shall ensure that the rooftop is waterproof. Waterproofing shall be done through one of the following methods:
· Patent stone (with NCF) with a finish of waterproofing roofing compound (Berger Roofing Compound).
· Epoxy based paint or water resistant roof coating/compound (approved by Motorola) to ensure a watertight seal in 2 layers over a sealing coat.
· Any other waterproofing method approved by Motorola. Use of any products shall be done in accordance with the manufacturer’s recommendations.
3.9.4 Floor
The floors shall be designed to support the loads of the equipment to be installed. For Rooftop sites the floor shall be elevated from the top of slab level by a minimum of 100 mm. In floor where necessary shall be made level using a suitable cement mortar/screed.
The finished floor surface shall be anti-static tiles of industrial standard durability and bonded into place using methods and materials as recommended by the manufacturer.
3.9.5 Finishes, Painting & Tiling
The finished walls and ceiling shall have a smooth and presentable finish with surfaces being flat and free from dents, ruts, cracks and other defects. This shall be achieved with a layer of plaster.
Tiling - Approved ceramic glazed tiles shall be used with a 1:4 cement-sand screed and mortar. Tiles shall be soaked in water for at least 6 hours before setting.
All painting shall be applied in accordance with the manufacturer’s instructions to give a uniform layer across all surfaces. The materials shall be specifically designed for their particular use for interior and/or external use.
The external surface of the room shall be painted with “white” weather coating in 3 layers. The ceiling shall be painted with a white acrylic paint in 3 layers. The door with one layer of steel primer and a light “Grey” synthetic enamel paint. All paints shall be “Berger” or approved equivalent by Motorola.
Any metallic surfaces where weatherproofing is required shall be painted with a synthetic enamel paint following priming.
3.9.6Greenfield Sites
The majority of Greenfield sites shall require a new equipment room to be installed to accommodate indoor equipment.
Standard Greenfield sites will contain one equipment room only. A similar space needs to be allowed for the possibility of a generator enclosure.
The foundation for the equipment room shall be in accordance with this Handbook. The height of the columns shall be a minimum of 500mm above the established flood level or existing level. The room should be support by four RC columns with ring beam supports and a concrete slab.
3.9.7 Rooftop Sites
The rooftop sites need to be properly evaluated prior to any additional loading is added to the structure. The layout of all components shall be agreed at the Technical Site Visit (TSV) and shall take into account the following considerations: -
· Deployment speed and costs
· Safety of building occupants and maintenance personnel
· Structural suitability
· Understanding of Building Owner
· Within the site acquisition requirements
· Compliance to local building regulations and specification
