The present invention relates to telecommunication towers. In particular the present invention described a tower structure constructed with bamboos for use in wireless communication networks.

BACKGROUND ART

Prevailing technology for telecommunication towers whether self supported or guyed masts, are constructed using steel, timber or reinforced concretes. Although these materials exhibit various conveniences in both functional and technical aspects, sustainable alternatives to these construction materials are desired. Sustainable material reduces global dependency towards non-renewable resources in the construction industry while providing material with no adverse impact on the environment. However, various improvements are required when considering sustainable materials for permanent or long term application such as durability, vulnerability to insect and fungal attack as well as effective joint design to ensure structural robustness.

An example of building material use for supporting structures was disclosed in an online journal (www. sciencedirect.com) on 23 ^rd February 2005 entitled "An Environmental, Economic and Practical Assessment of Bamboo as Building Material for Supporting Structures (Authors: P. Van der Lugt et. al). The P. Van der Lugt et. al paper discusses the potential use of bamboo as a building material for temporary European bamboo buildings, structure and bridges in the form of columns, beams and rails. The P. Van der Lugt et. al paper further compares the efficacy of various building materials such as bamboo, wood, steel and concrete and concludes that bamboo elements are on par with commonly used building materials in Western European countries in terms of mechanical and environmental performance.

An example which discloses bolted connection to securely anchor cooling towers to concrete foundation is disclosed in United Kingdom Patent No. GB 329715 (hereinafter referred to as the GB 715 Patent) entitled "Improvements in or relating to Water Cooling Towers" having a filing date of 26 November 1929 (Applicant: L.G. MOUCHEL AND PARTNERS LTD and MARCEL ERNEST GERARD). The GB 715 Patent divulges structural materials being securely anchored to concrete foundation by metal shoes through a bolted connection which provides robust joint design to hold the tower intact. Another example which relates to telecommunication tower was disclosed in Chinese Patent Publication No. CN 201730376 U (hereinafter referred to as the CN 376 Publication) entitled "Energy-saving Mobile Communication Tower" having a filling date of 1 June 2010 (Applicant: QIANGDAO TIANFU TELECOMMUNICATION EQUIPMENT CO. LTD). The CN 376 Publication provides a tower body and a base formed of a steel structure arranged at the bottom of the tower. The base of the CN 376 Publication comprises of load bearing elements with direct contact to the ground functioning to replace concrete foundation. The replacement feature reduces environment damages and resource waste caused by foundation construction. Although the above-mentioned prior arts provide various features and enhancements over tower constructions, there is a continued need to include sustainable capacities in tower structures. Hence, the present invention utilises bamboos as alternative material to traditional steel structures in telecommunication towers based on the properties of the bamboos.

SUMMARY OF INVENTION

The present invention relates to telecommunication towers. In particular the present invention described a tower structure constructed with bamboos for use in wireless communication networks. One aspect of the invention provides a telecommunication tower structure (100) for use in a wireless communication network. The telecommunication tower comprising at least one radio base station characterized in that the tower structure is constructed using selected bamboo culms. The bamboo culms form a lattice grid of vertical and horizontal members interconnected by bracing means to form support for continuous erection of tower to a desired height. The telecommunication tower is further attached by diagonal culms to the nearest lattice for diagonal support.

Another aspect of the invention provides that the bracing means comprises of metal clamps (302) and flat metal plates (300).

A further aspect of the invention provides that each metal clamp (302) has circular hollow pipe section positioned to receive horizontal and vertical members to form a lattice.

Yet another aspect of the invention provides that the flat metal plates (300) attach the diagonal members to the vertical members using nut and bolt assembly.

Preferably, the tower structure comprises a tower section of a square shape. Another aspect of the invention provides that the tower structure comprises of a concrete pedestal (200) to support the tower.

Still another aspect of the invention provides that the concrete pedestal (200) further comprises of pipe columns (206) to guide the bamboo culms in vertical position.

Yet another aspect of the invention provides that the bamboos culms are pre-treated with water and chemical preservatives comprising pesticides and bituminous paint and further coated with enamel paint.

Another aspect of the invention provides that the bamboos culms are naturally straight.

The present invention consists of features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings, it being understood that various changes in the details may be made without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

To further clarify various aspects of some embodiments of the present invention, a more particular description of the invention will be rendered by references to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the accompanying drawings. FIG.1 .0 is a photograph illustrating bamboo telecommunication tower of the present invention.

FIG 1 .0a is a photograph illustrating an exploded view of a part of tower structure of the present invention.

FIG 2.0 illustrates the layout of the concrete pedestal of the present invention. FIG 2.0a illustrates the overview of the concrete pedestal of the present invention.

FIG 2.0b illustrates the components in the column pedestal of the present invention.

FIG 2.0c illustrates the cross section of pedestal to roof slab connection of the present invention.

FIG 3.0 illustrates the layout plan of tower design of the present invention. FIG 3.0a illustrates the multiple joints of the present invention. FIG 4.0 illustrates the bamboo inserted with bolts.

DETAILED DESCRIPTION

The present invention relates to telecommunication towers. In particular the present invention described a tower structure constructed with bamboos for use in wireless communication networks. Bamboos are desirable sustainable replacements for building materials due to its versatility, renewability and tensile properties. Although most abundantly found in most tropical and subtropical region, bamboos are not fully utilized as permanent or long term building structures. A number of reasons can be attributed for the restricted incorporation in civil constructions such as durability, lack of governmental regulations and limited knowledge on tensile capacities of the properties of bamboos. Contrary to popular believe, bamboos exhibit superior tensile strength when compared to steel. The tensile strength of bamboo can reach up to 370MPa making it an attractive alternative to steel in tensile loading applications.

The present invention discloses a tower structure constructed by utilizing bamboos with enhanced joint design for structural robustness. The present invention is devised to minimize reliance on non-renewable resources for the construction of telecommunication towers. Hereinafter, this specification will describe the present invention according to the preferred embodiments. It is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned without departing from the scope of the appended claims

FIG 1 .0 illustrates a telecommunication tower structure of the present invention (100) for use in wireless communication network. The tower structure comprises at least one radio base station. The tower structure is constructed using selected bamboo culms. The selected bamboo culms form lattice grid of vertical and horizontal members. Additionally diagonal culms are attached to the nearest vertical member of the lattice for support as shown in FIG 1 .0a. The tower structure comprises a tower section preferably of a square shape. The selected bamboo culms are adjoined through bracing means. The tower further comprises of a concrete pedestal. The tower can be erected to a desired height. The tower is also provided with means to allow access to the radio station. FIG 2.0 illustrates the concrete pedestal of the present invention. FIG 2.0 (a) illustrates an overview of the concrete pedestal which comprises of a plurality of base plates in nut and bolt assembly. The columns in the concrete pedestal (200) are pipes (206) which guide the bamboo culms in vertical position. The concrete pedestal (200) supports the bamboo telecommunication tower. FIG 2.0 (b) illustrates the components in the column pedestal (200) which comprises of column bearing plate (202), base plates (204) containing bolted connections and metal pipe (206) affixed to the base plate. FIG 2.0 (c) illustrates a cross section of pedestal to roof slab connection according to present invention. The slab for the pedestal comprises of metal reinforced concrete. FIG 3.0 illustrates the tower structure of the present invention constructed with selected bamboo culms. The selected bamboo culms make up the vertical, horizontal and diagonal members of the lattice grid. The vertical and horizontal members are interconnected by bracing means to form support for continuous erection of the tower. FIG 3.0a illustrates the multiple joint utilized as the bracing means. FIG 3.0a (i) illustrate the metal plate utilized for vertical bracing of the bamboo culms. FIG 3.0a (ii) illustrates the horizontal bracing means to connect at least two horizontal bamboo culms with at least one bamboo culms. The horizontal bracing comprises of metal clamps (302) and flat metal plates (300). The metal clamps (302) has circular hollow pipe section positioned to receive horizontal and vertical members to form a lattice grid FIG 3.0a (iii) illustrates metal plates (300) for diagonal attachment of bamboo culms to form the lattice grid. All the bracing means are connected using nut and bolt assembly.

FIG 4.0 illustrates bamboo element in nut and bolt assembly. To provide a robust tower structure, the bamboo elements are inserted with nut and bolt in transverse direction at each end of the bamboos and thereafter are attached to metal plates. This feature increases the tensile strength of the bamboo telecommunication tower.

The selected bamboo culms in the present invention are pre-treated with water and chemical preservatives. The water preservation maintains the green condition of the bamboo culms. The chemical preservation which comprises of painting layers of pesticides and bituminous material on bamboo culms deters fungal and insect attacks. To increase the aesthetics, the bamboo culms are coated with enamel painting. For the purpose of building the bamboo telecommunication tower it is desirable to select bamboo culms which are naturally straight with no defect or decay.

The following experiments were carried out to determine suitability of bamboo for the construction of the telecommunication tower. The multiple destructive and non- destructive tests performed are as provided below:

Examples of experiments a) Physical Properties Three types of bamboos were selected for the investigation of physical properties. Physical dimensions such as diameter, wall thickness and distance between nodes for each of the bamboo types were measured. A node is the thickening part of bamboo at intervals along its length. The walls are the thicker parts on both sides of the node. Additionally, density of those bamboos specimens was also measured by taking small segments (i.e. 50mm to 100mm) and removing moisture prior to measuring volume and weight.

Table 1 : Physical Properties of Bamboos

As indicated in Table 1 , Chittagong bamboo provides the highest density (more than 10% higher than Tangail bamboo despite having greater wall thickness and diameter). Properties of Rangpur bamboo are inferior as compared to Tangail and Chittagong bamboos for all types of properties measured. b) Compressive Strength

Bamboo specimens were prepared to undergo compressive strength testing by including at least one node at the mid-height region having a length of 250 mm. A loading rate of 3.0KN/sec is applied to the bamboo specimens. The load was applied continuously until the specimen failed and the maximum load carried by the bamboos during the test was recorded in Table 2.

Table 2: Results of Compressive Strength of Bamboos

As indicated in Table 2, Tangail bamboo provides the highest compressive strength of 146 kN while Rangpur bamboo has the lowest compressive strength of 77kN. c) Splitting Tensile Strength

Splitting tensile strength is an indicator of bamboo strength perpendicular to its fiber direction. A length of 250mm for each type of bamboo is prepared and a loading rate of 3.0kN/ sec is applied. The load was applied continuously until the bamboos failed and the maximum load carried by said bamboos during the test was recorded in Table 3.

Table 3: Results of Splitting Tensile Strength

As indicated in Table 3, Tangail bamboo specimens were found to have higher splitting tensile strength as compared to Chittagong and Rangpur bamboo specimens. d) Compressive and Tensile Strength of Bamboo with Joints For the construction of bamboo telecommunication tower, it is essential to provide a robust joint design. The present invention provides a number of holes drilled in transverse direction at each end of the bamboos. Circular bolts of 12 mm diameter are utilized to pass through these holes and are further attached to steel plate. This arrangement is placed in the universal testing machine and followed by application of compressive and tensile loads. The tensile strength result is provided in Table 4.

Table 4: Results of Tensile Strength (Joint) of Bamboo

As indicated in Table 4, Tangail bamboo provides the highest tensile capacity which is about 60-65% higher than Chittagong and Rangpur bamboo. Accordingly, the Tangail type bamboo is selected for further test to determine maximum tensile capacity.

To analyse the feasibility of improve tensile capacity by increasing number of bolts, the number of bolts attached to Tangail bamboo specimen joints was increased from two to five as indicated in Table 5. The results show that its tensile capacity increases linearly when the number of bars through holes is increased and reaches 1 10kN for five steel bars (Graph 1 ).

Table 5: Results of Tensile Strength (Joint) of Graph 1 indicate relation between Tangail-type Bamboo with Increment of Bolt numbers of bolt against tensile strength (kN) Considering the linear relationship, it can be taken that when 5 bolts are utilized; the tension capacity of Tangail bamboo is 50kN.

A similar arrangement was tested by applying compressive loads on Tangail bamboo with a length of 1 .5m. The result of compressive strength (joint) of bamboo is provided in Table 6.

Table 6: Results of Compressive Strength (Joint) of Bamboo (length of 1 .5m)

with increment of Bolt

As indicated in Table 6, no benefit could be observed by increasing the numbers of bolt from two to five as the compressive strength consistently remained between 56 to 87 kN.

Bar chart 1 : Compressive Strength (Joint) of Bamboo with Increment of Bolt As illustrated in Bar chart 1 , average compressive strength is obtained with respect to number of bolts. During the compressive strength, the bamboos were observed to show splitting of fibre in parallel direction to load and bucking out of those fibres. Therefore, the compression capacity of bamboos is taken at 40kN. Criteria of Selected Bamboos

Based on the executed experiments, Tangail bamboo was found to be the most suitable type of bamboo for the construction of telecommunication infrastructure due to the following properties;

• Natural defect: Naturally straight with no defect and decay;

• Density: More than 150 gm/cc;

• Internode distance: Not more than 225mm;

• Diameter: Not less than 80mm;

• Wall thickness: not less than 16mm;

• Usable height: 5.5m and

• Color: Deep grey

Treatment of Bamboo

Prior to the construction of bamboo for the use in constructions of telecommunication tower, the selected bamboo undergo pre-treatment. The bamboos are preserved in green condition under water for at least 10 days. Two types of chemical preservatives were applied initially; termite control pesticide is applied to the bamboos in four layers to protect bamboos from degradation. Each layer of pesticide is applied within four hours. Subsequently, the bamboos are coated with bituminous materials to preserve bamboo in wet condition. For the pre-treatment one gallon of both termite control pesticide and bituminous coating is required. Finally, enamel coating is applied to the bamboos to improve its aesthetic feature.

Expected life

With periodic maintenance the expected life time of the bamboo tower is 5 years. The tower is subjected to routine maintenance every six months and any form of decay and insect or fungal attack observed should be immediately rectified.

Material Properties

The principal materials of the bamboo tower comprise of bamboo, steel and concrete. Physical properties of these materials are provided below: • Yield strength of deformed rebar, fy = 500.00 MPa

• Modulus of elasticity of deformed bar, Es = 200000.00 MPa

• Density of deformed bar, Psteel = 7850 kgm-3

• Compressive strength of concrete for pedestal, fc' = 21 .00 MPa

· Modulus of elasticity of concrete, Ec = 16993.83 MPa for brick aggregates

• Density of concrete, Pconcrete = 2162.82 kgm-3

• Allowable tensile force of bamboo, Ft = 54.00 kN (allowable tensile force is 45%)

• Allowable compressive force of bamboo, Fc = 40.00 kN (allowable compressive force is 65%)

· Modulus of elasticity of concrete, Ebm = 9120.00 MPa

• Density of bamboo, Pbamboo = 610 kgm-3

• Allowable Drift of bamboo tower= 0.00065

Strength analysis between galvanised iron pipe and bamboo

A comparison analysis on the strength of galvanised iron pipe and bamboo of the present invention is tabled below:

Table 7: Strength Analysis between Galvanised Iron Pipe and Bamboo

Gravity loads

The gravity loads of the bamboo tower of the present invention are described below; Dead loads:

Dead loads acts along the gravity direction without any change during the normal service life of the structure. Dead loads are normally classified into two types self- weight of structure and super imposed dead load from non-structural elements. The total weight of the structural members in each stage of the bamboo tower is considered as the self-weight of the structure.

Live loads Live loads are produced by the use or occupancy of the bamboo tower. The live loads used for the structural members shall be the greatest applied loads from the intended use. Therefore, the live load for the bamboo tower for the present invention includes the micro-wave dish and GSM antenna.

Details of live loads of according to an embodiment of the present invention are provided below:

Micro-wave antenna

• Diameter of micro-wave antenna = 0.9m

• Mass of micro-wave antenna = 35 kg

• Total number of micro-wave antenna = 4.0 kg

Global system for mobile (GSM)

• Physical dimension of each GSM antenna = 2.6m(H) x 0.26m(W) x 0.16m(D)

• Mass of each GSM antenna = 22 kg

• Total number of GSM antenna = 2.0

Lateral Loads and Wind Loads

The minimum design wind load on buildings and components is determined based on the velocity of the wind, size and shape of building and the terrain exposure condition of the site.

Building Location: Narayanqonj, Dhaka, Bangladesh

For lateral and wind load analysis for the present invention, a building location at Narayangonj, Dhaka, Bangladesh is investigated. The overall design of the structures is based on the general design requirements as specified in Bangladesh National Building Code (BNBC) 2006. The criteria for determining wind load are provided below:

Building location: Narayangonj, Dhaka, Bangladesh Basic wind speed: V _b = 210kmh ^-1

Building total height: h _n = 13.242 m from ground level Structural importance factor: C _l =1 (standard occupancy)

Exposure category: A

Gust coefficient: C _G = 1 .4406 To determine the wind pressure which the tower structure can withstand the following equation is used: The coefficients vary with respect to individual floor height from existing ground level and the geometry of the building plan. The overall pressure coefficient for the bamboo

tower of the present invention was calculated in accordance to BNBC 2006 (ref. BNBC 2006, part 6, Cha 2, Art. 2.4, and Table 6.2.20).

Load combinations

The load combination equations for the bamboo tower of the present invention are followed in accordance to Allowable Stress Design (ASD) Method. Notations for each load pattern are specified as: Dead loads = D, Live loads = L; Wind loads = W

Support conditions The support condition depends on the building structural system, configuration, and foundation type. The base point of all vertical structural members is hinged support. The hinged support condition implies that the point is restrained in translation movement along the three principal axes ( U _x , U _y , U _z ) and is unrestrained on the rotation of three principal axes (r _x , r _y , r _z ).

Application of loads

Analyses on applied loads on the bamboo tower built at Narayangonj, Dhaka, Bangladesh were carried out. Table 8 shows the maximum tensile and compressive forces applied to bamboo tower of the present invention.

Table 8: List of Maximum Tensile and Compressive Forces for Structural Members of the

Bamboo Tower Point drift for wind forces along x and y axis direction were also analysed. The result of the point drift is tabled below:

Table 9: Point drift for wind forces The bamboo telecommunication tower structure of the present invention can withstand wind pressure up to 210 Kmh ^-1 with an expected lifespan of about 5 years. Further, the use of bamboos in the tower structure of the present invention is low in cost as compared to existing steel based and galvanised iron type of tower structure. The bamboo telecommunication tower structure is environment friendly as bamboo is known to be low carbon structures as it emits negligible amount of carbon dioxide. Unless the context requires otherwise or specifically stated to the contrary, integers, steps or elements of the invention recited herein as singular integers, steps or elements clearly encompass both singular and plural forms of the recited integers, steps or elements. Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated step or element or integer or group of steps or elements or integers, but not the exclusion of any other step or element or integer or group of steps, elements or integers. Thus, in the context of this specification, the term "comprising" is used in an inclusive sense and thus should be understood as meaning "including principally, but not necessarily solely".