AU2011201492B2

AU2011201492B2 - Tailored Monopole Strengthening

Info

Publication number: AU2011201492B2
Application number: AU2011201492A
Authority: AU
Inventors: Alan Samuel Bennett
Original assignee: Crown Castle Australia Pty Ltd
Current assignee: Indara Infrastructure Pty Ltd
Priority date: 2011-04-01
Filing date: 2011-04-01
Publication date: 2013-05-30
Anticipated expiration: 2031-04-01
Also published as: AU2011201492A1

Abstract

This invention concerns the construction of telecommunications towers on which transmitters are mounted, and in particular it concerns strengthening for monopole towers. A monopole hollow strengthening tower comprising stages that each comprise a pair of half-pipe sections that are tailored to fit around the monopole; wherein each pair of sections are connected to the stage below and to each other; a first stage is connected to the footing of the monopole, a second stage is connected to the top of the first stage and includes cable ports designed for the particular cabling requirement of the monopole; subsequent stages extend above the second stage; finally there is a 'top stage' which incorporates a clamping system to grip the monopole, and this stage is the only stage where the monopole and jacket are in contact with each other. C* LZ ~It c'r a* rvl -LA r4- V

Description

1 AUSTRALIA Patents Act 1990 CROWN CASTLE AUSTRALIA HOLDINGS PTY LTD COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Tailored Monopole Strengthening The following statement is a full description of this invention including the best method of performing it known to us:- 2 Title Tailored Monopole Strengthening Technical Field 5 This invention concerns the construction of telecommunications towers on which transmitters are mounted, and in particular it concerns strengthening for monopole towers. 10 Background Art Telecommunications towers are usually high so that the transmitter and receiving antennas can broadcast and receive over the tops of nearby buildings and hills. There are several different types of towers suitable for mounting transmitters. First, guyed 15 masts that are supported by guy wires. Second, lattice towers that have a wide footprint and taper as they go up. And third, monopole towers that have a small footprint and are self-supporting. Ubiquitous wireless communication networks require broadcast and receive towers to 20 be located throughout populated areas. The location, elevation and concentration of these towers are determined by geographic factors and population density. Communication companies differentiate by providing superior network coverage and capacity. These conditions have led to a market for vertical real estate capable of accommodating communications equipment. This market need has been fulfilled by 25 existing communication towers and in urban areas rooftops. The demand in this market is balanced with costs to build and operate telecommunications towers and local authority delays and community resistance to building new facilities. As a result, over time more and more equipment tends to be mounted on each existing 30 tower until eventually the maximum structural capacity for a tower may be approached. Due to network operation issues and associated costs tearing down the existing tower and building a new and bigger tower is not an attractive solution. Accordingly, techniques have been developed for strengthening the towers.

3 Lattice towers and guyed masts are able to be incrementally strengthened, for instance by adding more lattice or additional guy wires, however it is much more difficult to strengthen a monopole. 5 Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 10 Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application. 15 Disclosure of the Invention The invention is a monopole hollow strengthening tower comprising stages that each comprise a pair of half-pipe sections that are tailored to fit around the monopole. 20 Wherein each pair of sections are connected to the stage below and to each other. A first stage is connected to the footing of the monopole, a second stage is connected to the top of the first stage and includes cable ports designed for the particular cabling requirement of the monopole. Subsequent stages extend above the second stage, finally there is a 'top stage' which incorporates a clamping system to grip the 25 monopole, and this stage is the only stage where the monopole and jacket are in contact with each other. The strengthening tower surrounds the monopole, and since it is required to be extremely stiff it may be fabricated from steel or carbon fibre half-pipe sections. 30 The half-pipe sections may include flanges along their vertical edges for connection to each other. The sections may also have semi-circular flanges around their top and bottom edges for connection to the stages above and below. Webs may be 4 incorporated between the flanges and the outer wall of each section for further stiffening. The cable ports may be located at joints in the half-pipe sections such that the 5 telecommunications cables remain undisturbed, and therefore operational, throughout the installation of the strengthening tower. The footing for the monopole may be strengthened before any stages of the hollow strengthening tower are installed. Strengthening the footing may include casting a 10 concrete foundation around the existing footing to provide additional overturning resistance to the tower. A bolt cage may be embedded in the new foundation to connect to the first stage of strengthening. Additional overturning resistance may be provided by means of screw piles, rock 15 anchors or bored piers, that are connected to the new foundation. Interaction with the existing monopole footing and the weight of the new foundation also assist in the resistance of the overturning moment. As well as the second stage, other stages may include portholes for cable entry into 20 the hollow tower. Since the portholes accommodate the cabling there is no need to disconnect the cables from the monopole when the hollow tower is being built. In a further aspect the invention is a method for strengthening a monopole, by installing a hollow strengthening tower around it, where the hollow strengthening 25 tower comprises a number of stages that each comprises a pair of half-pipe sections that are connected to the stage below and to each other. Wherein the method comprises the following steps: Installing a first stage that is connected to the footing of the monopole. Installing a second stage that is connected to the top of the first stage and 30 includes cable ports designed for the particular cabling requirement of the monopole. Installing subsequent stages that extend above the second stage.

4a Finally installing a 'top stage' which incorporates a clamping system to grip the monopole, wherein the top stage is the only stage where the monopole and strengthening stages are in contact with each other. 5 When stages are to be fitted around a part of the monopole that includes equipment, a crane may be used to move the equipment to another part of the tower. After the stages are fitted, the equipment may be returned to its original location, if desired. This minimises downtime for the transmitters during strengthening. 10 The strengthening technique has been developed to meet the following operational requirements during strengthening: Minimisation of outages and disturbances for transmitters on the monopole. Shortest timeframe. 15 Minimum strengthening to meet the additional strengthening required.

5 And, avoids enlargement of the telecommunications compound area. Brief Description of the Drawings 5 An example of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1(a) is a pictorial view of a monopole including its footing and equipment. Fig. 1(b) is an elevation of the lower part of the monopole of Fig. 1(a) 10 including its cable bundles. Fig. 2(a) is a pictorial view showing an upgraded footing for the monopole of Fig. 1. Fig. 2(b) is a pictorial view of the monopole of Fig. 2(a) after a first semi 15 circular strengthening section has been put in place. Fig. 2(c) is a pictorial view of the monopole of Fig. 2(b) after a second semi circular strengthening section has been secured in place; completing a first stage of strengthening. Fig. 2(d) is an elevation of one of the semi-circular strengthening sections of 20 Fig. 2(b) and (c). Fig. 2(e) is a plan view of the semi-circular strengthening of Fig. 2(b) and (c). Fig. 3(a) is a pictorial view of a further pair of semi-circular strengthening sections incorporating portholes for cables. 25 Fig. 3(b) is a pictorial sketch of the semi-circular strengthening sections of Fig. 3(a) incorporating port holes for cables. Fig. 4(a) is a pictorial view of the monopole fitted with the strengthening sections of Figs. 2 and 3. 30 Fig. 4(b) is a pictorial sketch of the arrangement of Fig. 4(a). Fig. 5 is a pictorial view of the monopole of Figs. 4 after a further pair of sections have been added.

6 Fig. 6(a) is a pictorial view of a 'top stage' for the strengthening, which is clamped to the monopole. Fig. 6(b) is a plan view of the 'top stage' of Fig. 6(a) showing the clamping arrangement. 5 Fig. 7(a) is a pictorial view of the monopole after the strengthening has been completely installed. Fig. 7(b) is a pictorial view of the monopole after strengthening and including an additional stage to the strengthening to increase its height. 10 Best Mode of the Invention Referring first to Fig. 1(a) monopole 10 can be seen to have a subterranean footing 12, and to be equipped with various transmitters 14. The transmitters are fed by cables 16 15 that run from a cable hut 18. The feed to the cable hut generally runs in underground ducts. It can be seen that monopole 10 tapers to increasingly narrow sections as it goes up. There are typically a bundle of cables for each customer who uses the tower. The first 20 customer will typically have their cables running up the interior of the tower, later customers will have their cables running up the exterior of the tower. Fig. 1(b) shows a first cable port 20 opening in the tower wall to receive a first cable bundle 22. A second cable bundle 24 runs up the outside of the tower. Underground, the bottom 26 of the monopole 10 is set in a concrete footing 28. 25 It will be appreciated that the greatest strain on the monopole is near its base. It follows that the first part that might need strengthening is the footing 28. Referring now to Fig. 2(a) the interior of the subterranean part of the monopole 26 is filled with concrete. Then a second large concrete foundation 30 is set around the base of the 30 monopole. All this extra weight increases the overturning resistance of the monopole. Rock anchors 32 are bored to the required depth to provide sufficient additional restraint as required. A bolt cage 34 is installed at the upper end of foundation 30.

7 Next, an extremely stiff hollow strengthening tower 120 is constructed around monopole 10. The hollow tower is placed around the monopole in stages with the first stage being placed on foundation 30. Each stage has two 'half-pipe' sections which are semicircular in horizontal section. They are placed around the monopole using a crane 5 40. The first section 50 of the hollow strengthening tower 120 is shown in place in Fig. 2(b). Its mating section 52 is shown in place in Fig. 2(c) which completes the first stage of tower 50. Figs. 2(d) and (e) show that each section has a semi-circular wall 10 54 with a top flange 56 and a lower flange 58. Reinforcing webs 60 are positioned around the bottom of the sections between the lower flange 58 and the wall 54 to increase stiffness. Vertical flanges 62 and 64 run up the edges of each section so they can be fastened 15 together. The sections are bolted to each other and to the bolt cage in foundation 30. It will be seen from Figs. 2 that the first sections 50 and 52 are tailor made with a height that stops below the height were cable trays 22 and 24 arrive at the monopole 10. 20 The second stage sections 70 and 72 of strengthening tower 120 have portholes to allow the cable bundles to enter under the hollow tower 50. Section 70 has a porthole 74 opening at the bottom, and both sections 70 and 72 have half of a mating porthole 76 that is formed when they are connected together. Sections 70 and 72 are also 25 bolted to sections 50 and 52 of the first stage. Cable tray 22 belonging to the first customer enters through port hole 74 and goes into the interior of monopole 10. The second customer's cable tray 24 enters porthole 76 slightly higher up the monopole 10 and runs up the outside of the monopole. 30 Above the cable portholes a third stage 80/82 of the strengthening tower 120 is added about the monopole 10, see Fig. 4(a). This section has no portholes. It can be clearly seen in Fig. 4(b) that the hollow tower does not contact the surface of the monopole 10.

8 Fig. 5 shows a further stage 90 of the strengthening tower 120 fitted around the monopole 10. This stage has a slight taper 92 along its length to tailor it to the shape of the monopole as it rises. Its length is also governed by the shape of the monopole. 5 Figs. 6(a) and (b) show a 'top stage' 100/102 which is fitted around the monopole at the top of strengthening tower 120. The top stage carries four clamps 110, 112, 114 and 116 that grip the outside of monopole 10. This is a 'pinned' connection that changes the existing cantilever structure of the monopole 10 into a 'propped' cantilever structure. The majority of any force caused by bending in the monopole 10 10 is transferred through this 'pinned' connection to the hollow strengthening tower 120. The height at which the 'top stage' 100/102 is clamped to the monopole 10, is determined by the degree of strengthening required. For instance, when a monopole is loaded to its design capacity and new equipment is to be installed, then the top stage 15 100/102 will be installed to the height required for that degree of strengthening. When further equipment is required then the 'top stage' will be taken off, one or more new stages of the hollow tower are added, and then the 'top stage' is reinstalled at a greater height; giving greater strength. This can happen several times during the life of a monopole. The clamps 110, 112, 114 and 116 are adjustable so that they can 20 accommodate to clamp different diameters of the monopole. This allows the same clamps to be used and re-used at any required height. Fig. 7(a) shows a monopole 10 that is completely encased by hollow tower 120. Fig. 7(b) shows a hollow tower 120 that extends above the existing monopole. 25 Although the invention has been described with reference to a particular example it should be appreciated that it may be embodied in many other forms and variations.

Claims

1. A monopole hollow strengthening tower comprising stages that each comprise 5 a pair of half-pipe sections that are tailored to fit around the monopole; wherein each pair of sections are connected to the stage below and to each other; a first stage is connected to the footing of the monopole, a second stage is connected to the top of the first stage and includes cable ports designed for the particular cabling requirement of the monopole; 10 subsequent stages extend above the second stage; finally there is a 'top stage' which incorporates a clamping system to grip the monopole, and this stage is the only stage where the monopole and jacket are in contact with each other. 15

2. A monopole hollow strengthening tower according to claim 1, wherein the strengthening tower is fabricated from steel or carbon fibre half-pipe sections.

3. A monopole hollow strengthening tower according to claim I or 2, wherein the half-pipe sections include flanges along their vertical edges for connection to each 20 other.

4. A monopole hollow strengthening tower according to claim 3, wherein the sections also have semi-circular flanges around their top and bottom edges for connection to the stages above and below. 25

5. A monopole hollow strengthening tower according to claims 2, 3 or 4, wherein webs are incorporated between the flanges and the outer wall of each section for further stiffening. 30

6. A monopole hollow strengthening tower according to claim 1, wherein the footing for the monopole is strengthened before any stages of the hollow strengthening tower are installed. 10

7. A monopole hollow strengthening tower according to claim 6, wherein strengthening the footing includes casting a concrete foundation around the existing footing to provide additional overturning resistance to the tower. 5

8. A monopole hollow strengthening tower according to claim 7, wherein a bolt cage is embedded in the new foundation to connect to the first stage of strengthening.

9. A monopole hollow strengthening tower according to claim 7 or 8, wherein additional overturning resistance is provided by means of screw piles, rock anchors or 10 bored piers, that are connected to the new foundation.

10. A monopole hollow strengthening tower according to claim 1, wherein the portholes for cable entry into the hollow tower are located at joints in the half-pipe sections such that the telecommunication cables remain undisturbed, and operational, 15 throughout the strengthening installation.

11. A method for strengthening a monopole, by installing a hollow strengthening tower around it, where the hollow strengthening tower comprises a number of stages that each comprises a pair of half-pipe sections that are connected to the stage below 20 and to each other; wherein the method comprises the following steps: installing a first stage that is connected to the footing of the monopole; installing a second stage that is connected to the top of the first stage and includes cable ports designed for the particular cabling requirement of the monopole; 25 installing subsequent stages that extend above the second stage; finally installing a 'top stage' which incorporates a clamping system to grip the monopole, wherein the top stage is the only stage where the monopole and strengthening stages are in contact with each other. 30

12. A method according to claim 11, wherein when stages are to be fitted around a part of the monopole that includes equipment, a crane is used to move the equipment to another part of the tower. 11

13. A method according to claim 12, wherein after the stages are fitted, the equipment is returned to its original location.

14. A monopole hollow strengthening tower substantially as hereinbefore 5 described with reference to the accompanying drawings.

15. A method for strengthening a monopole substantially as hereinbefore described with reference to the accompanying drawings.