Analysis of Tubular Telecommunication Tower

The telecommunication industry plays a great role in human societies and thus much more attention is now being paid to telecommunication towers than it was in the past. The Indian telecom service business is the fastest growing one in the world, with over seven million mobile subscribers being added every month. This expanding base possesses challenges to mobile operators in terms of augmenting and upgrading infrastructure to maintain to quality of services. During the natural disasters such as the earthquakes telecommunication towers have the crucial task of instant transmission of information from the affected areas to the rescue centres. The general availability of a wide range of square, rectangular, and round structural tubing increased. The use of tubular joints greatly improved the aesthetic qualities of the truss, and the higher load carrying capacity of the structural capacity of the structural tube members provided a wide range of applications for a triangular cross section truss. Tubular sections are used for truss members, the range of different standard shapes and sizes produced is much less than wide flange shapes and availability of some standard shapes is still limited. Due to these important roles, towers should preserve their immediate occupancy level when strong ground motion happen. Fastest growing telecommunication market has increased the demand of steel towers. The major loads considered for design of these towers are self-weight, wind load, seismic load, antenna load, platform load, steel ladder load etc. Failure of towers is generally due to high intensity winds. Several studies have been carried out by considering wind and earthquake loads. A failure of a telecommunication tower especially during a disaster is a major concern in two ways. Failure of telecommunication systems due to collapse of a tower in a disaster situation causes a major setback for rescue and other essential operations. Also, a failure of tower will itself cause a considerable economic loss as well as possible damages to human lives. Hence, analysis of telecommunication towers considering all possible extreme conditions is of utmost importance. The tubular sections are more efficient sections which are adoptable to many different situations. The tubular section cannot be surprised in its efficiency by other sections.

The tubular sections are used as structural component since along. A large no of tubular structures have been constructed in the past. The

become an important design consideration. The mast and transmission towers are other examples where tubular section are utilized effectively. In the past, the use of tube was hampered because of connection details. The tubular sections are more efficient sections which are adoptable to many different situations. The tubular section cannot be surprised in its efficiency by other sections.

When a tall structure is subjected to lateral or torsional deflections under the action of fluctuating wind loads, the resulting oscillatory movement can induce a wide range of responses in the structure‘s occupants from mild discomfort to acute nausea. As far as the ultimate limit state is concerned, lateral deflections must be limited to prevent second order p-delta effect due to gravity loading being of such a magnitude which may be sufficient to precipitate collapse. To satisfy strength and serviceability limit stares, lateral stiffness is a major consideration in the design of tall buildings. The simple parameter that is used to estimate the lateral stiffness of a structure is the drift index defined as the ratio of the maximum deflections at the top of the structure to the total height. Different structural forms of tall structures can be used to improve the lateral stiffness and to reduce the drift index. In this research the study is conducted for braced frame structures. Bracing is a highly efficient and economical method to laterally stiffen the frame structures against wind loads. A braced bent consists of usual columns and girders whose primary purpose is to support the gravity loading, and diagonal bracing members that are connected so that total set of members forms a vertical cantilever truss to resist the horizontal forces. Bracing is efficient because the diagonals work in axial stress and therefore call for minimum member sizes in providing the stiffness and strength against horizontal shear.

Because lateral loading on a structure is Reversible, braces will be subjected in turn to both tension and compression, consequently, they are usually designed For the more stringent case of compression. For this Reason, bracing systems with shorter braces, for example K bracing, may be preferred to the full diagonal types. As An exception to designing braces for compression, the Braces in the double diagonal is designed to carry in Tension the full shear in panel. A significant advantage of The fully triangulated bracing types is that the girders Moments and shears are independent of the lateral loading on the structure.

1. Keshav Kr. Sharma, S.K.Duggal, Deepa Kumar Singh And A.K.Sachan (2015)[6] : Over the past 30 years, the growing demand for wireless and broadcast communication has spurred a dramatic increase in communication tower construction and maintenance. Failure of such structures is a major concern. In this paper a comparative analysis is being carried out for different heights of towers using different bracing patterns for Wind zones I to VI and Earthquake zones II to V of India. Gust factor method is used for wind load analysis, modal analysis and response spectrum analysis are used for earthquake loading. The results of displacement at the top of the towers and stresses in the bottom leg of the towers are compared. 2. Siddesha.H (2010)[2]: Open latticed steel towers are used widely in a variety of civil engineering applications. The angle sections are commonly used in microwave antenna towers. This paper presents, the analysis of microwave antenna tower with Static and Gust Factor Method (GFM). The comparison is made between the tower with angle and square hollow section. The displacement at the top of the tower is considered as the main parameter. The analysis is also done for different configuration by removing one member as present in the regular tower at lower panels. 3. Ismail (2014)[3] : Telecommunication structures are essential components of communication and post-disaster networks that must remain operational after a designlevel of earthquake. This study provides dynamic field measurements of 138 m guyed tower located at Qussia city, Upper Egypt. In situ measurements of ambient tower vibrations are used to determine the dominant natural frequencies of the tower. The measurements were made using a LMS SCADAS system and four wireless vibration sensors for recording the ambient vibrations of the mast. The tension in the guy wires was measured by mechanical equipment. The dynamic properties of the guyed mast (natural frequencies and mode shapes) were extracted from these measurements. Results of the eigenvalue analysis of numerical models of the tower were compared with the natural frequencies and mode shapes extracted from the in situ measurements.

finite element model. The nonlinear static analysis based on the updated finite element model was carried out. Seismic assessment and comparison between the original and updated models taking into account the deterioration in elements are presented.

Modelling and Loading Details:

1) Zone factor: 0.16 (Zone III) 2) Response reduction factor: 4 3) Important factor: 1 4) Type of Soil: II, (Medium Soil)

1) Wind speed: 39 m/s 2) Terrain category: 4 3) Structure class: c 4) Risk Coefficient k: 1 5) Topography factor k3: 1

LIVE LOAD: 1 KN/m (Only one side of tower)

ANTEENA LOAD:

Table 1 ETABS. Also Response spectrum cases SPEC X & SPEC Y are applied in ETABS

1. The lateral displacement goes on increasing as the height of tower increases. 2. The base shear goes on increasing as the height of tower increases. 3. The inverted V bracing has less displacement as compare to X bracing. 4. Inverted V bracing is efficient than X Bracing under the seismic loading. 5. The lateral displacement goes on increasing as the height of tower increases. 6. The base shear goes on increasing as the height of tower increases. 7. The inverted V bracing has less displacement as compare to X bracing. 8. Inverted V bracing is efficient than X Bracing under the wind loading.

A. Ismail (2014). ―Seismic assessment of guyed towers: A case study combining field measurements and pushover Analysis‖ HBRC, Structure and Metallic Institute, Egypt pp. 47- 53 Gholamreza Soltanzadeh, Hossein Shad, Mohammadreza Vafaei, Azlan Adnan (2014) ―Seismic performance of 4-legged Self-supporting Telecommunication Towers‖ Faculty of civil engineering, University Teknology Malaysia, Vol. 3, Issue 2, ISSN 2277 – 9442 Ghyslaine Mcclure, Laura Georgi and Rola Assi (2004). ―Seismic Considerations for Telecommunication Towers Mounted On Building Rooftops‖13th World Conference On Earthquake EngineeringVancouver, B.C., Canada, Paper No. 1988 Hemal J. Shah Dr. Atul K. Desai (2014). ―Seismic Analysis Of Tall TV Tower Cosidering Different Bracing Systems‖ International Journal of Engineering, Business and Enterprise Applications (IJEBEA) www.iasir.net IS 1893:2002 (Part I), Indian Standard Criteria for Earthquake Resistant Design of Structures, Bureau of Indian Standards, New Delhi. General Construction in Steel, Bureau of Indian Standards, New Delhi. IS 875:1987 (Part I), Indian Standard Code of Practice for Design loads (Other than Earthquake) for buildings and structures, Part I Dead loads - unit weights of building materials and Stored materials (second revision), bureau of Indian standards, New Delhi. IS 875:1987 (Part II), Indian Standard Code of Practice for Design loads (Other than Earthquake) for buildings and structures, Part II Imposed loads - unit weights of building materials and Stored materials (second revision), bureau of Indian standards, New Delhi IS 875:1987 (Part III), Indian Standard Code of Practice for Design loads (Other than Earthquake) for buildings and structures, Part III Wind loads - unit weights of building materials and Stored materials (second revision), bureau of Indian standards, New Delhi. Jithesh Rajasekharan, S Vijaya (2014) ―Analysis Of Telecommunication Tower Subjected To Seismic and Wind Loading‖ International Journal Of Advancement In Engineering Technology, Management and Applied Science, Volume 1, Issue2 ISSN :2349-3224 Keshav Kr. Sharma, S.K. Duggal, Deepak Kumar Singh And A.K. Sachan (2015) ―Comparative Analysis Of Steel Telecommunication Tower Subjected To Seismic and Wind Loading‖ Civil Engineering And Urban Planning: An International Journal (Civej), Vol.2, No.3, Marcel Isandro R. de Oliveira, José Guilherme S. da Silva, Pedro Colmar G. da S. Vellasco, Sebastião Arthur L. de Andrade, Luciano R. O. de Lima ―Structural Analysis of Guyed Steel Telecommunication Towers for Radio Antennas‖ Universidade do Estado do Rio de Janeiro – UERJ Programa de Pós-Graduação em Engenharia Civil, Vol. XXIX, No. 2 / 185 Mohd Rafiq Mahboba, Jamaluddin Mahmuda, Mohd Azuan Mohd Azlanb, Aidah Jumahata (2013). ―Finite Element Analysis of Telecommunication Mini Mast Structure‖ University Teknologi MAR, Malaysia

Sachin Paul, Eldhose M Manjummekudiyil (2008). ―Seismic Study of Building with Roof Top Telecommunication Towers‘‘ International Journal of Emerging Technology and Advanced Engineering (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 3, Siddesha H. (2010). ―Wind Analysis of Microwave Antenna Tower‖ International Journal of Applied Engineering Research, Dindigul Volume 1, No 3, 2010

Assistant Professor, Civil Engineering Department, JSPM‘s ICOER, Wagholi, Pune, Maharashtra, India