STUDIES ON TELECOMMUNICATION TOWERS IN CUBA

Transcription

1 International Association for Shell and Spatial Structures Meeting of Working Group 4 on Mast and Towers September,11-15, 2011, Copenhagen, Denmark STUDIES ON TELECOMMUNICATION TOWERS IN CUBA Authors: Vivian Elena Parnás (vivian@civil.cujae.edu.cu) Patricia Martín Rodríguez (patriciamr@civil.cujae.edu.cu) Ingrid Fernández Lorenzo (ingridfl@civil.cujae.edu.cu) Abel Carrasco Luzardo (abelcl@civil.cujae.edu.cu) Alejandro López Llanusa (alo@civil.cujae.edu.cu) Faculty of Civil Engineering Instituto Superior Politécnico J.A.Echeverría (Cujae) La Habana, Cuba

2 CUBA The main island between Antilles, in the Caribbean 110,000 km 2 Surface 11.2 Million Inhabitants Average Cyclone Formation ( ): 10.4 per year

3 Telecommunication Towers Self-supported Towers Guyed Mast

4 13 TELEVISION TOWERS RADIO TOWERS AFFECTED PEOPLE: FALLAS DE TORRES ATIRANTADAS EN EL FAILURES OF TELECOMMUNICATION TOWERS UNDER EXTREME WIND ACTIONS MUNDO 5 TELEVISION TOWERS TROPICAL CYCLONE SEASON COMMUNITY RADIO TOWERS AFFECTED PEOPLE:

5 PROJECT TELECOMMUNICATION TOWERS : STRUCTURAL VULNERABILITY AND BASES FOR CUBAN CODE

6 MISSION To develop advanced studies on the area of Civil Engineering, which are applied mainly at analysis and design of lattice steel structures.

7 GENERAL AIMS To develop researches which allow reducing structural vulnerability of telecommunication towers, as well as introducing the results in the professional practice. The results should corresponding with world develop in this topic. To create the bases for future national code for telecommunication towers.

8 Senior Researchers (3) PhD candidates (2) Master candidates (4) MEMBERS OF THE GROUP Chair: Vivian Elena, PhD Students of Civil Engineering (15)

9 GUIDELINES Fluid (wind)-structure Interaction METHODS COMPUTATIONAL Dynamic Analysis of Structures EXPERIMENTAL Failures Analysis

10 RESEARCH RESULTS (1) Studies of structural failure on telecommunication lattice towers. Studies of anchors asymmetry in guyed towers under static wind forces. Evaluation of non-linear analysis of guyed tower. Changes on structural behaviour of guyed towers with outriggers.

11 RESEARCH RESULTS (2) Influence of variations on boundary conditions of the foundation in the mast in a guyed latticed tower mast. Variation on structural behavior for different initial tension on guyed tower. Influence of variations on sections members and geometry of the mast in a guyed latticed tower mast. Comparative study between telecommunication towers codes.

12 RESEARCH RESULTS (3) Failure analysis. Case of study: Najasa Tower Effect of deterioration due to corrosion Dynamic analysis for wind and seismic loads. Influence of local topography and non-linear analysis in the design of transmission towers.

13 TWO EXAMPLES

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15 Trajectory of Hurricanes which affected Cuba ( )

16 Methodology Study of relation tower-cyclone Speeds of H-3 ( Km./h) Speeds of Tropical Storm ( Km./h) Speeds of Tropical Storm( Km./h)

17 Summary Cyclone Name Year Max. Wind (km/h) Saffir Simpson Scale above Cuba Max. wind registered in Cuba (averg. 1 min) (km/h) Max. wind equivalent Cuban code. (averg. 10 min) Towers in area of speed winds higher 100km/h Total Failures Towers Lili ? Georges ? Michelle > Isidore Lili Charley > Iván Arlene TT < Dennis Wilma Total 42 13

18 Summary of Period Estimated wind speeds less than 165 Km/h on failure towers (except two towers) Guyed masts were 70 % of failure towers. 80% of failures were guyed mast with asymmetric anchors

19 Failures Failures on elements foundation, anchors, cables. Presence of a large number of antennas at the moment of the failure

20 Failures Connection Failures Flexion-torsion efforts

21 Conclusions Wind pressure on towers was lower than 0.9 kn/m 2 in the 60% of failures towers. The 80% failures towers were localized on high topography zones where the increments of wind pressure are higher than 100 %. The 70% failures towers were between 30 and 40 years old.these had more numbers of antennas in comparison with the time when they were built. Probable causes of failures on the towers: Increments of efforts due to a large number of antennas. Presence of asymmetric anchors which was not considered in the initial design of the towers. High non-lineal behavior which was not considered in the structural compute for the speed winds that influenced on the tower. No tension enough on the cables due to the passage of the time and lack of maintenance.

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23 LOCATION OF TOWERS WITH ANCHORS IN DIFFERENT LEVELS ON TOP OF HILLS Increments Incrementos of carga Wind de Load viento due to por Topographical relación topográfica Relationship % 100% 200% 300%

24 Location Conditions Wind Asymmetry Analysis H Δα L L Δα Ideal Land L L Real Land IRREGULAR TOPOGRAPHY VARIATIONS IN THE VERTICAL DIMENSIONS OF ANCHORS INCREMENTS OF WIND LOAD

25 Schematic representation of experimental study of vulnerability

26 INDEPENDENT VARIABLES ANCHORAGE ASYMMETRY CABLE TOPOLOGY 5 3 Variation of number of cables Variation of number of anchors 2 1

27 CABLE TOPOLOGY INDEPENDENT VARIABLES ASYMMETRY

28 INCREMENTS OF FORCES ON CABLES AND ANCHORS STUDIES OF CRITICAL WIND DIRECTIONS Por ciento de incremento 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% C WORTH DIRECTION Reference OF A CABLE Vertex AND ANCHORS Wind 90 B Wind 60 Wind 0 ANCLAJES ANCHORS 33 % - 45 % E1/ E12 E2/ E12 E3/ E34 E4/ E34 Altura de cable (m) CABLES Incremento CABLES 12 % -58 % ,0% 20,0% 40,0% 60,0% Incremento E1 /E12 E2/ E12 E3 /E34 E4/ E34

29 INCREMENTS OF FORCES ON MEMBERS MAST LEG A COLUMNA A C A Wind 0 B Reference Vertex WORTH DIRECTION OF MEMBERS MAST 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 12 % - 80 % E1/E12 E2/E12 1 E3/E34 E4/E34 DIAGONALES DIAGONAL MEMBERS 6 % - 45 % 1 E1/E12 E2/E12 E3/E34 E4/E34

30 CONCLUSIONS Results of this investigation show that asymmetry on anchors levels of guyed mast, under extreme wind loads, has a great influence on the magnitude of forces in all members; this condition, frequently disregarded in mast design, can produces a significant increase in expected vulnerability of the mast. Relative increments in internal forces in asymmetric models in relation to symmetric models were observed in all members. Both asymmetry and cable topology have a significant influence on internal forces in members of the mast under wind loading, but interaction between these factors was found to be not important compared to their isolated effects on structural response. According to results of the performed structural analysis, larger increments of forces were found on columns; consequently these are the more vulnerable elements of asymmetric guyed mast under extreme wind action. Comparison with actual failures of guyed masts under hurricane winds confirmed these results.

31 THANK YOU