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Journal of Wind Engineering

and Industrial Aerodynamics 91 (2003) 1007–1022

Experimental study of the wind forces on

rectangular latticed communication towers

with antennas

C!elio F. Carril Jr.

a,

*, Nicholas Isyumovb

,Reyolando M.L.R.F. Brasilc

aLaborat !orio de Estruturas e Materiais Estruturais, Departamento de Engenharia de Estruturas e

Funda@ *oes, Escola Polit!ecnica da Universidade de S *ao Paulo, Caixa Postal 61548,

S *ao Paulo CEP 05424-970, Brazil bBoundary Layer Wind Tunnel Laboratory, The University of Western Ontario, London, Ontario,

Canada N6A 5B9cDepartamento de Engenharia de Estruturas e Funda@ *oes, Escola Polit!ecnica da Universidade de S *ao Paulo,

Caixa Postal 61548, S *ao Paulo CEP 05424-970, Brazil

Abstract

With today’s expanding communication systems, a large number of lattice towers to

support cellular antennas are being constructed in Brazil. Due to the lightweight of these

structures, wind forces are the primary concern in the design. An experimental investigation

on the subject was carried out at the Boundary Layer Wind Tunnel Laboratory, University of

Western Ontario (UWO), Canada. Three section models were designed and constructed based

on existing latticed towers built in Brazil. The wind incidence angle; the tower solidity; the

shielding effect; the influence of the wind turbulence on the drag coefficient were analyzed.

Measurements were made of the mean and RMS drag and crosswind forces. The results were

compared with some existing codes and standards including the Canadian (NBCC, 1995),

American (ASCE 7-95, 1995), Australian/New Zealand (AS/NZS 1170.2-2002), Australian

(AS 3995-1994), British (BS8100, 1986), Eurocode 1 (European Committee for Standardiza-

tion, 1995) and Brazilian (NBR 6123, 1988). It is a common approach to consider the wind

forces on antennas independent of the lattice tower, without considering the effects of their

presence on the computation of the wind forces. The question arises whether this is a good

approach or not. These effects can be described by introducing an interference factor. This

factor depends, among other things, on the tower solidity. Two models with different

solidity were tested for wind incidence angle of 0 degrees and antenna dishes simulated

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*Corresponding author. Tel.: +55-11-38185705; fax: +55-11-38185181.

E-mail address: [email protected] (C.F. Carril Jr.).

0167-6105/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved.

doi:10.1016/S0167-6105(03)00049-7

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with disks made of Styrofoam attached to the windward face. The results were compared

with ESDU.

r 2003 Elsevier Ltd. All rights reserved.

Keywords: Lattice tower; Wind tunnel tests; Microwave antennas

1. Introduction

The use of freestanding latticed steel towers to support cellular and microwave

antennas in Brazil has been intensive in the last few years with the expanding of the

telecommunication systems. Due to the lightweight of these structures, wind forces

are the primary concern in the design. Also, in Brazil there are no codes specifying

how to consider the wind loads from microwave antenna dishes on lattice towers.

This paper presents an experimental investigation on the wind action on a

designed freestanding lattice tower made of angle members based on existing towers

used for telecommunication in Brazil. This work was carried out at the Boundary

Layer Wind Tunnel Laboratory of the University of Western Ontario.

For the present work, a lattice tower was designed based on existing towers for

telecommunication in Brazil. The tower geometry is presented in Fig. 1. I t i s

composed by 17 sections of 5.9 m. It is 100.3 m tall and can be used for smaller

heights by just subtracting some of the lower 5.9 m sections.On such structure, overall drag coefficients are used to calculate the wind forces.

Most of the codes present these drag coefficients as functions of the tower solidity.

The tower is separated in sections and for each section the force coefficients are

determined. The crosswind forces are negligible compared to drag forces. For square

towers most of the codes specify only drag coefficients at 0 and 45 of wind

incidence angle (the largest force coefficient).

Some important parameters, which influence the wind loading, and which are

contained in codes of practice related to lattice towers, are examined. These are:

effect of solidity on overall forces; shielding effect; wind incidence angle; influence of

turbulence. This is a long list of variables and it was a major challenge to select ameaningful combination of these for this study.

Another subject of this work is the interference of antenna dishes on the wind

forces of lattice towers. It is a common approach to consider the wind forces on

antennas independent of the lattice tower, without considering the effects of their

presence on the computation of the wind forces. The question arises whether this is a

good approach or not. To describe the influence of the antenna dishes an interference

factor is introduced. This factor depends, among other things, on the tower solidity.

This investigation does not intend to solve the problem of the interference factor

entirely due to the various parameters involved such as the position of the antenna,

type of tower, wind incidence angle, number of antennas and tower solidity. It isintended to examine just some of these important parameters. The tests were done

varying the number of the antennas and the tower solidity. The wind incidence angle

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C.F. Carril Jr. et al. / J. Wind Eng. Ind. Aerodyn. 91 (2003) 1007–10221008

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and the position of the antennas were fixed. The results of the interference factor

were compared with [1].

Holmes et al. [2] studied the interference factor of microwave antenna dishes

attached to lattice towers with different wind incidence angles, and found values

greater than unity for some wind directions. In their experiments Holmes et al. [2]

tested only one and two antennas at the same tower cross-section. The present study

is considering only the interference factor of antenna dishes attached to the

windward tower face with 0 wind incidence angle, In this case the interference factoris always less than unity.

2. Wind tunnel model

2.1. Section model

A section model was designed and constructed based on the tower described. The

model was built on a scale of 1:40 and represents part of the tower (Fig. 1) at 40 m

height approximately. It is 1 m long and 0.102 m wide (Fig. 2). Two solidities weretested. For the lowest model solidity, 0.162, the main bars were 4.6 mm thick and the

secondary bars constituted by diagonals and horizontal bars, 2 mm thick. For the

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10

5

. 9 5 . 9

5 , 9

5 . 9

9.5

14

5 . 9

5 . 9

5 . 9

5 . 916

17

15

13

12

11

5 . 9

17.7000 2

5 . 9

5 . 9

5 . 9

6

5 . 9

5 . 9

5 . 9

7

5 . 98

9

5

4

3

5 . 9

1

Horizontal bracing

1.8 m

8

2 . 6 m

Fig. 1. Lateral view of the tower.

C.F. Carril Jr. et al. / J. Wind Eng. Ind. Aerodyn. 91 (2003) 1007–1022 1009

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highest solidity, 0.267, pieces made of styrene were added to the model bars usingdouble-sided tape. The tests were conducted for Reynolds number for the main bars

of 5000 and 6000 for the lowest solidity, 7000 and 11000 for the highest solidity.

Despite the fact that the actual tower was designed for angle members, the secondary

model bars were designed with square members with the same external dimensions.

The thickness of main angle members was not properly scaled.

Force balances were mounted at each end of the model. A rig was prepared to

simulate two-dimensional flow, Fig. 5. To study the shielding effects with the

distance between frames, two other models were built with the ratio between distance

and width of s=B ¼ 2 and 3 besides the first of s=B ¼ 1 (Figs. 3 and 4). All

experiments were carried out in smooth flow (exposure 1) and turbulent flow(exposure 2) generated by a grid placed upstream, except the tests with the models

with the highest solidity carried out only in turbulent flow. The model wind spectra

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Fig. 2. Model 1 (0.102 0.102 1.035 m).

Fig. 3. Model 2 (0.102 0.204 1.035 m).


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fits better the wind spectra of ESDU 74031 [3] with zo ¼ 0:3 m and H ¼ 40m, Fig. 6.Only the highest frequency was simulated. The intensity of turbulence generated was

6.8% (Figs. 5 and 6).

2.2. Antenna model

Some disks made of Styrofoam (Fig. 7) were built at the same scale of the model to

simulate shrouded antenna dishes attached to the tower. The tests were done using 1,

2, 4, and 6 disks attached to the model by a double-sided tape in turbulent andsmooth flow. Only the wind perpendicular to one plane of the tower and to the disk

was tested.

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Fig. 4. Model 3 (0.102 0.304 1.035 m).

Fig. 5. View of the model, rig and grid.


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A small wind tunnel, with 0.5 0.5 m test section, was used for the determinationof the wind forces on the disks alone. The forces in one disk were measured

separately using a small sensitive balance. A grid was used to generate turbulence. To

minimize the disturbance caused by the load cell in the flow, the tests were conducted

with the disk connected and disconnected to the load cell, but fixed to the tunnel wall

with a rod of diameter 9.5 mm. The blockage effect was not considered because the

frontal disk area represents only 1.1% of the tunnel test section area. The

interference of the load cell on the drag force was found negligible.

All tests of the antenna attached to the section model were conducted in smooth

and turbulent flow. The mean forces were taken for two different wind speeds. The

measurements were made with and without the antennas. The disks were distributedsymmetrically along the front frame of the tower (Fig. 8). For each test, the antennas

were fixed in different positions: for one antenna, position 1 was used; for two

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0.0001

0.001

0.01

0.0001 0.001 0.01 0.1 1

Wave Number (f/V)

f S ( f ) / V 2 ESDU 74031

z o = 0.3 mz = 50 mLength scale 1:40

Velocity Scale 1:4

RMS = 0.196 volts

Test Speed at H: 9.0 m/s

o Measured data

____ ESDU 74031

Fig. 6. Wind spectrum generated by the grid and spectra from [3].

22.5 mm

60 mm

Fig. 7. Model of the shrouded microwave antenna dish (antenna disk). Scale 1:40.

4 3 2 1 2 3 4

Fig. 8. Position of the antenna disks on the model.


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antennas, position 2 was used; for 4 antennas, positions 2 and 3 were used; and for 6

antennas, positions 2, 3 and 4 were used.

3. Results

Mean and RMS drag and crosswind forces were measured at 15 intervals for the

full 180 azimuth range. The results are presented in tables and graphs. Sign

convention used is presented in Fig. 9.

The mathematical definition of these coefficients is indicated in sequence. All have

been rendered non-dimensional using the dynamic pressure at the model height

q ¼ ð1=2ÞrV 2; where r=air density and V is the mean hourly velocity at the

reference height. Other factors used in these definitions are nominal cross-sectionaldimensions B ; as defined in Fig. 10, H of the section model (B ¼ 0:102m andH ¼ 1:022 m) and tower solidity f defined as the ratio of the effective area of thetower to the area limited by the external bars. All coefficients vary with wind

incidence angle. The models tested are specified in Table 1.

C D ¼ mean along wind force

qBH f ; ð1Þ

C L ¼ mean cross wind force

qBH f : ð2Þ

3.1. Drag and crosswind forces

3.1.1. Model 1

Fig. 11 shows the results for drag and crosswind force coefficients for smooth

(exposure 1) and turbulent (exposure 2) flow.

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Wind

αCD

CL

B

B

Fig. 9. Model drag and crosswind force sign convention.


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3.1.3. Model 4

Fig. 12 shows the force coefficient results for drag and crosswind force for wind

incidence angle varying from 0 to 90 for turbulent flow.

3.1.4. Comparisons with codesFig. 13 shows a comparison between codes and test data. Table 5 shows the force

coefficients obtained from different codes compared to the test average. The test data

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Table 3

Model 5—drag and crosswind coefficients for exposure 2

Exposure C L RMS C D RMS Re

2 0.01 0.013 2.81 0.116 4031

2 0.01 0.013 2.77 0.109 5062

2 0.01 0.013 2.74 0.116 6485

-0.5

0

0.5

1

1.5

2

2.53

0 15 30 45 60 75 90

Angle

F o r c e C o e f f i c i e n t s

C

C

L

D

Fig. 12. Model 4—drag, C D; and crosswind, C L; coefficients for exposure 2 (Re ¼ 10800)– f ¼ 0:267:

Table 2

Models 2 and 3—drag and crosswind coefficients for exposures 1 and 2

Model 2 Model 3

Exp. C L RMS C D RMS Re Exp. C L RMS C D RMS Re

1 0.01 0.016 2.91 0.047 3976 1 0.04 0.020 3.04 0.025 3960

1 0 0.017 3.15 0.020 6875 1 0.04 0.016 3.04 0.029 4817

2 0 0.031 3.00 0.124 4012 1 0.05 0.016 3.05 0.022 6875

2 0.01 0.012 2.94 0.024 5019 2 0.04 0.042 3.19 0.127 4009

2 0 0.011 3.17 0.022 6414 2 0.01 0.043 3.18 0.127 5010

2 0.05 0.049 3.11 0.126 6424


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lead to drag coefficients slightly smaller than predicted by codes. Larger differences

between codes were expected as stated generally by Georgiou [4,5] about the

inconsistency of the data between codes and experiments. The data collected, within

the range of solidity studied, showed that all codes are on the safe side except [6] for

incidence angle of 45, which is almost the same from the average test results. For

solidity less than 0.2, the Canadian Code presented the mean drag forces in the range

of 10% higher than the average of the data from other codes.

In Table 4 and Fig. 13 the test data presented are from different experiments using

different setups. For each degree the model was fixed manually. The forcecoefficients that have the same setup are presented at the same table line with the

same incidence angle but different Reynolds numbers (Tables 4 and 5).

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1

1.5

2

2.5

3

3.5

4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

φ

C D

NBR6123, 1988

ASCE 7-95

EUROCODE 1

BS8100, 1986

NBCC, 1995

Exposure 1

Exposure 2

AS 3995-1994

Fig. 13. Drag coefficients from codes and tests.

Table 4

Drag coefficient: experimental data

Exposure 1 Exposure 2

Re ¼ 6000 Re ¼ 6800 Re ¼ 3900 Re ¼ 6800 Re ¼ 6400 Re ¼ 3900

f 0 45 0 45 0 45 0 45 0 45 0 452.86 3.35 2.85 3.35 2.80 3.35 2.84 3.40 2.85 3.34 2.90 3.41

0.162 2.80 3.31 2.78 3.37 2.75 — 2.77 — 2.91 — 2.98 —

2.86 2.84 — — — — — — —

Exposure 1 Exposure 2

f Re ¼ 6000 Re ¼ 6800 Re ¼ 3900 Re ¼ 6800 Re ¼ 10800 Re ¼ 6900

0.277 — — — — — 2.55 2.83 2.55 2.84

— — — — — — 2.59 — 2.59 —


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A conclusion may be reached that the mean force coefficients have no practical

variability with turbulence and model Reynolds number. Also it is noticed that most

of the code data are obtained from tests with smooth flow, which is reasonable.

3.2. Shielding factor

To study the variation of the shielding factor with tower frame spacing, the drag

force was measured for three different models with the ratio s=B ¼ 1; 2 and 3.Defining:

C Dn

C D1¼

ð1 þ K xÞnð1 þ K xÞ1

; ð3Þ

where n is the ratio s=B and K x is the shielding factor.The test results and code data are presented in Table 6 and Fig. 14. The tests

presented higher coefficients compared to codes showing that it might have a

contribution of the lateral members to the final load. This is not considered by thecodes of practice when determining the shielding effect. The differences in wind force

from s=B ¼ 1; 2 or 3 are so small that for practical cases it has no meaning. In most

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Table 5

Drag coefficient from codes and test average

f ¼ 0:162 f ¼ 0:277

0 45 0 45

NBR6123, 1988 [12] 3.09 3.58 2.59 3.01

ASCE 7-95 [8] 3.15 3.53 2.67 2.99

EUROCODE 1, 1995 [6] 2.98 3.34 2.51 2.94

AS 3395-1994 [10] 3.07 3.47 2.57 2.97

NBCC, 1995 [7] 3.34 4.15 2.73 3.41

BS8100, 1986 [11] 3.09 3.55 2.63 3.17

Test average 2.84 3.36 2.57 2.84

Table 6

Shielding factor: codes and tests

Codes K x Tests: C fn=C 1

f s=B ¼ 1 s=B ¼ 2 s=B ¼ 3 s=B ¼ 1 s=B ¼ 2 s=B ¼ 3

NBR 6123, 1988 [12] 0.162 0.884 0.902 0.93 1 1.01 1.024

0.277 0.731 0.785 0.823 1 1.031 1.053

AS/NZS 1170.2-2002 [9] 0.162 0.876 0.938 0.969 1 1.033 1.05

0.277 0.723 0.878 0.919 1 1.013 1.042

NBCC, 1995 [7] 0.162 0.878 0.919 0.929 1 1.022 1.027

0.277 0.687 0.762 0.785 1 1.045 1.058

Smooth 0.162 — — — 1 1.067 1.071

TEST smooth 0.277 — — — 1 1.047 1.09

Turbulent 0.277 — — — 1 1.09 —


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of the codes, the shielding factor in tower design is used only to determine the forces

that acts on each tower face and most of the towers are square or triangular with the

shielding factor of s=B ¼ 1:

3.3. Interference factor

While the shielding factor is applied to towers members, the interference factor f ais applied to the antenna–tower interaction. It is defined as

f a ¼ C Dantenna on the tower

C Dseparate antenna; ð4Þ

where C Dantenna on the tower is the drag coefficient of the antenna when it is attached to

the section model, and C Dseparate antenna is the drag coefficient of a separate antenna.

Fig. 15 shows the incremental drag coefficient derived from Eq. (5).

DC D ¼ F Dtower and antenna F Dtower

qBH f ; ð5Þ

where F Dtower and antenna is the drag force measured for the antenna disks attached to

the tower section model. F Dtower is the drag force measured for the tower section

model without antenna disk.

The interference factor, obtained from Eq. (4), is presented in Table 7. Fig. 16

presents a comparison of the interference factor with an empirical expression given

by [1]

f a ¼ exp½k ðC DfÞ2; ð6Þ

where k is 1.2 for square tower, C D is the tower drag coefficient and f is the solidity.

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1

1.01

1.02

1.03

1.04

1.05

1.06

1.07

1.08

1.09

1 21.5 2.5 3

s/B

C D n

/ C D 1

Test - 0.162 - exp. 1

Test - 0.277 - exp 1

Test - 0.277 - exp. 2

AS 1170.2 - 0.162

AS 1170.2 - 0.277

NBCC - 0.162

NBCC - 0.277

NBR6123 - 0.162

NBR6123 - 0.277

Fig. 14. Shielding effect. Comparison from experimental data and codes of practice for tower solidities of

0.162 and 0.267.


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Table 7

Interference factor C Ddisk on the tower=C Ddisk separate Re ¼ DmodelV =n

Antennas f ¼ 0:162 f ¼ 0:277

Smooth flow Turbulent flow Turbulent flow

Re ¼ 3900 Re ¼ 5900 Re ¼ 3900 Re ¼ 5900 Re ¼ 6900 Re ¼ 10; 800

1 0.908 0.898 0.915 0.691 0.660 0.369

2 0.832 0.839 0.827 0.701 0.583 0.355

4 0.838 0.778 0.851 0.754 0.531 0.386

6 0.832 0.793 0.847 0.749 0.468 0.484

00.10.20.30.40.50.6

0.70.80.9

1

0 2 4 6

Antennas

∆ C D

Re=3900 - smooth

Re=5900 - smooth

Re=3900 - Turbulent

Re=5900 - Turbulent

Re=6900 - Turbulent

Re=10800 - Turbulent

φ = 0.162

φ = 0.277

Fig. 15. Incremental drag coefficient DC D: Re ¼ DmodelV =n (Table 1).

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

Tower solidity without antennas

f a

ESDU Test data for solidity=0.162

test data for solidity=0.277

Fig. 16. Interference factor from experiments and ESDU [1].


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This expression does not take into account the study of [2], which considers the

variation of the interference factor with the wind incidence angle. Eq. (7), taken from

[2], is the modified empirical form of Eq. (6).

f a ¼ exp½k ðC DfÞ2½ð1 þ bÞ þ b cos 2ðy yd 90Þ; ð7Þ

where b is an adjustable parameter; yd is the angle of the normal to the dish

antenna relative to the tower; and y is the wind incidence angle relative to the

tower.

It is noted that the Australian Standards AS 3995-1994 and AS/NZS 1070.2:2002

use Eq. (7) for interference factor with b ¼ 0:5; k ¼ 1:2 for square towers and k ¼ 1:8for triangular towers.

Table 8 presents the drag force on a separate antenna disk taken from an

experiment in the small wind tunnel with similar conditions of turbulence, 9.7%.

Some change on the flow pattern between the antenna Reynolds number of 24,000and 44,000 was found. The experiment was repeated confirming the results as it is

seen in Table 8 (for turbulent flow the drag coefficient changes from 1.02 to 0.9 or

1.03–0.86). The explanation to this could be the combination of the antenna

geometry, roughness and wind turbulence. The antenna disk tested is not a flat disk,

Fig. 7. The flow must be reattaching due to turbulence and disk roughness when the

speed rises. More experiments are needed to check this flow pattern. Therefore, the

interference factor, Eq. (4), was determined using C Dseparate antenna of 1.13 for smooth

flow and 1.02 for turbulent flow.

From Fig. 15, it is observed that there are two tendency lines, which depends on

tower solidity. The slopes indicate that the interference is higher for higher towersolidity. It indicates also that, for the test conditions, the interference factor does not

depend much on the number of antennas. This may not be true for higher number of

antennas and different relative positions of the antennas on the tower. More

experiments are needed.

Depending on tower solidity, the consideration of wind forces from one antenna

disk separately is not a good approach. For 0 wind incidence angle, it seems that for

tower solidity of 0.2 or less, the consideration of the wind load on the antenna

separately is a good approach, but for higher solidity the designer should use the

interference factor taken from [1]. More research in this subject is needed because the

aerodynamic interference depends on other factors not studied here like the antennaposition on the tower and wind incidence angle. Also in this study the antenna

models are simulating only the front part of a shrouded antenna dish.

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Table 8

Drag coefficients on a separate antenna disk derived from the small wind tunnel test, Re ¼ DantennaV =n

Smooth flow Turbulent flow Turbulent flow

Re 24,192 44,405 24,342 42,542 24,342 44,405

C D 1.13 1.12 1.02 0.9 1.03 0.86


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4. Conclusions

There were no practical differences between the mean drag coefficients taken from

turbulent and smooth flow.The data from the mean drag coefficients showed good agreement with those

provided by codes within the range of solidity studied. Only the Canadian code

presented disparity from other codes and from experiment for lower solidities.

Experimental results indicate some differences between measured shielding factors

and those predicted by codes. This is attributed to lateral members, which increase

actual wind forces, but which usually are not considered in a code based analysis.

However the differences between forces are very small and it is not meaningful for

practical purposes, within the range of spacing ratio s=B studied.The shielding effect of the antenna rises with tower solidity. The authors suggest

use of interference factor of 1.0 for sections of lattice towers that has solidity of 0.2

or less. For higher solidities the authors suggest to use the curve taken from [1].

However more tests are needed as interference factor depends also on antenna

position and wind incidence angle.

Acknowledgements

We acknowledge the funding support given by FAPESP—Funda@*ao de Amparo "a

Pesquisa do Estado de S*ao Paulo and the funding support given by CAPES,

Funda@*ao Coordena@*ao de Aperfei@oamento de Pessoal de N!ıvel Superior, Brazil

that made this work possible.

We also acknowledge the contributions by various members of the technical staff

of the Boundary Layer Wind Tunnel Laboratory of the University of Western

Ontario to carry out the experimental phases of the study.

References

[1] ESDU Item 81028, Engineering Science Data Unit, Lattice Structures. Part 1: Mean Fluid Forces on

Tower-like Space Frames, London, October 1990.

[2] J.D. Holmes, R.W. Banks, G. Roberts, Drag and aerodynamic interference on Microwave dish

antennas and their supporting towers, J. Wind Eng. Ind. Aerodyn. 50 (1993) 263–270.

[3] ESDU Item 74031, Engineering Science Data Unit Characteristics of atmospheric turbulence near

ground, Part II single point data for strong winds (neutral atmosphere) London, March 1975.

[4] P.N. Georgiou, A study of the wind loads on building frames, Thesis (Master degree), Faculty of

Engineering Science, London, Canada, University of Western Ontario, 1979.

[5] P.N. Georgiou, B.J. Vickery, Wind loads on building frames, In: J.E. Cermak, (Ed.), Proceedings of

the Fifth International Conference, Vol. 1, Fort Collins, Colorado, USA, July 1979, Pergamon,

Oxford, 1980, pp. 421–433.

[6] European Committee for Standardization, Eurocode 1: Basis of design and actions on structures—

part 2–4: Actions on Structures—wind actions, CEN, 1995.

[7] National Building Code of Canada, NBCC—Live Loads Due to Wind, Canadian Commission on

Buildings and Fire Codes, National Research Council of Canada, 1995.

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[8] American Society of Civil Engineers, ASCE 7-95, Minimum Design Loads for Buildings and

Structure, New York, 1995.

[9] Standards Australia/Standard New Zealand AS/NZS 1170.2–2002, Structural design actions, Part 2:

Wind actions, Sydney, 2002.[10] Standards Association of Australia AS 3995–1994, Design of steel lattice towers and masts, Sydney,

1994.

[11] British Standard BS 8100, Lattice towers and mast, Part 1, Code of Practice for Loading, London,

1986.

[12] Associa@*ao Brasileira de Normas T !ecnicas, NBR-6123 For@as devidas ao vento em edifica@ *oes,

Rio de Janeiro, 1988.

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