In compliance with the technical specification, the document describes
the minimum criteria for specifying and designing of tower.
I. STANDARD / REFERENCE
a. TIA / EIA - 222 - STANDARD : Structural Standards for Steel
Antenna Towers and Antenna Supporting Structures.
b. AISC-ASD Code ' 89 - American Institute of Steel Construction
c. ACI 318-89 Code - American Concrete Institute
d. Indonesian Loading Code ( PMI 1970 N.I-I8 )
II. MATERIALS SPECIFICATION
a. Steel Structure
- Structure Type = Self Supporting Tower
- Steel Shapes & Plates = ASTM A 36 / JIS G3101 fy = 245 Mpa
b. Bolt & Nut
- Splice Bolts = ASTM A - 325 / JIS B1051 - Grade 8.8 fy = 560 Mpa
c. Anchor Bolt
- Grade of Anchor = ASTM A - 307 fy = 240 Mpa
d. First Coating
- Hot Dipped Galv. = ASTM A - 123 80 microns thickness
e. Concrete
- fc' = 19 Mpa ( 28 days ) / K-225
f. Rebars
- Grade of rebars = BJTP ( dia. ≤ 12 mm ) fy = 240 Mpa
- Grade of rebars = BJTD ( dia. ≥ 13 mm ) fy = 390 Mpa
g. Welding Electrodes
- Minimum Grade of Welding Electrode = AWS A5.1 E60XX. fy = 345 Mpa
II. LOADINGS
a. Dead Load
Consist of Weight of Tower structure including antenna, ladder
and appurtenances.
b. Wind Load
Calculated according to TIA / EIA - 222 - STANDARD : Structural
Standard for Steel Antenna Towers and Antenna Supporting Structures
The basic wind speed is based on peak gust velocity averaged over a short time
interval of 3 second = 120 kph ( 3 second gust ).
Where wind force applied to each section of the structure shall be calculated from
the equation :
F = horizontal force applied to a section of the structure ( KN )
qz * GH * , but not to exceed 2*qz*GH*AG
qz = Velocity pressure ( Pa )
= .613 Kz V2 for V in m/s
Kz = Exposure Coefficient
2/7 for z in meters
1.00 < Kz<2.58
V = basic wind speed for the structure location ( m.s-1)
z = height above average ground level to midpoint of panel of the structure and
appurtenances ( M )
GH = gust response factor
CF = structure force coefficient
e = (AF+AR)/AG
e = solidity ratio
AF = projected area of flat structural component in one face of the section ( m 2 )
AG = gross area of one tower face ( m2 )
AR = Projected area ( m2 ) of round structural component in one face of the section
AE = efective projected area of structural component in one face ( m2 )
= DF AF + DR AR RR (m2)
( Note : For tubular steel pole structure, AE shall be the actual projected area based on
diameter or overall width. )
RR = .51e2 + .57 RR<1.0
RR = The reduction factor for round structural component
DF = Wind direction factor
1 for square cross section and normal wind direction
1+ 0.75 e for square cross section and + 450 wind direction (1.2 max)
DR = Wind direction factor for round structural components
= 1 ; for square cross section and normal wind direction
= 1+ 0.75 e ; for square cross section and + 450 wind direction
(1.2 max)
CA = linear or discrete appurtance force coefficient
AA = projected area of a linear appurtance
CA is depended on Aspect ratio
Aspect Ratio = Overall length/width ratio in plane normal to wind direction
Wind Load Calculation method on the antennas is as follow:
Fa = Ca x A x Kz x GH x V2
Fs = Cs x A x Kz x GH x V2
M = Cm x D x A x Kz x GH x V2
Ha = (Fa2+Fs2 )1/2
Mt = Fa x X + Fs x Y + M
L = the distance the antenna's axis to the frame's joints
GH = Gust response factor from 2.3.4
= 0.65+0.6/(h/10)1/7 for h in meters
A = Outside aperture area of parabolic reflector, grid, or horn antenna
= Plate area of passive reflector ( ft2 )
D = Outside diameter of parabolic reflector, grid, or horn antenna ( ft )
= Width or length of passive reflector ( ft2 )
V = basic wind speed ( m.p.h ) from 2.3.3
KZ = Exposure coefficient from 2.3.3 with z equal to the hight
of the origin of the axis system
Kz = Exposure Coefficient
= 2/7 for z in meters
FA = axial force ( lb )
Fs = side force ( lb )
M = Twisting moment ( ft-lb )
Ca, Cs, Cm are load coeficients contained in tables B1
trough B6 as function of wind angle,…... TIA page 62-67
Ha = resultant of FA and FS ( lb )
Mt = Total twisting moment ( ft-lb )
X = The offset of the mounting pipe ( ft )
Y = The distance on the reflector axis from the reflector vertex to
the center of the mounting pipe ( ft )
Wind Load Calculation methode on the parabolic antenna is as follow:
Fa = Ca x A x Kz x GH x V2 where:
Fs = Cs x A x Kz x GH x V2 Fa = axial force ( kg )
M = Cm x D x A x Kz x GH x V2 Fs = side force ( kg )
Ha = (Fa2+Fs2 )1/2 M = Twisting moment ( kg-m )
Mt = Fa x X + Fs x Y + M Ca = Wind load coeficient
Cs = Wind load coeficient
Cm = Wind load coeficient
V = Wind velocity ( m.p.h )
c. Antennas Load and Top body part dimension.
Tower Structure considered to be able to support the antennas load as
table bellow :
elevation Weight + Support
m Kg.
1 MW Ant. Ø 2.0 m Radome - n pcs -
2 GSM Antenna ( 1.5 x 0.3 x 0.15 m ) - n pcs -
3 TMA Antenna (0.245 x 0.219 x 0.1 m) - n pcs -
IV. LOAD COMBINATION
According to AISC - ASD'89 Standard , only the following load combination shall be
investigated when calculating the maximum member stresses and structure reaction :
COMB 1 = DL
COMB 2 = DL + LL
COMB 3 = DL + LL ± WL
Where ;
DL : Dead Load
LL : Live Load
WL : Wind Load
V. DESIGN TOLERANCES
The design / analysis tolerances are :
a. Allowable Stress Ratio = 1
b. Slenderness Ratio : Leg ≤ 150
Bracing ≤ 200
Redudant ≤ 250
c. Allowable Twist = 0.5 degree
d. Allowable Sway = 0.5 degree
e. Allowable Horizontal Displacement = H/200 ( H= Tower Height )
f. Verticality = H/2000 ( H= Tower Height)
