Convert Graphics to UDP File

* Select the command

Tower > Build Tower > User Defined Panels > Graphics to UDP File

* In the displayed dialog box enter P3 for the UDP name.

* Select 3-DIM as the UDP type.

* To make the UDP known as a component of the tower select the command

Tower > Build Tower > Edit Tower Data

146^• 8:GraphicsInputforUDPs MSTowerV6

* The UDP file is displayed in the text editor, MsEdit, so you can make the necessary changes:

COMPONENT   P3 END

PANEL 3 HT 4.000

  $ FACE K $ LEG ? BR1 ? H1 ? R1 ?   FACE @P3

Here, the FACE K line has been commented out with the $ character but retained in the file to indicate the panel type used as the basis for the UDP.

* Save the edited TD file and close MsEdit.

* Rebuild the tower and inspect to ensure that the UDP is as required.

* If the UDP must be modified select the command

Tower > Build Tower > User Defined Panels > UDP File to Graphics and select the UDP to be modified (P3 in this case).

* After making any necessary modification select the command

Tower > Build Tower > User Defined Panels > Graphics to UDP File If the UDP file already exists a message box is displayed…

* Press Enter or click OK.

* Rebuild the tower.

MSTowerV6 9:TowerLoading^• 147

9:Tower Loading

General

This chapter describes the operation of the MStower loading module in computing loads on the tower and ancillaries in accordance with the requirements of:

•  BS 8100 Part 1 2005

•  BS 8100 Part 4 1995

•  BS 8100 Part 4 Amendment 1 2001

•  AS 3995-1994

•  AS 1170.2-2002

•  Malaysian Electricity Supply Regulations 1990

•  EIA/TIA-222-F-1991

•  TIA-222-G-2005

•  Institution of Lighting Engineers Technical Report No. 7 – 

 High Masts for Lighting and CCTV  – 2000 Edition

•  IS 875 (Part 3):1987

•  ^{ASCE 7-95}

•  BNBC 93 – Bangladesh National Building Code

Loading types include dead load, ice load (with and without wind), node loads, wind loading on the structure, its ancillaries, feeders, and

attachments, and temperature loads.

Tower loading represented as node loads are computed for wind acting at any angle to the tower, with and without icing of members, as well as gravity loads due to self weight and icing. Additional node forces may  be specified for any primary load case. Combination load cases may also  be defined.

Code partial safety factors may be specified directly or as factors in combination load cases.

148^• 9:TowerLoading MSTowerV6 Tower Faces

The faces of the tower are numbered 1, 2, 3 (and 4 for rectangular  towers) in an anti-clockwise direction with face 1 normal to the positive X axis. The locations of face ancillaries are specified by reference to the face numbers.

Towers With Cross-Arms

The wind resistance of a tower is generally computed as a function of the solidity of the faces of the tower. Members internal to the body of the tower are ignored in the determination of solidity. Members external to the body of the tower, such as cross-arms may be taken into account by adding face ancillaries to appropriate panels or by specifying an EXTERN factor for wind load cases.

The weight of the all members, including cross-arms and any encrusting ice is taken into account in DL and ICE load cases respectively.

The Tower Loading (TWR) File

Data describing the tower loading is entered into a free-format text file called Job.twr, where “Job” is the job name. A tower loading file may be generated by selectingTower > Load Tower > Make Tower Loading File. A series of dialog boxes will be displayed for you to select the loading code and various parameters. The resulting TWR file will require some editing to customize it to the particular tower you are modelling.

The data is organized into logical blocks:

1.  PARAMETERS block  2.  TERRAIN block 

3.  VELOCITY block (optional) 4.   Named node block (optional) 5.  Guy list block (optional) 6.  External block (optional) 7.  Loads block 

8.  Panel block (optional) 9.  Ancillaries block 

Each block commences with a keyword identifying the block and terminates with the keywordEND. The keywordEOF is used to terminate the file. Each data block is described in this chapter.

Parameters Block

PARAMETERS   ANGN an   [CODE code]

MSTowerV6 9:TowerLoading^• 149   [ICE RO ro RW rw]

  [ALTOP alt]

  [PSF-V gamma-v]

  [PSF-M gamma-m]

  [PSF-M2 gamma-m2]

  VB vb vtype   VICE vi   CLASS-G class   TOPCAT-G topcat   [OVERLAP n]

  [GRAV grav]

  [RHO rho]

  [RPSERV rpserv]

  [SDAMP sdamp]

  [ADAMP adamp]

  [TDAMP tdamp]

  [FREQ freq]

  [DMULT dmult]

  [CDMIN cdmin]

END where:

 ANGN Keyword.

an The angle, in degrees, measured anti-clockwise from the X axis to geographic north.

CODE Keyword.

code Character string indicating the code rules to be followed in computing the wind and other loading:

BS8100

 Use the rules of BS 8100 Part 1 with  Amendment 1 – May 2005.

BS8100A1

 Use the rules of BS 8100 Part 4 with  Amendment 1 – April 2003.

BS6399

 Use the rules of BS 6399.

MER

 Use the rules of the Malaysian Electricity Supply Regulations  1990 – See note below.

AS3995

 Use the rules of AS 3995.

AS1170

 Use the rules of AS 1170.

EIA222

 Use the rules of EIA/TIA-222-F.

TIA222G

 Use the rules of TIA-222-G.

ILETR7

 Use the rules of the Institution of Lighting Engineers  Technical Report No. 7.

150^• 9:TowerLoading MSTowerV6

ASCE795

Use the rules of ASCE 7-95. These wind rules are the same as those in Philippines NSCP C101-01.

IS875

Use the rules of IS 875 Part 3 1987.

BNBC

Use the rules of the Bangladesh National Building Code.

If omitted, the rules of BS 8100 Part 1 will be used. Unless specified otherwise all code references are to BS 8100.

ICE Keyword.

RO Keyword.

ro Radial ice thickness, mm or inches, in the absence of wind (BS 8100 Fig. 3.9).

RW Keyword.

rw Radial ice thickness, mm or inches, in presence of wind (BS 8100 Fig. 3.9).

 ALTOP Keyword.

alt Altitude of tower top, in m or ft. Used to determine basic ice thickness (BS 8100 Cl. 3.5.2).

PSF-V Keyword.

gamma-v Partial safety factor on wind speed and ice thickness, BS 8100 only (BS 8100 Fig 2.1).

PSF-M Keyword.

gamma-m Partial safety factor on design strength (BS 8100 Fig. 2.1). For  BS 8100 and ILE TR7.

PSF-M2 Keyword.

gamma-m2 Partial safety factor for bolt capacity, BS 8100 only (BS 8100-3:1999 Cl. 8.1).

VB Keyword.

vb Basic wind velocity in m/sec or miles/hour (BS 8100 Fig. 3.1).

vtype Character string whose value depends on loading code as shown below:

BS 8100, ILETR7

 MEAN = Mean hourly wind speed.

AS 1170.2 / AS 3995

 GUST = Gust wind speed.

EIA-222

 Blank = Fastest mile wind speed.

MER 

 GUST = No additional gust factor applied by program.

Refer to individual codes for a full definition of the wind speed to be used.

MSTowerV6 9:TowerLoading^• 151

VICE Keyword.

vi Wind speed to be used with WL + ICE cases for TIA-222-G.

CLASS-G Keyword.

class Tower classification, TIA-222-G Table 2-1, I=1, II=2, III=3.

TOPCAT-G Keyword.

topcat Topographic category, integer 1-4, as defined in TIA-222-G p. 13.

OVERLAP Keyword.

n Overlap flag; 0 if overlap between bracing and leg members is not to be taken into account; 1 otherwise. If overlap is taken into account, the computed wind resistance will be smaller, but computation time will be marginally longer. Overlap will be taken into account if flag is omitted.

GRAV Keyword.

grav Gravitational acceleration in Z direction. If omitted, an acceleration of -9.81 m/sec² or –32.2 ft/sec² will be used in computing gravitational loads from masses.

RHO Keyword.

rho Density of air at the reference temperature. If omitted, a value of 1.22 kg/m³ or 0.075 lb/ft³ will be used.

RPSERV Keyword.

rpserv Return period in years. Used for calculation of tower and ancillary rotations to BS8100. Ignored for other codes.

SDAMP Keyword.

sdamp Damping for structure and foundation. This value depends on the type of structure and its connections and the type of  foundation. Values are given in various codes.

 ADAMP Keyword.

adamp Aerodynamic damping.

TDAMP Keyword.

tdamp Total damping, the sum of structural and aerodynamic damping.

FREQ Keyword.

freq Frequency in Hertz for the first mode of vibration of the tower  or pole.

DMULT Keyword.

dmult Dynamic multiplier. Used in some cases to account for the dynamic sensitivity of a pole or tower.

CDMIN Keyword.

cdmin Minimum drag coefficient to be used in assessing the wind load on a tubular pole. This may be used where fittings and

attachments on a pole make the pole aerodynamically rougher  than the bare pole.

152^• 9:TowerLoading MSTowerV6 Note: Ifcode is specified asMER  the following default values will be used unless otherwise specified:

gamma-v = 1.0 gamma-m = 1.0

rho = 1.2 kg/m³

vb = 26.82 m/s

Damping

British codes BS 8100, BS 6399, and ILE TR7 use the logarithmic decrement of damping,

δ

. Other codes use the ratio of the actual damping to the critical damping,

ζ

, where

δ

 = 2^π 

ζ

 /

√

(1 –

ζ

²)

Basic Velocity

The definition of the basic velocityvb depends on the code being used.

AS 1170.2 VR , regional 3 second gust wind speed for required return  period, Fig. 3.1 and Table 3.1.

AS 3995 Vu, basic wind speed for ultimate limit state Fig. 2.2.

VR  and VU are not the same.

BS 8100 Part 1 Hourly mean wind speed, Fig. 3.1.

BS 8100 Part 4 Hourly mean wind speed, Fig. 2.

BS 6399 Hourly mean, BS 6399 Part 2, Fig. 6.

ILETR7 Hourly mean, BS 6399 Part 2, Fig. 6.

ASCE 7-02 3-second gust wind speed, ASCE 7-02, Fig. 6-1.

3-second gust wind speed, NSCP C101-1, Fig. 207-1.

EIA-222-F Fastest mile wind speed.

TIA-222-G 3-second gust wind speed.

IS 875 Part 3 3-second gust wind speed, Fig. 1.

BNBC Fastest mile wind speed, Fig. 6.2.1.

It is important that the basic velocity used in the tower data file is consistent with the specified code. The figures and tables referred to above are in the particular code. Meteorological specialists may need to  be consulted for sites for sites in other locations.

It is also important that the wind speeds conform to the requirements of  the code being used. Non-standard descriptions of wind speeds such as

“operational”, “survival”, or “extreme” are not used in any code

MSTowerV6 9:TowerLoading^• 153 supported by MStower. Where such terms are used in a specification additional information must be sought so that a wind speed conforming to the code requirements may be calculated.

Note: The table on p. 225 of TIA-222-G and Fig. A.1 of BS 8100 Part 1 may assist in the conversion of wind speeds.

Terrain Block

This block is used to specify the variation of terrain factor with wind direction around the tower. The data required depends on the loading code being used.

TheTERRAIN block forBS 8100 Part 1 is as follows:

TERRAIN

  ANGLE angle TCAT tcat [Kd kd] [KR kr] [HH hh]...

  [BETAH betah] [XLEE xlee]

END where:

 ANGLE Keyword.

angle Wind angle in degrees east of north.

TCAT Keyword.

tcat Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.

KR Keyword.

kr Terrain roughness factor. Interpolated from BS 8100 Table 3.1 if not specified.

KD Keyword.

kd Wind direction factor. Interpolated from BS 8100 Fig. 3.2 if not specified. If ice is present a maximum value of 0.85 will be used.

HH Keyword.

hh Height of hill above general terrain, in m or ft. Assumed to be zero if not specified.

BETAH Keyword.

betah Effective slope of hill , in degrees. Assumed to be zero if not specified.

XLEE Keyword.

xlee Downwind distance from the crest of the hill to tower site, in m or ft. Assumed to be zero if not specified.

 ABT Keyword.

abt The altitude of the general terrain in this direction. If defined this value will be used to apply an altitude correction to the

154^• 9:TowerLoading MSTowerV6

 basic wind velocityvb defined in the parameters block.

TheTERRAIN block forBS 8100 Part 4 is as follows:

TERRAIN

  ANGLE angle [SD sd] DSEA ds DTWN dt...

  [XO xo HO ho HE he LU lu X x]

END where:

 ANGLE Keyword.

angle Wind angle in degrees east of north.

SD Keyword.

sd Direction factor (BS 8100 Part 4 Cl. 3.1.5). If not specified a value will be interpolated from Table 1 of BS 8100 Part 4. If  ice is present a maximum value of 0.85 will be used.

DSEA Keyword.

ds Distance from the sea, in km or miles.

DTWN Keyword.

dt Distance to edge of town in windward direction, in km or  miles. Zero for country terrain.

XO Keyword.

xo Upwind spacing of permanent obstructions from mast, in m or  ft.

HO Keyword.

ho General level of rooftops, in m or ft.

HE Keyword.

he Effective height of topographic feature above general ground level in upwind direction, in m or ft.

LU Keyword.

lu Length of upwind slope in wind direction, in m or ft.

X Keyword.

x Horizontal distance of site from top of crest, in m or ft.

TheTERRAIN block forBS 8100 Part 4 Amendment 1 – 2003, Institution of Lighting Engineers Technical Report No. 7, andBS 6399 is as follows:

TERRAIN

  ANGLE angle [SD sd] DSEA ds DTWN dt...

  [XO xo HO ho HE he LU lu X x] [ABT abt]

END where:

 ANGLE Keyword.

MSTowerV6 9:TowerLoading^• 155 angle Wind angle in degrees east of north.

SD Keyword.

sd Direction factor (BS 8100 Part 4 Cl. 3.1.5). If not specified a value will be interpolated from Table 1 of BS 8100 Part 4. If  ice is present a maximum value of 0.85 will be used.

A value of 1.0 should be used for ILE TR7

DSEA Keyword.

ds Distance from the sea, in km or miles.

DTWN Keyword.

dt Distance to edge of town in windward direction, in km or  miles. Zero for country terrain.

XO Keyword.

xo Upwind spacing of permanent obstructions from mast, in m or  ft.

HO Keyword.

ho General level of rooftops, in m or ft.

HE Keyword.

he Effective height of topographic feature above general ground level in upwind direction, in m or ft.

LU Keyword.

lu Length of upwind slope in wind direction, in m or ft.

X Keyword.

x Horizontal distance of site from top of crest, in m or ft. Use  positive values to indicate that the site is downwind of the crest

and negative values to indicate that the site is upwind.

 ABT Keyword.

abt Altitude base for terrain in this direction.

TheTERRAIN block forAS 1170.2-2002 is as follows:

TERRAIN

  ANGLE angle TCAT tcat reg [MD md]...

  [H h LU lu X x] [MSH msh] [MLEE mlee]

END where:

 ANGLE Keyword.

angle Wind angle in degrees east of north.

TCAT Keyword.

tcat Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.

reg Regional code – A1,..A9, W, B, C, or D, as defined in Fig. 3.1 of AS 1170.2.

156^• 9:TowerLoading MSTowerV6

MD Keyword.

md Wind direction multiplier. If not specified, a value will be interpolated from Table 3.2 of AS 1170.2.

H Keyword.

h Height of feature, in m or ft.

LU Keyword.

lu Horizontal distance upwind from the crest of the feature to a level half the height below the crest, in m or ft.

X Keyword.

x Horizontal distance upwind or downwind from the structure to the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.

MSH Keyword.

msh Shielding multiplier, 4.3 of AS1170.2. If not defined, 1.0 will  be used.

MLEE Keyword.

mlee Lee multiplier, 4.4.3 of AS1170.2. If not defined, 1.0 will be used.

The topographic multiplier, Mt (AS 3995 Cl. 2.2.4), is computed in each direction from the values ofh,lu, andx entered in theTERRAIN block.

TheTERRAIN block forASCE 7-95 is as follows:

TERRAIN

  ANGLE angle TCAT tcat [MD md] [H h LH lh X x]

END where:

 ANGLE Keyword.

angle Wind angle in degrees east of north.

TCAT Keyword.

tcat Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.

MD Keyword.

md Optional wind velocity multiplier (see below).

H Keyword.

h Height of feature, in m or ft.

LH Keyword.

lh Horizontal distance upwind from the crest of the feature to a level half the height below the crest, in m or ft. See Fig 6.2 in ASCE 7-95.

X Keyword.

MSTowerV6 9:TowerLoading^• 157 x Horizontal distance upwind or downwind from the structure to

the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.

The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular  direction will be determined as the product (md ×vb). If not defined in the terrain blockmd will be taken as 1.0.

The wind specification in the Philippines code NSCP C101-01 is the same as that in ASCE 7-95.

TheTERRAIN block forTIA-222-G is as follows:

TERRAIN

  ANGLE angle TCAT tcat [MD md] [H h]

END where:

 ANGLE Keyword.

angle Wind angle in degrees east of north.

TCAT Keyword.

tcat Exposure category, 2=B, 3=C, 4=D (TIA-222-G p. 12).

MD Keyword.

md Optional wind velocity multiplier (see below). It should not be confused with the wind direction probability factor, Kd, in TIA-222-G Table 2-2, which is taken into account automatically in MStower.

H Keyword.

h Hill height (TIA-222-G 2.6.6.1 p. 13).

The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular  direction will be determined as the product (md ×vb). If not defined in the terrain blockmd will be taken as 1.0.

 Note that the importance factor, Table 2-3 p. 39, is computed automatically by MStower.

TheTERRAIN block forIS 875 (Part 3):1987 is as follows:

TERRAIN

  ANGLE angle TCAT tcat [MD md] [Z z LU lu X x]

END where:

 ANGLE Keyword.

158^• 9:TowerLoading MSTowerV6 angle Wind angle in degrees east of north.

TCAT Keyword.

tcat Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.

MD Keyword.

md Optional wind velocity multiplier (see below).

H Keyword.

h Height of feature, in m or ft.

LU Keyword.

lu Horizontal distance upwind from the crest of the feature to a level the full height of the feature below the crest, in m or ft.

See Fig. 13 in IS 875.

X Keyword.

x Horizontal distance upwind or downwind from the structure to the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.

The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular  direction will be determined as the product (md ×vb). If not defined in the terrain blockmd will be taken as 1.0.

TheTERRAIN block forBNBC is as follows:

TERRAIN

  ANGLE angle TCAT tcat [MD md] [H h LU lu X x]

END where:

 ANGLE Keyword.

angle Wind angle in degrees east of north.

TCAT Keyword.

tcat Exposure condition in Arabic numerals. Intermediate terrain conditions may be given as a decimal, e.g. 2.5. Note that while the code defines exposure conditions alphabetically, they must  be entered into the terrain block numerically, with A=1, B=2,

etc.

MD Keyword.

md Optional wind velocity multiplier (see below).

H Keyword.

h Height of feature, in m or ft.

LU Keyword.

lu Horizontal distance upwind from the crest of the feature to a