Mstower V6 Addendum

5/21/2018 Mstower V6 Addendum

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Mstower V6 Addendum, February 2008

Contents

1. Technical Notes1.1 Triangulation1.2 Wind Speed Conversions1.3 Tower Building Report

1.4 Structural Damping1.5 Note on IFACT1.6 Tension-only members under BS81001.7 Hot Keys

2. TIA/EIA-222-G Implementation

3. Program Changes

1. Technical Notes

1.1 Triangulation

Hip and plan bracing should be fully triangulated to provide the restraint assumed in checking thecapacity of restrained members (see p4 of the Mstower User Manual). Additional checks for non-triangulated redundants have been implemented and where detected are now neglected inassessing the capacity of restrained members. TIA-222-G Figures 4-1 and 4-2 show examples ofnon-triangulated bracing that either should not be used or which require further analysis andinvestigation to ensure effectiveness.

Triangulation checks in Mstower are not complete because they may not find all examples of non-triangulated bracing. The responsibility must remain with the tower designer to ensure that thetower is fully triangulated or, if not, additional checks are carried out to ensure the adequacy of therestraint system.

1.2 Wind Speed ConversionsWind speeds must conform to the requirements of the particular code being used. Code windspeeds are normally defined for a particular averaging period, return period, height and surfaceroughness (terrain or exposure category). If wind speeds are not directly available in a form that isrequired by the Code being used, it will be necessary to convert them. Commonly, the returnperiod is 50 years, in open terrain and at 10m above ground.

In the absence of other information, graphs in BS 8100:Part 1 or the table in TIA-222-G may beused.

The graph in BS 8100:Part1 A.1 p46 allows surface roughness and averaging period to be takeninto account when converting wind speeds.

The table in TIA-222-G p225 allows conversion between different averaging periods.

When conversions are done it is important that the factors that are not taken into account by theparticular conversion being used conform to the Code definitions.

It should be noted that the averaging period for "fastest mile wind speeds" is not constant butdepends on the wind speed itself and may require an iterative process to determine.

Terms such as "survival speed" and "operational speed" are not used in any tower codes that weare aware of. EIA-222-F p59 2.1.5 B states "the use of terms with an ambiguity in meaning andintent such as survival, shall withstand, etc is not appropriate". Where these terms are used, thedesigner should seek clarification from the client as to exactly how these wind speeds are definedand if necessary, what safety factors or load factors are to be used with strength calculations andserviceability conditions.


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It should also be noted that some values and factors may be peculiar to the locality for which thecode was written. For example, the "wind direction factor" Kd in BS8100 applies to wind conditionsin the United Kingdom; it is unlikely to apply to other parts of the world.

1.3 Tower Bui lding Report

A considerable amount of checking is done when the tower data file is processed and a report iswritten to the output window of the main screen. This report can provide valuable information onanomalies that have been detected and can be of assistance in debugging the data. Because

many users have ignored this report, a briefer form is now displayed in a list box in the centre ofthe screen. You should check the report and ignore the warnings only if you are sure that themodel conforms to your intention.

1.4 Structural Damping

Structural damping is expressed in two ways:

Logarithmic decrementof damping, which is the natural logarithm of the ratio of any twosuccessive amplitudes when the structure vibrates, or

The damping ratio, which is the value of the actual damping divided by the critical damping.

For small values, the logarithmic decrement equals 2 x pi x damping ratio.

ILE TR7

Uses logarithmic decrement of damping.

Value for steel lighting pole is 0.015

Foundation factors:Piled foundation or spread footingon stiff soil or rock: 1.0Spread-footing on stiff soil or rock: 1.5Spread-footing on stiff soil or rock: 3.0

BS 8100 Part 1 Appendix E, Table E.1Uses logarithmic decrement of damping.

Welded or friction grip bolted: 0.015Higher values are given in the table for black bolted towers.

Table E.2 gives damping factors for foundations similar to that in ILE TR7.

BS 8100 Part 4 Appendix M, Table M.1

Uses logarithmic decrement of damping.

Values are the same as in BS 8100 Part 1 but no damping factors for the foundation are given.

AS 3995 - 1994

Uses damping ratio.

Welded steel towers: 0.02Bolted steel towers: 0.05No foundation factors are given.

1.5 A Note on IFACT

The IFACT factor fact is normally set to 1. For values less than 1 member flexural stiffness isreduced and the typically small bending moments found in towers are reduced and the structurebehaviour is closer to that of a a pin-jointed structure.

Factor IFACT should be set to 1 for second-order analysis, ECL analysis, or dynamic analysis.


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1.6 Tension Only Members in BS8100 towers

Applying BS gust-factoring to a tower with TO members:

Analyse all cases. Normally for a second order/nonlinear analysis only the "complete" cases, iethose that could actually occur, are analysed. These are usually the DL case plus combinations asWL can never occur without DL and WL cases would not normally be analysed. However, thesecases must be analysed when gust-factoring is applied because the gust-factoring process usedby Mstower uses the results of the WL cases and subcases.

Because of the presence of TO members the non-linear analysis engine will automatically bechosen. If the characteristics of the TO members are the only non-linear effects to be taken intoaccount, turn OFF nodal coordinate update and axial force effects. Beware of reducing thetolerance to achieve "convergence" and check that the residuals reported on the analysis screenand analysis log are suitably small. Most structures with TO members should analyse in a fewiterations.

1.7 Hot Keys

Pressing U and D keys pan the view up and down the tower.

2. TIA/EIA-222-G Implementation

You should have a copy of the TIA/EIA-222-G code before attempting a design to this code.

Tower data File (.TD file)

Additional data is required in the BOLTDATA block:

FV_TIA keyword now included.FT must be defined for a tension connection - applies to all codes.

Data for a shear connection:

bolt_id grade D d As as FY fy FU fu FV_TIA fv [NSP nsp] [FYP fyp TP tp FUP fup] [..] optionalitems

FV_TIA keywordfv bolt shear strength

If FV_TIA is defined, shear capacity is computed as phi x fv x As, otherwise it is computed asphi x 0.4 x fu x As, assuming threads included in the shear plane (4.9.6.3 (b)).

The bearing capacity is computed as the minimum of phi x 2.4 x d x t x fu andphi x 2.4 x d x tp x fup.

Data for a connection with bolts in tension:

bolt_id grade D d As as FY fy FU fu TENS AT at [FT ft] [PR pr]

at - tensile area of bolt. Must be defined for tension type connections.ft - tensile strength of bolt (taken as fu if not defined).pr - prying factor (taken as 1.0 if not defined).

Tower Loading File (.TWR file)

Changes to the PARAMETER block:

CODE TIA222GVB vb $ 3-sec gust wind speed with 50 year return period

VICE vi $ wind speed to be used with WL + ICECLASS-G class $ classification of structure, Table 2-1, in Arabic numerals, page 39TOPCAT-G topcat $ topographic category, integer 1 - 4, page 13


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Changes to TERRAIN block:

TERRAIN ANGLE ang TCAT tcat [MD md] [H h] $ TIA222G ....................END

ang angle E of Ntcat exposure, 2=B, 3=C, 4=D page 12

md optional direction dependent velocity multiplier. It is not used in TIA-222-G but may be usedwith Mstower if the wind velocity at the site varies significantly with geographic direction. Ifomitted a factor of 1.0 is used. It should not be confused with the "wind direction probabilityfactor" Kd in Table 2-2 of TIA-222-G which is automatically taken into account in theprogram.

h hill height, 2.6.6.1 page 13

Note The Importance factor (Table 2-3 page 39) and Wind Direction factor (Table 2-6 page 40)are automatically taken into account in the program.

Wind Load Cases

If a tower is Eiffelised a number of "patch" load cases should be entered:

CASE case WL, first patch case WL ANGLX a1 ...... [ZGUST z1 ZGUST2 z2 GFACT gf]

The wind forces between "z1" and "z2" will be multiplied by the factor "gf". Factor "gf" should bethe mean wind conversion factor from Table 3-1, page 63.

Example

Assuming a single apex point at 50 metres above the tower base the following cases would berequired for a wind load direction:

CASE 200 WL WL ANGLX a1 ......

CASE 201 WL, first patch case WL ANGLX a1 ...... ZGUST 0.0 ZGUST2 50.0 GFACT gf

CASE 202 WL, second patch case WL ANGLX a1 ...... ZGUST 50.0 ZGUST2 1000. GFACT gf

Additional combination cases will be required for each case that reference a WL case, eg

CASE 1000 DL + WL COMBIN 100 1.2

COMBIN 200 1.6CASE 1001 DL + WL COMBIN 100 .90 COMBIN 200 1.6

CASE 1010 DL + WL, first patch case COMBIN 100 1.2 COMBIN 201 1.6

CASE 1011 DL + WL, first patch case COMBIN 100 .9 COMBIN 201 1.6

Mast patch loading should be input in a similar fashion with the mast spans defined by the z1 andz2 heights. A loading file with wind load and combination sub-load cases may be generated usingthe improved load file generator.


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A simple way to add sub-load cases to an existing loading file is to generate a loading file for adummy tower and then copy and paste the loading section.

Numerous load cases will be generated. For example, a square tower with two apexes, ice andwind in eight directions generates 244 load cases (82 primary, 162 combination cases).

Dead Load Cases

CASE 102 DL of GUYS DL GUYS

GUYS - keyword, indicating that the dead load of the guys only is required.

This instructs the program to form a case with DL of guys only, to be used in TIA-222-Gcombinations where different load factors are applied to the shaft of the mast and the guys:1.2*shaft + 1.0*guys + 1.6*WL

If the load cases are generated by the loading dialog, DL + WL combination cases will begenerated of the form:

CASE 100 Dead Load, complete mast DLCASE 102 Dead Load, guys only DL GUYSCASE 200 Wind Load

WL

CASE 1000 DL + WL combination COMBIN 100 1.2 $ DL of mast + guys COMBIN 102 -0.2 $ subtract 0.2 x DL of GUYS COMBIN 200 1.6 $ wind loads

3. Program Changes

Page numbers refer to March 2006 user manual.

EXTERNAL Block

A new data block has been added to the tower data file to allow greater control over the factorapplied to external members when computing wind loads.

EXTERNAL name ZB zb ZT zt EXTFACT f1 fnEND

EXTERNAL keywordname identifying name.ZB, ZT keywordszb, zt factors applied to all external members with midpoints between heights zb & zt.EXTFACT keywordf1 fn external factors. Eight factors for square towers applying to wind at 0, 45, 90, 135,

180, 225, 270 and 315 degrees to the X-axis. Six factors for triangular towersapplying to wind at 0, 60, 120, 180, 240 and 300 degrees to the X-axis.


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An EXTERN factor defined in a WL block will take precedence over factors defined in anEXTERNAL block.

p55. Additional item in section block

n sname ...... [FU fu]

FU keyword

fu ultimate tensile strength of the section materialIf fu is not specified the UTS of the material will be obtained as previously from a look-up tablebased on the yield strength of the steel.

p58. Additional item in bolt data block:

bolt_id grade ..... [FYP fyp FUP fup TP tp]

FUP keywordfup Ultimate tensile strength of plies for checking bearing capacity of joints where applicable.

If fup is not specified the tensile strength will be obtained as previously from a look-up table based

on the yield strength of the steel.

pp148,150. Addit ional Partial Safety factor for BS8100 Bolt checking

PARAMETERS CODE BS8100xx ...............................PSF-M psf-m[PSF-M2 psf-m2] $ optional ................................END

PSF-M2 is an optional partial safety factor on strength of material to be used in checking thecapacity of bolts in compression members using clause 8.1 of BS8100-3:1999.

PSF-M will be used if PSF-M2 has not been defined.PSF-M will be used in the calculation of member capacity.

P174, Addit ional keyword added to Resistances table:

name ZB zb ZT zt [ARES|TRES|BRES] res

BRES - Keyword indicating that resistance is that of the tower body including linear ancillaries.

The total resistance will be the BRES resistance plus the resistance of the large ancillaries.

Example for the input of resistances

ANCILLARIES RESISTANCE R1 ZB 36 ZT 39 TRES 4 4 4 4 4 4 4 4 $ total resistance, 36 - 39m Res=Cd.A/m R2 ZB 33 ZT 35.5 TRES 5 5 5 5 5 5 5 5 $ 33 - 35.5m R3 ZB 15 ZT 17 ARES 2 2 2 2 2 2 2 2 $ additional resistance, 15-17m $ NB resistances are per metre

LINEAR LIBR P:LIN LADDER1 LARGE LIBR P:ANC DISH1


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FACE SCREEN6 END

p183. Scale factors for large ancil lary icon graphics

name ... ishape sx xy sz

sx sy sz are scale factors applied to icons.Icon numbers and descriptions are listed in file Mstower.icn and illustrated in example jobIcontwr.mst.

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Mstower V6 Addendum