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IS802( Partl/Sec 1 ) :1995 vRT%mmF Indian Standard USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS - CODE OF PRACTICE IPJSRT 1 MATERIALS, LOADS AND PERMISSIBLE STRESSES Section 1 Materials and Loads (Third Revision) First Reprint MAY 1997 UDC 669.14.018.29 : 621.315.668.2 : 624.042 : 006.76 8 BIS 1995 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 September 1995 Price Group 8

IS 802 P 1 to 3

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Page 1: IS 802 P 1 to 3

IS802( Partl/Sec 1 ) :1995

vRT%mmF

Indian Standard

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS -

CODE OF PRACTICE IPJSRT 1 MATERIALS, LOADS AND PERMISSIBLE STRESSES

Section 1 Materials and Loads

(Third Revision)

First Reprint MAY 1997

UDC 669.14.018.29 : 621.315.668.2 : 624.042 : 006.76

8 BIS 1995

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

September 1995 Price Group 8

Page 2: IS 802 P 1 to 3

,

Structural Engineering Sectional Committee, CED 7

FOREWORD

This Indian Standard ( Third Revision ) was adopted by the Bureau of Indian Standards, after the draft finalized by the Structural Engineering Sectional Committee had been approved by the Civil Engineering Division Council.

The standards under IS 802 series have been prepared with a view to establish uniform practices for design, fabrication, inspection and testing of overhead transmission line towers. Part 1 of the standard covers requirements in regard to material, loads and permissible stresses apart from other relevant design provisions. Provisions for fabrication, galvanizing, inspection and packing have been covered in Part 2 whereas provisions for testing of these towers have been covered in Part 3.

This standard was first published in 1967 and subsequently revised in 1973 and in 1977. In this revision, the standard has been split in two sections, namely Section 1 Materials and loads, and Section 2 Permissible stresses.

Some

a)

b)

cl

of the major modifications made in this Section are as under:

Concept of maximum working load multiplied by the factors of safety as per IE Rules has been replaced by the ultimate load concept.

For assessing the loads on tower, concept of reliability, security and safety have been introduced on the basis of IEC 826 : 1991 ‘Technical report on loading and strength of overhead transmission lines’.

Basic wind speed based *on peak gust velocity, averaged over 3 seconds duration, as per’ the wind map of India grven in IS 875 ( Part 3 ) : 1987 ‘Code of practice for design loads ( other than earthquake ) for buildings and structures : Part 3 Wind loads ( second revision )’ has been kept as the basis of calculating reference wind speed. Terrain and topography characteristics of the ground have been taken into consideration in working out the design wind speeds.

d) Wind loads on towers and conductors have been revised. These are based on the modified wind map of the country. Reference wind speed averaged over 10 minutes duration has been used for the determination of wind loads.

Provisions for the ‘Temperature Effects’ have been modified. In order to permit additional current carrying capacity in the conductor the maximum temperature in the ACSR conductor has now been permitted to be 75°C in any part of the country. For aluminium alloy ( AAAC ) conductor, the corresponding maximum temperature has been permitted to be 85°C.

Provisions for anti cascading checks have been included for angle towers.

Provisions for multi circuit towers have been included.

h) Consequent to the merger of IS 226 : 1975 ‘Structural steel ( Standard quality )’ in IS 2062 : 1992 ‘Specification for weldable structural steel ( third revision )’ steels conforming to IS 2062 : 1992 and IS 8500 : 1992 ‘Specification for weldable structural steel ( medium and high strength qualities )’ have been included.

j) With the publication of IS 12427 : 1988 ‘Transmission tower bolts’ these bolts ( property class 5.6 ) and bolts of property class 8.5 conforming to IS 3757 : 1985 ‘High strength structural bolts ( second revision )’ have been included in addition to bolts, of property class 4.6 conforming to IS 6539 : 1972 ‘H:xagon bJlts for steel structures’.

As transmission line towers are comparatively light structures and also that the maximum wind pressure is the chief criterion for the design, the Sectional Committee felt that concurrence of earthquake and maximum wind pressure is unlikely to take place. However in earthquake prone areas the design of towers/foundations shall bs checked for earthquake forces correspond- ing to nil wind and minimum temperature in accordance with IS 1893 : 1984 ‘Criteria for earthquake resistant design of structures (fourth revision )‘.

( Continued on third cover )

Page 3: IS 802 P 1 to 3

IS 802 ( Part l/Set 1 ) : 1995

Indian Standard

USE QF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS -

I? PRACTICE PART 1 MATERIALS, LOADS AND PERMISSIBLE STRESSES

Section 1 Materials and Loads

( Third Revision )

I SCOPE

I.1 This stiindard ( Part I/SW 1 ) stipulates materials and !oads to be adopted in the design of I;c!f-<ul)porting steel lattice towers for ov::hzad t ran ;mission lines.

1.1.1 Permissible stresses and other design parrmftrrs are covered in IS 802 ( Part I/ Set 2 ) : i992 of this standard.

1.1.2’ Provisions on fabrication including galva- nizing, inspection and packing, etc, and testing of transmission line towers have been covered in IS 8{)2 ( Part 2 ) : 1978 and IS 802 ( Part 3 ) : 1978 respectively. I.2 This standard does not cover river crossing towers a:id g~tyed towers. These will be c,)vered in separ:i!c standards.

2 REFERENCL;S

‘The Indian StanLlards listed in Annex A are necessary adjuncts to this standard

3 STATUTORY REQIJIRENENTS

3.1 Statutory requirements as laid down in the ‘Indian Electricity Rules, 1956’ or by any other statutory body applicable to such structures ;IS

covered in this standard shall be satisfied.

3.2 Compliance with this standard does not relieve any user from the responsibility of observing local and provincial building byelaws, iire and safety laws and other civil aviation requirements appi.lcable to such structures.

4 TFRMINOL& 3 J

4.1 Return Period

Return period is the mean interval between recurrences of a climatic event of defined magnitude. The inverse of the return period gives the probability of exceeding the event in one year.

4.2 Reliability

Reliability of a transmission system is the probabi!ty that thr cystem would perform its function/task under the desigl7ed load condi- tions for a speci:i:: parioli in simple terms, the reliability mdy be defined as the probability that a giver? item will indzcd survive a give:l service t?nVirr~!llllCil t anf1 loxling for a prescri- bed period of time.

4.3 Security

The abi!ity of d system to be protected from any major collapse such a:, c:r\cading clfc.ct, if a faiiure i5 triggered in a give:1 comp<>?ent. Security is a deterii!initic cb)jlcept as opposed to rclinbilily which is a probabilistic.

4.4 Safety

The ability of a svstem not to cause human injur!ec. or loss of iife. I: relates, in this code, mainly to protection of Tw0l.kl’l.s during construc- tion and maintennnLr: operations.

5 MATERIALS

5.1 Structural Steel

The tower member; incluJing cross; arm3 shall be of stiuctural steel conforming to any of the grade, ah ap;>ropriate, of iS 2062 : 1992. Steel conforming to any of the appropriat<.: grade of IS 8500 : 1992 may also be used.

5.1.1 Meclium and high strength structural steels with known prdpertics conforming to other national and intrrnativnal standards may also be used subject to the approval of the purchaser.

5.2 Bolts

5.2.1 Bolts for- lower connections shall conform to TS 12427 : 1988 or of property class 4.6 con- forming to IS 6639 : 1972,

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IS 802 ( Part l/Set 1 ) : 1995

5.2.2 High strength bolts, if used ( only with structural steels of IS 8500 : 1992) shall conform to property class 8.8 of IS 3757 : 1985.

5.2.3 Foundation bolts shall conform to IS 5624 : 1970.

5.5 Galvanization

5.5.1 Structural members of the towers, plain and heavy washers shall be gaIvanizcd in accor- dance with the provisions of IS 4759 : 1984.

5.2.4 Step bolts shall conform to IS 10238 : 1982.

5.3 Nuts

5.5.2 Threaded fasteners shall be galvanized to conform to the requirements of IS 1367 (Part 13 ) : 1983.

5.3.1 Nuts shall conform to IS 1363 ( Part 3 ) : 1992. The mechanical properties shall conform to property class 4 or 5 as the case may be as specified in IS 1367 ( Part 6 ) : 1980 except that the proof stress for nuts of property class 5 shall be as given in IS 12427 : 1988.

5.5.3 Spring washers shall be hot dip galvanized as per service grade 4 of IS 4759 : 1984 or electro galvanized as per service grade 3 of IS 1573 : 1986 as specified by the purchaser.

5.6 Other Materials

5.3.2 Nuts to be used with high strength bolts shall conform to IS 6623 : 1985.

Other materials used in the constraction of the tower shall conform to appropriate Indian Standards wherever available.

5.4 Washers 6 TYPES OF TOWERS

5.4.1 Washers shall conform to IS 2016 : 1967. Heavy washers shall conform to IS 6610 : 1972. Spring washers shall conform to type B of 1s 3063 : 1972.

5.4.2 Washers to be used with high strength bolts and nuts shall conform to IS 6649 : 1985.

6.1 The selection of the most suitable types of tower for transmission lines depends on the actual terrain through which the line traverses. Experience has, however, shown that any com- bination of the following types of towers are generally suitable for most of the lines :

i) Suspension towers ( with I or V suspension insulator strings )

a) Tangent towers ( 0” ) with To be used on straight runs only. suspension string

b) Intermediate towers ( 0” to 2” ) To be used on straight runs and upto 2” line with suspension string deviation.

c) Light angle towers ( 0” to 5” ) To be used on straight runs and upto 5” line with suspension string deviation.

NOTE - In the selection of suspension tower either (b) above or a combination of (a) and (c) may be followed.

ii) Tension towers

a)

b)

cl

d)

e)

Small angle towers ( 0” to 15’ ) with tension string

Medium angle towers ( 0” to 30” ) with tension string

Large angle towers ( 30” to 60” ) with tension string

Dead-end towers with tension string

Large angle and dead-end towers with tension string

To be used for line deviation from 0” to 15”.

To be used for line deviation 0” to 30”.

To be used for line deviation from 30” to 60”.

To be used as dead-end ( terminal ) tower or anchor tower.

To be used for line deviation from 30” to 60” or for dead-ends.

NOTE- In the selection of tension towers either (e) above or a combination of (c) and (d) may be followed.

2

Page 5: IS 802 P 1 to 3

6.2 The angles of line deviation specified in 6.1 are for the design span. The span may, however, be increased upto an optimum limit with reducing angle of line deviation, if adequate ground and phase clearances are available.

7 RELIABILITY CONSIDERATIONS

7.1 Transmission lines shall be designed for the reliability levels given in Table 1. These levels arc expressed in terms of return periods in years of climatic ( wind ) loads. The minimum yearly reliability l’s, corresponding to the return

period, T, is expressed as Ps = (

1 - -& )

Table 1 Reliability Levels of Transmission Lines

( Clause 7.1 )

SI Description Reliability Levels No ~---_-A-_-_,

1 2 3

(1) (2) (3) (4)

i) Return period of design 50 150 500 loads, in years, T

ii) Yearly reliability, PB 1-10-s A-lo-8.5 l-lo-’ ____-- _- .-.

7.2 Reliability level 1 shall be adopted for EHV transmission lines upto 400 kV class.

7.3 Reliability level 2 shall be adopted for EHV transmission lines above 400 kV class.

7.4 Triple and quadruple circuit towers upto 400 kV lines shall be designed corresponding to the reliability level 2.

7.5 Reliability level 3 shall be adopted for tall river crossing towers and special towers, although these towers are not covered in this standard.

8 WIND EFFECTS

8.1 Basic Wind Speed, Vb

Figure 1 shows basic wind speed map of India as applicable at 10 m height above mean ground level for the six wind zones of the country. Easic wind speed ‘vb’ is based on peak gust velocity averaged over a short time interval of about 3 seconds, corresponds to mean heights above ground level iu an open terrain ( Category 2 ) and have been worked out for a 50 years return period [ Refer IS 875 ( Part 3 ) : 1987 for further details 3.

Basic wind speeds for the six wind zones ( see Fig. 1 ) are :

IS 802 ( Part l/Set 1 ) : 1995

Wind Zotie Basic Wind Speed, vb m/s

1 33

2 39

3 44

4 47

5 50

6 55

NOTE - In case the line traverses on the border of different wind zones, the higher wind speed may be considered.

8.2 Meteorological Reference Wind Speed, VR

It is extreme value of wind speed over an aver- aging period of 10 minutes duration and is to be calculated from basic wind speed ‘vb’ by the following relationship :

VR = vb/&

where

K0 is a factor to convert 3 seconds peak gust speed into average speed of wind during 10 minutes period at a level of 10 metres above ground. K,, may be taken as 1.375.

8.3 Design Wind Speed, v,

Reference wind speed obtained in 8.2 shall be modified to include the following effects to get the design wind speed:

a ) Risk coefficient, K,; and

b ) Terrain roughness coefficient, K,.

It may be expressed as follows:

vd = VR X K, X K,.

8.3.1 Risk Coefjcient, Kl

Table 2 gives the values of risk coefficients Kl for different wind zones for the three reliability levels.

Table 2 Risk Coefficient Kl for Different Reliability Levels and Wind Zones

( Clause 8.3.1 )

Reliability Coeftlcient K, for Wind Zones Level

-1 & -----

2 3 4 5 6 (1) (2) (3) (4) (5) (6) (7)

1 1.00 I*00 1.00 1.00 1.00 1.00 2 1.08 1.10 1.11 1.12 1.13 I.14 3 1.17 1.22 1.25 1.27 1.28 1.30

3

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IS 802 ( Part l,/Sec 1 ) : 1995

8.3.2 Terrain Roughness Coefjcient, K,

Table 3 gives the values of coefiicient K, fvr the three categories of terrain roughness (see 8.3.2.1 ) corresponding to 10 minutes averaged wind speed.

Table 3 Terrain Roughness Coefficient, K,

( CIause 3.3.2 )

Terrain Category

Coefficient, K,

1 2 3 ---

1.08 1.00 0.85

NOTE - For lines encountering hills/ridges, the value of K, for a given terrain shall be changed to next higher value of 4.

8.3.2.1 Terrain categories

a) Category 1 - Exposed open terrain with few or no obstruction and in which the average height of any object surrounding the structure is less than 1.5 m.

NOTE - This category includes open seacoasts, C$;xsssstretch of water, deserts and flat treeless

b) Category 2 - Open terrain with well scattered obstructions having height generally between 1.5 m to 10 m.

NOTE - This category includes normal country lines with very few obstacles.

c) Catcgcly 3 - Terrain with numerous closely spaced obstructions.

NOTE - This category includes buili up areas and forest areas.

8.4 Design Wind Pressure, Pd

The design win<! pressure on towers. conductors and il;sulators shall be obtained by the following relationship :

where

Pd = design wind pressure in N/m*, and

Vd = design wind speed in m/s.

8.4.1 Design wind pressures Pd for the three rrliability 1~ vcls and pertaining to six wind zones and the three terrain categories have been worked out and given in Table 4.

9 WIND LOADS

9.1 Wind Load on Tower

111 order to determine the wind load on tower, the tower is divided into different panels having a height ‘h’. These panels should normally be taken between the intersections of the legs and bracings. For a lattice tower of square cross- section, the resultant wind load Fwt in Newtons, for wind normal to the longitudinal face of tower,

Table 4 Design Wind Pressure P,J, in N/m”

( Clause 8.4.1 )

Reliability Level

(1)

1

2

3

Terrain Category

(2)

1

2 3

1 2

3

1

2

3

Design Wind Pressure Pd for Wind Zones r_____ __-._----h--_--_-----~

1 2 3 4 5 6

(3) (4) (5) (6) (7) (8) .~__--- -__.-

403 563 717 818 925 1 120 346 483 614 701 793 960 250 349 444 506 573 694

410 681 883 1 030 1 180 1 460 403 584 757 879 1 010 1 250 291 422 547 635 732 901

552 838 1 120 1 320 1 520 1890 413 718 960 1 130 1 300 1 620 342 519 694 x17 939 1 170

4

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As in the Original Standard, this Page is Intentionally Left Blank

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IS 802 ( Part l/Set 1 ) : 1995

on a panel height ‘h’ applied at the centre of gravity of this panel is:

Fwt = Pcj x Cat x Ae x GT

where Pd = design wind pressure, in N/m”:

Cdt = drag coefficient for panel under con- ”

A@ =

GT =

sideration against which the wind is blowing. Values of Cdt for different solidity ratios are given in Table 5.

Solidity ratio is equal to the effective area ( projected area of all the indivi- dual elements ) of a frame normal to the wind direction divided by the area enclosed by the boundry of the frame normal to the wind direction;

total net surface area of the legs, bracings, cross arms and secondary members of the panel projected normal to the face in m’. (The projections of the bracing elements of the adjacent faces and of the plan-and-hip bracing bars may be neglected while determ- ianjig the projected surface of a face );

gust response factor, peculiar to the ground roughness and depends on the height above ground. Values of GT for the three terrain categories are given in Table 6.

Table 5 Drag CoeiBcient, Cat for Tower

( CIuuse 9.1 )

Solidity Drag Coefficient Ratio Cdt

(1) (2)

up to 0.05 0.1 0.2 0.3 0.4

0.5 and above

NOTES

3.6 34

2.9 2.5 2.2 2.0

1 Intermediate values may be linearly interpolated. 2 Drag coefficient takes into account the shielding effect of wind on the leeward face of the tower. However, in case the bracing on the leeward face is not shielded from the windward face, then the projected area of the leeward face of the bracing should also be taken into consideration.

9.1.1 In case of horizontal configuration towers, outer and inner faces countering the wind between the waist and beam level should be

considered separately for the purposes of calculating wind load on the tower, as shown in Fig. 2.

Table 6 Gust Response Factor for Towers ( GT ) and for Insulators ( Gi )

( Clauses 9.1 and 9.3 )

Height Above Ground

m

(1)

up to 10 20 30 40 50 60 IO 80

Values of Gr and G, for Trerain Categories

r----- h---_$ 1 2 3

(2) (3) (4)

1.70 1.92 2.55 1.85 2.20 2.82 1.96 2.30 2.98 2.07 2.40 3.12 2.13 2.48 3.24 2.20 2.55 3.34 2.26 2.63 3.46 2.31 2.69 3.58

NOTE - lntermediatc values may be linearly interpolated.

9.2 Wind Load on Conductor and Groundwire

The load due to wind on each conductor and groundwire, F,, in Newtons applied at suppor- ting point normal to the line shall be determined by the following expression:

Fw, = Pd x Ca, x L x d x G,

where

Pd = design wind pressure, in N/m’;

CdC = drag coefficient, taken as 1.0 for conductor and 1.2 for groundwire;

L = wind span, being sum of half the span on either side of supporting point, in metres;

d = diameter of cable, in metres; and

G, = gust response factor, takes into account the turbulance of the wind and the dynamic response of the conductor. Values of G, are given in Table 7 for the three terrain catego- ries and the average height of the conductor/groundwire above the ground.

NOTE - Tho average height of conductor/ground- wire shall be taken up to clamping point of top conductor/groundwi re on tower less two-third the sag at minimum temperature and no wind.

9.2.1 The total effect of wind on bundle conduc- tors shall be taken equal to the sum of the wind load on sub-conductors without accounting for a possible masking effect of one of the subcon- ductors on another.

7

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IS 802 ( Part l/Set 1 ) : 1995

FIG. 2 HORIZONTAL CONFIGURATION Towm

Page 11: IS 802 P 1 to 3

IS 802 ( Part l/Set 1 ) : 1995

Table 7 Values of Gust Response Factor C;, for Conductor and Groundwire

( Clausl? 9.2 ) -”

Terrain Height Above Values of G, for Ruling Span of, in ru Category Ground, m r -_ ----- .----_-.- -_--_n. - _---__-___-________

UP to 300 400 500 600 700 8W au? 200 above

(11 (2) (3) (-1! (5) (6) (7) (8) (9) __~__._.__ .- ..-_-- ----. .-_____ _-

1 up to 10 1.70 1.65 1.60 1.56 I.53 I.50 1.47

20 1.90 1.87 1.83 I .79 1.75 1.70 1.66

40 2.10 2.04 2.00 1.95 1.90 1.85 1.80

60 2.24 2.18 2.12 2.07 2.02 1.96 1.90

80 2.35 2.25 2.18 2.13 2.10 2.06 2.03

2 up to 10 1.83 1.78 1.73 1.69 1.65 1.60 1.55

20 2.12 2.04 I .9.5 I.88 1 54 1.80 1.80

40 2.34 2.27 2.20 2.13 2.08 2.05 2.02

60 2.55 2.46 2.37 2.28 2.23 2.20 2.17

80 2.119 2.56 2.48 2.41 2.36 2.32 2.28

3 up to 10 2.05 1.98 1-93 I.88 i-83 1.77 1.73

20 2,44 2.35 2.25 2. I5 2.10 2.06 2.03

40 2.76 2.67 2.58 2-49 2.42 2.38 2.34

60 2.97 2.87 2.77 2.67 1’60 2.54 2.52

80 3.19 3.04 2.93 2.85 2.38 2.73 2.69

NOTE - Intermediate values may be linearly interpolated. -

9.3 Wind Load on Insnlator Strings

Wind load on insulator strings ‘J’*{ shall be determined from the attachment point to the centre line of the conductor in case of suspen- SIOII tower and up to the end of clamp in case of tension tower, in the direction of the wind as follows:

Fwi = Ck x PHI x Ai x Gi

where

cdi =

pd zz

Ai =

Gt :-

drag coefficient, to be taken as 1.2;

design wind pressure in N/ma;

50 percent of the area of insulator string projected on a plane which is parallel to the longitudinal axis of the string; and gust response factor, peculiar to the ground rougilncss and depends on the height of insulator attachment point above ground. Values of Gi for the three terrain categories are given in Table 6.

9.3.1 In case of multiple strings including V strings, no masking effect shall be considered.

10 TEMPERATPJRE EFFECTS

10.1 General

The temperature range varies for different loca- lities under different diurnal and seasonal conditions. The absolute maximum and mini- mum temperature which may be expected in different localities in the country are indicated on the map of India in Fig. 3 and Fig. 4 respec- tively. The temperature indicated in these maps are the air temperatures in shade. These may be used for assessing the temperature effects.

10.2 Temperature Variations 10.2.1 The absolute maximum temperature may be assumed as the higher adjacent isopleth temperature shown in Fig. 3. 10.2.2 The absolute minimum temperature may be assumed as the lower adjacent isopleth temperature shown in Fig. 4. 10.2.3 The average everyday temperature shali be 32°C anywhere in the country, except in regions experiencing minimum temperature of -5°C or lower ( see Fig. 4 ), where everyday temperature may be taken as 15°C or as specified by the power utilities.

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IS 802 ( Part l/Set 1 ) : 1995

10.2.4 The maximum conductor temperature may be obtained after allowing increase in temperature due to radiation and heating effect due to current etc over the absolute maximum temperature given in Fig. 3. The tower may be designed to suit the conductor temperature of 75°C ( Max ) for ACSR and 85°C ( Max ) for aluminium alloy col!ductor. The maximum temperature of groundwire exposed to sun may be taken as 53°C.

10.3 Sag Tension

Sag tension calculation for conductor and groundwire shall be made in accordance with the relevant orovisions of 1s 56 13 ( Part 2/ Set 1

a)

) : 1985 ibr the following combinations:

b)

100 percent design wind pressure after accounting for drag coefficient and gust response factor at everyday temperature, and

36 percent design wind pressure after accounting for drag coefficient and gust response factor at minimum temperature.

11 LOADS ON TOWER

11.1 Classification of Loads

Transmission lines are subjected to various loads during their lifetime. These loads are classified into three distinct categories, namely,

a) Climatic loads -- related to the reliability requirements.

b) Failure containment loads - related to security requirements.

c) Construction and maintenance loads - rela- ted to safety requirements.

11.2 Climatic Loads

These are random loads imposed on tower, insulator string, conductor and groundwire due to action of wind on transmission line and do not act continuously. Climatic loads shall be determined under either of the following climatic conditions, whichever is more strin- gent:

i) 100 percent design wind pressure at everyday temperature, or

ii) 36 percent design wind pressure at mini- mum temperature.

NOTE-Condition (ii) above is normally not crucial for tangent tower but shall be checked for angle or dead-end towers, particularly for short spans.

11.3 Failure Containment Loads

These loads comprise of:

i) Anti cascading loads, and

ii) Torsional and longitudinal loads.

11.3.1 Anti Cascading Loads

Cascade failure may be caused by failure of items such as insulators, hardware, joints, failures of major components such as towers, foundations, conductor due to defective mate- rial or workmanship or from climatic overloads or sometimes from casual events such as misdi- rected aircraft, avalanches, sabotage etc. The security measures adopted for containing cascade failures in the line is to provide angle towers at specific intervals which shall be checked for anti-cascading loads ( see 14 )_

11.3.2 Torsional and Longitudinal Loads

These loads are caused by breakage of conduc- tor(s) and/or groundwire. All the towers shall be designed for these loads for the number of conductor (s) and/or groundwire considered broken according to 16.

11.3.2.1 The mechanical tension of conductor/ groundwire is the tension corresponding to 100 percent design wind pressure at every day temperature or 36 percent design wind pressure at minimum temperature after accounting for drag coeficient and gust response factor.

11.4 Construction and Maintenance Loads

These are loads imposed on towers during construction and maintenance of transmission : lines.

12 COMPUTATION OF LOADS

12.1 Transverse Loads

Transvelse loads shall be computed for relia- bility, security and safety requirements.

12.1.1 Reliability Requirements

These loads shall be calculated as follows:

i) Wind action on tower structures, conduc- tors, groundwires and insulator strings computed according to 9.1, 9.2 and 9.3 respectively for both the climatic condi- tions specified in 11.2.

ii) Component of mechanical tension &a of conductor and groundwire due to wind computed as per 11.3.2.1.

10

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7@ I

w I

a# I

IS 802 ( Part l/Set 1 ) : 1995

1/ d lw- I I 1

.0-*-l ./ a., ‘L

2 ‘=a ,.- “)

.i 1

SRi+x’AGAA _\. I

MAP OF INDIA SHOWING HIGHEST MAXIMUM

TEMPERATURE ISOPLETHS’C

BASED ON DATA UP TO 1958 SUPPLIED BY

11

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IS 802 ( Part l/Set 1 ) : 1995

,NDIA METEOROLOGlCAL DEPARTMENT

PROJECT,ON:LAMBERTCON1CAL

-3.” . 3,. /--.I&=_

AGRA -2.53 JODHPUR AJMER l l

! i EOMBAYJ\\/ WNE

AKHAPATNAM

12

Page 15: IS 802 P 1 to 3

Thus, total transverse load = (i) + (ii) = Fwt + Fw, + Fwi + Fwa

where ‘FWC’, ‘FWi’ and (Fad’ are to be applied on all conductors/groundwire points and ‘Fwt’ to bc applied on tower at groundwire peak and cross arm levels and at any one convc- nient level between bottom cross arm and ground level for normal tower. In case of tower with extensions, one more application level shall be taken at top end of extension.

12.1.2 Security Requirements

These lcads shall be taken as under:

i) Suspension towers

a)

b)

Transverse loads due to wind action on tower structures, conductors, groundwires ant1 insulators shall be taken as nil. Transverse loads due to line deviation shall be based on component of mechanical tension of conductors and groundwires corresponding to everyday temperature and nil wind condition. For broken wire spans the component shall be corresponding to 50 percent mechanical tension of conductor and 100 percent mechanical tension of groundwire at everyday temperature and nil wind.

ii) Tension and dead end towers a) Transverse loads due to wind action

on tower structure, conductors, groundwires and insulators shall be computed as per 12.1.1 (i). 60 percent wind span shall be considered for broken wire condition and 100 percent wind span for intact span condition.

b) Transverse loads due to line deviation shall be the component of 100 percent mechanical tension of conductor and groundwire as defined in 11.3.2.1.

12.1.3 Safety Requirements

Transverse loads on account of wind on tower structures, conductors, groundwires, and insula- tors shall be taken as nil for normal and brokenwire conditions. Transverse loads due to mechanical tension of conditions and groundwire at everyday temperature and nil wind condition on account of line deviation shall be taken for both normal and broken wire conditions. 12.2 Vertical Loads Vertical loads shall be computed for reliability, security and safety requirements. 12.2.1 Reliability Requirements

These loads comprise of: i) Loads due to weight of conductors/

groundwire based on design weight span,

ii)

IS 802 ( Part l/Set 1 ) : 1995

weight of insulator strings and accesso- ries, and Self weight of tower structure up to point/level ut:der consideration.

The rffective weight of the conductor/ground- wire should be corresponding to the weight span on the tower. The weight span is the horizontal distance between the lowest points of the conductor/groundwire on the two spans adjacent to the tower under consideration. The lowest point is defined as the point at which the tangent to the sag curve or to the sag curve produced, is horizontal. 12.2.2 Security Requirements

These shall be taken as: i) Same as in 12.2.1 (i) except for broken

wire condition where the load due to weight of conductor/groundwire shall be considered as 60 oercent of weight span, and

acting at of weight

ii) Same as in 12.2.1 (ii). 12.2.3 Safety Requirements

These loads comprise of: i) Loads as computed in 12.2.2,

ii) Load of 1 500 N considered each cross arm, as a provision of lineman with tools,

iii) Load of 3 500 N considered acting at the tip of cross arms up to 220 kV and 5 000 N for 400 kV and higher voltage for design of cross arms, and

iv) Following erection loads at lifting points, for 400 kV and higher voltage, assumed as acting at locations specified below:

~~ ___.____ Tension Vertical Distance,

Tower with Load, N from the Tip of

Cross Arm, mm

Twin bundle conductor 10 000 600 Multi bundle conductor 20 000 I 000

-__ __- ____-. All bracing and redundant members of the tewers which are horizontal or inclined up to 15” from horizontal shall be designed to with stand an ultimate vertical loads of 1 500 N conside{ed acting at centre independent of all other loads.

12.3 Longitudinal Loads Longitudinal loads shall be computed for relia- bility, security and safety requirements. 12.3.1 Reliability Requirements

These loads shall be taken as under:

i) Longitudinal load for dead-end towers to be considered corresponding to

13

Page 16: IS 802 P 1 to 3

IS 802 ( Part l/See 1) : 1995

mechanical tension of conductors and groundwire as defined in 11.3.2.1.

ii) Longitudinal loads which might be caused on tension towers by adjacent spans of

iii)

unequal lengths can be neglected in most cases, as the strength of the supports for longitudinal loads is checked for security requirements and for construction and maintenance requirements.

NO longitudinal load for suspension and tension towers.

12.3.2

These

i)

Security Requirements

loads shall be taken as under:

ii)

For suspension towers, the longitudinal load corresponding to 50 percent of the mechanical tension of conductor and 100 percent of mechanical tension of groundwire shall be considered under every day temperature and no wind pressure. Horizontal loads in longitudinal direc- tion due to mechanical tension of conductors and groundwire shall be taken as specified in 11.3.2.1 for broken wires and nil for intact wires for design of tension towers.

iii) For dead end towers, horizontal loads in longitudinal directon due to mechanical tension of conductor and groundwire shall be taken as specified in 11.3.2 for intact wires. However for broken wires, these shall be taken as nil.

12.3.3

These

i)

Safety Requirements

loads shall be taken as under:

For normal conditions - These loads for dead end towers shall be considered as corresponding to mechanical tension of conductor/groundwire at every day temperature and no wind. Longitudinal loads due to unequal spans may be neglected_

ii) For brokenwire conditions

a) Suspension towers - Longitudinal load Per sub-conductor and groundwire shall be considered as 10 000 N and 5 000 N respectively.

b) Tension towers - Longitudinal load equal to twice the sagging tension ( sagging tension shall be taken as 50 percent of tension at everyday temperature and no wind ) for wires under stringing arid I.5 trmes the sagging tension for all intact wires ( stringing completed ).

13 LOADING COMBINATIONS 13.1 Reliability Conditions

i) Transverse loads - as Per 12.1.1. ii) Vertical loads - as per 12.2.1.

iii) Longitudinal loads - as per 12.3.1.

13.2 Security Conditions i) Transverse loads - as per 12.1.2.

ii) Vertical lauds -- as per 12.2.2. iii) Longitudinal loads - as per 12.3.2.

13.3 Safety Conditions i) Transverse loads - as per 12.1.3.

ii) VerticaZ loads - shall be the sum of: a) Vertical loads as per 12.2.2 (i) multi-

plied by the overload Factor of 2. b) Vertical loads calculated as per

12.2.2 (ii), 12.2.3 (ii), 12.2.3 (iii) and 12.2.3 (iv).

iii) Longitudinal loads - as per 12.3.3.

14 ANTI CASCADING CHECKS All angle towers shall be checked for the following anti-cascading conditions with all conductors and groundwire intact only on one side of the tower

a>

b)

c)

Transverse loads - These loads shall be taken under no wind condition.

Vertical loads - These loads shall be the sum of weight of conductor/groundwire as per weight span of intact conductor/ ground wire, weight of insulator strings and accessories. Longitudinal loads - These loads shall be the pull of conductor/groundwire at everyday temperature and no wind applied simultaneously at all points on one side with zero degree line deviation.

15 TENSION LIMITS Conductor/groundwire tension at everyday temperature and without external load, should not exceed the following percentage of the ultimate tensile strength of the conductor:

Initial unloaded tension 35 percent Final unloaded tension 25 percent

provided that the ultimate tension under everyday temperature and 100 percent design wind pressure, or minimum temperature and 36 percent design wind pressure does not exceed 70 percent of the ultimate tensile strength of the conductor/ground wire.

NOTE-For 400 kV and 800 kV lines, the tinal ~-~ UIibZtCd ftnslon of conductors at everyday tempe- raturc shall not exceed 22 perrent of the ultimate tensile strength of conductors and 20 percent of the ultimate tensile strength of groundwire

14

Page 17: IS 802 P 1 to 3

IS 802 ( Part l/See 1 ) : 19%

16 BROKEN WIRE CONDITION

The following broken wire conditions shall be assumed in the design of towers: -- ____________.~

a) Single circuit towers Any one phase or groundwire broken; bvhichever is more stringent for a particular member.

b) Double, triple circuit and quad- ruple circuit towers:

i) Suspension towers Any one phase or groundwire broken: whichever is more stringent for a particular member.

ii) Small and medium angle Any two phases broken on the same side and same towers span or any one phase and one groundwire broken OR

the same side and same span whichever combina- tion is more stringent for a particular member.

iii) Large angle tcniiion towers/ Any three phases broken on the same side and same dead end towers span or any two of the phases and one groundi>ire

broken on the same side and same span; whichever combination constitutes the most stringent condition for a particular member.

NOTE - Phase shall mean all the sub-conductors in the case of bundle conductors. __~--w

17 STRENGTH FACTORS RELATED TO QUALITY

i) If steel with minimum guaranteed yield strength is used for fabrication of tower,

The design of tower shall be carried out in accordance with the provisions covered in IS 802 ( Part l/Set 2 ) : 1992. However, to account for the reduction in strength due to dimensional tolerance of the structural sections and yield strength of steel used, the following strength factors shall be considered:

the estimated loads shall be increased by a factor of 1.02.

ii) If steel of minimum guaranteed yield strength is not used for fabrication of tower, the estimated loads shall be increased by a factor of 1.05, in addition to the provision (i) above.

ANNEX A

( Clause 2 )

LIST OF REFERRED INDIAN STANDARDS

IS No. Title IS No. Title

802 ( Part 1/ Code of practice for use of 1367 Technical supply conditions Set 2 ) : 1992 structural steel in overhead for threaded steel fasteners:

transmission line towers: Part 1 Material, loads and ( Part G ) : 1980 Part 6 Mechanical properties

permissible stress, Section 2 and test methods for nuts with

Permissible stresses ( third specified proof loads ( second

revision ) revision )

87f9\;art 3 ) : Code of practice for design ( Part 13 ) : 1985 Part 13 Hot-dip galvanized

loads ( other than earthquake ) coatings on threaded fasteners

for buildings and structures: ( second revision )

Part 3 Wind loads ( second 1573 : 1986 revision )

Electroplated coatings of zinc on iron and steel ( second

13;;J2Part 3 ) : Hexagon head bolts, screws revision ) and nuts of product Grade C : Part 3 Hexagon nuts ( size 2016 : 1967 Plain washers ( first revision )

range M 5 to M 64 ) ( third 2062 : 1992 Steel for general structural revision ) purposes (fourth revision )

15

Page 18: IS 802 P 1 to 3

IS 802 ( Part l/Set 1) : 1995

IS No.

3063 : 1972

3757 : 1985

4759 : 1984

5613 ( Part 2/ Set 1 ) : 1985

5624 : 1970

Title

Single coil rectangular section spring washers for bolts, nuts and screws ( jirst revision )

High strength structural bolts ( second revision )

Hot-dip zinc coatings on structural steel and other allied products ( third revision )

Code of practme for design, installation and maintenance of overhead lines: Part 2 Lines above 11 kV and up to and including 220 kV, Section 1 Design ( jrsr revision )

Foundation bolts

IS No.

6610 : 1972

6623 : 1985

6639 : 1972

6649 : 1985

8500 : 1992

10238 : 1982

12427 : 1988

Title

Heavy washers for steel structures

High strength structural nuts ( jirst revision )

Hexagon bolts for steel structures

Hardened and tempered washers tar high strength structural bolts and nuts (first revision )

Structural steel--Microalloyed ( medium and high strength qualities ) (first revision )

Step bolts for steel structures

Transmission tower bolts

Page 19: IS 802 P 1 to 3

IS 802 ( Part l/Set 1 ) : 1995

ANNEX B

( ForeWord )

Composition of Structural Engineering Sectional Committee, CED 7

Chairman

SHRI M. L. MIHIA

SHKI S. K. DATTA ( Alternate to Shri M. I,. MeWa )

SHRI R. N. BISWAS SHRI YOGENDRA SINGH ( Alternate )

SHRI RAMFSH CWAKRABORTY SHRI S. K. SUMAN ( Akv-nafe )

CHIEF MANAGER ( ENOIN~ERING ) GENERAL MANAGER ( STRUCTURAL )

( ,ghernate )

DR P. DAYARATNAM

DIRFCTOR ( TRANSMISSION ) DEPUTY DIRECTOR ( TRANSMISSION )

SHRI S. C. DUGGAL SHRI V. (3. MANGRULKAR ( Alttwmte )

SHRI D. K. DATTA SHRI A. K. SEN ( Alterrrole )

SHRI S. K. GANGOP~ADHYAY SIIKI P. BIMAL ( Ahcrnate )

SHRI S. GANGULI SrfRl S,. P. C;ARARI ( Altcrrlnre )

DR JANARDAN JifA

SHRI S. P. JAMDAR SFrRl S. S. RATHORE ( Alternate )

Richardson & Cruddas ( 1972 ) Ltd, Bombay

Jessop & Co Limited. Calcutta

Braithwaite & Co Ltd, Calcutta

Projects & Development India Ltd. Dhanbad

Institution of Engineers ( India ), Calcutta Road & Building Department, Gandhinagar

Ministry of Railways, Lucknow JUINT DIRECTOR STAUDARDS ( B & S )-Se-1 DL-PIJTY DIRECTOR STANDARDS ( B & S )-SB

Representing

Metallurgical and I?ngineering Consultant ( India ) I.td, Ran&i

Intlian Oil Corpwation, New Delhi

Joint PIalit Committee, Calcutta

RITES, New Delhi

IIT, Kanpur

Central Electricity Authority, New Delhi

DR V. KALYANARAMAN

DR J. N. KAR

PROF SAIBAL GHOSH ( Alternate ) SHKI N. K. MAJUMUAR

SHRI D. M. SRIVASTAVA ( Alternate )

SHRI S. M. MUNJAL SHRI A. K. VERMA ( Alfernale )

SHRt M. K. MUKHERIEE SHRI S. K. SINHA ( Alfernate )

SHRI B. B. NAO SHRI G. P. LAHIRI ( Alternate )

SHRI V. NARAYANAN SHRI A. K. BAJAJ ( Alternate )

SHRI P. N. NARKHADE SHRI M. V. BEDEKAR ( Alternate )

DR S. M. PATFL S&t D. P. PAL

SHRI B. P. DE ( Abernate )

SHRI D. PAUL SHRI N. RADHAKRISHNAN

SHRI P. APPA RAO @[ternate ) SHRI M. B. RANGARAO

SHRI M. S. C. NAYAR ( Alternate ) SHRI C. S. S. RAO

SHRI P. S. RAY ( Alternate ) DR T. V. S. R. APPA RAO

SHRI P. R. NATARAJAN ( Alternafe )

IIT, Madras Bengal Engineering College, Civil Engineering Department.

Governmcnt of West Bengal, Calcutta

Hindustan Steel Works Construction Ltd, Calcutta

DGS &D, Inspection Wing, New Delhi

Indian Roads Congress, New Delhi

EngineenIndia Limited, New Delhi

Central Water Commission, New Delhi

Bombay Port Trust, Bombay

Birla Vishvakarma Mahavidyala, Vallabh Vidyasagar, Gujarat M. N. Dastur & Co Pvt Ltd, Calcutta

Industrial Fasteners Association of India, Calcutta Binny Ltd, Madras

Tata Consulting Engineers, Bombay

Engineer-in-Chief’s Branch, Ministry of Dsfence, New Delhi

Structural Engineering Research. Madras

( Continued on page 18 )

17

Page 20: IS 802 P 1 to 3

IS 802 ( Part l/Set 1 ) : 1995

( Continued from page 17 )

Members

snur A. G. ROY SHRI K. B . CHAKRABORTY ( Afternate )

SENIOR SHIPPINQ ENGINEER ASSETANT NAVAL ARCHITECT ( A lrernare )

SHRI A. K. SEN

SHRI G. SRLIENIVASAN SHRI P. SIJRYA ( Altcrnare )

DR C. N. SRINIVA~AN !&RI C. R. ARVIND ( ANernure )

DR D. N. TRIKHA DR P. N. GODBELE ( Alternare )

SHRI U. H. VARYANI

SHR~ J. R. MEHTA Director ( Civ Engg )

Representing

Bridge & Roof Co ( India ) Ltd, Howrah

Indian Register of Shipping, Bombay

Jessop & Co Limited, Calcutta Bharat Heavy Electricals Ltd, Hyderabad

C. R. Narayana Rao, Madras

University of Roorkee, Roorkee

Kothari Associates Private Ltd, New Delhi Director General, BIS ( Ex-officio Member )

Member Secretary

SHR~ S. S. SETHI

Director ( Civ Engg, BIS )

Subcommittee for Use of Steel in Over-Head Line Towers and Switchyard Structures, CED 7 : 1

Convener

SHRI M. L. SACHDEVA

Members SHRI RAW-WDDIN ( AfIernale to

Shri M. L. Sachdeva ) ADVISOR ( POWER )

SHRI D. K. NARSIMHAN (A lrermre )

SHRI MUSTAG AHMED SHRI Y. R. NAGARAIA ( .tlrernate )

SHRI D. K. BHATTACHAKJEE SHRI S. K. SINHA (Ahrnare )

DR P. BOSE

Central Electricity Authority, New Delhi

Central Board of Irrigation and Power, New Delhi

Karnataka Blectricity Board, Bangalore

Damodar Valley Corporation, Calcutta

Electrical Manufacturing Ltd ( Projects Construction Division ), Calcutta

!&RI L. N. BAN~RJEC ( Ahernare )

SHRI UMESH CHANDRA SHRI D. CHOWDHURY ( Alternate I ) SHRI E. V. RAO ( Alternate II )

Power Grid Corporation of India Ltd, New Delhi

CHIEF ADMINISTRATOR-CUM-ENGINEER-IN- Bihar State Electricity Board, Patna CHIEF

CHIEF ENGINEER Andbra Pradesh Electricity Board, Hj’derabad

SUPERINTENDING ENQINEER ( TRANSMISSION ) ( Alrernare )

SHRI S. DATTA GUPTA Larsen and Toubro Ltd, Madras

SHRI S. Z. HUSSAIN Madhya Pradesh Electricity Board, Jabalpur SHRI A~HOK BAJPAI ( Abernare )

JOINT DIRECTOR ( BRIDGE AND STRUCTURE ) Ministry of Railways, New Delhi ASSISTANT DIRECTOR ( TI ) ( AIrernare )

SHRI H. C. KAUSHIK Haryana Electricity Board, Hissar

SHRI LAL KHUBCHANDAN I KEC International Ltd. Bombay SHRI B. N. PAI ( Aflernure )

SHRI D. L. KOTHARI Bhakara Beas Management Board, Patiala SHRI P. S. Tu~sr ( Alternate )

DR D. M. LAKHAPATI SHRI P. BHATTACHARYA ( Alterme )

SAE ( India ) Ltd, Calcutta

( Conlinued on page 19)

18

Page 21: IS 802 P 1 to 3

IS $02 ( Part l/Set 1 ) : 1995

( Conrinued from page 18 )

Members

DR S. N. MANDAL SHRI K. MOHANDAS ( Ahmate )

&RI P. R. NATARAJAN &RI K. MIJRALIDHARAN ( Alternate )

SHRI R. V. NEDKARNI SHRI K. N. AWATE ( Alternate)

SHRI G. D. RATHOD SHRI A. D. TKIVEDI ( Alternate )

SHRI V. B. SINGH SHRI SURENDRA NARAIN ( Alternate )

SHRI B. SRINIVASAN SHIU M. A. MAJEETH ( Alfernafe )

SUPERINTENDING ENGINEER

SHKI R. SUSENDKAN SHRI N. V. RAMESH ( Alternute )

SHRI S. M. TAWLKAR SHRI 0. C. MEHTA ( Alternafe )

Representing

National Thermal Power Corporation Ltd, New Delhi

Structural Engineering Research Ccntre, Madras

Maharashtra State Electricity Board, Bombay

Transpower Engineering Ltd, Bombay

UP State Electricity Board, Lucknow

Tamil Nadu Electricity Board, Madras

Punjab State Eleciricity Board, Patiala Central Power Research Institute, Bangalore

Gujarat Electricity Board, Baroda

19

Page 22: IS 802 P 1 to 3

While preparing this code, practices prevailing in the country in this field have been kept in Assistance has been derived from the following publications: view.

i)

ii)

iii)

iv)

IEC 826 : 1991 ‘Technical report on loading and strength of overhead transmission lines’, issued by the International Electrotechnical Commission.

Project report NO. EL-643 ‘Longitudinal unbalanced loads on transmission line struc- tures’ issued by the Electric Power Research Institute USA.

CIGRE Report No. 22-13 of 1978 ‘Failure containment of overhead lines design’ by H. B. White.

v)

Loading and strength of transmission line system, Part 1 to Part 6 issued by ‘IEEE Transmission and Distribution Committee Sub-Group on Line loading and strength of transmission line structures’, IEEE, PESj Summer 1977 Conference Papers.

‘Guide for design of steel transmission line towers’ issued by American Society of Civil Engineers, New York, 1988.

vi) ‘Guide for new code for design of transmission line towers in India; Publication No. 239, issued by the Central Board of Irrigation and Power, New Delhi.

( Continuedfrom second cover )

Ice loadings on towers and conductors/ground wires for lines located in the mountaineous regions of the country subjected to snow fall, may be taken into account on the basis of available meteorological data both for ice with wind and without wind. A separate Indian Standard on ice loadings to be considered in the design of transmission line towers has been proposed to be brought out.

Formulae and the values have been given in SI Units only.

While formulating the provisions of this code it has been assumed that structural connections are through bolts only.

The composition of the technical committee responsible far the formulation of this standard is given in Annex B.

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall he rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( revised )‘. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

Page 23: IS 802 P 1 to 3

IS 802 (Part 1/Sec 2) : 1992(Reaffirmed 1998)

Edition 4.1(1998-01)

Indian Standard

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS — CODE

OF PRACTICEPART 1 MATERIAL, LOADS AND PERMISSIBLE STRESSES

Section 2 Permissible Stresses

( Third Revision )(Incorporating Amendment No. 1)

UDC 621.315.668.2

© BIS 2002

B U R E A U O F I N D I A N S T A N D A R D SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Price Group 6

Page 24: IS 802 P 1 to 3

Structural Engineering Sectional Committee, CED 7

FOREWORD

This Indian Standard (Third Revision) was adopted by the Bureau of Indian Standards, after thedraft finalized by the Structural Engineering Sectional Committee had been approved by the CivilEngineering Division Council.This standard has been prepared with a view to establish uniform practices for design, fabrication,testing and inspection of overhead transmission line towers. Part 1 of the standard coversrequirements in regard to material, types of towers, loading and permissible stresses apart fromother relevant design provisions. Provisions for fabrication, galvanizing, inspection and packinghave been covered in Part 2 whereas provisions for testing of these towers have been covered inPart 3 of the standard.This standard (Part 1) was first published in 1967 and subsequently revised in 1973 and 1977. Inthis revision, the code has been split in two sections namely Section 1 Materials and loads, andSection 2 Permissible stresses. Other major modifications effected in this revision (Section 2) areas under:

a) Permissible stresses in structural members have been given in terms of the yield strength ofthe material. With the inclusion of bolts of property class 5.6 of IS 12427 : 1988, permissiblestresses for these bolts have also been included.

b) Critical stress in compression Fcr has been modified for width/thickness ratio of the anglesexceeding the limiting value for calculating the allowable unit compressive stresses.

c) Effective slenderness ratios ( KL/r ) for redundant members have been included andprovisions further elaborated.

d) Examples for the determination of slenderness ratios have been extended to include ‘K’ and‘X’ bracings with and without secondary members.

Designs provisions or other items not covered in this standard shall generally be in accordancewith IS 800 : 1984 ‘Code of practice for general construction in steel ( second revision )’.While preparing this standard, practices prevailing in the country in this field have been kept inview. Assistance has also been derived from the ‘Guide for design of steel transmission line towers’(second edition) — ASCE Manual No. 52, issued by American Society of Civil Engineers (ASCE)New York, 1988.This edition 4.1 incorporates Amendment No. 1 (January 1998). Side bar indicates modification ofthe text as the result of incorporation of the amendments.For the purpose of deciding whether a particular requirement of this Code is complied with, thefinal value, observed or calculated, expressing the result of a test, shall be rounded off inaccordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( revised )’. The number ofsignificant places retained in the rounded off value should be the same as that of the specifiedvalue in this standard.

Page 25: IS 802 P 1 to 3

IS 802 (Part 1/Sec 2) : 1992

1

Indian Standard

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS — CODE

OF PRACTICEPART 1 MATERIAL, LOADS AND PERMISSIBLE STRESSES

Section 2 Permissible Stresses

( Third Revision )1 SCOPE

1.1 This standard (Part 1/Sec 2) stipulates thepermissible stresses and other designparameters to be adopted in the design ofself-supporting steel lattice towers for overheadtransmission lines.

1.1.1 Materials, type of towers, loading andbroken wire conditions are covered in Section 1of this standard.

1.1.2 Provisions on fabrication and testing oftransmission line towers have been covered inPart 2 and Part 3 respectively of the standard.

NOTE — While formulating the provisions of thisstandard it has been assumed that the structuralconnections are through bolts.

1.2 This standard does not cover guyed towers.These will be covered in a separate standard.

2 REFERENCES

The Indian Standards listed in Annex A arenecessary adjuncts to this standard.

3 STATUTORY REQUIREMENTS

3.1 Statutory requirement as laid down in the‘Indian Electricity Rules, 1956’ or by any otherstatutory body applicable to such structures ascovered in this standard shall be satisfied.

3.2 Compliance with this code does not relieveany one from the responsibility of observinglocal and state byelaws, fire and safety lawsand other civil aviation requirementsapplicable to such structures.

4 CONDUCTOR TENSION

4.1 The conductor tension at everydaytemperature and without external load should not

exceed the following percentage of the ultimatestrength of the conductor:

provided that the ultimate tension undereveryday temperature and full wind orminimum temperature and two-thirds windpressure does not exceed 70 percent of theultimate tensile strength of the cable.

5 PERMISSIBLE STRESSES

5.1 Axial Stresses in Tension

The estimated tensile stresses on the neteffective sectional areas ( see 9 ) in variousmembers, shall not exceed minimumguaranteed yield stress of the material.However in case the angle section is connectedby one leg only, the estimated tensile stress onthe net effective sectional area shall not exceedFy, where Fy, is the minimum guaranteed yieldstress of the material.

5.2 Axial Stresses in Compression

5.2.1 The estimated compressive stresses invarious members shall not exceed the valuesgiven by the formulae in 5.2.2.

5.2.2 The allowable unit stress Fa, in MPa onthe gross cross sectional area of the axiallyloaded compression members shall be:

Initial unloaded tension 35 percentFinal unloaded tension 25 percent

a)

and,

b)

Page 26: IS 802 P 1 to 3

IS 802 (Part 1/Sec 2) : 1992

2

where

5.2.2.1 The formulae given in 5.2.2 areapplicable provided the largest width thicknessratio b/t is not more than the limiting valuegiven by:

( b/t )lim = 210/where

5.2.2.2 Where the width thickness ratio exceedsthe limits given in 5.2.2.1, the formulae givenin 5.2.2 shall be used substituting for Fy thevalue Fcr given by:

a)

and

b)

NOTE — The maximum permissible value of b/t for anytype of steel shall not exceed 25.

5.3 The redundant members shall be checkedindividually for 2.5 percent of axial load carriedby the member to which it supports.

5.4 Stresses in Bolts

Ultimate stresses in bolts conforming toproperty class 4.6 of IS 6639 : 1972 and toproperty class 5.6 of IS 12427 : 1988 shall notexceed the value given in Table 1. For boltsconforming to IS 3757 : 1985, permissiblestresses and other provisions governing the useof high strength bolts reference shall be madeto IS 4000 : 1992.

5.4.1 Where the material of bolt and thestructural member are of different grades, thebearing strength of the joint shall be governedby the lower of the two.

6 SLENDERNESS RATIOS

6.1 The slenderness ratios of compression andredundant members shall be determined asfollows:

Ce =

Fy = minimum guaranteed yield stress ofthe material, MPa

E = modulus, of elasticity of steel that is2 × 105 MPa,

KL/r = largest effective slenderness ratio ofany unbraced segment of themember,

L = unbraced length of the compressionmember ( see 6.1.1 ) in cm, and

r = appropriate radius of gyration incm.

b = distance from edge of fillet to theextreme fibre in mm, and

t = thickness of flange in mm.

π 2 E/Fy

Fy

Table 1 Ultimate Stresses in Bolts, MPa( Clause 5.4 )

Nature of Stress Permissible Stress for Bolts

of Property Class

Remarks

4.6 5.6(1) (2) (3) (4)

Shear

Shear stress on gross area of bolts

218 310 For gross area ofbolts ( see 10.4 ).For bolts in doubleshear the area tobe assumed shallbe twice the areadefined

Bearing

Bearing stress on gross diameter of bolts

436 620 For the bolt area inbearing ( see 10.5 )

Tension

Axial tensile stress 194 250 —

Type of Members Value of KL/r

a) Compression Members

i) Leg sections or jointmembers bolted in bothfaces at connections for0 < L/r < 120

L/r

ii) Members withconcentric loading atboth ends of theunsupported panel for0 < L/r < 120

L/r

iii) Member withconcentric loading atone end and normalframing eccentricity atthe other end of theunsupported panel for0 < L/r < 120

30 + 0.75 L/r

iv) Member with normalframing eccentricitiesat both ends of theunsupported panel for0 < L/r < 120

60 + 0.50 L/r

v) Member unrestrainedagainst rotation at bothends of the unsupportedpanel for 120 < L/r <200

L/r

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IS 802 (Part 1/Sec 2) : 1992

3

NOTE — The values of KL/r corresponding to (a) (vi)and (a) (vii), the following evaluation is suggested:

1 The restrained member must be connected to therestraining member with at least two bolts.

2 The restraining member must have a stiffness factorI/L in the stress plane ( I = Moment of inertia and L =Length ) that equals or exceeds the sum of thestiffness factors in the stress plane of the restrainedmembers that are connected to it.

3 Angle members connected by one leg should have theholes located as close to the outstanding leg asfeasible. Normal framing eccentricities at loadtransfer connection imply that connection holes arelocated between the heel of the angle end thecentreline of the framing leg.

6.1.1 In calculating the slenderness ratio of themembers, the length L should be the distancebetween the intersections of the centre ofgravity lines at each end of the member.

6.2 Examples showing the application of theprocedure given in 6.1 and 6.1.1 and method ofdetermining the slenderness ratio of legs andbracings with or without secondary membersare given in Annex B.

NOTE — Where test and/or analysis demonstrate thatany other type of bracing pattern if found technicallysuitable, the same can be adopted.

6.3 The limiting values KL/r shall be as follows:

6.4 Slenderness ratio L/r of a member carryingaxial tension only, shall not exceed 400.

7 MINIMUM THICKNESS

7.1 Minimum thickness of galvanized andpainted tower members shall be as follows:

7.2 Gusset plates shall be designed to resist theshear, direct and flexural stresses acting on theweakest or critical section. Re-entrant cutsshall be avoided as far as practical. Minimumthickness of gusset shall be 2 mm more thanlattice it connects only in case when the latticeis directly connected on the gusset outside theleg member. In no case the gusset shall be lessthan 5 mm in thickness.

8 NET SECTIONAL AREA FOR TENSION MEMBER

8.1 The net sectional area shall be the leastarea which is to be obtained by deducting fromthe gross sectional area, the area of all holescut by any straight, diagonal or zigzag lineacross the member. In determining the totalarea of the holes to be deducted from grosssectional area, the full area of the first holeshall be counted, plus a fraction part X, of eachsucceeding hole cut by the line of holes underconsideration. The value of X shall bedetermined from the formula:

X. = 1 –

where

For holes in opposite legs of angles, the value ofg should be the sum of the gauges from theback of the angle less the thickness of theangle.

vi) Member partiallyrestrained againstrotation at one end ofthe unsupported panelfor 120 < L/r < 225

28.6 + 0.762 L/r

vii) Member partiallyrestrained againstrotation at both ends ofthe unsupported panelfor 120 < L/r < 250

46.2 + 0.615 L/r

b) Redundant Members

i) For 0 < L/r < 250 L/r

Leg members, ground wire peakmember and lower members of thecross arms in compression

120

Other members carrying computedstresses

200

Redundant members and thosecarrying nominal stresses

250

Minimum Thickness, mm

Galvanized Painted

Leg members, groundwire peak member andlower members of crossarms in compression

5 6

Other members 4 5

P = longitudinal spacing (stagger), that isthe distance between two successiveholes in the line of holes underconsideration;

g = transverse spacing (gauge), that is thedistance between the same twoconsecutive holes as for P; and

d = diameter of holes.

P2

4gd----------

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IS 802 (Part 1/Sec 2) : 1992

4

9 NET EFFECTIVE AREA FOR ANGLE SECTION IN TENSION

9.1 In the case of single angle connectedthrough one leg, the net effective section of theangle shall be taken as:

A1 + A2k

where

where lug angles are used, the effectivesectional area of the whole of the angle membershall be considered.9.2 In the case of pair of angles back to back intension connected by one leg of each angle tothe same side of gusset, the net effective areashall be taken as:

A1 + A2k

whereA1 and A2 are as defined in 9.1, and

k =

9.3 The angles connected together back-to-back(in contact) or separated back-to-back by adistance not exceeding the aggregate thicknessof the connected parts shall be provided withstich bolt at a a pitch not exceeding 1 000 mm.The slenderness ratio of individual componentbetween adjacent stich bolts shall not be morethan that of the two members together.9.4 Where the angles are back to back but notconnected as per 9.3, each angle shall bedesigned as a single angle connected throughone leg only in accordance with 9.1.9.5 When two tees are placed back to back butare not connected as per 9.3, each tee shall be

designed as a single tee connected to one side ofa gusset only in accordance with 9.2.

NOTE — The area of the leg of an angle shall be takenas the product of the thickness and the length from theouter corner minus half the thickness, and the area ofthe leg of a tee as the product of the thickness and thedepth minus the thickness of the table.

10 BOLTING

10.1 Minimum Diameter of Bolts

The diameter of bolts shall not be less than12 mm10.2 Preferred Sizes of Bolts

Bolts used for erection of transmission linetowers shall be of diameter 12, 16 and 20 mm.10.3 The length of bolts shall be such that thethreaded portion does not lie in the plane ofcontact of members. The projected portion ofthe bolt beyond the nut shall be between 3 to8 mm.10.4 Gross Area of Bolt

For the purpose of calculating the shear stress,the gross area of bolts shall be taken as thenominal area of the bolt.10.5 The bolt area for bearing shall be taken asd × t where d is the nominal diameter of thebolt, and t the thickness of the thinner of theparts jointed.

10.6 The net area of a bolt in tension shall betaken as the area at the root of the thread.10.7 Holes for Bolting

The diameter of the hole drilled/punched shallnot be more than the nominal diameter of thebolt plus 1.5 mm.

11 FRAMING

11.1 The angle between any two memberscommon to a joint of a trussed frame shallpreferably be greater than 20° and never lessthan 15° due to uncertainty of stressdistribution between two closely spacedmembers.

ANNEX A( Clause 2 )

LIST OF REFERRED INDIAN STANDARDS

A1 = effective sectional area of theconnected leg.

A2 = the gross cross-sectional area of theunconnected leg, and

k =3A1

3A1 A2+( )-----------------------------

5A15A1 A2+------------------------

IS No. Title

800 : 1984 Code of practice for use ofstructural steel in generalbuilding construction ( revised )

3757 : 1985 High strength structural bolts( second revision )

IS No. Title

4000 : 1992 Code of practice for highstrength bolts in steelstructures

6639 : 1972 Hexagonal bolt for steelstructures

12427 : 1988 Transmission tower bolts

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5

ANNEX B( Clause 6.2 )

EXAMPLES OF DETERMINATION OF SLENDERNESS RATIOS

B-0 Example of determining the effective length of compression members of towers based on theprovision given in 6.1 are given below.

B-1 LEG MEMBER USING SYMMETRICAL BRACING

B-2 LEG MEMBER USING STAGGERED BRACING

Method of Loading/Rigidity of Joints

Slenderness Ratio

Concentric loading from 0 to 120

No restraint at ends from 120 to 200

Method of Loading/Rigidity of Joints

Slenderness Ratio

Concentric loading or 0.67 from 0

to 120

No restraint at ends or 0.67 from 120

to 200

Lrvv-------- KL

r-------- L

rvv--------=

Lrvv-------- KL

r-------- L

rvv--------=

Lrxx-------- or L

ryy-------- L

rvv--------

KLr

-------- Lr----=

Lrxx-------- or L

ryy-------- L

rvv--------

KLr

-------- Lr----=

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6

B-3 EFFECT OF END CONNECTIONS ON MEMBER CAPACITY

Method of Loading/Rigidity of Joints

Slenderness Ratio

Tension system with compressionstrut (eccentricity in criticalaxis)

from 0 to 120

Bracing Requirements ( SingleAngle Members ):

Single bolt connection, norestraint at ends

from 120 to 200

Multiple bolt connection partialrestraint at both ends from 120 to 250

B-4 CONCENTRIC LOADING TWO ANGLE MEMBER

Method of Loading/Rigidity of Joints

Slenderness Ratio

Tension system strut compressionconcentric loading or from 0 to 120

Bracing Requirements ( Two AngleMember ):

Single bolt connection, norestraint at ends

or from 120 to 200

Multiple bolt connection, partialrestraint at ends or from 120 to 250

Lrvv--------

KLr

-------- 60 0.5 Lr----+=

Lrvv--------

KLr

-------- Lr----=

Lrvv--------

KLr

-------- 46.2 0.615 Lr----+=

Lrxx-------- L

ryy--------

KLr

-------- Lr----=

Lrxx-------- L

ryy--------

KLr

-------- Lr----=

Lrxx-------- L

ryy--------

KLr

-------- 46.2 0.615 Lr----+=

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7

B-5 HORIZONTAL MEMBER OF K-BRACING-TWO ANGLE MEMBER

Method of Loading/Rigidity of Joints

Slenderness Ratio

Tension-compression systemwith compression strut:

Multiple bolts connectionpartial restraint at endsand intermediate

0.5 from 120 to 250

Bracing Requirements ( TwoAngle Member ):

Concentric load at ends,eccentric loading atintermediate in bothdirections

0.5 from 0 to 120

Concentric loading at endsand intermediate 0.5 from 0 to 120

Lryy-------- or L

rxx--------

KLr

-------- 46.2 0.615 Lr----+=

Lryy-------- or L

rxx--------

KLr

-------- 30 0.75 Lr----+=

Lryy-------- or L

rxx--------

KLr

-------- Lr----=

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8

B-6 EFFECT OF SUBDIVIDED PANELS FOR THE HORIZONTAL MEMBER AND ENDCONNECTIONS ON MEMBER CAPACITY

Method of Loading/Rigidityof Joints

Slenderness Ratio

Tension system withcompression strut:

Eccentricity in critical axis 0.5 from 0 to 120

Bracing Requirements:

Single bolt connection, norestraint at ends forintermediate

0.5 from 120 to 200

Multiple bolt connection atends. Single bolt connectionat intermediate point:

Partial restraint at one end,on restraint at intermediate

0.5 from 120 to 225

Partial restraint at both ends from 120 to 250

Multiple bolt connection

Partial restraint at ends andintermediate

0.5 from 120 to 250

Lrvv-------- or L

rxx--------

KLr

-------- 60 0.50 Lr----+=

Lrvv-------- or L

rxx--------

KLr

-------- Lr----=

Lrvv--------

KLr

-------- 28.6 0.762 Lr----+=

Lrxx--------

KLr

-------- 46.2 0.615 Lr----+=

Lrvv-------- or L

rxx--------

KLr

-------- 46.2 0.615 Lr----+=

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9

B-7 CONCENTRIC LOADING TWO ANGLE MEMBER, SUBDIVIDED PANELS OF AHORIZONTAL MEMBER

Method of Loading/Rigidity of Panel

Slenderness Ratio

Tension system withcompression strut:

0.5 from 0 to 120 Concentric loading

Bracing Requirements:

Single bolt connection, norestraint at ends andintermediate

0.5 from 120 to 200

Multiple bolt connection atends. Single bolt connectionat intermediate joint

Partial restraint at one end,no restraint at intermediate 0.5 from 120 to 200

Partial restraint at both ends from 120 to 250

Multiple bolt connectionPartial restraint at endsand intermediate

0.5 from 120 to 250

Lryy-------- or L

rxx--------

KLr

-------- Lr----=

Lryy-------- or L

rxx--------

KLr

-------- Lr----=

Lryy--------

KLr

-------- 28.6 0.762 Lr----+=

Lrxx--------

KLr

-------- 46.2 0.615 Lr----+=

Lryy-------- or L

rxx--------

KLr

-------- 46.2 0.615 Lr----+=

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IS 802 (Part 1/Sec 2) : 1992

10

B-8 X-BRACINGS WITH AND WITHOUT SECONDARY MEMBERS

Slenderness Ratio Critical of:

B-8.1 AB/rvv

B-8.2

a) AC/rvv or CB/rvv or*AB/rxx or *AB/ryy or*AD/rvv

b) AC/rvv or CB/rvv or*AD/rvv

B-8.3a)

AD/rvv or *AF/rxx orDC/rvv or *AE/rvv orCB/rvv or

*AB/rxx or *AB/ryy orEF/rvv

b)

AD/rvv or *AF/rxx orDC/rvv or *AE/rvv orCB/rvv orAC/rxx or *AC/rvy orEF/rvv

c)

AD/rvv or *AF/rxx orDC/rvv orCB/rvv or *AE/rvv orEF/rvv

B-8.4 AE/rvv or *AF/rxx orED/rvv or *AE/rvv orDC/rvv or CB/rvv

*Application for tension compression system only i.e. tensile stresses in one bracing must be at least equal to 75 percent of the compressive stress in the other bracing.

#The corner stay should be designed to provide lateral support adequately.

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11

B-9 K-BRACINGS WITH AND WITHOUT SECONDARY MEMBERS

Slenderness Ratio Critical of:

B-9.1 AB/rvv

B-9.2a)

AC/rvv orCB/rvv orAB/rxx or AB/ryy

b) AC/rvv orCB/rvv

B-9.3a)

AD/rvv orDC/rvv orCB/rvv orAB/rxx or AB/ryy

b)

AD/rvv orDC/rvv orCB/rvv orAC/rxx or AC/ryy

c)AD/rvv orDC/rvv orCB/rvv

B-9.4 AE/rvv orED/rvv orDC/rvv orCB/rvv

#The corner stay should be designed to provide lateral support adequately.

Page 36: IS 802 P 1 to 3

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goods andattending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are alsoreviewed periodically; a standard along with amendments is reaffirmed when such review indicates that nochanges are needed; if the review indicates that changes are needed, it is taken up for revision. Users ofIndian Standards should ascertain that they are in possession of the latest amendments or edition byreferring to the latest issue of ‘BIS Catalogue’ and ‘Standards : Monthly Additions’.

This Indian Standard has been developed from Doc : No. CED 7 (4725)

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

Amd. No. 1 January 1998

BUREAU OF INDIAN STANDARDS

Headquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002.Telephones: 323 01 31, 323 33 75, 323 94 02

Telegrams: Manaksanstha(Common to all offices)

Regional Offices: Telephone

Central : Manak Bhavan, 9 Bahadur Shah Zafar MargNEW DELHI 110002

323 76 17323 38 41

Eastern : 1/14 C. I. T. Scheme VII M, V. I. P. Road, KankurgachiKOLKATA 700054

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Page 37: IS 802 P 1 to 3

© BIS 2003

B U R E A U O F I N D I A N S T A N D A R D SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

IS : 802 (Part II) - 1978(Reaffirmed 2001)

Edition 1.1(1992-08)

Price Group 3

Indian StandardCODE OF PRACTICE FOR

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS

PART II FABRICATION, GALVANIZING, INSPECTION AND PACKING

(Incorporating Amendment No. 1)

UDC 621.315.668.2:006.76

Page 38: IS 802 P 1 to 3

IS : 802 (Part II) - 1978

© BIS 2003

BUREAU OF INDIAN STANDARDS

This publication is protected under the Indian Copyright Act (XIV of 1957) andreproduction in whole or in part by any means except with written permission of thepublisher shall be deemed to be an infringement of copyright under the said Act.

Indian StandardCODE OF PRACTICE FOR

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS

PART II FABRICATION, GALVANIZING, INSPECTION AND PACKING

Structural Engineering Sectional Committee, SMBDC 7

Chairman Representing

DIRECTOR STANDARDS (CIVIL) Ministry of Railways

Members

SHRI R. M. AGARWALDR SHAMSHER PRAKASH ( Alternate )

Institution of Engineers (India), Calcutta

SHRI A. K. BANERJEESHRI S. SANKARAN ( Alternate )

Metallurgical and Engineering Consultants(India) Ltd, Ranchi

SHRI S. N. BASUSHRI D. B. JAIN ( Alternate )

Inspection Wing, Directorate General ofSupplies and Disposals, New Delhi

SHRI P. C. BHASIN Ministry of Shipping and Transport(Department of Transport) (Roads Wing)

SHRI V. S. BHIDEDEPUTY DIRECTOR (GATES AND

DESIGNS) ( Alternate )

Central Water Commission, New Delhi

DR P. N. CHATTERJEE Government of West BengalDR P. DAYARATNAM Indian Institute of Technology, KanpurSHRI D. S. DESAI

SHRI S. R. KULKARNI ( Alternate )M. N. Dastur & Co Pvt Ltd, Calcutta

DIRECTOR (TRANSMISSION)DEPUTY DIRECTOR (TRANSMISSION)

( Alternate )

Central Electricity Authority, New Delhi

JOINT DIRECTOR STANDARDS (B & S)ASSISTANT DIRECTOR (B & S)-SB

( Alternate )

Ministry of Railways

SHRI K. K. KHANNASHRI K. S. SRINIVASAN ( Alternate )

National Buildings Organization, New Delhi

( Continued on page 2 )

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IS : 802 (Part II) - 1978

2

( Continued from page 1 )

Members Representing

SHRI P. K. MALLICK Jessop & Co Ltd, CalcuttaSHRI P. K. MUKHERJEE

SHRI P. T. PATEL ( Alternate )Braithwaite & Co (India) Ltd, Calcutta

SHRI. S. MUKHERJEE Hindustan Steel Ltd, DurgapurSHRI S. K. MUKHERJEE

SHRI B. K. CHATTERJEE ( Alternate )Bridge & Roof Co (India) Ltd, Howrah

SHRI P. N. BHASKARAN NAIRSHRI A. B. RIBEIRO ( Alternate )

Rail India Technical and Economics Services,New Delhi

SHRI R. NARAYANAN Structural Engineering Research Centre(CSIR), Roorkee

PROF H. C. PARMESHWARAMSHRI C. S. S. RAO ( Alternate )

Engineer-in-Chief’s Branch, Ministry of Defence

SHRI DILIP PAUL Industrial Fasteners Association of India,Calcutta

REPRESENTATIVESHRI A. P. KAYAL ( Alternate )

Burn Standard Co Ltd, Howrah

REPRESENTATIVE Hindustan Steel Works Construction Ltd,Calcutta

REPRESENTATIVESHRI P. V. NAIK ( Alternate )

Richardson & Cruddas Ltd, Bombay

SHRI P. SENGUPTASHRI M. M. GHOSH ( Alternate )

Stewarts & Lloyds of India Ltd, Calcutta

SHRI G. SRINIVASANSHRI G. L. NARASAIAH ( Alternate )

Bharat Heavy Electricals Ltd, Tiruchirapalli

SHRI D. SRINIVASANSHRI B. P. GHOSH ( Alternate )

Joint Plant Committee, Calcutta

SHRI M. D. THAMBEKAR Bombay Port Trust, BombaySHRI L. D. WADHWA

SHRI B. B. NAG ( Alternate )Engineers India Ltd, New Delhi

SHRI C. R. RAMA RAO,Director (Struc & Met)

Director General, BIS ( Ex-officio Member )

SecretarySHRI S. S. SETHI

Assistant Director (Struc & Met), BIS

Subcommittee for Code of Practice for Use of Steel in Overhead Transmission Line Towers, SMBDC 7 : 1

Convener

SHRI V. D. ANAND Central Electricity Authority, New Delhi

Members

SHRI H. S. SEHRA ( Alternate to Shri V. D. Anand)

SHRI M. ARUMUGAM Tamil Nadu Electricity Board, MadrasASSISTANT DIRECTOR STANDARDS

(B & S)-IDEPUTY DIRECTOR STANDARDS

(C-OHE) ( Alternate )

Ministry of Railways

( Continued on page 10 )

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IS : 802 (Part II) - 1978

3

Indian StandardCODE OF PRACTICE FOR

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS

PART II FABRICATION, GALVANIZING, INSPECTION AND PACKING

0. F O R E W O R D0.1 This Indian Standard (Part II) was adopted by the IndianStandards Institution on 25 October 1978, after the draft finalized bythe Structural Engineering Sectional Committee had been approvedby the Structural and Metals Division Council and the CivilEngineering Division Council.0.2 With the publication of IS : 802 (Part I)-1977* provisions-regarding loads, material, permissible stresses and design aspect havebeen covered. In this part requirements regarding fabrication,galvanizing, inspection and packing of overhead transmission linetowers have been covered.0.3 This standard keeps in view the practices being followed in thecountry in this field. Assistance has been derived from the ‘Guide fordesign of steel transmission line towers’ issued by the AmericanSociety of Civil Engineers.0.4 This edition 1.1 incorporates Amendment No. 1 (August 1992).Side bar indicates modification of the text as the result ofincorporation of the amendment.0.5 For the purpose of deciding whether a particular requirement ofthis standard is complied with, the final value, observed or calculated,expressing the result of a test, shall be rounded off in accordance withIS : 2-1960†. The number of significant places retained in the roundedoff value should be the same as that of the specified value in thisstandard.

1. SCOPE1.1 This standard (Part II) covers the provisions relating to thefabrication, galvanizing, inspection and packing requirements ofself-supporting steel lattice towers for overhead transmission lines.1.1.1 Provisions regarding loads, permissible stresses and designconsiderations have been covered in Part I of this standard.

*Code of practice for use of structural steel in overhead transmission line towers:Part I Loads and permissible stresses ( second revision ).

†Rules for rounding off numerical values ( revised ).

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4

1.1.2 Provisions regarding testing of towers have been covered in PartIII of this standard.1.1.3 For provisions regarding erection of towers, reference shall bemade to IS : 5613 (Part II/Sec 2)-1976*.1.2 This code does not cover guyed towers and special towers for rivercrossing or other long spans. These will be covered by separate codes.

2. PLAN AND DRAWING

2.1 Plans and drawings shall be prepared according to IS : 696-1972†and IS : 962-1967‡.2.2 Structural Assembly Drawings2.2.1 The drawings shall show the complete design dimensions,member length, slope factors or triangles, section sizes, bend lines,gauge lines, diameter, length and number of bolts, spacers, washers,sizes of gusset plates, position of holes, etc, and relative location ofvarious members.2.2.1.1 Sufficient number of elevation, cross section and plan viewsshall be presented to clearly indicate the details of joints andarrangement of members.2.2.2 All members shall be clearly shown and the respectiveidentification mark allotted to each member.2.2.3 The drawings shall be drawn to a scale large enough to conveythe information adequately.2.2.4 All connections shall be detailed to minimize eccentricity of theconnection.

NOTE — Due consideration shall be given to the additional stresses introduced in themembers on account of eccentricity of the connection.

2.3 Shop Drawing — Shop drawings, containing completeinformation necessary for fabrication of the component parts of thestructures shall be prepared. These drawings shall clearly show themember sizes, length and marks, hole positions, gauge lines, bendlines, edge distances, amount of clipping, notching, etc.2.3.1 In the case of members to be bent, the shop drawings shallindicate provision for the variation in length to be made.2.4 Bill of Material — Bill of material for each type of tower shall beprepared separately. This shall indicate grade of steel, mark numbers,

*Code of practice for design, installation and maintenance of overhead power lines:Part II Lines above 11 kV up to and including 220 kV, Section 2 Installation andmaintenance.

†Code of practice for general engineering drawings ( second revision ).‡Code of practice for architectural and building drawing ( first revision ).

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5

section sizes, member lengths, their calculated weights, number ofbolts, nuts and washers and their sizes, total quantities required andstructural drawing numbers.2.4.1 No reduction in weight due to drilling, punching of bolt holes,screw cuts, clipping, notching, chamfering, etc, shall be made whilecomputing the calculated weight of the members.

3. FABRICATION

3.1 General — The fabrication of transmission line towers shall bedone in accordance with this code. A reference may, however, be madeto IS : 800-1962* in case of non-stipulation of some particular provisionin this standard.3.2 Material Quality Control — In cases where more than one gradeof steel is used in the structural members, proper identification marksof the various grades of steel being used shall be made on the materialto ensure their ultimate use in the proper location in the towers beforetaking up the fabrication.

4. OPERATIONS IN FABRICATION

4.1 Straightening — All material shall be reasonably straight and, ifnecessary, before being worked shall be straightened and/or flattenedby pressure, unless required to be of curvilinear form and shall be freefrom twists. Straightening shall not damage the material. Theadjacent surfaces of the parts when assembled, shall be in closecontact throughout keeping in view the tolerances specified.Hammering shall not be permitted for straightening and/or flatteningof members. Sharp bends shall be cause for rejection.4.2 Cutting — Cutting may be effected by shearing, cropping, flamecutting or sawing. The surfaces so cut shall be clean, smooth,reasonably square and free from any distortion.4.3 Bending4.3.1 Mild steel angle sections up to 75 × 75 mm (up to 6 mm thick)shall be bent cold up to and including bend angle of 10°; angles above75 × 75 mm (thickness up to 6 mm) and up to and including 100 × 100mm (thickness up to 8 mm) may also be bent cold up to the bend angleof 5°. All other angle sections and bend angles not covered above shallbe bent hot.4.3.2 All plates up to 12 mm thickness shall be bent cold up to amaximum bend angle of 15°. Greater bends and other thicknessesshall be bent hot.4.3.3 Bends on all high tensile steel sections shall be done hot.

*Code of practice for use of structural steel in general building construction ( revised ).

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6

4.3.4 All hot bent material shall be air cooled.

4.3.5 The bends shall be of even profile and free from any surfacedamages.

4.4 Holing

4.4.1 Holes in the members shall either be drilled or punched to jig andshall not be formed by flame cutting process. All burrs left by punchingor drilling shall be completely removed.

4.4.2 Punching may be adopted for sections up to 12 mm thick. Forthicker sections, drilling shall be done.

4.4.3 The holes near the bend line of a bent member, on both sides ofbend line, shall be punched/drilled after bending and relative positionof these holes shall be maintained with the use of proper template/jigsand fixtures.

5. FASTENERS AND JOINTS

5.1 General — It shall be ensured that the fasteners provide positiveattachment at all times and under the conditions when the towerstructures are subjected to vibratory loads.

5.2 Bolts — Bolts used for erection of transmission line tower shallpreferably be of 12, 16 and 20 mm diameter and in no case boltdiameter shall be less than 12 mm.

5.2.1 Only one diameter of bolts shall preferably be used in one towertype.

5.2.2 The length of the bolt shall be such that the threaded portiondoes not lie in the plane of contact of members.

5.2.3 It shall also be ensured that the threaded portion of the boltprotrudes not less than 3 mm and not more than 8 mm over the nutafter it is fully tightened.

5.3 Holes for Bolting — Holes shall be cylindrical. Oval or lobedforms of holes shall not be permitted. The diameter of the hole shall beequal to the diameter of the bolt plus 1.5 mm.

5.3.1 Holes shall be perpendicular to the plates or angles.

5.3.2 The accuracy of the location of holes shall be such that for anygroup of members when assembled the holes shall admit the bolt atright angle to the plane of connection.

5.4 Spacing of Bolts and Edge Distance — The minimum spacingof bolts and edge distance shall be as given in Table 1.

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7

5.5 In dimensioning gauge lines, allowance shall be made for the milltolerance in width of flange in accordance with IS : 1852-1973* so as toensure minimum edge distance specified in 5.4.

5.6 Locking Devices — Spring washers of positive lock type of thefollowing thicknesses shall be provided for insertion under all nuts.

5.7 To obviate bending stress in bolts or to reduce the same to aminimum, no bolt shall connect aggregate thickness of more thanthree times the bolt diameter and also the number of memberscarrying stress to be connected by a single bolt shall not generallyexceed three (excluding gussets and packing).

5.8 The gap between the ends of two connected members in a butt jointshall not be more than 6 mm and less than 4 mm.

5.9 Bolt Gauge Distances in Flanges of Angles — The bolt gaugedistances in flanges of angle sections shall generally be in accordancewith Table XXXI of SP : 6(Part 1)-1964†.

TABLE 1 SPACING OF BOLTS AND EDGE DISTANCE( Clause 5.4 )

BOLTDIAMETER

HOLEDIAMETER

BOLT SPACING, Min

EDGE DISTANCE, Min

Hole Centreto Rolled orSawn Edge

Hole Centreto Sheared or

Flame CutEdge

(1) (2) (3) (4) (5)

mm mm mm mm mm

121620

13.517.521.5

324048

162025

202328

*Specification for rolling and cutting tolerance for hot rolled steel products ( secondrevision ).

Bolt Diamm

Thickness of Spring Washermm

121620

2.53.54.0

†ISI Handbook for structural engineers — Structural steel sections ( revised ).

Page 45: IS 802 P 1 to 3

IS : 802 (Part II) - 1978

8

6. TOLERANCES6.1 Fabrication tolerances shall conform to those specified in 6.2 to 6.5.Tolerances not specified in this code shall in general conform toIS : 7215-1974*.6.2 The maximum allowable difference in diameter of the holes on thetwo sides of plate or angle shall be 0.8 mm, that is, the allowable taperin a punched hole shall not exceed 0.8 mm on diameter.6.3 Tolerance cumulative and between consecutive holes shall bewithin ± 2 mm and ± 1 mm respectively.6.4 Tolerance on the overall length of a member shall be within± 2 mm.6.5 Tolerance on gauge distance shall be within ± 1 mm.7. MARKING7.1 The identification mark allotted to each member shall be distinctlystamped before galvanizing with marking dies of 16 mm size.8. SHOP ERECTION8.1 The steel work shall be temporarily shop erected complete inhorizontal or vertical position (one tower of each type including everycombination of leg extensions) so that accuracy of the members may bechecked before commencing mass fabrication.9. PAINTING AND GALVANIZING9.1 Painting — Preparation of surface for painting (pretreatment)and application of primer and finishing coats shall be done inaccordance with the relevant clauses of IS : 1477 (Part I)-1971† andIS : 1477 (Part II)-1971‡ respectively.9.1.1 The pretreatment to the members and application of primer coatshall be done immediately after fabrication. Another primer coatfollowed by two coats of finishing paint shall be given at site after thefabricated steel work is erected. In case the primer coat is scrapedduring transportation, the member surface shall be cleaned beforeapplying the primer coat in the field.9.2 Galvanizing — Bolts and other fasteners shall be galvanized inaccordance with IS : 5358-1969§ galvanizing of members of the towershall conform to IS : 4759-1968| | and spring washers shall begalvanized in accordance with IS : 1573-1970¶.

*Tolerances for fabrication of steel structures.†Code of practice for painting of ferrous metals in buildings: Part I Pretreatment

( first revision ).‡Code of practice for painting of ferrous metals in buildings: Part II Painting ( first

revision ).§Specification for hot-dip galvanized coatings on fasteners. ||Specification for hot-dip zinc coating on structural steel and other allied products.¶Specification for electroplated coatings for zinc on iron and steel.

Page 46: IS 802 P 1 to 3

IS : 802 (Part II) - 1978

9

10. INSPECTION

10.1 The inspector shall have free access at all reasonable times tothose parts of the manufacturer’s works which are concerned with thefabrication of the steel work and shall be afforded all reasonablefacilities for satisfying himself that the fabrication is being done inaccordance with the provisions of this standard.

10.2 Unless specified otherwise, inspection, shall be made at the placeof manufacture prior to despatch and shall be conducted so as not tointerfere unnecessarily with the operation of the work.

10.3 The manufacturer shall guarantee compliance with theprovisions of this standard, if required to do so by the purchaser.

10.4 Should any member of the structure be found not to comply withany of the provisions of this standard, it shall be liable to rejection. Nomember once rejected shall be resubmitted for inspection, except incases where the purchaser or his authorized representative considersthe defect as rectifiable.

10.5 Defects which may appear during fabrication shall be made goodwith the consent of and according to the procedure laid down by theinspector.

10.6 All gauges and templates necessary to satisfy the inspector shallbe supplied by the manufacturer.

10.7 The correct grade and quality of steel shall be used by themanufacturer. To ascertain the quality of steel used, the inspector athis discretion may get the material tested at a suitable or approvedlaboratory.

11. PACKING

11.1 Angle sections shall be wire bundled or despatched loose as maybe mutually agreed upon.

11.2 Cleat angles, gusset plates, brackets, fillet plate, hanger andsimilar loose pieces shall be nested and bolted together in multiples orsecurely wired together through holes.

11.3 Bolts, nuts, washers. and other attachments shall be packed indouble gunny bags accurately tagged in accordance with the contents.

11.4 The packings shall avoid losses/damages during transit. Eachbundle or package shall be appropriately marked.

Page 47: IS 802 P 1 to 3

IS : 802 (Part II) - 1978

10

( Continued from page 2 )

Members Representing

SHRI S. K. BHATTACHARJEESHRI V. NARAYANAN ( Alternate )

SAE (India) Ltd, Calcutta

CHIEF ENGINEERSUPERINTENDING ENGINEER ( Alternate )

Andhra Pradesh Electricity Board,Hyderabad

SHRI K. R. DEBSHRI SWARAJ GUPTA ( Alternate )

Damodar Valley Corporation, Calcutta

SHRI J. C. GUPTA Beas Construction Board, ChandigarhSHRI J. C. GUPTA

SHRI V. B. SINGH ( Alternate )U. P. State Electricity Board, Lucknow

SHRI OM KHOSLASHRI S. N. SINGH ( Alternate )

EMC Steelal Ltd, Calcutta

SHRI S. N. MISRASHRI S. R. JOSHI ( Alternate )

Maharashtra State Electricity Board,Bombay

SHRI NIRVAIR SINGH Punjab State Electricity Board, ChandigarhSHRI N. D. PARIKH

SHRI S. D. DAND ( Alternate )Kamani Engineering Corporation Ltd,

BombaySHRI R. N. PENDSE

DR R. RANJAN ( Alternate )Tata Hydro Electric Power Supply Co Ltd,

BombaySHRI P. V. RAMAIAH Karnataka State Electricity Board,

BangaloreSHRI N. V. RAMAN

SHRI R. NARAYANAN ( Alternate )Structural Engineering Research Centre

(CSIR), RoorkeeSHRI T. K. RAMANATHAN

SHRI K. V. S. MURTHY ( Alternate )Triveni Structurals Ltd, Naini, Allahabad

REPRESENTATIVESHRI NIRPINDER SINGH ( Alternate )

Bhakra Management Board, Chandigarh

SHRI A. P. SHARMA Madhya Pradesh Electricity Board,Jabalpur

SHRI N. SINHA Bihar State Electricity Board, PatnaSHRI S. N. VOHRA Inspection Wing, Directorate General of

Supplies and Disposals, New Delhi

Page 48: IS 802 P 1 to 3

Bureau of Indian StandardsBIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification ofgoods and attending to connected matters in the country.

CopyrightBIS has the copyright of all its publications. No part of these publications may be reproduced in anyform without the prior permission in writing of BIS. This does not preclude the free use, in the courseof implementing the standard, of necessary details, such as symbols and sizes, type or gradedesignations. Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian StandardsAmendments are issued to standards as the need arises on the basis of comments. Standards are alsoreviewed periodically; a standard along with amendments is reaffirmed when such review indicatesthat no changes are needed; if the review indicates that changes are needed, it is taken up forrevision. Users of Indian Standards should ascertain that they are in possession of the latestamendments or edition by referring to the latest issue of ‘BIS Catalogue’ and ‘Standards : MonthlyAdditions’.This Indian Standard has been developed by Technical Committee : SMBDC 7 and amended byCED 7

Amendments Issued Since Publication

Amend No. Date of IssueAmd. No. 1 August 1992

BUREAU OF INDIAN STANDARDSHeadquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002.Telephones: 323 01 31, 323 33 75, 323 94 02

Telegrams: Manaksanstha(Common to all offices)

Regional Offices: Telephone

Central : Manak Bhavan, 9 Bahadur Shah Zafar MargNEW DELHI 110002

323 76 17323 38 41

Eastern : 1/14 C. I. T. Scheme VII M, V. I. P. Road, KankurgachiKOLKATA 700054

337 84 99, 337 85 61337 86 26, 337 91 20

Northern : SCO 335-336, Sector 34-A, CHANDIGARH 160022 60 38 4360 20 25

Southern : C. I. T. Campus, IV Cross Road, CHENNAI 600113 235 02 16, 235 04 42235 15 19, 235 23 15

Western : Manakalaya, E9 MIDC, Marol, Andheri (East)MUMBAI 400093

832 92 95, 832 78 58832 78 91, 832 78 92

Branches : AHMEDABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE.FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR. LUCKNOW.NAGPUR. NALAGARH. PATNA. PUNE. RAJKOT. THIRUVANANTHAPURAM.VISHAKHAPATNAM

Page 49: IS 802 P 1 to 3

IS : 802 ( Part III ) - 1978

Indian Standard CODE OF PRACTICE FOR

USE OF STRUCTURAL STEEL IN i OVERHEAD TRANSMISSION LINE TOWERS

PART III TESTING

( Second Reprint MARCH 1993 )

UDC 621.315.668.2.006.76:620.1

@ CoPyright 1979

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARC

NEW DELHI 110002

Gr2 February 1979

Page 50: IS 802 P 1 to 3

IS : 802 ( Part III ) - 1978

Indian Standard CODE OF PRACTICE FOR

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWERS

PART III TESTING

Structural Engineering Sectional Committee, SMBDC 7

Ckairman

DIRECTOR STANMHDS ( CIVIL )

Members

Representing

Ministry of Railways

SHRI R. M. AQARWAL Institution of Engineers ( India );Calcutt;\ Dn S1iar.r~~~~ ~‘I<AKASU I AItcrrtn!c )

Metallurgical and Engineering Consultants ( India ) Ltd, Ranchi

Suar A. K. BANE~JEE

Snnr S. SANK.~RAN ( Alternate ) buzzr. S. N. Basu

Snax D. B. JOIN ( Allnnotc ) Snrsr P. C. BH.UIN

Suns V. S. Barnx DEPUTY DIRECTOR ( GATES

AND DEMONS ) ( dlfcrnotc ) Dn P. N. CHATTEI~JPE

Inspection Wing, Directorate General ol’ Supplies and Disposals, New Delhi

Ministry of Shipping and Transport ( Department of Transport ) ( Roads Wing )

Central Water Commission, New Delhi

Du 1’. DAYARATNAM SHUI D. S. DvsAt

Govcmmcnt of West Bengal Indian Institute of Technology, Kanpur M. IN. Dastur & Co Pvt Ltd, Calcutta

SHICI S, R. KUI.~AIZNI ( Altcmars ) Drnnorotr ( TI~ANSJ~ISSXON ) Central Electricity Authority, New Delhi

DEPUTY Druecron ( TRANS- nIIJYlON ) ( Alternate )

JOINT DIRECTOR STAN~A~IX~ Ministry of Railways

( ‘A~:?,N, DII~ECT~R ( B St S )-SB ( Alfcmafe )

SUXI 6. K. KHANN~ National Building:; Organization, New Delhi SHBI K. S. SMNIVAsAN ( Alfrrnafc )

( Co&sued on pace 2 )

@ Copyrighf I979

BUREAU OF INDIAN STANDARDS

This publication is protcctcd under the Irrdiarr Copgrighl rlct ( XIV of 1957 ) and rrproduction in whole or in part by any means rxccpt with written pcrurission of the publisher shall be deemed to be an infringement of copyright under tbc said Act.

I I

Page 51: IS 802 P 1 to 3

IS : 802 ( Part Ii1 ) - 1978

( Conrinwdfrom pop I )

Mcmbars

SHRI P. K. MALLICK SHBI P. K. MU~HERJEE

Repestnting

Jessop & Co Ltd, Calcutta

SHRI P. T. PATEL ( Alternate ) Braithwaitc & Co ( India ) Ltd, Calcutta

SHRI S. MUKHERJEZ SHRI S. K. MUKHERJEE

Hindustan Steel Ltd, Durgapur Bridge & Roof Co ( India ) Ltd, Howrah

SHRI B. K. CHATTZRJEE ( Alternate ) Rail India Technical and Economics Services,

New Delhi SHRI P. N. BHASKA~AN NAIR-

SHRI P;. B. RIBEIRO ( A!fcrnafs SHRI R. NARAYANAN

)

Pzo~ H. C. PARMESHWARAM SERI C. S. S. RAO ( Alfernafs )

SHRI DILIP PAUL REPRESENTATIVE

SHRI A. P. KAYAL ( Alternate) REPRESENTATIVE REPRESENTATIVE

SHRI P. V. NAIK ( Altcrn~fc ) -

Srructzxlcnginccring Research Ccntre ( CSIR ),

Engineer-in-Chief’s Branch, Ministry of Defencc

Industrial Fasteners Association of India, Calcutta Burn Standard Co Ltd, Howrah

Hindustan Steel Works Construction Ltd, Calcutta Richardson 8; Cruddas Ltd, Bombay

Stewarts & Lloyds of India Ltd, Calcutta ‘1

SI3RI P. SEaoI?pTA SHRI M. M. GHOSH ( Alternate,

&RI G. SRINIVASAN Bharat Heavy Elcctricals Ltd, Tiruchirapalli SARI G. L. NARASAIBH ( Al&male )

SHRI D. SRINIVASAN SRKI B. P. GROW ( ANemote )

Joint Plant Committee, Calcutta

SHRI M. D. THAMBERAR Bombay Port Trust, Bombay SHRI L. D. WAnIlWA Engineers India Ltd, New Delhi

SARI B. R. NAQ ( Alternate ) &RI C. R. R4Ma Rao,

Director ( Strut & Met ) Director General, IS1 ( Ex-o&o Member )

SHRI S. S. SETHI Assistant Director ( Strut & Met ). IS1

Subcommittee for Code of Practice for Use of Steel in Overhead Transmission Line Towers, SMBDC 7 : 1

Co?ZrOlsr

SIIRI V. D. ANAND

Membcrr

Central Electricity Authority, New Delhi

SHRI H. S. SEERA ( Alternuts to Shri V. D. Anand )

SIIRI M. ARUMUQAM ASSISTANT DIRECTOR STANDARDS

Tamil Nadu Electricity Board, Madras

(B & S)-I Ministry of Railways

DLPUTY DIRECTOR STAND- ARDS ( C.-OWE ) ( &tGr,Wts )

( Continued on page 8 )

2

Page 52: IS 802 P 1 to 3

IS t 802 ( Part III ) - 1978

Indian Standard CODB OF PRACTICE FOR

USE OF STRUCTURAL STEEL IN OVERHEAD TRANSMISSION LINE TOWEiXS

PART III TESTING

0. FOREWORD

0.1 This Indian Standard ( Part III ) was adopted by the Indian Standards Institution on 25 October 1978, .after the draft finalized by the Structural Engineering Sectional Committee had been approved by the Structural and Metals Division Council and the Ci+ Engineering Division Council.

0.2 With the publication of IS : 802 ( Part I )-1977* and IS : 802 ( Part II )-19787 provisions regarding loads, material, permissible itresses, design aspects, fabrication, galvanizing, inspection and packing require- ments of overhead transmission line towers have been covered. In this part requirements regarding testing of overhead transmission line towers have been covered.

0.3 This standard keeps in view the practices being followed in the country in this field. Assistance has also been derived from the ‘Guide for design of steel transmission line towers’ issued by the American Society of Civil Engineers and from the draft ‘Loading tests of overhead line towers ’ issued by International Electrotechnical Commission.

0.4 For the purpose of deciding whether a particular requirement of this standard is complied with, khe final value, observed or calculated, expressing the result of a test, shall be rounded off in accordan’ce with IS : 2-1960:. The number of significant places retained in the rounded off vahie should be the same as that of the specified value in this stahdard.

*Code of practice for use of structural steel in overhead transtiission line towers: Part I Loads and permissible stresses ( ~ccond revision ). .

tCode of practice for use of structural steel in overhead transmission line tow&: Part II Fabrication, galvanizing, inspection and packing.

jllules for rounding off numerical values ( revised ).

3

Page 53: IS 802 P 1 to 3

IS : 802 ( Part III ) - 1978

1. SCOPE

1.1 This standard ( Part III ) covers the provisions relating to the testing requirements of prototype self supporting steel lattice towers for overhead transmission lines.

1.1.1 Provisions regarding loads, permissible stresses and design requirements have been covered in Part I of this standard.

1.1.2 Provisions regarding fabrication, galvanizing, inspection and packing requirements have been covered in Part II of this standard.

1.1.3 For provisions regarding erection of towers, reference shall be made to IS : 5613 ( Part II/Set 2 )-1976’.

1.2 This code does not cover guyed towers and special towers for river crossing or other long spans.

2. GENERAL

2.1 Testing of tower generally serves as a guide to good tower design and therefore shall not be considered as a requisite proof test for all towers. The test shall be conducted on full scale prototype tower as per the approved loading schedules and rigging diagrams. The members constituting the prototype shall be of the same grade of steel as specified in the design and fabrication shall conform to the provisions stipulated in IS : 802 ( Part II )-1978t. The tower shall be tested on rigid foundation.

2.1.1 The test tower shall successfully withstand the ultimate loads specified for various conditions.

2.2 Leg Anchorages - The tower shall be erected vertically on rigid foundations with as much unbraced portion of the stub protruding above ground level as provided in the drawing.

2.3 The tower erected on test bed shall not be out of plumb by more than 1 in 360.

3. CALIBRATION OF MEASURING INSTRUMENTS

3.1 All measuring instruments shall be calibrated in a systematic manner with the help of standard weights. The calibration shall, before com- mencing the test on each tower, be done up to the maximum anticipated load to be applied during testing. Calibration curves for the instruments to be used during testing shall be drawn by the testing authorities and the test loads shall be suitably corrected with the help of these curves.

*Code of practice for design, installation and maintenance of overhead power lines: Part II Lines above 1 I kV and up to and including 220 kV, Section 2 Installation and maintenance.

tCudc of practice for use of structural steel in overhead transmission line towers: Parr II Fabrication, galvanizing, mspection and packing.

4

Page 54: IS 802 P 1 to 3

IS t 802 ( Part III ) - 1978

4. METHOD OF LOAD APPLICATION

4.1 Loads shall be applied according to rigging diagram through normal wire attachments, angles, or bent plates. U bolts/D shackles or swinging brackets ( hangers ) may be used in the test tower if desired by the purchaser, provided that satisfactory and safe rigging is attained.

4.2 The various types of loads; transverse, vertical and longitudinal shaU be applied in such a way that there is no impact loading on the tower due to jerks from the winches.

’ 4.3 Loading cases (values, directions and points of application of loads) are to be given by the client.

5. LOAD AND DEFLECTION MEASUREMENTS

5.1 All loads shall be measured through a suitable arrangement of strain devices or by using weights. Positioning of strain devices shall be such that the effect of pulley friction IS eliminated. In case the pulley friction cannot be avoided the same shall be measured by means of standard weights and accounted for in the test loads.

5.2 Tower deflections under load shall be measured by suitable procedure at the top cross arm level on the front sides of the transverse and longitudinal faces or front and rear sides of transverse facesa Deflection readings shall be recorded for the ‘ before load’, ‘ load on’ and ‘ load off’ conditions.

.

6. TESTING PROCEDURES

6.1 Bolt Slip Test - In a bolt slip test, the test loads are gradually applied up to the design loads, kept constant for 2 minutes at the design loads and then the loads are released gradually.

The initial and final readings on the scales before application and after the release of loads respectively shall be taken with the help of theodolite. The difference between these readings gives the values of the bolt-slip.

6.2 Normal Load/Broken Wire Load Tests - All the loads shall be applied gradually up to the ultimate design loads ( design load x F.O.S. ) in the following steps and shall be released in the similar manner:

25 percent, 50 percent, 75 percent, 90 percent, 95 percent, and

100 percent.

5

Page 55: IS 802 P 1 to 3

I$ I 802 ( Part III ) - 1978

7. OBSERVATION PERIODS

7.1 Under normal and broken wire load tests, the tower shall be kept under observation for sign of failure for two minutes (excluding the time for adjustment of loads) for all intermediate steps of loading up to and including 95 percent of ultimate design loads. -

7.2 For normal as well as broken wire tests, the tower shall be kept under observation for five minutes after it is loaded up to 100 percent ultimate design loads. 0

7.3 While the loading operations are in progress, the tower shall be constantly watched, and if it shows any tendency of failure anywhere, the loading shall be immediately stopped, released and then the entire tower shall be inspected. The re-loading shall be started only after the corrective measures are taken.

8. RECORDINGS

8.1 The deflections of the tower shall be recorded at each intermediate and final stage of normal load/broken wire load test by means of a thcodolite and grxduatcd scales.

8.2 The graduated scales which are fitted on the tower shall be about one metrc long with marking up to 5 mm accuracy.

3. DESTRUCTION TEST

9.1 If the purchaser so desires, the tower shall be tested to destruction,

9.2 Destruction test shall be carried out under normal condition or broken wire condition as agreed between the purchaser and the contractor.

9.3 All the provisions of this code for normal load/broken wire load test are applicable to destruction test as well. However, the loads shall be increased in steps of 5 pcrccnt after the ultimate design loads have been reached.

10. CHECK FOR MECHANICAL STRENGTH OF TOWER.

lo.1 The structure is considered to be satisfactory if it is able to support the specified ultimate load for 5 minutes as stipulated in 6.2, with no visible local deformation after unloading ( such as‘bowing, buckling), and no breakage of clrmrnts or constituent parts.

IO.2 Ovaiization of holes and permanent deformation of bolts shall not be corrsidcred as failure.

16.3 Material Test - If so tlesirrd by the purchaser, coupons shall be cut from tcsl tower uieriil~crs anti tcWxl iri ii laboratory.

Page 56: IS 802 P 1 to 3

IS : 802 ( Part III ) - 1978

11. PROCEDURE FOR REPETITION OF TESTS IN’THE EVENT OF PREMATURE FAILURE

11.1 In the event of premature failure of tower, the part that has failed may be replaced by another with greater mechanical strength. The modified structure shall be required to pass the test for the specified ultimate load values ( 100 percent step ).

12. TEST REPORT

12.1 The report shall include the following:

a) The type of tested tower.

b) The name and address of the tower manufacturer.

c) The name and address of the client.

d) The dates and location of testing.

e) The names of persons present during the tests.

f) A list of various assembly and shop drawings relating to the tower tested, including any modification of the drawings referred to.

g) A dimensioned line diagram of the tower showing the various load points and directions of loading to be applied and table with the specified loads.

h) Diagram showing the rigging arrangement used to apply the test loads.

j) Brief description of the test facility including the number, location, range and calibration charts or tables of every load transducer, as well as the accuracy of the equipment used to measure the test loads.

k) One table per test, showing the loads required at the various points on the structure and for the various loading steps.

m) One table per test, showing the various deflection values which may have been recorded.

n) In the case of failure: 1) a table showing the maximum loads applied to the structure,

just before the collapse; 2) a brief description of the failure; and 3) the dimensional and mechanical characteristics of the failed

elements.

p) A certain number of photographs, showing the whole of the structure and, possibly, details of the failure.

12.2 Certified steel producer test reports and physical test reports for members used in test towers shall be furnished as specified by the purchaser.

12.3 Test reports of coupons ( see IO.3 ) shall also be furnished.

7

Page 57: IS 802 P 1 to 3

IS : 802 ( Part III ) - 1978

( Continutd front pap 2 )

Members , Rcprarrnf ing

SW S. K. BRATTA~IIA&EE SAE ( India ) Ltd, Calcutta SHR~ V. NARAYANAW( Altrmats )

CHIEF ENQINEEB Andhra Pradesh Electricity Board, Hyderabad SUPERINTENDIN@ ENQXNEER ( Altcmats )

Sasr K. R. DEB Damodar Valley Corporation, Calcutta SHR~ SWARAJ GUPTA (Altcrn

SHRI J. C. GUPTA 74 SHRI J. C. GUPTA

i as Construction Board, Chandigarh U. P. State Electricity Board, Lucknow

SHRI V. B. SINQE ( Alfarnafc ) SHRI Oar KaosLa

SanI S. N. SINQH ( &tcrnate ) San1 S. N. MISRA

SHRI S. R. JOSEI ( AItcmafc ) SIIRI biIXVAIR SIXQH SllRI N. D. PAHIKH

SHHI S. D. DANEI ( Alfcmafc ) Sqrtr R. N. PEXDSE

DIL lt. RANJAX ( Alternate ) Smu P. V. RAMAIAH Saxr N. V. RAWN

BMC Steelal Ltd, Calcutta

Maharashtra State Electricity Board, Bombay

Punjab State Electricity Board, Chandigarh Kamani Engineering Corporation Ltd, Bombay

Tata Hydra Electric Power Supply Co Ltd, Bombay

Karnataka State Electricity Board, Bangalore Srru;cI;~engmecrmg Research Ccntre ( CSIR ),

Snn~ R. NARAYANAN ( Alternate ) SHRI T. K. RAXANATHAN Triveni Structurals Ltd, Naini, Alfahabad

SHRI K. V. S. MUIWIIY ( ( Altcrnotc) REPRBSBNTATIVE Bhakra Management Board, Chandigarh

SHIII NIRPINDER SIXion ( Alters& ) SHRI A. P. SIIAI<MA Madhya Pradesh Electricity Board, Jabalpur San1 N. SlNNA Bihar State Electricity Board, Patna SKRI S. N. VQIIRA Inspection Wing, Directorate General of Supplier

and Disposals, New Delhi

8

Page 58: IS 802 P 1 to 3

BUREAU OF INDIAN STANDARDS

Headquarters;

Manak Bhavan, 9 Bahadur Shah Zafar Marg, NEW DELHI 110002

Telephones: 331 01 31, 331 13 75 Telegrams: Manaksanstha ( Common to all Off ices )

Regional Offices: Telephone

Central Manak Bhavan, 9 Bahadur Shah fafar Marg, 331 01 31 NEW DELHI 110002 331 1375

*Eastern : 1 /14 C. I. T. Scheme VII M, V. I. P. Road. ’ 36 24 99 Maniktola, CALCUTTA 700054

Northern : SC0 445-446, Sector 35-C,

I

21843 CHANDIGARH 160036 3 1641

I

41 24 42 Southern : C. I. T. Campus, MADRAS 600113 41 25 19

41 2916 tWestern : Manakalaya, E9 MIDC, Marol, Andheri ( East ), 6 32 92 96

BOMBAY 400093

Branch Offices:

*Pushpak’. Nurmohamed Shaikh Marg, Khanpur,

I

2 63 48 AHMADABAD 380001 2 63 49

SPeenya Industrial Area 1 st Stage, Bangalore Tumkur Road BANGALORE 560058

I

Ifi “49” ii

Gangotri Complex, 5th Floor, Bhadbhada Road, T. T. Nagar, 667 16 BHOPAL 462003

Plot No. 82183. Lewis Road. BHUBANESHWAR 751002 531’5. Ward No: 29, R.G. Barua Road, 5th Byelane,

GUWAHATI 781003

5 36 27 3 31 77

5-8-56C L. N. Gupta Marg ( Nampally Station Road ), HYDERABAD 500001

23 1083

R14 Yudhister Marg. C Scheme, JAIPUR 302005

117/418 B Sarvodaya Nagar, KANPUR 208005

{ 63471 6 98 32

{ 21 68 76 21 82 92

Patliputra Industrial Estate. PATNA 800013 6 23 05 T.C. No. 14/1421. Universitv P.O.. Palayam 16 21 04

TRIVANDRUM 695035 1621 17 /nspection Offices ( With Sale Point ):

Pushpanjali. First Floor, 205-A West High Court Road, 2 51 71 Shankar Nagar Square, NAGPUR 440010

Institution of Engineers ( India ) Building, 1332 Shivaji Nagar, 5 24 35 PUNE 411005

*Sales Office in Calcutta is at 5 Chowringhre Approach, P. 0. Princep 27 68 00 Street. Calcutta 700072

tSales Office in Bombay is at Novelty Chambers, Grant Road, 89 66 28 Bombay 400007

ISales Office in Bangalore is at Unity Building, Narasimharaja Square, 22 36 71 Bangalore 560002

Reprograplly Unit, BIS, New Delhi, India