- 2. PAGE NO. 2 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 TABLE OF CONTENTS 1.0 SCOPE 2.0 MATERIALS 2.1 Structural Steel 2.2 Bolts, Nuts and Washers 2.3 Galvanizing 2.4 Other Materials 3.0 CLASSIFICATION OF LOADS 3.1 Climatic Loads 3.2 Longitudinal and Torsional Loads 3.3 Construction and Maintenance Loads 4.0 APPLICATION OF WIND LOAD ON TOWERS 5.0 OVERLOAD CAPACITY FACTORS 6.0 TYPES OF TOWERS 7.0 BROKEN WIRE CONDITIONS 7.1 Single Circuit Towers 7.2 Double Circuit Towers 8.0 COMPUTATION OF LOADS 8.1 Types of Loads 8.2 Sag and Tension 8.3 Tabulation of Loads and Loading Trees 8.4 Transverse Loads 8.5 Vertical Loads 8.6 Longitudinal Loads 8.7 Other Loads
- 3. PAGE NO. 3 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 9.0 PERMISSIBLE STRESSES 9.1 Axial Stresses in Tension 9.2 Axial Stresses in Compression 9.3 Stresses in Bolts 10.0 EFFECTIVE SLENDERNESS RATIOS AND LIMITING CONDITIONS 10.1 Leg Members 10.2 Other Compression Members 10.3 Redundant Members 10.4 Joint Restraint 10.5 Limiting Values of Slenderness Ratios 11.0 MINIMUM THICKNESSES 11.1 Structural Members 11.2 Gusset Plates 12.0 CONNECTIONS, END & EDGE DISTANCES 12.1 Bolting 12.2 Framing 12.3 End & Edge Distances 12.4 Center-to-Center Bolt Hole Spacing 13.0 ADDITIONAL REQUIREMENTS 13.1 Single Circuit Strung Condition 13.2 Stub Angle Sizing 13.3 Considerations for Linemen Weight APPENDIX 1 14.0 BIBLIOGRAPHY
- 4. PAGE NO. 4 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 1.0 SCOPE 1.1 This standard stipulates various design considerations to be adopted in the design of self supporting, latticed steel, square based towers for use in the overhead transmission line system of Saudi Electricity Company (SEC), Saudi Arabia. 1.2 This standard includes classification of loads, loading conditions, combination of loads, overload factors and permissible stresses. 1.3 This standard does not cover design considerations for guyed steel towers and special towers for river crossings and other long span crossings. 2.0 MATERIALS 2.1 Structural Steel The tower members including cross-arms shall be of structural steel made by either open hearth, basic oxygen or electric furnace process and shall conform to the provisions of latest revisions of the following standards or equivalent: ASTM A36M 250 MPa, minimum yield stress ASTM A572M (Grade 345) 345 MPa, minimum yield stress 2.2 Bolts, Nuts and Washers Bolts, nuts and washers shall conform to ASTM A394, ASTM A563M and ASTM F436M respectively or equivalent. 2.3 Galvanizing Structural steel members, including stub angles, shall be hot-dip galvanized after fabrication in accordance with the requirements of 01-TMSS-01 to a galvanizing thickness as specified in 20-TMSS-01. Bolts and other fasteners shall be galvanized in accordance with the requirements of 01-TMSS-01 and 20-TMSS-01. 2.4 Other materials used in the construction of towers shall conform to 20-TMSS- 01. 3.0 CLASSIFICATION OF LOADS Transmission lines are subjected to various types of loads during their lifetime. These loads are broadly classified into three distinct categories:
- 5. PAGE NO. 5 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 - Climatic Loads: Loads imposed on towers and line components by the action of wind and coincident temperature. - Longitudinal and Torsional Loads: Loads imposed on towers due to breakage of line components, sabotage, or cascade failure. - Construction and Maintenance Loads: Loads imposed on towers during construction and maintenance activities. Checking of strength of tower members for these loads ensures safety of workmen during construction and maintenance activities. Towers shall be designed to withstand factored loads, including their simultaneous application, arising out of above loading conditions, per details given below for each category: 3.1 Climatic Loads These are random loads imposed on towers, insulator strings, hardware, conductors and ground wires due to the action of wind and do not act continuously. Loads due to climatic effects shall be considered for the following wind and coincident temperature conditions and applied on towers and line components (conductors, ground wires, insulators, spherical markers, warning lights, spacer dampers, hardware etc.). -Standard Wind: A wind pressure of 430 N/m2 at minus 1°C (-1°C) -High Wind: A wind pressure of 1064 N/m2 at an every day temperarure Notes: i. The word “wire” shall mean conductor, ground wire, and OPGW when used as “intact wire”, wire tension, wire loading, etc. ii. The word “ground wire” shall mean OHGW and OPGW. iii. Every day temperature for various SEC Operating Areas shall be as in Table 05-1 below: Table 05-1: Every Day Temperature SEC Operating Area Every Day Temperature, o C Central 25 Eastern 27 Western 30 Southern 25 & 30
- 6. PAGE NO. 6 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 3.1.1 Standard Wind Loading Under this condition of loading, the following shall be assumed: a. All wires intact b. Wind acting normal to the longitudinal face of tower c. A wind pressure of 430 N/m2 acting on the projected area of tower members of front face multiplied by the shape factor as given in Clause 4.0 d. A wind pressure of 430 N/m2 acting on the projected area of ground wires and conductors, on effective projected area of insulator strings, spherical markers, warning lights, spacer dampers, hardware, etc. e. Wire (conductor, ground wire, OPGW) tensions corresponding to 430 N/m2 wind at minus 1°C (-1°C) temperature, final condition 3.1.2 High Wind Loading (Transverse) Under this condition of loading, the following shall be assumed: a. All wires intact b. Wind acting normal to the longitudinal face of tower c. A wind pressure of 1064 N/m2 acting on the projected areas of tower members of front face multiplied by the shape factor as given in Clause 4.0 for heights up to 10m above ground level. For tower heights above 10m, the wind pressures shall be increased per the procedure given in Clause 4.0 multiplied by the shape factor. Basic wind pressures and wind pressures inclusive of shape factors for heights above 10m are given in Table 05-2 for guidance. d. A wind pressure of 1064 N/m2 acting on full projected area of ground wires and conductors, on effective projected area of insulator strings, spherical markers, warning lights, spacer dampers, hardware, etc. e. Wire tensions corresponding to 1064 N/m2 wind at an every day temperature, final condition
- 7. PAGE NO. 7 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 3.1.3 High Wind Loading (Longitudinal) Under this condition of loading, the following shall be assumed: a. All wires intact b. Wind acting normal to the transverse face of tower c. Same as in Clause 3.1.2c except that the front face is transverse face. d. Wind load on conductors and ground wires due to longitudinal wind shall be taken as nil. Wind load on insulator strings, spherical markers, warning lights, spacer dampers, hardware, etc., same as that for High Wind Loading (Transverse) case Clause 3.1.2d, but in longitudinal direction. e. Same as in clause 3.1.2.e 3.1.4 High Wind Loading (Oblique, 45°wind) Under this condition of loading, the following shall be assumed: a. All wires intact b. Wind acting at 45 degree to the longitudinal face of tower c. A wind pressure of 1064 N/m2 x 0.71 acting on projected areas of tower members on transverse and longitudinal faces simultaneously multiplied by the shape factor as given in Clause 4.0 for heights up to 10m above ground level For tower heights above 10m, the wind pressures shall be increased as per the procedure given in Clause 4.0 and 71 percent of full wind pressure multiplied by the shape factor applied on transverse as well as on longitudinal faces simultaneously d. A wind pressure of 532 N/m2 (1064 x Cos2 45º) acting on full projected area of ground wires and conductors, on effective projected area of insulator strings, spherical markers, warning lights, spacer dampers, hardware, etc. e. Same as in Clause 3.1.2.e
- 8. PAGE NO. 8 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 Notes: i. For the purpose of calculating wind load on bundled conductors, wind pressure shall be considered acting on full projected area of each conductor in the bundle ii. For the purpose of computing the wind load on insulator strings, the effective projected area of the insulator string shall be assumed as 50 percent of the projected area of the cylinder with diameter equal to that of the insulator skirt. For multi-strings, wind shall be considered acting on each limb of multi-string. iii. No reduction in wind span shall be considered for oblique wind and for line deviation on angle towers. 3.2 Longitudinal and Torsional Loads Designing a tower for longitudinal and torsional loads ensures adequate strength of tower in longitudinal direction and provides margin for containment of failure due to cascading effect. Longitudinal loads may be imposed on towers due to failure of line components, conductors, ground wire or reduction/removal of one side tension. 3.2.1 Broken Wire Loading The number of conductors and/or ground wire to be considered broken shall be as defined in clause 7.0 “Broken Wire Conditions” for Tangent/Suspension, Angle (Tension), Anchor and Dead-End towers. Under this condition of loading, the following shall be assumed: a. Conductor(s) and/or ground wire(s) broken as given in Clause 7.0 b. Wind acting normal to the longitudinal face of tower c. A wind pressure of 430 N/m2 applied to the sum of the projected areas of tower members of front face multiplied by shape factor as given in Clause 4.0 d. A wind pressure of 430 N/m2 acting on full projected areas of ground wires and conductors, on effective projected area of insulator strings, spherical warning markers, warning lights, spacers, hardware, etc. e. Wire tensions corresponding to 430 N/m2 wind at minus 1°C (- 1°C), initial condition
- 9. PAGE NO. 9 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 3.2.2 Anti Cascading Loadings Cascade failures may be caused by failure of items such as insulators, hardware, joints, failure of major components such as towers, foundations, conductors or from climatic overloads or from casual events such as misdirected aircraft, sabotage etc. The security measures adopted for containing cascade failures in the line are to provide anchor towers at specific intervals of every 10 to 12 km, which shall be designed for anti-cascade loads. These towers serve the purpose of sectionalizing the line for containing the cascade failure. Loads and application of loads specified in Clause 3.3.1 for Angle (Tension), Anchor and Dead-End towers under “Stringing Loads” shall meet the requirement for anti-cascading checks. 3.3 Construction and Maintenance Loads 3.3.1 Stringing Loads Stringing loads are imposed on towers during stringing and pulling operations. These loads shall be assumed to act at wires (conductors/ground wires) attachment points in longitudinal direction, normal to the transverse face of tower. a. Under this condition of loading, the following shall be assumed: i. Pulling load due to stringing equal to tension of conductors/ground wires at minus 1°C (-1°C), no wind, initial condition ii. Transverse loads on account of wind on tower and line component shall be taken as nil. iii. Transverse loads due to line deviation shall be based on wire tensions at minus 1°C (-1°C), no wind, initial condition. b. Application of stringing loads on Tangent/Suspension, Angle (Tension), Anchor and Dead-End towers shall be as follows: i. Tangent/Suspension Towers - Stringing load at any one phase conductor attachment point with remaining phase conductors and ground wires intact - Stringing load at any one ground wire attachment point with other ground wire, if provided, intact
- 10. PAGE NO. 10 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 - Stringing of any one phase conductor and/or ground wire when temporarily dead-ended (anchored) at a distance such that the angle between the traveler on the tower and anchor on the ground is 15º to the horizontal. ii. Angle (Tension), Anchor and Dead-End Towers Stringing loads at all phase conductor and ground wire attachment points simultaneously. All stringing loads shall be considered acting in one direction only and all wires considered intact. 3.3.2 Heavy Vertical Loads This loading condition represents the pick up load during stringing. The upper tie members and lower main chord members of cross-arms are subjected to heavy stresses due to heavy vertical loads during construction activities and are required to be adequately sized for the safety of workmen. Under this loading condition, loads shall be considered acting at any one conductor or ground wire attachment point at a time, the following shall be assumed: a. A vertical load equal to twice the vertical load resulting from intact maximum design weight span plus weight of insulator strings and 1500 Newtons to account for the weight of linemen and tools b. Transverse loads on account of wind on tower and line components shall be taken as nil. c. Transverse loads due to line deviation shall be based on wire tensions at minus 1°C (-1°C), no wind, initial condition. d. Pulling loads due to stringing shall be equal to tension of conductors/ground wires at minus 1°C (-1°C), no wind, initial condition. 4.0 APPLICATION OF WIND LOAD ON TOWERS The wind pressure, qf, in N/m² is given by: qf = Kz q10 SF (Eq. 05-1)
- 11. PAGE NO. 11 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 Where: Kz = Exposure coefficient, which increases with height above ground level = 7/2 10 H ⎥⎦ ⎤ ⎢⎣ ⎡ H = Height above ground level, in meters q10 = Basic wind pressure at 10 meters above ground, in N/m2 = 0 613 10 2 . × V V10 = Wind velocity at 10 meters above ground. For high wind loading V10 = 150 km/hr = 41.67 m/sec q10 = 0.613 x (41.672)2 = 1064 N/m2 SF = Shape Factor (Pressure Coefficient) = 2.0 Applied to the sum of the projected areas of members on the front face of tower having cylindrical surfaces = 3.2 Applied to the sum of the projected areas of members on the front face of tower having flat surfaces Wind pressures for high wind conditions for heights above 10 meters are given below in Table 05-2 for guidance: Table 05-2: Wind Pressures for Heights above 10 meters Height Above Ground (m) Exposure Coefficient (Kz) Basic Wind Pressure (N/m2 ) Wind Pressure on Cylindrical Surface (N/m2 ) Wind Pressure on Flat Surface (N/m2 ) 10 1.000 1064 2128 3405 20 1.219 1297 2594 4150 30 1.369 1457 2914 4660 40 1.486 1581 3162 5060 50 1.584 1685 3370 5395 60 1.669 1776 3552 5685 70 1.744 1856 3712 5940 80 1.811 1927 3854 6170
- 12. PAGE NO. 12 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 5.0 OVERLOAD CAPACITY FACTORS The overload capacity factors to be applied to various loads under different loading conditions shall be as given in Table 05-3. Table 05-3: Overload Capacity Factors Types of Loads Standard Wind Loading High Wind Loading Broken Wire Loading Stringing Loading Heavy Vertical Loading Wind Load 2.50 Transverse Loads Wire Tension Load at angle 1.65 1.10 1.50 1.25 1.25 Vertical Loads 1.50 1.10 1.50 1.25 1.25 In general 1.10 Longitudinal Loads At dead-ends 1.65 1.10 1.50 1.25 1.25 Oblique Loads - 1.10 - - 1.25
- 13. PAGE NO. 13 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 6.0 TYPES OF TOWERS The selection of the most suitable types of towers for transmission lines depends on the actual terrain of the line. The types of towers generally suitable for most of the SEC transmission lines are given in Table 05-4. Table 05-4: Types of Towers Type of Tower Deviation Angle 0º to 3º for 69kV to 230kV Transmission LinesTangent Tower with Suspension Strings 0º to 2º for 380 kV Transmission Lines Small Angle Tower with Tension Strings 2º to 10º for 69kV to 230kV Transmission Lines 10º to 30º for 69kV to 230kV Transmission LinesLight Angle Tower with Tension Strings 2º to 10º for 380kV Transmission Lines 30º to 45º for 69kV to 230kV Transmission LinesMedium Angle Tower with Tension Strings 10º to 35º for 380kV Transmission Lines 45º to 60º for 69kV to 230kV Transmission LinesLarge Angle Tower with Tension Strings 35º to 60º for 380kV Transmission Lines Heavy Angle Tower with Tension Strings 60º to 90º for 69kV to 380kV Transmission Lines Anchor Tower with Tension Strings 0º to 3º for 69kV to 380kV Transmission Lines (for sectionalizing the line to avoid cascade failures) Dead-End/Terminal Tower with Tension Strings 0º to 20º angle of entry/take-off for 69kV to 380kV Transmission Lines Transposition Tower with Tension Strings 0º to 2º for 69kV to380 kV Transmission Lines Notes: i. The angles of line deviation specified are for the design span (design ruling span). The span may, however, be increased up to an optimum limit by reducing the angle of line deviation, provided the required ground and phase clearances are met. ii. Dead-End towers shall be designed for the maximum as well as minimum angle of entry/take-off angle as specified in the above table. iii. Tangent towers may be designed for zero angle of deviation and may be used up to the maximum deviation angle specified in the above table by reducing the design wind span corresponding to equivalent transverse loads due to line deviation angle.
- 14. PAGE NO. 14 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 7.0 BROKEN WIRE CONDITIONS The following broken wire conditions shall be assumed for the design of towers: 7.1 Single Circuit Towers The combination of broken wire cases, whichever is more stringent than others for a particular member. 7.2 Double Circuit Towers 7.2.1. Tangent/Suspension Towers – Any one phase or ground wire broken, whichever is more stringent for a particular member. 7.2.2 Angle (Tension) Towers – Any two phases broken on the same side and same span or any one phase and one ground wire broken on the same side and same span, whichever combination is more stringent for a particular member. 7.2.3 Anchor and Dead-End Towers – All phases and ground wires intact on one side and broken on the other side of towers. Notes: i. Phase shall mean all the sub-conductors in the case of bundled conductors. ii. Broken conductor shall mean all sub-conductors of bundle broken. 8.0 COMPUTATION OF LOADS 8.1 Types of Loads Three types of loads act on transmission towers, namely transverse, vertical and longitudinal. Towers shall be designed to withstand simultaneous action of these loads multiplied by overload factors as in Clause 5.0, depending on design condition. 8.2 Sag and Tension Sag and tension values for conductors and ground wires shall be determined for various loading conditions keeping in view the tension limiting conditions specified in TES-P-122.03 for computing tower loads. 8.3 Tabulation of Loads and Loading Trees Transverse, vertical and longitudinal loads for various loading conditions specified in this standard shall be determined in accordance with the procedures
- 15. PAGE NO. 15 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 given in Clauses 8.4, 8.5 and 8.6 and tabulated or loading trees prepared before proceeding with stress calculations and design. Sample loading calculations for a tangent tower are given in Appendix-1. 8.4 Transverse Loads 8.4.1 Wind on Conductors and Ground Wires Loads due to wind on wires (conductors/ground wires) Fwc, in Newtons, applied at wire attachment points in the direction of transverse axis of tower, shall be determined by the following expression: Fwc = Pd L D N (Eq. 05-2) Where: Pd = Design wind pressure in N/m² L = Wind span, being sum of half the spans on both sides of attachment point, in meters. Values of wind spans as specified in the Scope of Work and Technical Specifications (SOW/TS) or the relevant engineering standard (as the case may be) shall be adopted. D = Diameter of conductor/ground wire, in meters N = Number of sub-conductors in a bundle Note : Wind span for broken conductor is generally in the range of sixty percent (60%) of intact wind span. 8.4.2 Wind on Insulator Strings Wind load on insulator strings, Fwi, in Newtons, applied at attachment points shall be determined from the following expression: Fwi = Pd Ai (Eq. 05-3) Where: Pd = Design wind pressure in N/m2 Ai = Effective projected area of insulator strings in sq. m. Effective projected area of the insulator strings shall be assumed as fifty percent (50%) of the projected area of the
- 16. PAGE NO. 16 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 cylinder with a diameter equal to that of the insulator skirt. Note: In case of multi-strings including V-strings, wind pressure on all strings of multi-string shall be considered without any masking effect. 8.4.3 Line Deviation Load due to line deviation, Fd, in Newtons, applied at attachment points in the direction of transverse axis of tower, shall be determined by the following expression: Fd = 2 N T Sin θ/2 for intact spans (Eq. 05-4) Fd = N T Sin θ/2 for broken spans (Eq. 05-5) Where: N = Number of sub-conductors in a bundle T = Tension of conductor/ground wire under a given loading condition, in Newtons θ = Angle of line deviation, in degrees 8.4.4 Wind on Tower A latticed tower consists of panels of varying heights. These panels are formed between the intersection of legs and bracings. It is conventional to determine wind load on each panel and transfer the same to wire attachment points as point loads. In addition to lumping the wind loads on wire attachment points, it is sometimes desirable (in case of taller towers) to lump wind loads at extension tops and at one or two points in the tower body also. The practice of lumping tower wind loads at wire attachment points reflects a practical approach and facilitates application of tower wind loads during full scale testing of tower. Tower wind may also be distributed throughout the height of tower, as is the case when tower is designed on computer and wind loads are not input as point loads at wire attachment points. This may reflect true field conditions provided that all the tower members are included in tower model during analysis. Further this may require redistribution of wind loads at wire attachment points and at some panel points to facilitate application of wind loads during full scale tower testing. Wind load, Fwt, in Newtons, for wind normal to the latticed face of the tower, on a panel height “H” assumed to be acting at center of gravity is given by the expression:
- 17. PAGE NO. 17 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 Fwt = Pd Ae (Eq. 05-6) Where: Pd = Design wind pressure in N/m2 Ae = Net projected surface area of legs, bracings, cross-arms and secondary members of latticed face of the panel, in sq.m. Projections of bracing members of the adjacent faces and of the plan and hip bracings may be neglected while determining net projected area of members. Note: For transverse wind, longitudinal face of tower is latticed face and for longitudinal wind, transverse face of tower is the latticed face. For diagonal (oblique, 45°) wind, wind pressure for both transverse and longitudinal faces is 0.71 times the design wind pressure. Total transverse load at each conductor/ground wire attachment points is the sum of Fwc, Fwi and Fd. Transverse loads due to tower wind of each panel, Fwt is distributed as explained above. 8.5 Vertical Loads 8.5.1 Weight of Conductors, Ground Wires and Hardware Loads due to weight of wires, Vc, in Newtons, shall be determined as below and applied at wire attachment points: Vc = W1 Wt N + W2 (Eq. 05-7) Where: W1 = Unit weight of conductors and ground wires, in N/m W2 = Weight of spherical warning markers, warning lights, spacers and hardware, etc., in Newtons Wt = Weight span, being the horizontal distance between the lowest points of conductors/ground wires on the two spans adjacent to the tower under consideration, in meters The lowest point is defined as the point at which the tangent to the sag curve or to the extended sag curve is horizontal. Values of weight spans as specified in SOW/TS or relevant engineering standard (as the case may be) shall be adopted. N = Number of sub-conductors in a bundle
- 18. PAGE NO. 18 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 In a transmission line, three types of weight spans may be encountered. They are: - Minimum weight span - Maximum downward weight span and - Maximum upward weight span Tangent/Suspension towers shall be designed for both minimum and maximum downward weight spans. Minimum weight span may govern design of foundation under uplift and also some tower members. Minimum weight span also governs the swing of suspension insulator strings. Tangent/Suspension tower shall never be used at locations, which are subjected to uplift. Angle (Tension), Anchor and Dead-End towers may be required to be designed for upward weight span in addition to downward weight span. Upward forces on a tower result due to higher elevation of wire attachment points on adjacent towers. 8.5.2 Weight of Hardware and Insulator Strings Load due to weight of hardware and insulator strings, VL,in Newtons, shall be applied at wire attachment points. Weight of insulator string shall be taken as the sum of weight of all the insulators and hardware in a string/multi-string. 8.5.3 Weight of Linemen and Tools Weight of Linemen and tools, VL , in Newtons, shall be applied at ground wire and conductor attachment points for the specified loading conditions. 8.5.4 Self-Weight of Tower Self-weight of tower is the weight of all the structural members, plates, nuts, bolts, washers, step bolts, ladders and all other accessories of tower. The weight of insulator washing facilities such as wash platforms, interconnecting walkways and handrails are to be included where the insulators are at a height of forty (40) meters and above. Self-weight of tower shall either be calculated on the basis of unit weight of each member of tower and increased by about 10 to 12 percent to account for the weight of nuts, bolts, washers, cleats, plates etc. and distributed at panel points or shall be generated and distributed automatically when tower will be designed on computer. The computer
- 19. PAGE NO. 19 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 generated weight shall also be increased by a suitable percentage to account for weight of above items plus weight of redundant members. Total vertical load at each wire attachment point is the algebraic sum of Vc, Vi, and VL . 8.6 Longitudinal Loads Longitudinal loads are caused by any of the following loading conditions: 8.6.1 Longitudinal and Oblique Winds Under High Wind condition Longitudinal loads due to high wind in longitudinal and oblique directions shall be calculated for insulator strings and towers as per procedure in Clauses 8.4.2 and 8.4.4 and in accordance with assumptions in Clauses 3.1.3.c and 3.1.4.c. These loads shall be applied in longitudinal direction, normal to the transverse face of tower for longitudinal wind and in transverse and longitudinal directions for diagonal/oblique wind. 8.6.2 Broken Wire Condition Unbalanced pulls shall be based on wire tensions determined according to loading criteria specified in Clause 3.2.1.e and applied at wire attachment points, normal to the transverse face of tower. Number of conductors and ground wires to be considered broken shall be as in Clause 7.0. a. Tangent/Suspension Towers Longitudinal loads for broken conductors get reduced due to swing of suspension strings. The longitudinal load shall be calculated using tension in the broken conductor as sixty percent (60%) of the tension in the intact conductor. Longitudinal loads for broken ground wires shall be without any reduction in tension. b. Angle (Tension), Anchor and Dead-End Towers Longitudinal loads for broken conductors/ground wires shall be the component of tension in longitudinal direction corresponding to minimum design angle of deviation for angle (tension) towers. Longitudinal loads for broken conductors/ground wires shall be taken as nil for Anchor and Dead-End towers.
- 20. PAGE NO. 20 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 8.6.3 Stringing Condition Stringing loads shall be assumed equal to tension of conductors/ground wires at minus 1°C (-1°C), no wind, initial condition and applied in the longitudinal direction: - at any one conductor or ground wire attachment point at a time in case of Tangent/Suspension towers. - at all conductor and ground wire attachment points simultaneously in case of Angle (Tension), Anchor and Dead-End towers. - Stringing of any one phase conductor and/or ground wire when temporarily dead-ended (anchored) at a distance such that the angle between the traveler on the tower and anchor on the ground is 15º to the horizontal. 8.6.4 Intact Span Condition for Anchor and Dead-End Towers Longitudinal loads due to one sided tensions for Anchor and Dead-End towers shall be equal to full tension of conductors and ground wires under worst loading condition. These loads shall be applied simultaneously at all wire attachment points in one direction only. 8.7 Other Loads Towers shall be designed to include the effects of transverse loads due to wind on spherical markers and phase conductor warning lights etc. and their vertical weights. These loads including the overload capacity factors shall be included in the phase conductors and overhead ground wires loads and shall be considered mandatory in the design of towers regardless of the actual project requirements. 9.0 PERMISSIBLE STRESSES 9.1 Axial Stresses in Tension 9.1.1 The design tensile stress on the net cross-sectional area An of concentrically loaded tension member, shall not exceed minimum guaranteed yield stress Fy of the material. In case the angle section is connected by one leg only, the design tensile stress on the net sectional area shall not exceed 0.9 Fy. 9.1.2 The net cross-sectional area, An, is the gross cross-sectional area Ag (the sum of the products of the thickness and the gross width of each element as measured normal to the axis of the member) minus the loss due to holes or other openings at the section being investigated. If there
- 21. PAGE NO. 21 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 is a chain of holes in a diagonal or zigzag line, the net width of an element shall be determined by deducting from the gross width the sum of diameters of all the holes in the chain and adding for each gage space in the chain the quantity s²/4g, where s = longitudinal spacing (pitch) and g = transverse spacing (gage) of any two consecutive holes. The critical net cross-sectional area, An, is obtained from the chain which gives the least net width. 9.1.3 Plain angle sections bolted in both legs at both ends shall be considered to be concentrically loaded. Leg members of latticed steel towers fall in this category. 9.1.4 Plain angle sections used as bracing members in latticed towers are connected by one leg only. The allowable tensile stress for such members shall be limited to 0.9 Fy. If the legs are unequal and the short leg is connected, the unconnected leg shall be considered to be of the same size as the connected leg. 9.1.5 While developing structural drawings, care shall be taken such that the centroid of the bolt pattern lies between the heel of the angle and the center line of the connected leg. If this condition is not met, the connection shall be checked for block shear in accordance with equation (3.10-1) of ASCE Standard 10-97 “Design of Latticed Steel Transmission Structures”. 9.2 Axial Stresses in Compression 9.2.1 The following provisions are applicable only to 90° angle sections. 9.2.2 The design compressive stresses in various members shall not exceed the values given by the formulas in Clause 9.2.3. 9.2.3 The allowable unit stress, Fa, in MPa on the gross cross-sectional area or on the reduced area where specified, of axially loaded compression members shall be: Fa = ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − 2 / 2 1 1 cC rKL Fy when KL/r ≤ Cc (Eq. 05-8) Fa = ( )2 2 / rKL Eπ when KL/r > Cc (Eq. 05-9) Cc = yF E2 π (Eq. 05-10)
- 22. PAGE NO. 22 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 Where: Fy = Minimum yield stress of steel, MPa E = Modulus of elasticity of steel = 2 x 105 MPa K = Effective length factor KL/r = Largest effective slenderness ratio of any unbraced segment of a compression member L = Unbraced length of the compression member, cm r = Appropriate radius of gyration, cm 9.2.4 The formulas given in Clause 9.2.3 are applicable provided that the largest value of w/t (width-thickness ratio) does not exceed the limiting value given by (w/t)Lim = 210 Fy (Eq. 05-11) Where: w = Distance from edge of fillet of angle section to the extreme fiber, mm. t = Thickness of leg, mm 9.2.5 Where the width-thickness ratio exceeds the limit given in Clause 9.2.4, equations (05-8) and (05-10) given in Clause 9.2.3 are used by substituting for Fy the value Fcr given by Fy tw Fcr ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ −= (w/t) )/(677.0 677.1 Lim when (w/t)Lim ≤ w/t ≤ 378 Fy (Eq. 05-12) and Fcr = 2 )w/t( 65550 when w/t > 378 Fy (Eq. 05-13) 9.2.6 The maximum permissible value of w/t for any type of steel shall not exceed 25.
- 23. PAGE NO. 23 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 9.3 Stresses in Bolts 9.3.1 Shear Stress: The shear strengths of bolts conforming to ASTM A394, Type 0, are given in Table 05-5 and these shall not be exceeded. For bolts in double shear the specified single shear values shall be multiplied by 2. Table 05-5: Shear Strengths of ASTM A394 Type 0 Bolts Nominal Bolt Size (mm) Single Shear Strength Through Threads (kN) Single Shear Strength Through Body (kN) 16 50 60 20 80 95 22 100 120 24 120 140 Notes: i. The above Table for ASTM A394, Type 0, bolts is based on shear strength of 380 MPa (55,200 psi unit shear strength) across the area at root of threads and 316 MPa (45,880 psi unit shear strength) across the nominal area. ii. For bolts conforming to other recognized International Standards and sizes, the chemical composition shall conform to or be better than ASTM A394, Type 0 and the allowable shear stress Fv on the effective area shall be 0.62Fu where Fu is the specified minimum tensile strength of the bolt material. The effective area is the gross cross- sectional area of the bolt if threads are excluded from the shear plane or the root area if the threads are in the shear plane. iii. It is recommended that shear strength values through threads shall be used for design purposes to take care of any possibility of threaded portion of bolt extending into plane of shear during erection. 9.3.2 Bearing Stress The maximum bearing stress, calculated as the force on a bolt divided by the product of the bolt diameter and the thickness of the connected part is limited between 1.2 to 1.5 times the specified minimum tensile stress Fu of the connected part (member) or the bolt. A bearing stress value of 1.25 times the minimum tensile stress Fu shall be adopted in this standard to permit reduction in the end and edge distances.
- 24. PAGE NO. 24 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 For bolts conforming to ASTM A394, Type 0, the bearing stress on bolt diameter for structural steels specified in this standard shall be as follows: ASTM A36M 500 MPa ASTM A572M (Grade 345) 560 MPa 10.0 EFFECTIVE SLENDERNESS RATIOS AND LIMITING CONDITIONS The effective slenderness ratio, KL/r, of compression and redundant members shall be determined as follows: 10.1 Leg Members For leg members bolted in both faces at connections, r L r KL = 0 ≤ L r ≤ 150 (Eq. 05-14) 10.2 Other Compression Members For members with a concentric load at both ends of the unsupported panel, KL r L r = 0 ≤ L r ≤ 120 (Eq. 05-15) For members with a concentric load at one end and normal framing eccentricity at the other end of the unsupported panel, KL r L r = +30 0 75. 0 ≤ L r ≤ 120 (Eq. 05-16) For members with normal framing eccentricities at both ends of the unsupported panel, KL r L r = +60 05. 0 ≤ L r ≤ 120 (Eq. 05-17) For members unrestrained against rotation at both ends of the unsupported panel, KL r L r = 120 ≤ L r ≤ 200 (Eq. 05-18) For members partially restrained against rotation at one end of the unsupported panel,
- 25. PAGE NO. 25 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 KL r L r = +28 6 0 762. . 120 ≤ L r ≤ 225 (Eq. 05-19) For members partially restrained against rotation at both ends of the unsupported panel, KL r L r = +46 2 0 615. . 120 ≤ L r ≤ 250 (Eq. 05-20) 10.3 Redundant Members KL r L r = 0 ≤ L r ≤ 120 (Eq. 05-21) If members are unrestrained against rotation at both ends of the unsupported panel, KL r L r = 120 ≤ L r ≤ 250 (Eq. 05-22) If members are partially restrained against rotation at one end of the unsupported panel, KL r L r = +28 6 0 762. . 120 ≤ L r ≤ 290 (Eq. 05-23) If members are partially restrained against rotation at both ends of the unsupported panel, KL r L r = +46 2 0 615. . 120 ≤ L r ≤ 330 (Eq. 05-24) 10.4 Joint Restraint A single bolt connection at either the end of a member or a point of intermediate support shall not be considered as furnishing restraint against rotation. A multiple bolt connection, detailed to minimize eccentricity, shall be considered to offer partial restraint if the connection is to a member capable of resisting rotation of the joint. A multiple bolt connection to an angle or angle chord member, detailed to minimize eccentricity, shall not be considered to offer partial restraint if the connection is made only on a gusset plate without also being framed to the restraining member. To justify using the values of KL/r in equations 05-19, 05-20, 05-23 and 05-24, the following evaluation is suggested: - The restrained member must be connected to the restraining member with at least two bolts.
- 26. PAGE NO. 26 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 - The restraining member must have a stiffness factor I/L in the stress plane (I = Moment of inertia and L = Length) that equals or exceeds the sum of the stiffness factors in the stress plane of the restrained members that are connected to it; and - Angle members connected solely to a gusset plate should not be considered to have end restraint against rotation. An angle member with an end connection to both a gusset plate and the restraining angle member should have adequate bolts in the restraining angle member to provide end restraint against rotation. Angle members connected by one leg shall have the holes located as close to the outstanding leg as practical. Except for some of the smaller angles, normal framing eccentricity implies that the centroid of the bolt pattern is located between the heel of the angle and the centerline of the connected leg. In calculating the slenderness ratios of the members, the length L shall be the distance between the intersection of the center of gravity lines at each end of the member. 10.5 Limiting Values of Slenderness Ratios 10.5.1 The limiting values of effective slenderness ratio, KL/r, for compression members shall be as follows: Leg members, ground wire peak members, and main members of cross-arms in compression 150 Other members carrying computed stresses 200 Redundant members/secondary members carrying nominal stresses 250 10.5.2 Slenderness ratio, L/r, of a member carrying axial tension only shall not exceed 375 Other tension members 500
- 27. PAGE NO. 27 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 11.0 MINIMUM THICKNESSES 11.1 The minimum thickness of structural members shall be as given in Table 05-6: Table 05-6: Minimum Thickness of Members Type of Members Minimum Thickness, mm Leg members, ground wire peak members and main members of cross-arms in compression 6 Other stress carrying members 5 Redundant members* 4 Stub Angle 8 Note: *The redundant members shall be designed for 2.5% of the load in the supported member. 11.2 Gusset plates These shall be designed to resist the shear, direct and flexural stresses acting on the weakest or critical sections. Minimum thickness of gusset plate shall be 2mm more than the lattice connected to it only in case when the lattice is directly connected on gusset plate outside the leg member. In no case the thickness of gusset plate shall be less than 5mm. 12.0 CONNECTIONS, END & EDGE DISTANCES Bolted connections for transmission towers are normally designed as bearing type connections. It is assumed that bolts connecting one member to another carry the load in the connection equally. The end and edge distances specified in this standard are based on bearing stress value of 1.25 times the minimum specified tensile stress of weaker of the material of bolt or connected part and these do not include any allowance for fabrication and rolling tolerances. 12.1 Bolting 12.1.1 Minimum Diameter of Bolts The diameter of bolts shall not be less than 16mm. 12.1.2 Preferred Sizes of Bolts Bolts used for erection of transmission line towers shall preferably be of diameter 16mm and 20mm. Preferably one size of connection bolts and nuts shall be used for Tangent/Suspension type towers. However,
- 28. PAGE NO. 28 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 for Angle (Tension), Anchor and Dead-End type towers, two sizes of connection bolts may be used. All bolts shall be provided with hot-dip galvanized steel locknuts. The length of bolts shall be such that the threaded portion does not lie in the plane of contact of members. The projected portion of the bolt beyond the locknut shall be between 3 to 8mm but not less than three (3) effective threads. 12.1.3 Gross and Net Area of Bolts For the purpose of calculating the shear stress the gross area of bolt is taken as the nominal area of bolt only when it is ensured that the threaded portion of bolt will not extend into the plane of contact of connected members. In this standard the shear area of bolts has been taken as the area at the root of threads (see Clause 9.3.1 and Table 05- 5). The bolt area for bearing shall be taken, as d x t where d is the nominal diameter of the bolt, and t is the thickness of the thinner of the parts joined. The net area of a bolt in tension shall be taken as the area at the root of the thread. 12.1.4 Holes for Bolting The diameter of the hole drilled/punched shall be 1.5mm more than the nominal diameter of the bolt. 12.2 Framing The angle between any two members common to a joint of a trussed frame shall preferably be greater than 20° and never less than 15° due to uncertainty of stress distribution between two closely spaced members. 12.3 End & Edge Distances The end distance is the distance from the center of a hole to the end of the member, whether this end is perpendicular or inclined to the line of force. The edge distance is the distance from the center of a hole to the rolled or sheared edge. It is a perpendicular distance between the nearest gage line of holes to the rolled or sheared edge running parallel to the gage line. 12.3.1 Stressed members The required end distance is a function of the load being transferred in the bolt, the tensile strength and thickness of the connected part.
- 29. PAGE NO. 29 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 For stressed members the end and edge distances are given in Table 05- 7. These are minimum and shall not be underrun by fabrication & rolling tolerances. Table 05-7: End and Edge Distances for Stressed Members Bolt diameter (mm) Description 16 20 22 24 Thickness limitation for punched holes for ASTM A36M Steel (mm) 16 20 22 24 End distance (sheared or mechanically guided flame cut end) 24 30 33 36 Edge distance (Rolled Edge) 21 26 28 32 Edge distance (sheared or mechanically guided flame cut edge) 23 28 30 34 The values of end and edge distances given in Table 05-7 are applicable for all types of steels specified in this standard except that punching thickness limitations are applicable to ASTM A36M steel. For high strength steels (ASTM A572M, Grade 345) the thickness of material for punched holes shall be the thickness specified in Table 05- 7 minus 1.5mm for maintaining the same end and edge distances. Where the thickness of the angle section is more than the limiting value of thickness given in Table 05-7 and holes are punched, the end and edge distances will be governed by the following equations. End distance (mm) = t + d/2 when t ≥ d (Eq.05-25) Edge distance (mm) = 0.85[t + d/2]when t ≥ d (Eq. 05-26) (Rolled edge) Edge distance (mm) = 0.85[t + d/2] + 2.0 when t ≥ d (Eq. 05-27) (sheared or mechanically guided flame cut) Where: d = Nominal diameter of bolt, mm t = Thickness of connected leg, mm The above provisions shall not apply if holes are drilled. Values of end and edge distances shown in the Table 05-7 shall also be applicable for member thicknesses in excess of those shown in Table 05-7, for drilled holes.
- 30. PAGE NO. 30 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 12.3.2 Redundant Members. The end and edge distances of redundant members shall not be less than the values given in Table 05-8. Table 05-8: End and Edge Distances for Redundant Members Bolt diameter (mm) Description 16 20 22 24 End distance (sheared or mechanically guided flame cut end) 20 24 27 30 Edge distance (Rolled Edge) 17 21 23 26 Edge distance (sheared or mechanically guided flame cut edge) 19 23 25 28 12.4 Center-to-Center Bolt Hole Spacing The center-to-center bolt hole spacing is fixed to meet the following requirements: 12.4.1 Strength requirement, given by: Smin= tF 2.1 U Ρ + 0.6d (Eq. 05-28) Where: Smin= Minimum center-to-center spacing between two holes in the line of transmitted force, mm P = Load transmitted through the bolt, Newtons UF = Minimum tensile strength of steel, MPa. t = Thickness of connected part (leg), mm. d = Diameter of bolt, mm. 12.4.2 Installation requirement, given by: Sinst = Width across flats of nut + 10mm.
- 31. PAGE NO. 31 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 The minimum bolt spacing for various bolt diameters, considering above requirements and bolt bearing stresses specified in this standard are given in Table 05-9. Table 05-9: Minimum Center-to-Center Bolt hole Spacing Bolt diameter (mm) Description 16 20 22 24 Minimum Spacing (mm) 35 45 50 55 13.0 ADDITIONAL REQUIREMENTS 13.1 Single Circuit Strung Condition For double circuit towers the design shall be suitable both for single circuit and double circuit strung conditions. 13.2 Stub Angle Sizing The unbraced portion of the stub between the last bracing connection and top of concrete is subjected to combined axial and bending stresses. The stub angle shall be suitable to withstand combined stresses. The stub angle and the shear connectors shall be designed in accordance with the ASCE Standard 10-97 “Design of Latticed Steel Transmission Structures” for the maximum groundline reactions with overload capacity factors. Bonding between the stub angle and concrete shall be ignored. The thickness of the stub angle shall be 2mm more than the thickness of the leg member to which it is connected. 13.3 Considerations for Linemen Weight Horizontal or near horizontal tower members shall be capable of supporting a vertical load of 1100 Newtons (vertical weight of linemen and tools). This load shall be applied independently of all other loads without permanent distortion of the members.
- 32. PAGE NO. 32 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 APPENDIX - 1 (Sheet 1 of 2) Project Title: __________ Code No. ________ Tower Type _________ Drawing No. __________ Page No. _______ Design Span (m) Line Angle (Deg): Wind Span (m) Normal: Broken: Max. Weight Span (m) Normal: Broken: Min/Uplift Weight Span (m) Normal: Broken: LOADING CONDITION (Tick as Applicable) Standard Wind High Wind Transverse High Wind Longitudinal High Wind Oblique Broken Wire Stringing Heavy Vertical TRANSVERSE LOADS OLF Newtons OHGW/OPGW Wind Load on OHG Wire..................................................................... Wind Load on SM, VD, HS*................................................................ Angle Pull............................................................................................ TOTAL x....... x....... x....... = = = = Conductor Wind Load on Conductor..................................................................... Wind Load on Insulators...................................................................... Wind Load on SP, VD, WL*............................................................... Angle Pull........................................................................................... TOTAL x ...... x ...... x ...... x....... = = = = = VERTICAL LOADS MAXIMUM OHGW/OPGW Weight of OHG Wire............................................................................ Weight of SM, VD, HS*....................................................................... Weight of Lineman and tools................................................................. TOTAL x...... x...... x...... = = = = Conductor Weight of conductor............................................................................. Weight of SP, VD, WL*.................................................................... Weight of Insulators.............................................................................. Weight of Lineman & tools................................................................. TOTAL x...... x...... x...... x...... = = = = = * SM = Spherical Markers VD = Vibration Dampers HS = Hardware Sets SP = Spacer Dampers WL = Warning Lights NOTE: Loads due to wind on tower shall be calculated and applied in transverse and longitudinal directions as the case may be. Continued on sheet 2
- 33. PAGE NO. 33 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 APPENDIX - 1 (Sheet 2 of 2) Project Title: ___________ Code No. _________ Tower Type __________ Drawing No. __________ Page No. _______ Design Span (m) Line Angle (Deg): Wind Span (m) Normal: Broken: Max. Weight Span (m) Normal: Broken: Min./Uplift Weight Span (m) Normal: Broken: LOADING CONDITION (Tick as Applicable) Standard Wind High Wind Transverse High Wind Longitudinal High Wind Oblique Broken Wire Stringing Heavy Vertical VERTICAL LOADS MINIMUM OLF Newtons OHWG/OPGW Weight of OHG Wire........................................................................... Weight of SM & VD*.......................................................................... Weight of Lineman and tools................................................................ TOTAL x...... x...... x........ = = = = Conductor Weight of conductor............................................................................. Weight of SP, VD, WL*....................................................................... Weight of Insulators.............................................................................. Weight of Lineman & tools.................................................................... TOTAL x...... x...... x...... x........ = = = = = * SM = Spherical Markers VD = Vibration Dampers HS = Hardware Sets SP = Spacer Dampers WL = Warning Lights LONGITUDINAL LOADS (WIRE PULL, WIND ON INSULATORS**) Newtons OHGW/OPGW .................................................................................. Conductor .................................................................................. (**Applicable for longitudinal and diagonal winds only) = = NOTE: Loads due to wind on tower shall be calculated and applied in transverse and longitudinal directions as the case may be.
- 34. PAGE NO. 34 OF 34TEP122.05PIR0/MAA TRANSMISSION ENGINEERING STANDARD TES-P-122.05PI, Rev. 0 Date of Approval: May 7, 2007 14.0 BIBLIOGRAPHY 1. ASCE Manual No. 74 “Guidelines for Electrical Transmission Line Structural Loading”, American Society for Civil Engineers, First Edition (1991). 2. ASCE Standard 10-97 “Design of Latticed Steel Transmission Structures”, American Society for Civil Engineers, Second Edition (2002). 3. IEC 60826: "Design Criteria of Overhead Transmission Lines", Third edition 2003. 4. Holland H. Farr, "Transmission Line Design Manual", United States Department of the Interior. 5. Rural Electrification Administration (U.S. Department of Agriculture), "Design Manual for High Voltage Transmission Lines".