Wind Load Calculations for Structures
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Questions and Answers

What is the reduced wind pressure for structures less than 30 m after the 1971 amendment?

  • 75 kg/m2 (correct)
  • 112.50 kg/m2
  • 150 kg/m2
  • None of the above

In the measurement of spans, where should measurements be taken on curves for an odd number of tracks?

  • Inner rail of the first outside track
  • Outer rail of the middle track (correct)
  • Any rail as long as it is consistent
  • Middle rail of the middle track

Which zone has the highest standard wind pressure for new works?

  • Green zone
  • Blue zone
  • Yellow zone
  • Red zone (correct)

What percentage of the projected area is used for calculating wind loading for fabricated structures?

<p>150% (B)</p> Signup and view all the answers

What should be checked for the safety of masts and portals according to the specified conditions?

<p>Temperature and wind pressure (B)</p> Signup and view all the answers

What is the maximum influence on the span length due to conditions in overhead equipment erection?

<p>Blow-off of overhead equipment (D)</p> Signup and view all the answers

What is the prescribed method for accurately measuring spans?

<p>Using a steel tape (C)</p> Signup and view all the answers

Which drawing number corresponds to conventional Over Head Equipment (OHE) standards?

<p>Drg.No.ETI/OHE/G/00202 (B)</p> Signup and view all the answers

What profile is adopted for conductor loading calculations?

<p>2/3rd of the projected area (B)</p> Signup and view all the answers

What is the fundamental aim of the design of overhead equipment?

<p>To install the contact wire at the requisite height. (B)</p> Signup and view all the answers

What type of bond is used to connect two rails of a track?

<p>Bond, Cross (A)</p> Signup and view all the answers

Which component keeps the overhead catenary system in position?

<p>Cantilever (B)</p> Signup and view all the answers

What is the purpose of a rail bond used for maintaining continuity?

<p>To ensure constant electric current flow at junctions. (A)</p> Signup and view all the answers

What structural member is insulated from the mast by a stay arm insulator?

<p>Bracket tube (B)</p> Signup and view all the answers

Which type of rail bond is specifically designed for electric traction in ac track circuited sections?

<p>Bond, Impedance (C)</p> Signup and view all the answers

Which features should be considered when preparing layout plans for overhead equipment?

<p>Technical and economic implications. (A)</p> Signup and view all the answers

What is the maximum speed for which a short neutral section of ceramic beaded resin bonded glass fibre rod insulators is considered fit?

<p>130 km/h (C)</p> Signup and view all the answers

What is the minimum distance a neutral section should be located from a stop signal?

<p>400 m (A)</p> Signup and view all the answers

If a neutral section is placed before a stop signal, what is the required distance to ensure the train does not cross the signal?

<p>1600 m (A)</p> Signup and view all the answers

In which scenario can a different arrangement for neutral section location be directed by the Chief Electrical Engineer?

<p>When complying with guidelines is difficult or costly (C)</p> Signup and view all the answers

What is the primary type of equipment recommended for points and crossings?

<p>Overlap type (D)</p> Signup and view all the answers

What is the maximum length difference allowed between two consecutive spans on main tracks?

<p>18 m (A)</p> Signup and view all the answers

What should the axial distance between the Catenary and the contact wire at the minimum dropper not be less than when lengths of spans have unequal encumbrances?

<p>150 mm (D)</p> Signup and view all the answers

Which of the following is a type of mast used for OHE conductors?

<p>K-150 (B)</p> Signup and view all the answers

In the vicinity of over line structures, spans should be determined with reference to what?

<p>Electrical clearances (A)</p> Signup and view all the answers

What is the restriction for anchor spans when using crossed type equipment at facing turnouts?

<p>54 m (A)</p> Signup and view all the answers

Which of the following types of masts can be used in lieu of K-Series masts?

<p>B-series (B)</p> Signup and view all the answers

What is the maximum span over level crossings where an earth wire is provided?

<p>58.5 m (A)</p> Signup and view all the answers

How many types of masts are designated for use in OHE installations?

<p>Nine (C)</p> Signup and view all the answers

Which of the following is NOT a stated condition for determining span lengths with unequal encumbrances?

<p>Both ends must be the same length (A)</p> Signup and view all the answers

What is the maximum length for spans loaded with section insulators according to the mentioned restrictions?

<p>Variable with context (B)</p> Signup and view all the answers

What determines the bearing capacity of the soil for foundation placement?

<p>Soil type and location of measurement (C)</p> Signup and view all the answers

Which type of foundation is specifically mentioned for black cotton soil?

<p>Pure gravity foundation (A)</p> Signup and view all the answers

How does placing a foundation on the slope of banks affect bearing capacity?

<p>Decreases the bearing capacity (A)</p> Signup and view all the answers

What is the primary function of volume charts in foundation selection?

<p>To select foundation type and size based on FBM code (B)</p> Signup and view all the answers

Which of the following foundation types is designed specifically for use in hard rock?

<p>Foundations in hard rock (C)</p> Signup and view all the answers

What should be ensured when constructing foundations in deep rock cutting?

<p>They are installed below the drain (A)</p> Signup and view all the answers

What is the bearing capacity of foundations in soft rock?

<p>45000 kg/m2 (B)</p> Signup and view all the answers

Which type of foundation does NOT fall under the category for OHE mast and portals?

<p>Deep pilings foundation (A)</p> Signup and view all the answers

What is indicated by the drawing number ETI/C/0058?

<p>Side bearing foundation types (D)</p> Signup and view all the answers

What characteristic does a 'New pure gravity foundation' for black cotton soil have?

<p>500 mm exposure (B)</p> Signup and view all the answers

What is the maximum stagger of the contact wire at supports on curved tracks?

<p>300 mm (A)</p> Signup and view all the answers

How is the stagger of the catenary determined on curved track?

<p>With reference to Drg.No.ETI/OHE/G/00202. (A)</p> Signup and view all the answers

What is the stagger limit for the contact wire of the branching line at turnouts?

<p>300 mm (C)</p> Signup and view all the answers

What is the stagger requirement for un-insulated overlaps on tangent track?

<p>200 mm (C)</p> Signup and view all the answers

In which situation is stagger at mid-span allowed to exceed permissible values?

<p>In difficult locations with requisite clearances. (A)</p> Signup and view all the answers

What is the minimum required height for the broad gauge to allow movement of 'C' class ODCs without lifting wires?

<p>4.92 m (A)</p> Signup and view all the answers

What is the maximum allowed difference in height of the contact wire at two adjacent supports?

<p>20 mm (B)</p> Signup and view all the answers

What is the maximum gradient allowed for a change in contact wire height on main lines?

<p>3 mm/m (D)</p> Signup and view all the answers

What is the minimum height of contact wire required at electric locomotive sheds for broad gauge?

<p>5.80 m (B)</p> Signup and view all the answers

What provision should be made for possible future lifting of track according to the specifications?

<p>275 mm (A)</p> Signup and view all the answers

What stagger distance is typically given to the contact wire on tangent track?

<p>200 mm (C)</p> Signup and view all the answers

What is the maximum gradient that can be tolerated for contact wire on sidings?

<p>10 mm/m (B)</p> Signup and view all the answers

What is the minimum height at level crossings for both broad and metre gauges?

<p>5.50 m (C)</p> Signup and view all the answers

What maximum tolerance is allowed for height measurements at a point of support near an over bridge?

<p>10 mm (C)</p> Signup and view all the answers

What is the maximum height that can be reduced if rolling stock higher than 4.265 m is not allowed on the lines?

<p>4.65 m (C)</p> Signup and view all the answers

What is the primary purpose of maintaining electrical continuity in rail bonds?

<p>To enable effective current return in AC traction systems (A)</p> Signup and view all the answers

Which structural member is specified to support the overhead catenary system without interfering with the pantograph?

<p>Stay arm (A)</p> Signup and view all the answers

Which type of rail bond is particularly utilized to bridge an insulated joint in AC track circuits?

<p>Impedance bond (A)</p> Signup and view all the answers

In terms of structural integrity, what is the significance of the stay arm insulator in the cantilever assembly?

<p>It maintains electrical insulation between the arm and mast (D)</p> Signup and view all the answers

What defines the optimal working height for the contact wire in overhead equipment design?

<p>Efficiency in current collection under all conditions (D)</p> Signup and view all the answers

Which of the following statements accurately reflects the principles for layout plans in overhead equipment design?

<p>They allow for customization based on project-specific evaluations. (A)</p> Signup and view all the answers

What is the function of the bond structure in relation to overhead equipment?

<p>To electrically connect the steel infrastructure to the track return (A)</p> Signup and view all the answers

What is the primary role of a paralleling interruptor in overhead equipment systems?

<p>To connect overhead equipment of different tracks (D)</p> Signup and view all the answers

Which of the following accurately describes a jumper?

<p>An arrangement of conductors for electrical continuity (D)</p> Signup and view all the answers

What defines a neutral section in overhead equipment?

<p>An insulated dead section separating two power phases (D)</p> Signup and view all the answers

In what condition is an overlap arrangement used in overhead equipment?

<p>To provide a smooth passage for pantographs over a short distance (D)</p> Signup and view all the answers

What is the main function of masts in an overhead equipment system?

<p>To support and stabilize the overhead equipment (D)</p> Signup and view all the answers

What characterizes insulated overlaps in overhead equipment?

<p>They separate conductors by 500 mm in air (A)</p> Signup and view all the answers

Which statement accurately describes the function of the pantograph?

<p>It collects electrical current from the overhead equipment (D)</p> Signup and view all the answers

What is the role of the sectioning interruptor within an overhead equipment system?

<p>To connect adjacent sub-sectors to maintain continuity (D)</p> Signup and view all the answers

Which of the following best defines overhead equipment (OHE)?

<p>The entire assembly of electrical conductors and fittings over the track (A)</p> Signup and view all the answers

What drawing number should be referred to for selecting masts in light wind pressure conditions for Composite OHE?

<p>ETI/C/0701 (B)</p> Signup and view all the answers

What is the permissible maximum span for masts in the medium wind pressure zone?

<p>63 m (B)</p> Signup and view all the answers

For structures on long bridges exceeding 150 m, what wind pressure should not be reduced due to height?

<p>200 kg/m2 (A)</p> Signup and view all the answers

Which drawing number pertains to the permissible bending moments for masts?

<p>ETI/SK/C/122 (C)</p> Signup and view all the answers

Which catenary type must be used in applications with a 1000 tension in each conductor?

<p>Composite OHE (C)</p> Signup and view all the answers

What is the maximum reduction of the wind pressure factor allowed within 100 m of a bridge abutment?

<p>25% (C)</p> Signup and view all the answers

On which drawing is the standard setting distance specified for mast employment schedules?

<p>ETI/IHE/G/00111 (B)</p> Signup and view all the answers

What is the purpose of separate mast employment schedules?

<p>To provide guidelines for various wind pressure zones (D)</p> Signup and view all the answers

What is the effective wind pressure for heavy wind pressure zones for designing masts?

<p>200 kg/m2 (A)</p> Signup and view all the answers

What type of OHE is designated for masts under heavy wind pressure at 150 kgf/m2?

<p>Conventional OHE (C)</p> Signup and view all the answers

Flashcards

Bond

An electrical connection across a joint in or between adjacent lengths of rail.

Bond (Continuity)

A rail bond used to maintain continuous rail circuit at crossings and junctions.

Bond (Cross)

A rail bond connecting rails of a track or adjacent tracks.

Bond (Impedance)

A special rail bond used to bridge insulated rail joints for AC track circuits.

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Cantilever (Assembly)

An insulated support structure for the overhead catenary system.

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Stay arm

Part of a cantilever assembly, made of steel tubes, supporting catenary.

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Overhead Equipment Layout Plans

Diagrammatic representations of overhead contact wire systems for railways.

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Wind Pressure Design

Wind pressures for overhead equipment are based on IS-875-1964, with reduced pressures for structures under 30m.

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Wind Pressure Zones

Structures are categorized into green (light), yellow (medium), and red (heavy) zones based on wind intensity.

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Projected Area Calculation

For wind load calculations, different multipliers are applied to projected areas for rolled sections, fabricated structures, and circular members.

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Temperature Impact

Mast and portal safety is evaluated at 35°C and full wind pressure, and then at 4°C and 20% of the maximum wind pressure.

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Span Measurement

Spans are precisely measured using steel tapes, following specific guidelines for curves and number of tracks.

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Standard Spans

Standard span diagrams (drawings) guide the span determination based on different OHE (Overhead Equipment) types.

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Span Optimization

Span size should be as large as feasible, ensuring acceptable stagger and considering the equipment's stability.

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Stagger Limit

The allowed vertical difference between contact wire supports.

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Protection for Exposed Areas

Structures lacking obtained clearance should be protected by metal screens or warning boards.

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Mid-span stagger

The difference in vertical position of the mid-span points of two adjacent catenary spans.

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Stagger at common support

The difference in vertical position of the catenary wire at the point where two spans meet.

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Stagger at extreme supports

The difference in vertical position of the catenary wire at the supports furthest away from the common support.

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Span lengths: maximum difference

The maximum allowable difference in length between two consecutive spans on the main track is 18 meters.

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Unequal encumbrances: span length

Span lengths with unequal encumbrances must maintain a minimum vertical distance of 150 mm between the catenary and the contact wire.

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Over line structures: span length

Span lengths near over line structures with restricted headroom are determined by the available electrical clearances.

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Section insulators: span length

Span lengths loaded with section insulators may require specific restrictions, as specified in paragraph 3.11.

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Non-standard spans

Spans with lengths different from standard values can be adopted in challenging locations.

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Crossed type equipment: anchor span

Anchor spans for crossed type equipment at facing turnouts are restricted to 54 meters.

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Earth wire: maximum span

The maximum span for catenary with an earth wire over level crossings is 58.5 meters.

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Short Neutral Section (PTFE)

A short section of track where the overhead contact wire is disconnected, typically used to allow trains to coast without drawing power. It uses PTFE material and is suitable for speeds up to 130 km/h.

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Neutral Section Location

Neutral sections should be located away from stop signals, level crossings, and on tangent track as much as possible.

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Neutral Section after Stop Signal

If a neutral section follows a stop signal, the distance between them must allow trains to accelerate from a stop and safely coast through the neutral section.

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Neutral Section before Stop Signal

When a neutral section is placed before a stop signal, the distance must prevent trains from crossing the signal while attempting to coast through the neutral section.

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PTFE Neutral Section Location

PTFE-type short neutral sections are typically located on level tangent track, at least 400 meters after a stop signal and 200 meters before it.

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Foundation Bending Moment (FBM)

A measure of the bending force on a foundation, determined by the mast's loading and its position in the mast employment schedule or by calculations.

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Bearing Capacity

The maximum weight a soil can support without failing, determined at the foundation's outer toe and also on slopes.

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Volume Chart

A diagram used to select the appropriate type and size of foundation based on FBM, soil conditions (bearing capacity and shoulder width), and desired projection above ground level.

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Side Bearing Foundation

A type of foundation for OHE masts and portals that supports the mast through a horizontal side contact.

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Side Gravity Foundation

A foundation with a slanted surface that supports the mast by its weight through the inclined side.

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Pure Gravity Foundation

A foundation that supports the mast entirely by its weight, with no lateral support.

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Pure Gravity Foundation (Black Cotton Soil)

A specialized pure gravity foundation designed for black cotton soil, a type known for its expansive properties.

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New Pure Gravity Foundation (NG or SPL)

A newer type of pure gravity foundation, adapted for a variety of soil conditions and designed for different site requirements.

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Foundations in Soft Rock

Foundations designed for softer rock formations, with a bearing capacity of 45,000 kg/m2.

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Foundations in Hard Rock

Foundations designed for hard rock formations, with a high bearing capacity of 90,000 kg/m2.

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What is a Bond (continuity)?

A type of rail bond used to maintain a continuous electrical path at crossings and junctions, ensuring uninterrupted flow of current.

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What is a Cantilever Assembly?

A specialized type of insulated support structure designed to hold the overhead catenary system in place, allowing it to adjust and move with the train's pantograph.

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What is a Stay Arm?

A component of a cantilever assembly, made of steel tubes, used to support and position the bracket tube that holds the catenary.

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What is Wind Pressure Design?

The process of designing overhead equipment structures considering wind forces based on Indian Standard IS-875-1964, with adjustments for structures under 30 meters.

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What are Wind Pressure Zones?

Categorization of structures based on wind intensity, with zones classified as 'Green' (light), 'Yellow' (medium), and 'Red' (heavy) to denote the expected severity of wind pressure.

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What is Span Measurement?

The precise measuring of the distance between support structures for the overhead catenary system using steel tapes, with specific guidelines for curves and multiple tracks.

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What are Standard Spans?

Predefined span lengths for overhead equipment, categorized by type and design, which provide guidance for determining the optimal span size for each type.

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Sectioning Interrupter

An electrical switch that connects adjacent sections of overhead equipment to maintain a continuous power supply. It typically stays closed for uninterrupted service.

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Paralleling Interrupter

A switch that connects overhead equipment on two different tracks, typically used to reduce voltage drop. It usually remains closed for efficient power distribution.

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Jumper

A conductor or set of conductors used to provide electrical continuity between two components, not under electrical tension. It acts as a bridge for power flow.

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Mast

A sturdy vertical support embedded in the ground or rigidly fixed to hold overhead equipment. It can be made from rolled sections or fabricated materials.

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Neutral Section

A short, insulated segment of overhead equipment that separates sectors fed by two different substations. It allows for different phases to be isolated.

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Overhead Equipment (OHE)

All the electrical conductors above the track, including supporting structures, insulators, and other components that deliver power to trains.

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Overlap

A portion of overhead equipment where two sets of conductors run parallel to each other for a short distance, allowing a smooth transition for the pantograph. This provides redundancy and smoother electrical contact.

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Pantograph

A collapsible device mounted on a train's roof, specifically designed for collecting electrical power from overhead equipment.

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Over-line Structure

Any fixed structure that exists above a track. It must provide sufficient overhead clearance for safe train operation.

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Mast Employment Schedules

Tables that specify the appropriate mast types to use based on wind pressure zone, OHE type, and setting distance.

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Permissible Bending Moments

The maximum amount of bending force a mast can withstand before failure, specified in a separate document.

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Mast Design for Bridges

Masts on bridges longer than 150 meters or higher than 30 meters use full wind pressure for design, regardless of wind pressure zones.

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Maximum Span Limits

The longest distance allowed between masts, varying based on wind pressure zone. For heavy zones: 54m; for medium zones: 63m.

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Span Reduction in Curves

On curved sections of bridges, the maximum span is reduced by 4.5 meters due to increased wind loads.

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Conventional OHE

Overhead equipment using standard 65 mm2 copper catenary and 107 mm2 copper contact wire, commonly used in railways.

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Composite OHE

Overhead equipment composed of aluminum alloy catenary and 107 mm2 copper contact wire with 1000 tension.

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Standard Setting Distance

A specific distance between mast supports, defined in a standard drawing, used for selecting mast types.

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Load Calculations for Non-Standard Locations

Masts in locations like turnouts, diamond crossings, or umbrella-type OHE require individual load calculations.

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Catenary Stagger

The vertical difference between the contact wire at supports in the overhead catenary system.

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Stagger on Tangent Track

On straight tracks, the catenary stagger is zero for single-equipment support masts, but fixed vertically over contact wire for multi-equipment supports, flexible head spans, and reduced encumbrance supports.

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Stagger on Curved Track

On curves, the contact wire stagger should not exceed 300mm, determined by the drawing ETI/OHE/G/00202. Standard values are 0, +200, -200.

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Stagger at Turnouts

At turnouts (track switches), the main track contact wire stagger follows ETI/OHE/G/00202, and the branching line stagger should not exceed 300mm. Mast placement or contact wire crossing adjustment ensures this.

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Stagger at Un-insulated Overlaps

At un-insulated overlaps, the stagger is determined by drawing RE/33/G/02121, sheet 1. On non-uniform curves, the in-running contact wire stagger should not exceed 200mm on tangent and 300mm on curves.

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Minimum Height (Broad Gauge)

The minimum required vertical clearance for overhead equipment on broad gauge tracks is 4.92 meters to allow movement of 'C' class ODCs without lifting wires, but can be reduced to 4.80 meters without 'C' class ODC movement.

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Minimum Height (Metre Gauge)

The minimum vertical clearance for overhead equipment on metre gauge tracks is 4.02 meters for 'C' class ODCs. It can be reduced to 4.65 meters if rolling stock higher than 4.265 meters is not allowed.

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Electric Loco Shed/Pit Height

The minimum vertical clearance at electric locomotive sheds and inspection pits is 5.80 meters for broad gauge and 5.50 meters for metre gauge.

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Level Crossing Height

The minimum height for overhead equipment at level crossings is 5.50 meters for both broad and metre gauges.

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Contact Wire Tolerance

A tolerance of 20 mm (except at over bridges) is allowed for the height of contact wire at each support point, with a maximum difference of 20 mm between adjacent supports.

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Contact Wire Gradient

The change in contact wire height should be gradual, with a maximum slope of 3 mm/m on main lines and 10 mm/m on sidings. The difference in gradient between spans should not exceed 1.5 mm/m on main lines and 5 mm/m on sidings.

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Track Raising Provision

Overhead equipment must accommodate a potential track raising of 275 mm due to future track strengthening or concrete sleepers.

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Span Length (Max Difference)

The maximum allowable difference in length between two consecutive spans on the main track is 18 meters.

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Study Notes

Overhead Equipment Principles

  • These principles standardize overhead equipment layout plans for railway electrification projects.
  • Some principles are obligatory, others are best practice solutions based on cost and technical merit.
  • Overhead equipment design prioritizes installing the contact wire at the correct height for pantograph operation.

Definitions

  • Bond: An electrical connection across a rail joint.

    • Bond, continuity: Maintains rail circuit continuity at crossings and junctions.
    • Bond, cross: Connects rails on a single or adjacent track.
    • Bond, impedance: Used to bridge insulated rail joints in AC traction tracks.
    • Bond, rail: An electrical connection between adjacent rail sections as part of the track circuit.
    • Bond, structure: Connects track structure and the overhead equipment to the track return circuit.

  • Cantilever (assembly): An insulated, swiveling structural member supporting the overhead catenary system.

    • It facilitates current collection by the pantograph.
    • Made of steel tubes with various sizes.
      • Stay arm, with adjuster, keeps the bracket in place and insulates it from the mast.
      • Bracket tube, keeps the catenary supported.
      • Standardizes current collection by the pantograph at all speeds without obstructing the structural members.

  • Other terms in the document are from General and Subsidiary Rules / ac Traction Manual; these have standard meanings unless stated otherwise.

  • Crossings: Electrically live members crossing each other without physical contact.

    • Power line crossing: An electrical transmission or distribution line crossing the tracks.
    • Crossing OHE: Intersection of two OHE conductors without physical contact.

  • Dropper: A fitting that supports the contact wire from the catenary.

  • Electrical Clearance: Distance in air between live equipment and the nearest earthed part.

  • Encumbrance: The axial distance in the vertical plane between the catenary and contact wire at its mounting support.

  • Feeder: A conductor that connects a substation/feeding post to the overhead equipment (OHE).

  • Height of contact wire: The distance from rail level to the under-side of the contact wire.

  • Interrupter: A single-phase vacuum SF/oil circuit breaker utilized as a load switch, closing circuits during faults but not opening them.

  • Bridging Interrupter: An interrupter positioned in the neutral section to provide a feed from one substation to the OHE during emergencies or if the other substation is out of use.

  • Jumper: A conductor or arrangement of conductors enabling electrical continuity between electrical conductors or equipment.

  • Mast: A vertical support structure for overhead equipment (typically fabricated or rolled sections).

  • Neutral Section: A short, insulated section of OHE separating sectors of power fed by distinct substations.

  • Overlap: A structure wherein two sets of conductors run parallel for short distances to avoid pantograph interference.

  • Pantograph: A device on trains that collects electricity from OHE contact wires.

  • Return Conductor: The conductor that returns current from the tracks to the substation.

  • Regulating Equipment: A device maintaining constant OHE conductor tension regardless of varying temperatures.

  • Setting Distance: The horizontal distance from the nearest traction mast face to the centre line of the track.

  • Span: The distance between adjacent supporting masts of overhead equipment lines.

  • Stagger: The horizontal distance of the contact wire from the vertical plane through the centre of the track.

  • Section Insulator: A device insulating portions of the contact wire for maintaining continuous electrical current flow while isolating different portions of the wire.

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Related Documents

OHE-34-96 PDF - Principles for Layout Plans and Sectioning Diagrams for 25 KV AC Traction

Description

This quiz focuses on the calculations and standards related to wind pressure on structures, especially those under 30 meters, after the 1971 amendment. It will address specific questions about span measurements and safety checks necessary for masts and overhead equipment. Test your knowledge on wind loading calculations and related standards!

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