Manual for Grade Separators and Elevated Structures
2010 Edition

Overview of Scope

• Clause 2 (Scope, Page 2): Defines the coverage of design, construction, and maintenance aspects of bridge lighting and related road structures.

• Clause 15.1.2 (Design Inputs): Specifies requirements for lighting design data from manufacturers, including:

  • Spectral distribution (polar) curves
  • Iso-Candela diagrams
  • Iso-Lux spacing charts
  • Iso-Luminance diagrams
  • Utilization coefficients

• Clause 8.1 (Material Specifications): Details the standards materials must adhere to, aligned with IRC guidelines.

Summary Table:

This framework ensures a thorough approach from initial design through maintenance, highlighting manufacturer data for lighting and quality materials for construction.

flowchart LR
    A[Scope: Bridge Lighting & Structures] --> B[Design Input Requirements]
    B --> C[Manufacturer Data]
    C --> D[Spectral Distribution Curves]
    C --> E[Iso-Candela Diagrams]
    C --> F[Iso-Lux Charts]
    C --> G[Iso-Luminance Diagrams]
    C --> H[Utilization Coefficient]
    A --> I[Material Standards (Clause 8.1)]

Essential Specifications and Design Recommendations for Foot Over Bridges (IRC SP 90)

1. Load Criteria

• Design for crowded pedestrian load of 500 kg/m² as per IRC:6 (Section II).
• Account for dynamic effects caused by pedestrian movement and occasional cycles or animals.

2. Clearance Standards

• Vertical and lateral clearances should comply with IRC:5.
• Minimum vertical clearance above carriageways is generally 5.5 m (see IRC:5 or IRC:54 for underpasses).

3. Structural Types

• Structures exclusively for pedestrians.
• Typical forms include steel trusses, RCC slabs, prestressed girders, and composite types.
• Design according to IRC:21 (RCC), IRC:24 (Steel), and IRC:22 (Composite).

4. Geometric Layout

• Width depends on expected pedestrian traffic, commonly ranging from 3.0 m to 4.5 m.
• Ramps and stairs designed for accessibility without blocking footpaths.
• Entry and exit points should maintain pedestrian flow and avoid encroachment.

5. Applicable IRC Codes

Example Calculation for Foot Over Bridge Deck Loading

[ Design Load = 500 , kg/m^2 = 5 , kN/m^2 ]

For deck width (b) and span (L):

• Uniform Load (w = 5 imes b ) kN/m
• Maximum Bending Moment (simply supported): ( M = \frac{w L^2}{8} )
• Maximum Shear Force: ( V = \frac{w L}{2} )

Diagram: Components of a Foot Over Bridge

graph TD
    A[Foot Over Bridge]
    A --> B[Deck Slab]

Primary Guidelines for Selecting Grade Separator Types (Clause 5.7):

The selection depends on a variety of factors:

• Area Characteristics: Whether urban, semi-urban, or rural influences design complexity.
• Traffic Analysis: Current and forecasted traffic volumes and vehicle mix.
• Development Plans: Anticipated urban growth or expansion.
• Road Classification: Road hierarchy affects facility choice.
• Service Level Objectives: Desired traffic flow and congestion levels.
• Local Limitations: Right-of-way constraints, utilities, environmental issues.
• Design and Cost Factors: Construction feasibility, budget, and schedule.

General Rule:

• The road with lower traffic flow or lesser significance is usually elevated over the other.
• Site-specific factors or environmental concerns may necessitate exceptions.

Decision Matrix for Facility Type

Foundation Choice (Clause 7.4.3)

• Crucial for cost and timeline.
• Options between shallow and deep foundations considered based on soil, load, and efficiency.

flowchart TD
    Start[Traffic and Site Analysis] --> Location{Urban or Rural?}
    Location -->|Urban| Complex[Complex Grade Separator]
    Location -->|Rural| Simple[Simple Grade Separator]
    Complex --> TrafficVol{Traffic Volume}
    Simple --> TrafficVol
    TrafficVol -->|High| AtGrade[At-grade or Flyover (lower traffic road)]
    TrafficVol -->|Low| Flyover[Flyover or Underpass]

Summary of Geometric Design and Clearance Requirements (IRC SP 90)

Refer to associated IRC codes and IRC:103 for detailed pedestrian and geometric design standards at grade separators.

Highlights:

• Pedestrian Facilities (Clause 5.20):

  • Ensure safe pedestrian crossings at all arms of grade separators.
  • Options include signalized crossings, pedestrian subways, and foot over bridges depending on traffic and feasibility.
  • Detailed design is covered in IRC:103.

• Geometric Design Aims (Clause 6):

  • Maximize safety and traffic efficiency at reasonable cost.
  • Follow IRC standards like IRC:73 for horizontal curves and IRC:112 for vertical curves.

Typical Geometric Parameters (per IRC):

Pedestrian Facility Dimensions (IRC:103):

• Foot Over Bridge minimum width: 1.8 m
• Pedestrian subway minimum width: 2.5 m
• Maximum ramp slope: 1:12 for accessibility

flowchart LR
    TrafficVolume & PedVolume --> FacilityTypeDecision
    FacilityTypeDecision -->|Low Pedestrian| SignalCrossing
    FacilityTypeDecision -->|Medium Pedestrian| PedSubway
    FacilityTypeDecision -->|High Pedestrian| FootOverBridge
    SignalCrossing & PedSubway & FootOverBridge --> DesignStandards[Design per IRC:103]

Structural Forms and Construction Types (Clause 7.2 of IRC SP 90)

Common Superstructure Types:

Selection depends on site conditions, budget, and practicality:

• Solid Slabs: Reinforced or prestressed concrete.
• Beam-Slab Systems: RCC beams supporting slabs, suitable when aesthetics below the deck are less critical.
• Box Girders: Offering high torsional resistance.
• Closely Spaced Beams
• Voided Slabs
• Composite Structures: Precast prestressed concrete beams or steel girders combined with in-situ RCC decks.
• Integral Structures: Rigid frame units.
• Extradosed Bridges
• Cable-Stayed Bridges

Material and Construction Standards:

• Material quality per Clause 8.1, including concrete grades and reinforcement specifications.
• Construction methods per Clause 7.3, covering casting, precasting, and prestressing processes.

Selection Factors for Structural Forms:

flowchart LR
    SiteConditions --> FormChoice
    FormChoice --> SolidSlab
    FormChoice --> RCCBeamSlab
    FormChoice --> BoxGirder
    FormChoice --> PrecastPrestressed
    FormChoice --> IntegralRigidFrame
    FormChoice --> Extradosed
    FormChoice --> CableStayed

Material Requirements and Standards (Clause 8.1 of IRC SP 90)

• Clause 8.1.8: All construction materials must comply with pertinent Indian Standards (IS codes) to guarantee quality and durability.

Key Materials and Respective IS Codes:

General Recommendations:

• Use only certified and tested materials.
• Ensure materials meet design specifications.
• Follow proper storage and handling to preserve quality.

flowchart TD
    MaterialSelection --> ISCodeCompliance{Conforms to IS Codes?}
    ISCodeCompliance -->|Yes| UseMaterial
    ISCodeCompliance -->|No| RejectMaterial
    UseMaterial --> QualityControl
    QualityControl --> Construction

Key Considerations for Embankments, Retaining Walls, and Drainage (IRC SP 90)

Embankments and Drainage Layer (Clause 9.8.9)

• Design drainage layers to prevent clogging by silt.
• Purpose is to reduce water pressure buildup and avoid embankment failure.
• Utilize well-graded granular material or geotextiles as per design.
• Regular maintenance and inspection for silt accumulation are essential.

Retaining and Return Walls (Clause 9.7)

• Walls must withstand lateral earth pressures.
• Both active and passive earth pressures considered using Rankine or Coulomb theories.
• Active earth pressure formula (Rankine):

[ P_a = \frac{1}{2} \gamma H^2 K_a ]

Where:

• (P_a): Active earth pressure
• (\gamma): Soil unit weight
• (H): Height of wall
• (K_a = \tan^2(45^\circ - \frac{\phi}{2})): Active earth pressure coefficient
• (\phi): Soil internal friction angle

Drainage Behind Walls

• Provide drainage to relieve hydrostatic pressure.
• Use perforated pipes with filter media.
• Keep outlets free from blockages.

Summary Table

flowchart LR
    SoilFill -->|Water Flow| DrainageLayer
    DrainageLayer -->|Prevents clogging| Outlet
    RetainingWall -->|Resists lateral pressure| SoilFill
    DrainageLayer -.->|Relieves pressure| RetainingWall

Construction Procedures, Scheduling, and Quality Control (Clause 10)

Highlights:

• Construction Methodology (Clause 10.1):

  • Develop a comprehensive methodology statement prior to construction.
  • Ensure compliance with design, safety, traffic regulations, and site constraints.
  • Include details of equipment, materials, and timelines for each activity.

• Quality Assurance and Control Plan (Clause 10.10):

  • Create a QA/QC plan tailored for the project.
  • Enforce strict quality checks during construction.

Recommended Content:

Quality Control Measures:

• Testing of materials (cement, aggregates, soil)
• Equipment calibration
• Monitoring workmanship
• Documentation and record maintenance

gantt
    title Project Schedule Example
    dateFormat  YYYY-MM-DD
    section Construction
    Site Preparation        :done,    step1, 2024-07-01, 10d
    Foundation Work         :active,  step2, after step1, 15d
    Superstructure Erection :         step3, after step2, 20d
    Finishing and QA        :         step4, after step3, 10d

Summary: Early planning of construction methodology and work scheduling facilitates smooth progress. A stringent quality control plan is vital for durability and compliance.

Signage and Identification Protocols (IRC SP 90)

• Reference Standard: Signage design, placement, and materials must comply with IRC:67 (Clause 13.2).

• Design and Visual Appeal (Clause 13.8):

  • Signage should be functional, visually pleasing, and elegant.
  • Size and shape must balance visibility with aesthetic harmony.

• Visibility Requirements (Clause 13.5):

  • Ensure adequate illumination during nighttime.
  • Signs must be clearly visible from appropriate distances.

Key Specifications from IRC:67

flowchart LR
    SignageDesign --> IRC67Guidelines
    IRC67Guidelines --> KeyElements
    KeyElements --> SizeAndShape
    KeyElements --> VisibilityAndLighting
    KeyElements --> AestheticConsiderations
    VisibilityAndLighting --> NightIllumination

Summary: Follow IRC:67 for detailed signage dimensions and materials. Ensure signage is legible day and night with proper lighting and reflective materials, while maintaining visual appeal.

Roadway Drainage Essentials (Clause 14 of IRC SP 90)

• Cross-Slope Drainage:

  • Provide camber (cross slope) on pavement surface to guide water to edges.
  • Typical camber ranges between 2% and 3% for bituminous surfaces.

• Longitudinal Drainage:

  • Incorporate scuppers, inlets, or drainage channels at regular intervals.
  • Dimensions and spacing designed to accommodate peak runoff from heavy rain.

• Drainage Network:

  • Prevent standing water on road or near grade separators.
  • Connect drainage outlets to the overall project drainage system for safe disposal.

Typical Parameters

Runoff Calculation Formula:

[ Q = C i A ]

Where:

• (Q) = peak runoff (m³/s)
• (C) = runoff coefficient (0.7–0.95 for paved surfaces)
• (i) = rainfall intensity (m/s)
• (A) = catchment area (m²)

flowchart LR
    PavementSurface -->|Camber directs water| EdgeDrainage
    EdgeDrainage --> Scuppers/Inlets
    Scuppers/Inlets --> DrainagePipes
    DrainagePipes --> MainDrainageSystem

Summary: Employ a 2–3% pavement camber for transverse drainage, position sufficiently sized scuppers and inlets for longitudinal drainage, and ensure proper discharge into the main drainage system to avoid waterlogging and pavement damage.

Illumination and Electrical Installation Guidelines (IRC SP 90)

1. Photometric Design Inputs (Clauses 15.1.2.6 & 15.1.2.7)

• Required inputs include:

  • Lantern mounting height and spacing.
  • Road surface photometric classification (CIE R1 to R4).
  • Lantern photometric data: spectral distributions, iso-candela, iso-lux, and iso-luminance curves.
  • Observer position and luminance fields.
  • Maintenance factor (MF).

• Maintenance Factor (MF): Accounts for lamp lumen depreciation and dirt accumulation; typically 0.75 for R3 pavement (Table 15.5).

• Voltage Drop Limit: Maximum permissible voltage drop at the last lighting pole is 3% of supply voltage.

2. Pavement Classes and Maintenance Factors (Table 15.5)

3. Illuminance Calculation:

[ E = \frac{I \times MF}{d^2} ]

where:

• (E) = illuminance on surface (lux)
• (I) = luminous intensity in candela
• (d) = distance from light source (m)
• (MF) = maintenance factor

4. Design Guidelines:

• Follow CIE standards for luminance uniformity.
• Use manufacturer's photometric data for lantern spacing and height.
• Ensure uniformity ratios meet safety standards.
• Electrical supply should be 3-phase, 380 V.

Environmental Provisions in IRC SP 90

1. Climatic and Environmental Data Collection (Clause 5.15)

• Capture annual temperature range, maximum expected wind speeds, rainfall patterns, humidity, salinity, presence of corrosive chemicals, groundwater levels, and vulnerability to storms or cyclones.
• Use this information for:
  • Structural and material design.
  • Durability assessments.
  • Drainage planning.

2. Environmental Impact and Clearance (Clause 5.19)

• Conduct environmental impact assessments prior to project commencement.
• Secure requisite environmental clearances early.
• Develop an Environment Management and Mitigation Plan addressing:
  • Plant site selection.
  • Choice of materials.
  • Construction methods minimizing pollution (air, soil, water).
  • Energy efficiency.

3. Space Allocation (Clause 6.11)

• Provide adequate space for environmental buffers, drainage, and green areas.

Environmental Design Consideration Table

flowchart TD
    ClimateDataCollection --> DesignParameters
    DesignParameters --> DurabilityAndDrainage
    ClimateDataCollection --> EnvironmentalImpactAssessment
    EnvironmentalImpactAssessment --> ClearancesAndMitigation
    ClearancesAndMitigation --> MaterialAndMethodChoice
    MaterialAndMethodChoice --> PollutionControlAndEnergySaving

Summary: Environmental and climatic data play a crucial role in design and construction to ensure durability, regulatory compliance, and minimal ecological impact as specified in IRC SP 90.

Inspection, Maintenance, and Safety Guidelines in IRC SP 90

1. Maintenance and Inspection (Clause 17)

• A comprehensive maintenance manual is mandatory for all grade separators, especially those with unique designs or site constraints.
• Manual should include:
  • Scheduled inspections.
  • Maintenance procedures.
  • Safety checks.
• Objective: Sustain structural health and safety over the lifespan.

2. Safety Requirements (Clause 12)

• Safety measures must comply with IRC standards covering:
  • Structural integrity.
  • Safe construction practices.
  • Traffic safety during maintenance.

3. Maintenance Manual Contents

• Inspection intervals (daily, monthly, yearly).
• Components to inspect (bearings, joints, decks, substructures).
• Maintenance tasks (drainage clearing, crack repair, repainting).
• Emergency response procedures.

Typical Inspection Frequency Table

Safety Checklist Highlights

• Use of barricades and warning signage during maintenance.
• Provision of personal protective equipment (PPE).
• Load restrictions during repair works.
• Emergency contact and rescue protocols.

flowchart TD
    InspectionSchedule --> IdentifyDefects
    IdentifyDefects --> SeverityAssessment{Severity?}
    SeverityAssessment -->|Minor| RoutineMaintenance
    SeverityAssessment -->|Major| UrgentRepair
    UrgentRepair --> SafetyMeasures
    RoutineMaintenance --> SafetyMeasures
    SafetyMeasures --> Reinspection