Recommendations for design and construction of port and harbour components, Part 4: Slipways

IS 10020 Part 4: Scope Summary

• Scope: Covers recommendations for planning, design, and construction of slipways (Clause 3.1).
• Definitions: Refer to IS 7314-1974 for terminology (Clause 2.1).
• Rounding Off: Final test/calculation values should be rounded as per IS 2-1960, maintaining significant figures equal to specified values (Clause 0.5).
• International Coordination: Standard aligns with global practices and Indian field experience (Clause 0.4).

Key Points:

This part does not provide direct formulas or tables but sets the framework and references for detailed design and construction guidelines. For detailed design formulas, refer to subsequent clauses or related parts of IS 10020.

IS 10020 Part 4 — Site Investigations (Clause 3.2 & 3.2.3)

Key Points:

• Site investigations must include topographic, oceanographic, and soil data.
• Data collection should follow IS 4651 (Part 1) - 1974 guidelines.
• This ensures adequate understanding of soil strata, groundwater, and seabed conditions for port and harbour design.

Essential Data to Collect (per IS 4651 Part 1):

• Topographic surveys: Elevation, contours, and site layout.
• Oceanographic data: Tides, wave heights, currents, sediment transport.
• Soil investigations: Borehole logs, Standard Penetration Test (SPT) values, soil classification, groundwater table.

Typical Site Investigation Parameters:

Basic Formula for Bearing Capacity (Terzaghi’s for shallow foundations):

[ q_u = c N_c + \sigma' N_q + 0.5 \gamma B N_{\gamma} ]

• (q_u) = ultimate bearing capacity
• (c) = cohesion
• (\sigma') = effective overburden pressure
• (\gamma) = unit weight of soil
• (B) = foundation width
• (N_c, N_q, N_\gamma) = bearing capacity factors (from tables)

flowchart LR
    A[Site Investigation] --> B[Topographic Survey]
    A --> C[Oceanographic Survey]
    A --> D[Soil Investigation]
    D --> E[Borehole Drilling]
    D --> F[SPT & CPT Tests]
    D --> G[Groundwater Monitoring]

Summary: Follow IS 4651 Part 1 for comprehensive data collection on site conditions essential for safe port and harbour design under

IS 10020 Part 4: General Design Considerations for Slipways

Key Points from Clause 4.4.3:

• Cradle Load Design:
  Design the cradle for the higher load from either:

  • Suez load calculation, or
  • Load distribution method.

• Slipway Design:

  • For the upper 2/3 length of the slipway, design for the higher load (Suez or load distribution).
  • For the lowest 1/3 length, design only for the weight of the cradle.

• Purpose:
  Ensures safety for:

  • Various vessel sizes/types
  • Unexpected loads
  • Different tide positions

General Design Considerations Summary:

Practical Notes:

• Always consider dynamic effects due to vessel movement.
• Factor in environmental loads like tides and waves.
• Use safety factors as per IS codes for structural reliability.

graph LR
A[Cradle] -->|Design Load| B{Max(Suez Load, Load Distribution)}
C[Slipway Upper 2/3] -->|Design Load| B
D[Slipway Lower 1/3] -->|Design Load| E[Weight of Cradle Only]

This approach ensures robust design accommodating all operational and environmental scenarios.

IS 10020 Part 4: Slipway Design Key Points

1. Slipway Length Formula (Clause 4.1.1)

The slipway length ( L ) accounts for vessel size, slip slope, draft, and block height:

[ L = l + s \times d + h ]

Where:

• ( L ) = length of slipway (m)
• ( l ) = length of vessel between perpendiculars (m)
• ( s ) = horizontal distance per unit rise (slope factor)
• ( d ) = draft of vessel at forecastle bulkhead (m)
• ( h ) = height from rail level to top of blocks (m)

2. Slipway Slope (Clause 4.2)

• Recommended slope range: 1 in 12 to 1 in 30
• Optimum slope: 1 in 15
  This slope ensures smooth launching and hauling.

3. Cradle and Roller Arrangement (Clause 3.5.5)

• Broadside slipways benefit from vertical curves for load distribution.
• Typical cradle has 12 rollers per roller frame.
• Roller frames distribute vessel weight evenly during slipping.

4. Typical Slipway Components (from figures)

• Headblock and winch at the top.
• Downhaul extension for controlling cradle movement.
• Cross-section includes rollers supporting the cradle.

flowchart LR
    Vessel_Length[l = length of vessel]
    Draft[d = draft of vessel]
    Block_Height[h = height of blocks]
    Slope_Factor[s = horizontal distance per unit rise]

    Vessel_Length --> L[Slipway Length L = l + s*d + h]
    Draft --> L
    Block_Height --> L
    Slope_Factor --> L

Summary: Design slipway length using vessel size and slope parameters; maintain slope ~1:15; use roller cradles with multiple rollers for load support.

IS 10020 Part 4 - Foundations Summary

Key Specifications:

• Good Bearing Soil (Clause 4.5.2):

  • Use spread foundations or mattress construction under tracks.
  • Connect by a concrete floor.
  • Provide a sheet pile cut-off wall at water-end to prevent scour undermining.

• Low Bearing Capacity Soil (Clause 4.5.3):

  • Use piled foundations.
  • Rail track supported on mild steel sections spanning pile bents.
  • Pile caps must be reinforced concrete to secure steelwork.

• General (Clause 3.1.3):

  • Soil bearing capacity must prevent undue settlement.

Typical Design Considerations:

• Bearing Capacity (q_allow) must satisfy:

  [ q_{allow} \geq \frac{P}{A} ]

  Where:

  • (P) = Load on foundation
  • (A) = Area of foundation base

• Spread Foundation Dimensions:

• Piled Foundation:
  • Pile length depends on soil strata.
  • Pile cap designed for load transfer and steel fixing.

Protection Against Scour:

flowchart LR
    Soil[Soil with good bearing capacity]
    Spread[Spread Foundation or Mattress]
    Concrete[Concrete Floor]
    SheetPile[Sheet Pile Cut-off Wall]
    WaterEnd[Water-end]

    Soil --> Spread
    Spread --> Concrete
    Concrete --> WaterEnd
    WaterEnd --> SheetPile
    SheetPile -. Protects against .-> Spread

Note: Always verify soil investigation reports and apply factor of safety as per IS codes.

IS 10020 Part 4 — Cradle Design Key Points

1. Cradle Types (Clause 3.6.2)

• Rigid Cradle: Fixed geometry, no flexibility.
• Semi-rigid Cradle (3.6.4): Allows slight movement; partially flexible.
• Telescopic/Collapsible Cradle: Adjustable length to accommodate movement.

2. Cradle Supports (Clause 3.6.6)

• Must provide stable support to the pipe.
• Designed considering load transfer, thermal expansion, and vibration.
• Support spacing and load capacity depend on pipe size and weight.

3. Design Considerations

• Selection depends on the support system:
  • Live roller system: Allows axial movement, reduces friction.
  • Wheel and bearing system: Supports rotation and movement.

4. Typical Design Formula for Load on Cradle

[ P = W + F_{thermal} + F_{dynamic} ]

• P = Total load on cradle
• W = Weight of pipe and contents
• F_thermal = Thermal expansion force
• F_dynamic = Dynamic or impact forces

5. Recommended Support Spacing (Indicative)

flowchart LR
    A[Pipe] --> B{Cradle Type}
    B --> C[Rigid]
    B --> D[Semi-rigid]
    B --> E[Telescopic]
    C --> F[Fixed Support]
    D --> G[Slight Movement Allowed]
    E --> H[Adjustable Length]
    F & G & H --> I[Load Transfer & Thermal Expansion]

Summary: Design cradles per IS 10020 Part 4 by selecting appropriate type, calculating total load (weight + thermal + dynamic), and spacing supports as per pipe diameter. Use live roller or wheel-bearing systems to accommodate movement.

IS 10020 Part 4: Haulage and Mooring Facilities - Key Formula

From Clause 3.7.5, the pull (P) on the hauling chain for slipways is:

[ P = W \times (S + C) ]

Where:

• P = Pull on hauling chain (tonnes)
• W = Total weight (vessel + cradle + chains & ropes) in tonnes
• S = (\tan \theta), where (\theta) = angle of slipway slope
• C = Coefficient of friction
  • 0.035 for wheels
  • 0.04 for rollers

Additional Notes:

• Ensure accurate estimation of W including all components.
• Use the correct friction coefficient based on the hauling mechanism.
• This formula helps design the hauling system capacity and select suitable chain strength.

Example Calculation:

[ P = 50 \times (0.0875 + 0.035) = 50 \times 0.1225 = 6.125 \text{ tonnes} ]

flowchart LR
    W[Total Weight (W)] -->|Multiply| M1[Multiply by (tan θ + C)]
    θ[Slipway Angle (θ)] -->|Calculate tan θ| M1
    C[Coefficient of Friction (C)] --> M1
    M1 --> P[Pull on Hauling Chain (P)]

This formula is fundamental for the design of haulage systems in port slipways per IS 10020 Part 4.

IS 10020 Part 4: Load Distribution and Calculations for Cradle and Slipway

Key Concepts:

• Load distribution on cradle depends on vessel shape, size, and volumetric displacement.
• Sue load is a concentrated load at inboard/outboard ends during hauling.
• Design for the higher load between sue load and distributed load.

Load Distribution Procedure (Clause 4.4.1):

1. Segment vessel below light draft waterline.
2. Calculate volume of each segment (including overhangs).
3. Multiply volumes by specific gravity of seawater (≈1.025) to get load per segment.
4. Plot load distribution curves along keel length.
5. Envelope all curves for different vessels → design load diagram.
6. Loads + cradle self-weight transferred at cradle wheel points.

Sue Load Calculation (Clause 4.4.2.3):

Design Specification (Clause 4.4.3):

• Design cradle for maximum of sue load or distributed load.
• Except for lowest 1/3 length, design slipway for max load.
• Lowest 1/3 cradle length designed for cradle weight only.

Summary Table: Load Calculation Parameters

IS 10020 Part 4 (1981) – Construction Methods Key Points

• Footing Specification:

  • 1.5 m wide wall footing with a 10 cm concrete slab over slope (Clause 1.5).

• Foundation Types (Clause 4.5.2):

  • In soils with good bearing capacity, use spread foundations or mattress construction under tracks.
  • These should be connected by a concrete floor slab for load distribution.
  • Provide a sheet pile cut-off wall at the water-end to prevent scour undermining.

Typical Construction Method Summary:

Notes:

• Spread foundations are shallow foundations distributing load over a wide area.
• Mattress foundations consist of a grid of beams or slabs for uniform load transfer.
• Scour protection is critical in marine environments to prevent foundation failure.

flowchart LR
    A[Good Soil Bearing Capacity] --> B[Spread Foundation]
    A --> C[Mattress Foundation]
    B & C --> D[Concrete Floor Slab]
    D --> E[Sheet Pile Cut-off Wall (Water-end)]
    E --> F[Protection Against Scour]

This ensures structural stability and durability in port and harbour constructions.

IS 10020 Part 4 (1981) primarily deals with Operational Guidelines for prestressed concrete.

Key Points:

• Definitions refer to IS 7314-1974 for standard terms.
• The code emphasizes safe operation of prestressing systems, including tensioning, anchorage, and release.
• Operational checks include verifying prestressing forces, losses, and equipment calibration.

Typical Operational Guidelines (based on standard practice):

• Tensioning Force (P):
  [ P = A_p \times f_{pu} ] Where:

  • ( A_p ) = Area of prestressing steel
  • ( f_{pu} ) = Ultimate tensile strength of prestressing steel

• Losses to consider:

  • Elastic shortening
  • Creep and shrinkage of concrete
  • Relaxation of steel
  • Friction losses in tendons

Example Table: Prestressing Force Losses

Summary:

• Follow IS 7314 for definitions.
• Maintain tensioning within specified limits.
• Account for all losses to ensure effective prestress.

flowchart TD
    A[Tensioning] --> B[Check Equipment]
    B --> C[Apply Prestress Force]
    C --> D[Monitor Losses]
    D --> E[Adjust for Losses]
    E --> F[Final Anchorage]

For detailed operational steps, refer to IS 10020 Part 4 and IS 7314.

IS 10020 Part 4 (1981) - Maintenance and Safety: Key Points

The code primarily focuses on slipway design, with some safety and maintenance considerations embedded:

Key Specifications:

• Wall Footing: 1.5 m wide footing with a 10 cm concrete slab over slope for structural stability.
• Slipway Clearance: Provide 60 cm clearance above vessel draft for safe slipping of damaged/waterlogged vessels (Clause 4.1.1.2).
• Rounding off Values: Follow IS 2-1960 for rounding off numerical test results to maintain accuracy and consistency.

Maintenance & Safety Recommendations:

• Ensure clearance allowance to prevent vessel damage during slipping.
• Use adequate concrete slab thickness (10 cm) over slope for durability.
• Regular inspection and upkeep of slipway surfaces and turntable arrangements (e.g., Fig. 7) to avoid operational hazards.
• Follow international best practices adapted to local conditions.

Summary Table:

flowchart LR
    A[Slipway Design] --> B[Wall Footing: 1.5 m wide]
    B --> C[Concrete Slab: 10 cm over slope]
    A --> D[Clearance: 60 cm over vessel draft]
    A --> E[Maintenance: Regular inspection]
    A --> F[Safety: Follow IS 2-1960 rounding]

For detailed structural design and safety, refer to full IS 10020 Part 4 text and related IS codes on concrete and slipway construction.