Code of practice for planning and design of ports and harbours, Part 4: General design consideration

IS 4651 Part 4 (1989) - Scope: Key Formulas, Tables & Specifications

1. Scope Overview

• Applies to design and construction of port and harbour structures.
• Covers load combinations, material specifications, and safety factors.
• Refers to related IS codes for materials and loadings.

2. Partial Safety Factors for Loads (Table 1)

Note: Some factors have alternative values (e.g., 0.9) depending on conditions.

3. Increase in Permissible Stresses & Bearing Pressure (Table 2)

IS 4651 Part 4 - Definitions: Key Formulas, Tables & Specifications

1. Partial Safety Factors for Loads (Table 1, Clause 5.1)

Note: For serviceability limit states, factors apply to short-term effects; consider creep for long-term.

2. Increase in Permissible Stresses (Table 2, Clauses 5.1 and 7.1.2)

3. Referenced Indian Standards (Annex A)

• IS 875 (Part 3): Wind Loads
• IS 1893: Earthquake Resistant Design
• IS 456: Plain & Reinforced Concrete
• IS 800: Structural Steel Design
• IS 2911: Pile Foundation Design

IS 4651 Part 4 — Loads, Forces, and Stresses Key Points

1. Loads to Consider (Clause 4.1)

• Dead Load (DL)
• Vertical Live Load (LL)
• Impact/Dynamic effects of live load
• Forces from tractive effort/breaking of vehicles, cranes, etc.
• Centrifugal forces on curves
• Earth pressure
• Hydrostatic & hydrodynamic forces
• Berthing & mooring forces
• Wind forces
• Secondary stresses (shrinkage, creep, temperature)
• Erection stage stresses
• Seismic forces

2. Partial Safety Factors (Table 1)

Note: For serviceability limit states, consider short-term effects. For long-term creep effects, only permanent parts of DL and LL are considered.

3. Design Formula (General Load Combination)

[ \text{Design Load} = \gamma_D \times DL + \gamma_L \times LL + \gamma_E \times \text{Earth Pressure} + \ldots ]

Where:

• (\gamma_D), (\gamma_L), (\gamma_E) = partial safety factors from Table 1.

4. Summary Diagram of Load Types

graph LR
  A[Loads & Forces] --> B[Dead Load]
  A --> C[Live Load]
  A --> D[Impact/Dynamic Effects]
  A --> E[Earth Pressure]
  A --> F[Hydrostatic Forces]

IS 4651 Part 4: Combination of Loads, Forces, and Stresses

1. Partial Safety Factors (Table 1)

2. Increase in Permissible Stresses (Table 2)

3. Notes

• Loads should be computed as per **IS 4651 Part 3 (1974

IS 4651 Part 4 — Method of Design: Key Points

Design Methods (Clause 6.1)

• Working Stress Method (WSM)
• Limit State Method (LSM)

Working Stress Method (Clause 7.1)

• Use permissible stresses under working loads.
• Stresses must not exceed allowable limits for materials.

Load Combinations & Partial Safety Factors (Clause 5.1, Table 1)

Summary:

• WSM: Use permissible stresses directly on working loads.
• LSM: Multiply characteristic loads by partial safety factors (γ) before design.
• Refer to Clause 5.1 Table 1 for specific γ values per load type.
• Combine loads as per IS 4651 guidelines for design checks.

flowchart TD
    A[Start Design] --> B{Select Method}
    B -->|Working Stress| C[Use permissible stresses]
    B -->|Limit State| D[Apply partial safety factors]
    D --> E[Calculate design loads]
    E --> F[Check stresses against design strength]
    C --> F
    F --> G[Design Structural Element]

This concise approach ensures safety and economy in structural design per IS 4651 Part 4.

IS 4651 Part 4: Permissible Stresses Summary

1. Basic Permissible Stresses (Clause 7.1)

• Use Working Stress Method for design until full adoption of Limit State Method.
• Permissible stresses are based on safe working loads, ensuring stresses do not exceed yield or 0.2% proof stress.

2. Increase in Permissible Stresses (Clause 7.1.2 & Table 2)

Notes:

• DL = Dead Load, LL = Live Load.
• Permissible stresses must not exceed yield stress or 0.2% proof stress.
• For wind and seismic forces, refer to IS 875 (Part 3) and IS 1893 respectively.

Visual Summary:

flowchart TD
    A[Load Combinations] --> B[Permissible Stress Increase]
    B --> C{i) DL+LL+Impact+Traction+Centrifugal}
    B --> D{ii) + Earth Pressure}
    B --> E{iii) + Hydro + Berthing/Mooring}
    B --> F{iv) +

IS 4651 Part 4 — Choice of Construction Material: Key Points

1. Increase in Permissible Stresses (Clause 7.1.2, Table 2)

2. Permissible Stresses per Material (Clause 7.1.1)

• Reinforced Concrete: IS 456 : 1978
• Prestressed Concrete: IS 1343 : 1980
• Structural Steel: IS 800 : 1984
• Timber: IS 883 : 1970
• Piles (Timber/Concrete): IS 2911 (Parts 1 & 2)

3. Partial Safety Factors for Loads (Table 1, Clause 5.1)

Corrosion Protection Measures (IS 4651 Part 4)

Key Remedial Measures (Clause 8.2.3):

• a) Protective Coatings
  • Barrier to environment; delays corrosion.
  • Important factors: coating type, application method, thickness, recoating possibility.
• b) Cathodic Protection
  • Effective for steel submerged or buried with electrolytic corrosion risk.
  • Methods: Impressed current or sacrificial anode systems.
• c) Increased Section / Reduced Stresses
  • Use thicker steel if coatings/cathodic protection not feasible.
  • Minimum thickness:
    • With cathodic protection: 6 mm
    • Without cathodic protection: 10 mm
  • Always use protective coatings in marine conditions.
• d) Use of Special Steel
  • Alloy steels (e.g., with 2% copper) reduce corrosion rate.

Additional Specifications:

• Concrete Cover (Clause 8.3.5):
  • Increase cover by 25 mm over IS 456:1978 for marine exposure (sea water, splash zone, marine atmosphere).

Summary Table: Minimum Steel Thickness in Marine Environment

Corrosion Severity Zones (Clause 8.2.2):

• Severe corrosion in:
  • Saline water
  • Splash zone (wet/dry cycles)
  • Tidal range
  • Buried steel under certain conditions

Related Load Increase Table (Clause 5.1):

(DL = Dead Load, LL = Live Load)

IS 4651 Part 4 – Design of Fenders: Key Points

1. Design Parameters (Clause 9.3)

• Berth loads: As per IS 4651 Part 3 (1974).
• Ship size & frequency: Fender capacity depends on ship size and arrival frequency.
• Berthing velocity: Adopt values from IS 4651 Part 3 (1974).
• Importance of structure: Consider consequences of failure.
• Energy absorption:
  • Energy stored as strain energy.
  • Shear > tension/compression in energy absorption.
  • Torsion effective for thin-walled tubes.
  • Include flexibility of berthing structure + fender system.
• Reaction force & deflection:
  • Consider hull and structure strength.
  • Use manufacturer data with a factor of safety = 1.4 on ultimate energy absorption.
• Fender disposition:
  • Longitudinal spacing: 0.3 to 0.4 × length of smallest ship (L).
  • Vertical range: From cope level to low water level to protect hull and structure.

2. Types of Fenders (Clause 9.2)

• Rubber (cylindrical, rectangular, sandwich types)
• Steel spring, timber, brushwood, rope, concrete, floating, torsion, etc.
• Choice based on specific berth conditions.

3. Functional Requirements (Clause 9.1)

• Absorb berthing energy.
• Prevent direct hull-structure contact.
• Transmit controlled thrust to structure.

4. Partial Safety Factors for Loads (Table 1, Clause 5.1)

**Typical Energy Absorption

Expansion Joints: Key Specifications from IS 4651 Part 4

1. Spacing of Expansion Joints (Clause 10.2):

• Recommended spacing: 39 m for solid quay walls or walls on piles.
• For better stiffness, spacing can be increased to 60 m.

2. Design Requirements (Clause 10.1 & 10.3):

• Provide sufficient expansion joints to accommodate movements due to:
  • Shrinkage
  • Temperature changes
  • Foundation yieldings
• Steel reinforcement should be designed to control shrinkage and temperature cracks.
• Joints must be keyed to transfer shear forces and allow free length changes.
• Key arrangement depends on soil, structure, and loading.
• Expansion joints must be covered to prevent backfill washout.

Summary Table for Expansion Joint Spacing

Design Considerations

• Shear transfer: Use keyed joints to transfer shear between sections.
• Movement accommodation: Joints must not hinder thermal/shrinkage movement.
• Protection: Cover joints to avoid backfill erosion.

flowchart LR
    A[Structure Length] -->|Divide into sections| B[Expansion Joints]
    B --> C{Spacing}
    C -->|39 m| D[Standard spacing]
    C -->|60 m| E[For better stiffness]
    B --> F[Keyed joints for shear transfer]
    B --> G[Allow free expansion/contraction]
    B --> H[Covered joints to prevent backfill washout]

For detailed design, refer to related IS codes:

• IS 456 (Concrete design)
• IS 800 (Steel structures)
• IS 2911 (Pile foundations)

These ensure proper detailing of reinforcement and joint construction.

List of Referred Indian Standards in IS 4651 Part 4

Notes:

• These standards cover materials (steel, cement, timber), design codes (loads, earthquake), and construction practices relevant to ports and harbours.
• Always refer to the latest edition or amendments for compliance.
• BIS ensures quality and conformity through inspection and certification under the BIS Act, 1986.

flowchart LR
    A[IS 4651 Part 4] --> B[Structural Steel - IS 226, IS 800, IS 2062]
    A --> C[Cement - IS 455, IS 1489]
    A --> D[Concrete - IS 456, IS 1343]
    A --> E[Timber - IS 401, IS 883, IS 2911 Part 2]
    A --> F[Loads - IS 875 Part 3, IS 1893]
    A --> G[Ports & Harbours Design