Exploring IRC:83-2018 (Part II) – Standard Specifications for Road Bridges: Elastomeric Bearings

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The Indian Roads Congress (IRC) plays a pivotal role in setting standards for road and bridge construction in India. Among its significant contributions is the IRC:83-2018 (Part II), which serves as the Standard Specifications and Code of Practice for Road Bridges (Section IX: Bearings). This revised document focuses on elastomeric bearings, a critical component in modern bridge design and infrastructure.

This blog explores the key features, applications, and updates included in the IRC:83-2018 (Part II), ensuring compliance with the latest engineering practices.

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What Are Elastomeric Bearings?

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Elastomeric bearings are specialized components designed to support vertical loads while allowing for controlled movements and rotations of a bridge. Made from vulcanized elastomer, these bearings are often reinforced with steel plates to ensure durability and stability. Their primary function is to accommodate deformations caused by thermal expansion, vehicular loads, and seismic activities.

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Scope of IRC:83-2018 (Part II)

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The code covers:

• Types of Bearings: Laminated bearings, plain pad bearings, and strip bearings.
• Dimensions: Suitable for bearings with plan dimensions up to 1200 x 1200 mm.
• Temperature Range: Applicable for locations where operating temperatures are between -10°C to +50°C.
• Seismic Considerations: Incorporates guidelines for designing bearings to resist seismic actions.

It excludes high-damping elastomeric bearings and other materials not specified, like EPDM.

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Key Updates in IRC:83-2018 (Part II)

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1. Seismic Provisions: Enhanced focus on designing bearings to resist seismic forces.
2. Material Standards:
   • Natural Rubber (NR) or Chloroprene Rubber (CR) are the mandated raw materials.
   • Prohibits the use of reclaimed rubber or similar substances.
3. Manufacturing Tolerances: Defines stricter tolerances for consistent quality.
4. Design Advancements:
   • Shape factors and stress-strain limits are better defined.
   • Factors for rotational and translational movements are included.
5. Testing Requirements:
   • Ozone resistance, shear modulus, and adhesion tests are mandatory.
   • Stricter criteria for material properties and aging tests.

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Design Considerations

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The document emphasizes the Ultimate Limit State (ULS) approach, ensuring safety and durability. Key parameters include:

• Compressive and Shear Strains: Limits to ensure long-term performance.
• Reinforcement Design: Use of steel plates with minimum yield stress of 250 MPa.
• Stability and Deflection: Guidelines for rotational and translational movements under various load conditions.

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Applications of Elastomeric Bearings

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These bearings are widely used in:

1. Bridge Construction: To provide flexibility and minimize structural stress.
2. Seismic Zones: For absorbing vibrations and protecting the superstructure.
3. Temperature Variations: To accommodate expansions and contractions due to climatic changes.

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Importance of Compliance with IRC:83-2018

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Adhering to the IRC:83-2018 (Part II) ensures:

• Safety: Reduces risks of structural failure.
• Durability: Enhances the lifespan of infrastructure.
• Global Standards: Aligns with international practices for elastomeric bearing design.

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Conclusion

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The IRC:83-2018 (Part II) serves as a benchmark for designing elastomeric bearings in road bridges, combining safety, durability, and advanced engineering. As India modernizes its infrastructure, these standards ensure the resilience and longevity of bridges across the country. For stakeholders in road infrastructure, understanding and implementing these guidelines is crucial for creating sustainable and efficient transportation networks.

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