Segmental Bridge Construction: An Overview (IRC Code SP 65)

Introduction

Segmental bridge construction represents a modern, efficient, and economical technique for building long-span bridges in difficult terrain and congested urban environments. The IRC Code SP 65 titled “Guidelines for Design and Construction of Segmental Bridges” provides comprehensive technical guidance specifically tailored for Indian conditions. This method has proven particularly effective in minimizing disruption, improving quality, and enabling faster construction of elevated corridors, metros, and highway overpasses.

This blog offers a detailed, easy-to-understand explanation of segmental construction, types, advantages, and implementation guidelines as per IRC SP:65.

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What is Segmental Bridge Construction?

Segmental bridge construction is a method where the bridge superstructure is built in short sections or "segments", either in a precast or cast-in-situ manner. These segments are then joined together using high-strength post-tensioning cables. This construction style is structurally efficient, enables repetitive manufacturing processes, and is ideal for rapid construction.

IRC SP 65 defines segmental construction as a technique primarily used for:

• Large-span bridges
• Elevated corridors
• Flyovers with restricted access
• Metro viaducts and interchanges

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Why IRC Code SP 65 Recommends Segmental Construction?

The IRC SP 65 code recognizes the growing demand for rapid infrastructure development in India. Segmental construction is recommended due to its:

• High structural efficiency
• Faster construction timelines
• Superior aesthetics
• Cost competitiveness in long spans
• Minimized disruption to traffic below

It also aligns well with urban flyover and metro construction projects where space, time, and environmental impact are critical factors.

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Types of Segmental Construction Methods in IRC SP 65

1. Precast Segmental Construction

Precast segments are manufactured in a controlled factory or casting yard, then transported and assembled on-site. This method ensures:

• Uniform quality
• Speedy installation
• Minimal site disruption

Variants include:

• Span-by-span erection
• Balanced cantilever method
• Launching girder system

2. Cast-in-situ Segmental Construction

In this method, segments are cast directly at the bridge site. It is preferred for locations where transportation of precast segments is difficult or where casting yards are unfeasible.

3. Incremental Launching Method (ILM)

Segments are cast at one end of the bridge and progressively launched longitudinally using hydraulic jacks. ILM is ideal for viaducts over water bodies or deep valleys where ground access is limited.

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Advantages of Segmental Bridge Construction (as per IRC SP 65)

1. Speed and Efficiency

Segmental methods reduce construction time significantly. Precasting enables simultaneous substructure and superstructure work.

2. Quality Control

Factory casting under controlled conditions ensures consistent concrete strength, curing, and finishing.

3. Reduced Environmental Impact

By minimizing on-site activities, noise, dust, and traffic disruptions are reduced — critical in densely populated urban zones.

4. Economical for Long Spans

Segmental bridges offer a cost-effective solution for spans over 30 meters, especially when multiple spans are required.

5. Safety and Sustainability

Improved safety for workers and surroundings due to reduced site clutter and reliance on heavy in-situ formwork.

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Applications of Segmental Bridges in India

Segmental construction has become standard practice in:

• Urban elevated corridors and metro rail systems
• High-speed expressways and ring roads
• River crossings and flyovers
• Interchanges and cloverleaf junctions

Projects like the Delhi Metro, Mumbai Metro, Bengaluru Elevated Expressway, and the Lucknow-Agra Expressway feature segmental construction extensively.

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Challenges and Mitigation Measures (IRC Recommendations)

1. Precision in Alignment

Segments must be cast and matched precisely. IRC SP 65 recommends use of match-casting techniques and alignment jigs.

2. Handling and Erection

Heavy-duty cranes or launching girders are required. Proper load-path and temporary supports are critical.

3. Post-tensioning Control

Proper stressing of cables is essential to maintain structural integrity. IRC SP 65 provides clear guidelines on anchorage systems and stressing sequences.

4. Maintenance of Bearings and Expansion Joints

Although segmental bridges reduce joints, some remain at end spans. IRC advises use of modular joints and elastomeric bearings for durability.

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Key Design Guidelines as per IRC SP 65

• Minimum concrete grade: M40 or higher
• Segment length: typically 3–5 meters
• Shear keys and epoxy joints between segments
• Transverse and longitudinal post-tensioning layouts
• Quality assurance protocols for segment casting and erection
• Stress checks for all erection stages, including temporary and final loads

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Conclusion

Segmental bridge construction is revolutionizing India’s urban and highway infrastructure. IRC Code SP 65 ensures that this innovation is implemented with safety, durability, and efficiency at its core. For engineers, contractors, and stakeholders, following these standards helps deliver sustainable transport networks suited for the future.

As cities expand and demand for seamless mobility increases, segmental bridges will remain essential in building tomorrow’s India — faster, safer, and stronger.

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FAQs

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Q1. What is segmental bridge construction as per IRC Code SP 65?

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It is a bridge construction technique where precast or cast-in-situ segments are joined using post-tensioning to form the complete superstructure.

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Q2. Why is segmental construction preferred in metro and urban projects?

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Because it allows fast, modular construction with minimal site disruption, making it ideal for congested areas and elevated corridors.

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Q3. What are the key benefits of segmental bridges?

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Rapid construction, cost-effectiveness, quality control, minimal environmental impact, and suitability for long spans are major advantages.

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