The scope of this document is to provide the calculations for the analysis and design of Box culvert design . The software used for structural analysis and design is STAAD Pro connect Edition.

Box culvert design according to IRC 6 (Standard Specifications and Code of Practice for Road Bridges, Section II) involves several considerations for structural strength, stability, and durability. Here are the main design bases to consider:

Load Considerations

• Dead Load: Weight of the box culvert, including the self-weight of the concrete, parapets, and other permanent structural components.
• Live Load: Vehicular load as per IRC 6, generally adopting IRC Class A, AA, or 70R loading, depending on the culvert’s location and importance.
• Impact Load: Apply an impact factor as per IRC 6 if vehicles can travel directly over the culvert, based on the design speed and load class.
• Surcharge Load: Lateral earth pressure due to embankment or backfill material on top of the box culvert.
• Water Load: Hydrostatic pressure exerted by water on the culvert, considering maximum water levels and pressure distributions.
• Earth Pressure: Lateral and vertical earth pressure, depending on soil type, compaction, and depth of the cover.

Structural Design Checks

• Bending Moment and Shear Force: Calculate moments and shear at various sections (e.g., midspan, supports) using the loads and support conditions. Ensure compliance with bending and shear capacities as per IS 456 and IRC standards.

Serviceability Checks: Check for deflection, cracking, and durability. IRC specifies crack width limits and deflection limits based on service life requirements

Load Combinations

• Apply various load combinations as per IRC, including:
  • Dead Load + Live Load
  • Dead Load + Surcharge Load + Live Load
  • Water Pressure + Dead Load + Live Load

Example Design Considerations:

• For a 2-lane box culvert, with Class AA loading:
  • Top Slab: Designed to resist bending moments due to dead load, live load, and surcharge.
  • Walls: Designed for both axial and flexural stress due to earth pressure and surcharge.
  • Bottom Slab: Resists uplift pressure and bending due to subgrade reaction.

References

• IRC 6-2017: General Specifications for Loads and Stresses
• IRC 21: For the concrete mix and structural detailing requirements.
• IS 456: For concrete design and reinforcement detailing

A three-dimensional model of Box culvert is created in STAAD software by plate modelling and all relevant loads are applied on the structure are in accordance with IRC 6 Class AA loading and member design as per plate moment and shear from STAAD analysis.

Following are the available files

1. Design of Box culvert Report – Word file
2. Design of Box culvert Report – pdf
3. Design of Box culvert Report – Staad analysis
4. Design of Box culvert plate model results(bottom, Top slab and walls) – Excel file “Editable format Not Password protect”

The calculation files will be very useful for the FEED stage and also detail phase of engineering for Piperack structural calculation.

Open and edit the files to make it your own.