Structural design of belled caissons (tubulões)

What the tool calculates

• Shaft checked as a column, with reinforcement criteria of 0.5%·Ac or 0.15%·Ac depending on the adopted case
• Plain concrete base with an angle ≥ 60°
• Minimum cover by environmental exposure class
• Minimum shaft diameter for inspection

What you enter

• Design actions and concrete strength
• Shaft and base diameters
• Environmental exposure class

What you receive

• Shaft reinforcement, where required
• Plain concrete base angle and check
• Minimum shaft diameter for inspection

References and limits of applicability

• ABNT NBR 6118:2023 — Design of concrete structures (reinforced shaft, cover)
• ABNT NBR 6122:2019 + Emenda 1:2022 — Foundation design and construction (enlarged base, minimum diameter for inspection)

Checks and considerations

• Shaft diameter below the minimum for inspection
• Base angle below 60°

How it works

The design distinguishes the shaft under compression from the enlarged base and applies the corresponding structural checks. A plain concrete solution depends on the loading conditions and base geometry. Inspection, cover and construction requirements must be reviewed alongside the soil's geotechnical bearing capacity.

Example of use

After studying soil bearing capacity, enter the shaft diameter, base dimensions and design actions. Review the required reinforcement, enlarged base geometry and inspection conditions before issuing the details.

Generated documents

These documents are assembled within your project using data from the corresponding tools.

• Foundation calculation report — Combine the project's SPT logs, bearing capacity calculations and structural designs for piles, pile caps, footings and belled caissons in one PDF. The document consolidates selected items; technical checks remain within each tool.
• Structural calculation report — Combine the project's saved structural results in one PDF, with the selected calculations and their references, including NBR 6118:2023 for concrete members. Check the standards applicable to each member before issuing the document; consolidation does not replace design review.
• Concrete, formwork and reinforcement quantities — Determine concrete volumes, formwork areas and steel masses from the structural designs of piles, pile caps, footings and belled caissons, with recalculation of the members and reference to NBR 7480 for mass per unit length. Review quantities, allowances for waste and assumptions; export to PDF, Word, Excel/XML (.xls), XML or DXF. Pricing is not included.