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The Anchoring configuration defines how the vessel support structure is fastened to its concrete foundation. These parameters apply across all support types — saddles, skirts, legs, lugs, and rings — and govern the design of the anchor bolt group against tension pull-out, shear breakout, and concrete cone failure modes.

Bolt group design

PSI calculates the governing tensile and shear demand on the anchor bolt group from overturning moments, seismic shear, and thermal expansion forces.

Concrete capacity

Concrete strength and anchor embedment depth together determine the concrete pull-out and breakout capacities per ACI 318 Appendix D / EN 1992-4.

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Parameters

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Bolt Pattern

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boltQuantity
select
required
Total number of anchor bolts in the group. Options: 2, 4, 6, 8, or 12. Bolts are assumed to be equally spaced on the bolt circle. Even numbers are required for symmetric load distribution.
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boltDiameter
number
required
Nominal diameter of each anchor bolt (mm). Used to calculate the tensile stress area and the bearing area for shear. Ensure the selected diameter is consistent with the bolt material and grade.

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Bolt Material

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boltMaterial
select
required
Material grade of the anchor bolts. Options:
  • Carbon steel — Standard low-carbon steel. Suitable for ambient temperature, non-corrosive service.
  • Stainless steel — Austenitic stainless (304/316). Used in corrosive environments or where bolt exposure is a concern.
  • A325 — High-strength structural bolt per ASTM A325. Minimum tensile strength 120 ksi (827 MPa). Common in structural connections.
  • A490 — Very high-strength structural bolt per ASTM A490. Minimum tensile strength 150 ksi (1034 MPa). Used where bolt size must be minimised.

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Embedment and Concrete

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embedmentDepth
number
required
Depth from the top of the concrete foundation to the bottom of the anchor bolt bearing surface (hook tip or nut). Deeper embedment increases the concrete cone pull-out capacity.
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concreteStrength
number
required
Specified compressive strength of the foundation concrete, f’c, in MPa. Higher concrete strength increases all concrete-controlled failure capacities (pull-out, breakout, pry-out, splitting).

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Anchor Type

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anchorType
select
required
Mechanical form of the anchor. Options: Hex Head Bolt, L-Hook Bolt, J-Hook Bolt, or Epoxy Anchor.
A straight bolt with a hex head at the embedded end and a nut and washer at the surface. Load transfer is primarily through bearing of the hex head against the concrete. Suitable for new construction where the foundation is cast around the bolt template.

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Edge Distance

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anchorEdgeDistance
number
required
Distance from the anchor bolt centreline to the nearest free edge of the concrete foundation (mm). Edge distance directly affects the concrete breakout and splitting capacities.
ACI 318 Appendix D and EN 1992-4 both specify a minimum edge distance of 6 × bolt diameter for cast-in headed anchors and 10 × bolt diameter for post-installed (epoxy) anchors. Using edge distances below these minimums requires a significant capacity reduction factor and is generally not recommended. Where layout constraints force small edge distances, consider enlarging the foundation pedestal or increasing the number of bolts.

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