Base Plate Calculator: complete engineering guide

The calculation follows the physical load path from the column through the weld and plate, into a concrete bearing block and—when required—a tension anchor row. Shear is distributed to the anchor group; the Eurocode route also exposes the friction-plus-anchor base-shear component explicitly. Concrete anchorage checks use projected-area geometry that accounts for group overlap and pedestal-edge truncation.

• The support idealisation used in the global frame model: pinned or moment-resisting.
• The governing design standard, edition, amendments, jurisdiction, and National Annex where applicable.
• Factored base actions for every relevant ULS/LRFD design situation, with a consistent sign convention.
• Column section and certified material properties—not only a nominal grade name.
• Available pedestal/footing dimensions, thickness, concrete strength, cracking assumption, and specified cover.
• Anchor rod thread series, tensile stress area, steel properties, head or plate-ending geometry, and effective embedment.
• Weld process/detail, electrode classification, effective profile, and fabrication constraints.
• Scope items to be checked separately: footing, pedestal reinforcement, shear key, seismic/fatigue, erection, durability, and tolerances.

3.1 Select the exact design-code route

Route names are edition-specific. They identify the resistance factors, partial factors, failure modes, and source references used by the engine. They are not a promise that the named editions are currently adopted on your project.

3.2 Pinned versus fixed is a frame-model decision

“Fixed” in this tool means moment-resisting for strength verification; it does not calculate a rotational stiffness for semi-rigid frame analysis. If foundation flexibility or joint rotation affects the global response, determine that stiffness separately.

3.3 Select I/H, RHS/SHS, or CHS

Shape selection controls the column footprint, editable section dimensions, welded profile, plate cantilever distances, and anchor-clearance geometry. I/H and RHS/SHS templates use a centred rectangular grid by default; CHS uses a centred bolt circle. Presets only populate dimensions—every value remains editable.

The load eccentricity reported by the moment interface is $e=M/N$ for net compression. Load reversal should be entered as separate cases so edge-directed anchor shear and the compression/tension sides are evaluated correctly.

5.1 Details and design basis

5.2 Column, plate, and pedestal geometry

The calculator assumes the column is centred on the plate and the plate is centred on the pedestal. Do not simulate an eccentric arrangement by altering loads alone—the physical edge distances and projected areas would still be wrong.

5.3 Anchor pattern and anchor properties

5.4 Column-to-plate weld

Enter the equal fillet leg size and electrode classification strength. The model uses a continuous weld along the full RHS/CHS perimeter; for I/H sections it follows the outer flange faces, inner flange returns, and both web faces, conservatively omitting flange-tip returns. The effective throat is the leg size divided by $\sqrt{2}$.

• For EN, verify the correlation factor ${\beta }_w$ for the weaker joined steel and the project partial factor.
• For AS 4100, select Structural Purpose (SP) or General Purpose (GP) intentionally.
• The tool models fillet welds only. PJP/CJP preparations, access holes, backing, lamellar tearing, local column wall/flange resistance, and weld procedure qualification require separate review.

5.5 Load cases

Add up to 20 factored cases. Give each a traceable label such as ULS-WIND-X+, not only “LC1.” The engine evaluates all cases inside every check; one check may govern in compression while another governs under uplift or reversed shear.

6.1 Rigid bearing equilibrium

The plate is treated as rigid for contact equilibrium. Concrete resistance comes from the selected code; the shared kernel only solves statics using a uniform rectangular stress block. Depending on N and My, it returns one of four physical states—or marks equilibrium infeasible.

The middle-third value $L/6$ is reported as a useful small-/large-moment classifier. Actual transition to a pressure-limited block depends on the code bearing resistance and the available anchor lever arm.

6.2 Plate flexure

For AISC, AS, CSA, and NSCP routes, plate flexure uses a one-way cantilever measured from the exact column footprint to the plate edge. Compression-side demand comes from bearing pressure; tension-side demand comes from anchor force about the nearest column face. The strip reaches the plastic moment $F_y{t}^2/4$ per unit width, multiplied by the route's sourced resistance factor.

This footprint-cantilever model deliberately does not credit code-specific effective-width reductions or interior/two-way yield-line refinements. That is generally conservative for outer-cantilever-governed plates, but large lightly loaded plates where an interior mechanism may govern need separate verification. The EN route instead exposes its compression and tension T-stub components.

6.3 Weld line group

The welded profile is analysed as an elastic line group. Axial force and moment produce normal line force; biaxial shear produces shear line force. Route-specific weld strength and directional rules then convert the demand into utilisation.

6.4 Cast-in anchor demand and concrete geometry

In a bearing–anchor couple, tension is shared by the anchors on the tension side. Under net uplift, a non-negative rigid-group distribution satisfies axial and moment equilibrium. Shear components are shared equally among all anchors. The code route then checks individual and group effects as required.

The anchor kernel builds idealised tension and shear projected areas, unions overlapping anchor regions, and clips them to pedestal boundaries. Code-specific spread distances, strength coefficients, modification factors, and resistance/partial factors are supplied by the active sourced check—not invented by the geometry kernel.

For the live implementation status, validation notes, and clause-level source registry, use the dedicated methodology and traceability page.

1. 1

   Confirm the arrangement

   Compare the live plan and elevation to the connection drawing: axes, plate and pedestal dimensions, section orientation, anchor count/pattern, embedment, grout, and units.

2. 2

   Read the overall state

   Pass, Fail, or Indeterminate is stated in text. The banner names the governing check and, when unlocked, its utilisation and demand/resistance pair.

3. 3

   Open the governing card

   Identify its governing load case, demand, resistance, formula, decisive intermediate values, assumptions, and exact source references.

4. 4

   Scan every other check

   A low governing margin does not excuse missing or physically inconsistent checks. Confirm finite values and plausible load cases throughout.

5. 5

   Resolve warnings and scope flags

   Layout conflicts and infeasible equilibrium invalidate reliance on downstream results. A warning is part of the calculation, not decorative advice.

6. 6

   Review assumptions and sources

   Confirm each assumption matches the detail and each route/edition matches the project design basis.

Status language

After any change, repeat three checks in order: arrangement still matches the drawing; every load case is still present; and the new governing mode makes physical sense. A lower headline number is not, by itself, evidence of a better detail.

1. 1 · Complete metadata

   Enter project, client, revision, and useful notes before opening the final report.

2. 2 · Preserve the state

   Save to the account or copy the share link. The calculator state is encoded so a reviewer can reopen the same inputs.

3. 3 · Preview

   Use the free report preview to inspect pagination, schematic, input summary, checks, warnings, assumptions, and references.

4. 4 · Independent review

   Give the reviewer the report and source model/reaction set—not only a pass banner or cropped screenshot.

5. 5 · Export

   With report access, print or download the clean PDF. Confirm unit labels, revision, generation time, and engine version.

6. 6 · Archive

   Store the PDF with the connection drawing, analysis reaction source, design-basis note, and any supplementary calculations.

Assumptions used by implemented checks

Automatic out-of-scope triggers

Important limitations not represented as a complete design

• Column, beam-column, frame, and second-order member design
• Footing/pile-cap flexure, one-way shear, punching, sliding, overturning, soil or pile response
• Pedestal reinforcement, anchor reinforcement, dowels, confinement, and strut-and-tie design
• Weak-axis or biaxial moment, torsion, eccentric column/plate/pedestal arrangements
• Post-installed mechanical or adhesive anchors and product qualification data
• Seismic anchorage, overstrength/capacity design, ductility systems, fatigue, impact, or cyclic degradation
• Shear lugs/keys, friction from pretension, sleeves, oversized holes, and alternative shear distributions
• PJP/CJP welds, base-metal local limit states, weld access/procedure/inspection and lamellar tearing
• Rotational stiffness, base fixity calibration, local plate deformation, grout flexibility, and contact nonlinearity
• Erection stability, temporary bracing, tolerances, leveling nuts, corrosion, fire, durability, and constructability

• Route edition, amendments, National Annex, and jurisdiction match the project.
• Pinned/fixed idealisation matches the global model and real connection behaviour.
• Actions are concurrent, factored, complete, signed correctly, and traceable to analysis combinations.
• Live plan/elevation match the drawing, axes, units, anchor count, pattern, and embedment.
• Material strengths and anchor thread/head properties come from project specifications or certified data.
• Cracked/uncracked classification, normal-weight concrete assumption, cover, grout and friction inputs are justified.
• Governing check and governing load case are physically credible; nearby checks have adequate margin.
• Layout conflicts, infeasible states, warnings, and >85% review triggers have been resolved or formally addressed.
• Footing/pedestal, reinforcement, shear-transfer, column local resistance, weld procedure, erection and durability checks exist separately.
• Report metadata and revision match the drawing/calculation register; engine version and unit system are recorded.
• A second competent engineer can reproduce the input actions and understand every assumption and exclusion.
• Any departure from calculator scope is covered by a referenced hand calculation, specialist method, test basis, or refined analysis.