Base Plate Design

Design and check a steel column base plate connection — base plate, anchor bolts, welds and the concrete below — with the SkyCiv standalone.baseplate API.

Prerequisite: open the session with standalone.baseplate.start, not S3D.session.start (verified: a check after S3D.session.start returns "Session has not been started. Please call standalone.baseplate.start first."). Auth, options and the { auth, options, functions } envelope are in skyciv-api-v3.

Only concentric column / plate / foundation layouts with symmetric anchors are supported.

Workflow

1. Choose design_code and load its reference file — it holds every accepted material, grade, diameter, electrode and the factors block for that code: American · Australian · Canadian · Europe.
2. Start from that code's sample-api/<country>/input.js (see Worked examples) and change only what you need. Every key must be present, even unused ones.
3. Send standalone.baseplate.start then standalone.baseplate.check in one request. design_obj is the arguments object — not nested under another key.
4. Check response.status. On 1, read errors / warnings / conflicts (below) and fix the input.
5. Scan every check for its ratio (see Reading the response).

"functions": [
  { "function": "standalone.baseplate.start", "arguments": { "keep_open": true } },
  { "function": "standalone.baseplate.check", "arguments": { "design_code": "American", "...": "..." } }
]

Several checks can follow one start in a request (verified; top-level response is the last). Each check takes about 11–20 s and uses one API credit.

Gotchas

• Invalid strings are silently replaced, not rejected. An unknown material, concrete grade or anchor diameter returns status: 0 with results computed on a default value (verified for column, base plate, anchor and concrete grades, and Canadian diameters). Copy values exactly from the reference file, and confirm the relevant capacity moved when you change one.
• Canadian anchor diameters are imperial sizes in mm (12.7, 15.9, 19.1, 22.2 …). The 12, 16, 20… list in the live docs is silently ignored — see canadian.md.
• A failing detailing check hangs the call instead of erroring. Verified with embed_plate (embedded plate side < 4 × anchor diameter): no conflicts are returned — the call runs until the server timeout (~45 s) and returns "standalone.baseplate.check timed out". options.timeout does not extend it. Treat any timeout as an input problem: check the detailing rules below against your geometry before retrying.
• My must be "0". It is reserved for future weak-axis support; any non-zero value ("1", "10") hangs the call until timeout.
• A fixed base needs a non-zero Mz in every load case. Otherwise status: 1 with the conflict "configured as a fixed support, but the load combination does not include a moment". Axial-only or axial + shear cases go on a pinned base.
• A wrong section name fails fast with an unhelpful message — "could not be completed for an unknown reason" in ~5 s. steel-column-database is the third level of the section library path and steel-column-profile the fourth (e.g. American › AISC › Pipes › Pipe6STD → "Pipes", "Pipe6STD"). Resolve both with section-selector.
• status: 0 does not mean the design passes — a run returned a breakout ratio: 1.248 with status: 0. Derive pass/fail from the ratios.
• capacity: 0 with ratio: 0 means "not evaluated", not a pass with infinite margin — e.g. Weld Capacity on an axial-only pinned base, Side-Face Blowout (Y-Direction) when no anchor is near that edge. Report these as N/A.
• Concrete Bearing Capacity sits at ratio: 1 for American/Canadian fixed bases under large moment. Ratio 1 = demand equals capacity (limit reached). This method takes bearing stress at its limit and solves for the bearing length, so the ratio stayed 1.000 when the plate grew 400 → 500 mm and the footing 450 → 900 mm. Report it as at-limit, but size the connection on the other checks — enlarging the plate won't move it. Small eccentricity (Nx = 200, Mz = 2) gave 0.102.
• Load values are strings ("Mz": "10") in every sample; keep them strings.
• Report URLs are temporary (solver.skyciv.com/temp/...).
• Strip screenshot before logging a failure — status: 1 responses carry a 60–200 KB base64 PNG of the calculator UI. Decode it only when diagnosing.

design_obj — top level

Units

units_data.units (metric / imperial) and project_details.project_units control the unit system. Imperial is American-only; the other three codes are metric.

All request values and all response demand/capacity values use these units. Copy the remaining units_data keys (first_init, length_factor, strength_factor, strength_factor_steel, to_mm, to_in, kNm_Kipft, kN_Kip) from the sample unchanged — verified to have no effect on results in either unit system (the American sample's length_factor: 25.4 is harmless).

steel_parts.data

Code-only keys (steel-column-height, grout-material-selected, steel-grouting-material, steel-column-rot) are listed in the Canadian and Europe reference files.

anchors.data

For a fixed base the anchors must sit in the tension zone — Web Only under moment returns a conflict.

welds.data

loads

An array of load cases. Give factored (ULS / LRFD) combinations — the factors in factors are resistance factors only.

detailing and design_settings

detailing flags (true enables the check; a failed enabled check hangs the call):

design_settings change the method — only change them with review by a suitably qualified engineer; keep the sample values otherwise. Which ones apply to which code is in the reference files.

Reading the response

response.data holds one key per applicable check, e.g. "Concrete Breakout Capacity (Tension Load)": { "demand": 27.511, "capacity": 33.143, "ratio": 0.83, "units_on_UI": "force", "lc_number": 1 }, plus the non-check keys version, file_name, reports (html_view_link, html_download_link, pdf_download_link) and, for Europe, rotational_stiffness.

There is no pass/fail or governing-ratio field, and the set of check keys depends on code, support type and which load components are non-zero (shear adds five shear checks, tension adds the anchor checks). Never look up a fixed key name — scan:

const data = res.response.data;
const checks = Object.entries(data)
  .filter(([, v]) => v && typeof v === 'object' && typeof v.ratio === 'number')
  .map(([name, v]) => ({ name, ...v, evaluated: v.capacity !== 0 }));
const evaluated = checks.filter(c => c.evaluated);
const governing = evaluated.reduce((a, c) => (!a || c.ratio > a.ratio ? c : a), null);
const passes = evaluated.every(c => c.ratio <= 1);

units_on_UI is the kind of quantity (force, stress, length, moment, force_per_unit_length, …, "" = unitless) in your units — it varies per code for the same check.

On status: 1 the reason is in arrays next to msg (HTML strings — strip tags before showing):

Minimal working example

Verified live: American, metric, pinned pipe column, 100 kN compression (governing ratio 0.17).

{
  "design_code": "American",
  "support_type": "pinned",
  "units_data": {
    "first_init": true, "units": "metric", "units_length": "mm", "axial_f_units": "kN",
    "units_strength": "MPa", "units_strength_steel": "MPa", "bending_f_units": "kN-m",
    "length_factor": 1, "strength_factor": 0.00689476, "strength_factor_steel": 6.89476,
    "to_mm": 1, "to_in": 1, "kNm_Kipft": 1, "kN_Kip": 1
  },
  "project_details": { "project_units": "metric", "company": "", "designer": "", "project_name": "", "project_id": "", "project_notes": "", "client": "" },
  "steel_parts": { "data": {
    "custom-column-fy": 240, "custom-column-fu": 400, "custom-bp-fy": 240, "custom-bp-fu": 400,
    "custom-conc-fc": 20, "use-cracked-concrete": true,
    "steel-column-shape": "pipe", "steel-column-database": "Pipes", "steel-column-profile": "Pipe6STD",
    "steel-column-material": "A53 grB",
    "steel-baseplate-width": 300, "steel-baseplate-height": 300, "steel-baseplate-thickness": 20,
    "steel-baseplate-material": "A36", "steel-baseplate-grouting-thickness": 0,
    "steel-foundation-material": "20.68", "steel-foundation-width": 450, "steel-foundation-height": 450, "steel-foundation-thickness": 380
  } },
  "anchors": { "data": {
    "custom-anchor-fy": 240, "custom-anchor-fu": 400,
    "anchor-pattern": "Four Corners", "anchor-prop-diam": "16", "anchor-prop-material": "F1554 Gr.36",
    "anchor-thread-included": "included", "anchor-web-bending": "web-bending",
    "use-welded-plate-washers": false, "anchor-plate-washer-thickness": 0,
    "anchor-prop-length": 250, "anchor-prop-ending": "straight",
    "anchor-numbers": 1, "anchor-numbers-z": 2, "anchor-numbers-y": 2,
    "anchor-spacing-z": 200, "anchor-spacing-y": 200,
    "anchor-edge-distance-z": 50, "anchor-edge-distance-y": 50,
    "line-anchor-edge-distance-z": 50, "line-anchor-edge-distance-y": 50
  } },
  "welds": { "data": {
    "box-weld-size": 8, "input_table_col_weld_size": [], "custom-weld-fexx": 482,
    "use_welds_for_comp": "false", "weld-type": "fillet", "weld-setback": 0, "welds-column-mat": "E70xx"
  } },
  "loads": [ { "lc": "1", "Mz": "0", "My": "0", "Nx": "100", "Vz": "0", "Vy": "0", "moment_label": "" } ],
  "factors": {
    "concrete_bearing_factor": 0.65, "steel_bearing_factor": 0.75, "steel_flexure_factor": 0.9,
    "weld_factor": 0.75, "steel_tension_factor": 0.9, "steel_shear_rupture_factor": 0.75,
    "anchor_tension_factor": 0.75, "anchor_shear_factor": 0.65, "anchor_bolts_factor": 0.75,
    "concrete_tension_factor": 0.7, "concrete_shear_factor": 0.65, "concrete_normal_weight_factor": 1
  },
  "detailing": { "weld_size": true, "anchor_clearance": true, "bp_edge_distance": true, "embed_plate": true, "concrete_splitting": true, "min_anchors": true },
  "design_settings": {
    "neglect_concrete_breakout_for_tension": false, "neglect_concrete_breakout_for_shear": false,
    "neglect_concrete_pryout": true, "distribute_shear_to_all": true, "simplified_approach_shear": true,
    "consider_both_directions": false, "include_embedded_head_radius": false, "use_sci_for_welds": false
  },
  "version": 2
}

Feeding S3D results into a base plate check

1. Solve the frame in s3d-api (its own S3D.session.start session — a separate request from the base plate one). Don't use result_filter to fetch reactions; read them from the full results as described in analysis-results.
2. For each factored load combination, take the column's member forces at its base station (local axes; bending_moment_z = strong axis) and write one loads entry: Nx ← axial, Mz ← strong-axis moment, Vy ← shear_force_y, Vz ← shear_force_z, My ← "0". Convert to the base plate's units.
3. Confirm the sign before trusting it: Nx is positive for compression here, and the S3D sign convention is not documented in these skills. Run one gravity-only combination — the column must come out with Nx > 0. If it doesn't, negate axial for every case.
4. My is unsupported — flag a significant weak-axis moment to the user rather than dropping it. A fixed base needs Mz ≠ 0 in every case; never invent a nominal moment to get past that.
5. Use section-selector to get the column's database/profile names, and hand the finished results to qa-engineer for review.

Worked examples

Verified request/response pairs (re-run live 2026-09-22, results unchanged):

Copy the design_obj literal from each input.js. The American and Canadian samples have breakout ratios of 0.83 / 0.976 — little margin if you only raise the loads.