Connection design (AS 4100)

Connection design is one of the main reasons engineers reach for separate software. CivilKit Studio designs the three most common steel connections in place - the demand is pulled straight from the analysis, so you go from forces to a checked connection without leaving the model or re-keying numbers.

Connection	Where	Demand pulled from	Standard
Base plate	a support node	the support reaction (N*)	AS 4100 Cl 9 / bearing
Fin plate (shear)	a member end	the member's peak end shear (V*)	AS 4100
End plate (moment)	a member end	the member's peak end moment (M*)	AS 4100

There are two ways to work: auto-design the whole model from the connection schedule (fastest), or design one connection at a time in the inspector (most control). Both use the same engine and the same checks.

Actively maturing - not yet hardened

Connection design is the newest part of CivilKit and is still maturing. About a dozen check types are wired and the demands come from the verified analysis, but the checks are not yet fully hardened or independently benchmarked the way member design is. Treat the output as a first-pass aid: confirm every connection (bolts, welds, plate, block shear, detailing) against AS 4100 and your own judgement before it leaves your desk. The engine is steel / AS 4100 only - timber and multi-code connections are not designed.

Once designed, connections feed the fabrication schedules - the per-joint schedule, the fabricator worksheet and the take-off for estimators.

Auto-design the whole model (Connection schedule)

Most engineers don't hand-design every joint - they size the governing ones and specify the rest by category. The connection schedule mirrors that: it walks every joint at once and proposes a sized connection from the analysis.

1. Solve the model.
2. Open the Design → Connections tab and click Auto-design all.
3. The engine, for every node, classifies the joint from the members framing in and their end forces - beam-into-column shear (fin plate), beam-into-column moment (end plate), or column base plate - then auto-sizes it (stepping bolt count → diameter → plate thickness) until it passes, pulling the design action straight from the solved end forces.

The schedule lists every connection with its joint, class, template, governing utilisation, OK / OVER status, and source:

Source	Meaning
auto	the engine assumed and sized this connection for you
manual	you edited it (see below)
design	imported as an engineer-specified connection

The summary line reads, e.g. "47 connections: 12 specified, 35 assumed", so an estimate is honest about what is real versus assumed. Use Show OVER only to jump straight to the joints that fail.

Click a row to open that joint in the inspector with its utilisation bars. Edit the bolt count, bolt diameter or plate thickness and it re-checks live - the connection flips to manual and the schedule updates. Export PDF sends the whole schedule into the report.

The schedule is saved on the model (model.connections[]), so it rides along with export / import and share links - and the same data feeds CivilKit Fab so a fabricator can cost the connections without re-keying anything.

One engine, two front doors

Auto-design and the per-element inspector panels (below) run the same@civilkit/connections engine and the same AS 4100 checks - the schedule just applies it to every joint at once. Today the checks are closed-form; the data model is shaped so a future component-based FE (CBFEM) backend can slot in behind the same interface.

Connection library

The connection library is a browsable catalogue of standard steel connection templates covering five families: shear, moment, base, splice, and brace. Every entry is drawn as a 2D joint detail and tagged with one of two check types:

Tag	What it means
checked	A real AS 4100 closed-form check runs - you get a utilisation and an OK / OVER verdict
detail	A standard detail, verified against a published capacity table. The table reference is shown; no auto-utilisation is computed

Applying a template from the library - you can use either entry point:

• Inspector - click "Browse library" from a selected connection to apply a template to that one joint. Checked templates re-run the check immediately; detail templates set the status to detail and show the capacity table reference.
• Schedule - use "Apply to all of class" in the connection schedule to apply a template to every joint of the same class (e.g. all beam_col_shear joints at once).

The applied template (template, view, libraryRef, checkStatus) is stored on the connection and survives export / import and share links.

How it works (single connection, in the inspector)

1. Solve the model so the reactions and member end forces exist.
2. Select the support node (base plate) or member (fin / end plate).
3. Expand the connection panel in the inspector and set the connection details (plate size, bolts, weld). The design action is pre-filled from the analysis.
4. Read the live utilisation bars, the governing utilisation with OK / OVER, and the required vs provided values.

Connection inputs live on the element (n._baseplate, m._finplate, m._endplate) and ride along with export / import and share links, but they are stripped before the model reaches the solver - they never affect the analysis.

Tidy inspector

The member's optional checks (fin plate, end plate, plus the concrete / composite panels) sit under a single collapsed "Connection & material checks (optional)" expander, so a plain steel member stays clean. Expand the group, then the specific check you need.

Base plate

Select a support node. The panel:

• pulls N* straight from the support reaction;
• pre-fills the column d / bf from the connected column's catalogue section;
• lets you set plate B / D / t, f'c (concrete bearing strength) and the bolt count;
• shows utilisation bars for bearing (Cl 9, confined), plate bending, and bolt uplift, plus the required vs provided plate thickness.

Fin plate (shear connection)

Select a member. The panel pulls V* from the member's peak end shear and takes bolt count / diameter, plate depth / thickness and weld leg. Utilisation bars cover the bolt group, plate shear, bearing, tear-out and the weld, with the governing utilisation and φVdes.

End plate (moment connection)

Select a member. The panel pulls M* from the member's peak end moment and shows tension-bolt and end-plate-bending utilisation bars, the governing OK / OVER, and φMdes.

3D joint view

Selecting a connection in the schedule opens it in the inspector and also renders the joint as a 3D solid in the model viewport. The solid shows the real geometry oriented to the actual members: fin-plate or end-plate with hex bolts through it, fillet weld beads at the plate-to-column face, and short member stubs so you can see the plate relative to the beam depth and flange width. Bolt heads, nuts and plate thickness are drawn to scale with the model.

The Connections layer (View menu toggle) shows every joint in the model simultaneously rather than just the selected one - useful for a quick scan of geometry consistency across the whole frame. Turning the layer off reverts to single-selected display.

Wheel-zoom in the viewport zooms toward the cursor position, so you can scroll in on a tight joint without re-centring the view first.

Into the report

Every connection you design lands in the PDF report: a Connection design section tabulates each base / fin / end plate with its bolts, plate size, design action, the component utilisations and the governing verdict. The report re-runs the same check at print time, so the inspector and the submittable calc always agree.

Verify before professional use

These are early, transparent connection checks. Confirm bolt grade, weld category, edge distances, plate steel grade and the governing load combination against AS 4100 and your fabricator's standard details before relying on them.