Steel & fabrication engineering

A fabrication package is read by people who are not engineers. A fitter reads a single-part drawing at a bench, a machine reads a CNC file, a storeman reads a bolt list, and a crew on a site reads an erection drawing in weather. Each needs the same decision resolved the same way — and it is resolved once, in the model, or it is resolved four times and three of those are wrong.

The bands below are what an engagement here can cover. Each says what the work is done from and what leaves it.

The detailing basis

Detailing is the first stage with nothing left to assume, so it starts by fixing what it is allowed to assume. Written down before the first assembly is drawn: which issue of which drawing set is being detailed and its date, the governing code and the specification, the shop's own standards — hole and slot sizes, weld access, maximum piece length and weight, paint marks — the bolt grades allowed and excluded, camber and fit-up tolerances, and the erection sequence the pieces will be flown in. The point of writing it down is the revision that follows: the assembly drawing, the single-part drawing, the CNC file, the bolt list and the bill of material all come out of one model, so a change reaches all five of them or it reaches none, and a drawing corrected on its own no longer matches the part the machine cut. How a revision is issued, marked and superseded is set out once under revision control.

Structural steel detailing

The primary frame: columns, beams, braces, trusses and girders, with the girts, purlins, sag rods and eaves members that carry cladding into it. The work is turning a member schedule into parts — piece marks, assembly logic, what is welded in the shop and what is bolted in the field, what ships as one piece and what has to be spliced to fit a truck or clear a site gate. Repetition is worth money here: two assemblies differing by a 5 mm hole gauge are two piece marks, two fabrication setups and two things to get wrong on site, and the detailer is the last person who can still merge them. Steel detailing is the page for what leaves — the package, sheet by sheet, and the model it is generated from.

Miscellaneous steel

Stairs, ladders, handrail and guarding, platforms and mezzanines, grating and chequer plate, lintels, embeds, bollards, pipe supports, door and louvre frames — the package priced by the tonne and delivered by the piece. Two things make it harder than the frame rather than easier. Its geometry comes from the architectural drawings while its supports come from the structural ones, and the two sets stop agreeing at exactly the points miscellaneous steel attaches to. And much of it is detailed last and wanted first, because handrail cannot be dimensioned until the stair is set and the stair cannot be set until the frame is plumbed. Detailing it early means deciding which connections are field-fit and saying so on the drawing, rather than discovering it with a crew standing on the landing.

Joist and deck detailing

Open-web steel joists, joist girders, bridging, and the metal deck spanning between them. A joist is a manufacturer's product, sized by the supplier against the loads it is given, so the work here is the placement plan and the loading that plan is made against: uniform and net uplift loads, bridging lines and where bridging has to be bolted rather than welded, and — the one that causes the most trouble — every concentrated load hung from a joist, with its position stated relative to a panel point. A duct hanger at mid-panel loads a chord in bending nobody sized it for, and it surfaces as a question from site months after the joists were rolled. Deck takes the same discipline: sheet layout, side-lap direction, edge angles and pour stops, and openings sized and reinforced on the drawing rather than cut by whoever needs one.

Connection design

Connections are the largest single variable in what a frame costs to fabricate, so they are treated as one subject rather than as a property of each drawing. Connection design is the canonical page for it: the calculations per connection type and load case, the sketches carrying bolt grade, weld size, plate thickness and edge distance, and the schedule keyed to the joint marks in the model. What belongs here is the loop around it — the reactions a connection is designed to and what is done when none was issued, the anchorage into concrete at every base plate and embed, and the rule that a resolved connection goes back into the same model the drawings come out of before anything is issued for fabrication.

Engineering calculations

Not every calculation a fabrication package needs is a connection calculation. A shop asks to substitute a section it already has in stock; a service run needs a hole through a beam web; a piece is too long for the road and has to be spliced where nobody designed a splice; a heavy assembly has to be picked and needs a lifting point that will not fold it. Each of those is a check against the governing code, and what leaves is a written deviation carrying the demand, the assumption and the result — so the change is decided by the engineer of record against a document rather than on a telephone call. Undocumented deviations are how a frame ends up as-built to a design nobody can produce.

Erection drawings

An erection drawing is not a shop drawing with more sheets on it. It is drawn for a crew with a crane, in weather, and it answers different questions: which piece goes up when, which bolts are field bolts and in what size and grade, where temporary bracing stays until the diaphragm closes, and what the anchor rods were set to before any steel arrived. The one that catches people is the shipping list. Pieces have to be loaded in the reverse of the order they are erected, or the crew unloads a truck twice to reach the column it needed first. Anchor rod setting plans are issued early for the same reason: a setting plan issued with the rest of the package is a plan that arrives after the concrete.

Design-assist

Design-assist is fabrication knowledge applied while the design can still change, which is the only time it is worth anything. The questions are budget-level tonnage against two or three framing schemes; whether a braced bay costs less than the moment frame it replaces once the connections are drawn; splice positions set by the crane and the road rather than by the analysis; connection types a shop's own equipment can produce without a bespoke welding procedure; and which sections to release to the mill first, so a long-lead order is not the thing holding the programme. Design-assist produces decisions rather than drawings, and an undocumented decision is a variation later — so what leaves the band is the decision itself: the option taken, the assumption it rests on, and whose call it was. It moves no design responsibility: the engineer of record holds that.

Fabrication coordination

Once drawings are released, the job stops being a drawing problem and becomes a sequence problem — what was released, at which revision, to whom, and what came back. Fabrication coordination is the page for it: release packages by lot or by erection sequence, the inspection and test plan issued with them, and a production status record reconciled against what was released rather than against what was drawn. Seimora operates no fabrication shop, so this is coordination of a fabrication programme against the shop that will build the job, and not the fabrication itself.