Erection, site work and site modifications

Who does what on site

Section 11 covers the assembly of steelwork at site. It does not stand alone: site cutting, holing, welding, bolting and painting must meet Sections 6 to 9, erection tolerances come from Appendix F, inspection follows Section 13 and any modification must meet Section 14 (Clause 11.1). Damaged elements must be assessed and repaired to in-service requirements, preferably with a competent person's approval.

The Standard distinguishes the fabricator (Clause 3.1.15) from the erector (Clause 3.1.13). World Steel is a fabricator: on Australian and New Zealand projects erection is normally carried out by the client's local erector, and World Steel's role is to deliver steel that can be erected efficiently and to support the erector technically.

Planning before steel arrives

Clause 11.2 requires the site work to be planned and managed. An erection plan is mandatory for high risk construction work and for structures with unusual features. Erection operations must run under a quality management system whose depth increases from CC1 to CC4 (Appendix D). A documented work method statement must exist before erection begins, ideally including the erection drawings and each item of temporary bracing with the period it must stay in place. Hazard identification and risk assessment precede erection; large or complex lifts warrant lift studies, lifting maps and sequence diagrams, and registration, maintenance records and operator licences must be available for inspection.

Clause 11.3 requires a documented set-out system, surveys by competent personnel and a reference temperature of 20°C. Deviations in footings must be measured against that system, and any rectification follows a written procedure. Clause 11.4 then requires the stability of the whole structure to be verified for every erection stage, with particular attention to progressive collapse.

Sequence, temporary works and stability

For high risk or atypical work, an erection sequence methodology (ESM) must be prepared and reviewed by a competent person (Clause 11.5.1). The key controls in Clauses 11.5.2–11.5.5 and 11.8 are:

• cranes, plant and stacked materials on the steelwork must stay within design capacity to AS 4100 or NZS 3404, and slabs carrying plant must be checked;
• steel must be secured against wind and erection loads throughout, with no permanent distortion from stacking or temporary loads;
• bracing and props follow the ESM, and are not moved or removed without written approval from a competent person;
• temporary connections, backing bars and pull-in cleats must not weaken the finished structure and must be designed for the loads they carry;
• a competent person inspects the permanent stability system before temporary supports are removed;
• jacks must lock under load, and rolled or launched structures need controlled braking.

Under Clause 11.9, erection at CC2, CC3 and CC4 must be supervised by competent personnel; the informative note gives a rigging qualification with long erection experience as an example.

Handling, fit-up, bolting and site welding

Clause 11.5.6 requires steel and fasteners to be stored without abrasion or permanent deformation, fasteners kept in their original packages, and painted or galvanized surfaces protected (Clauses 9.9.19 and 9.10.10). Under Clause 11.5.7:

• matching holes must allow a drift pin of hole diameter to pass freely, and drifting must not distort or enlarge holes;
• misaligned holes are corrected by reaming or hollow milling – hand flame cutting of bolt holes is prohibited except as a rectification for column base plates;
• bolts are snug-tightened to Clause 8.3 and tensioned to Clause 8.5 (see mechanical fastening);
• permanent connections wait until enough of the frame is aligned and plumbed; packers and shims are secured;
• site welding complies with Section 7, with the welding return made local to the joint.

Where specified, steelwork is trial erected at the fabrication works (Clause 11.5.10). Weathering steel joints need good fit-up and close bolt spacing to limit crevice corrosion (Clause 11.5.11), and AESS members carry the extra requirements of Section 10 (Clause 11.5.9; see AESS).

Supports, anchor bolts and grouting

Erection must not begin until the location, level and condition of supports, anchor bolts and bearings have been checked by a documented survey and visual examination (Clause 11.6.1). Clause 11.6.2 recommends that adjustable cast-in bolts have sleeves of three times the bolt diameter, at least 75 mm, and no deeper than half the embedment; threads must be protected and nuts must run freely before steel is landed. Shims left in place must match the adjacent steel and its protection and be enclosed by at least 25 mm of grout (Clause 11.6.3). Grouting under Clause 11.6.4 happens only after the frame is aligned and braced, into a clean, dry space, completely filled, and hold-down nuts must not be slackened to suit grouting without a competent person's review. See anchor bolt assemblies.

Erection drawings – the fabricator's key deliverable

Clause 11.7 expects the specification to say whether erection drawings are required and who prepares them; failing that, compliant shop drawings serve. Erection drawings must show plans and elevations with every erection mark, grids, bearing positions and their tolerances; footing plans with levels, datum and steel orientation; anchor bolt or bearing details with the packing method and grout requirements; temporary steelwork; the weight of items over 5 t and the centre of gravity of large or irregular items; and any required erection sequence. Marks must be visible in storage and after erection and comply with Clause 6.2. World Steel produces erection drawings from its Tekla model, together with bolt lists.

Inspection of erection (Clause 13.11)

For every category except CC1, Clause 13.11.1 requires an erection ITP naming who inspects, when, which members and by what method. A competent person inspects (Clause 13.11.2), and every result is recorded with inspector, item, date, requirement and outcome (Clause 13.11.3).

Clauses 13.11.4–13.11.7 require a survey of the completed structure tied to the site grid, using methods from ISO 7976-1 and -2, accuracy assessed to ISO 17123 and a 20°C reference, measured near site connection nodes under self-weight only unless specified otherwise. See geometrical tolerances.

Site modifications, repairs and heat straightening

Section 14 covers changes made to fabricated steel during erection and repairs to existing structures. No member, connection, fastener, weld or coating may be modified without a detailed written procedure – from a competent person during erection, or within the construction specification for an existing structure (Clause 14.2). For existing steel, materials must be identified before work, by records or positive material identification where weldability is uncertain (Clauses 14.3 and 14.6). Surfaces to be welded are cleaned of coatings for 50 mm each side of the weld (Clause 14.5), and welding sequences balance heat input to limit distortion. Heat straightening is limited to 620°C for ordinary steels, and for quenched and tempered steels to the lower of 590°C or 20°C below the tempering temperature, with no accelerated cooling (Clause 14.7). Testing follows Section 13 (Clause 14.8).

An offshore fabricator cannot rework steel on site, so a site deviation should be reported back promptly with photographs and measurements; the fabricator and designer can then agree a written rectification procedure before anyone cuts or welds.