Prestressed Concrete Beam Installation SWMS

Prestressed concrete beam work is the fabrication, transport, lifting, placement and tensioning of concrete beams in which high-strength steel tendons are stressed to pre-compress the concrete. It is high risk construction work under the WHS Regulation because it involves precast concrete, a risk of a person falling more than 2 m, structural alterations or repairs requiring temporary support to prevent collapse, and the movement of powered mobile plant (s291), so a SWMS is mandatory (s299). The defining hazard is the stored strain energy in the tensioned strand. During stressing, a proprietary anchor head can blow out and release a strand fragment at high velocity, a strand can fracture and whip with lethal force, or an anchor wedge can slip and partially release the force — anyone in the line of the strand or behind the anchor is at risk of fatal injury. Layered onto the stressing hazard are crane overload and long-span beam instability (beams are typically 20–50 tonnes and 15–30 m long, prone to torsion and lateral buckling during the lift), beams falling from bearings before adequate support, grout chemical exposure, crystalline silica dust from cutting cured concrete, and, for pre-tensioned beams cast off site, over-dimensional transport on public roads. This SWMS supports the engineered work — the Stressing Method Statement and beam design signed by a structural engineer with prestressed expertise — and controls the stressing exclusion zone, the lift, temporary support, and chemical and dust exposure around it. It is supplied in eight jurisdiction editions, each citing its own Act, Regulation and regulator.

Hazards identified

8 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Carry out all stressing strictly to the engineered Stressing Method Statement so no strand is tensioned outside its certified sequence and force
2. 2Substitution — Substitute pre-tensioned beams cast and stressed in a controlled yard for on-site post-tensioning where the design allows, removing on-site stressing energy
3. 3Engineering — Stressing Method Statement and beam design signed by a chartered (NER/CPEng) engineer with prestressed expertise, with the proprietary anchor system to supplier specification
4. 4Engineering — Exclusion zone behind and in line with the anchors during stressing, with no person in the strand line and blast protection at the live end
5. 5Engineering — Certified lifting gear and a spreader configured for the long-span beam to control torsion and lateral buckling, with temporary support designed for camber and deflection
6. 6Administrative — Pre-stressing coordination meeting and documented engineer attendance at stressing and lift days, with a hold point before support removal
7. 7Administrative — Sequenced stressing and locking procedure, and over-dimensional transport managed under the applicable load-restraint and permit requirements
8. 8Administrative — Grout-handling procedure and silica dust controls (wet cutting, on-tool extraction) with exposure monitoring
9. 9PPE — Type 1 hard hat with chin strap, eye and face protection at the live anchor end, gloves and steel-toe, steel-midsole boots
10. 10PPE — P2/P3 respiratory protection for silica and grout dust, and fall-arrest for work above 2 m

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

At 7:00 am a stressing crew from Tensile Structures prepares to post-tension a row of bridge beams. The supervisor confirms the Stressing Method Statement is on site and the prestressed engineer is attending. The proprietary anchor system and concrete cover are checked against the supplier specification before any jack is connected. The dominant rule is stated at the toolbox: no one stands behind or in line with an anchor while it is live, because a blow-out or strand fracture sends a fragment at lethal velocity. An exclusion zone is set behind each live anchor, blast protection is fitted at the live end, and the crew works to the sequence, watching for wedge slip as each strand is locked off. The beams, already placed by crane earlier, sit on temporary supports designed for camber until the permanent connection is made — those supports are not touched. When cured concrete needs trimming, it is wet-cut to control silica, and grout is mixed and handled in gloves and eye protection. A hold point keeps the temporary supports in place until the engineer signs off the permanent connection.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 3600 Concrete structures
• AS 3850 Prefabricated concrete elements

Frequently asked questions