Preventing formwork failures

Background

There have been several recent incidents where formwork has failed during concrete pours. Formwork failure can result in concrete blowouts, falling formwork components or structural collapse, and has the potential to cause death or serious injury.

Formwork failures are often caused by:

• formwork not being designed by a competent person
• formwork not constructed in accordance with the formwork design or specifications
• onsite modifications to formwork due to site conditions not addressed in the design
• damaged or sub-standard formwork components being used
• removal of formwork before the concrete achieves adequate strength
• overloading of the formwork during concrete pouring operations.

Formwork can be constructed to meet a custom design produced by a competent person or a proprietary system can be used in accordance with the manufacturer’s recommendations.

Safe work method statement

Safe work method statements (SWMS) must be developed for all high risk construction work that forms any part of the formwork erection, concrete pouring and formwork stripping processes.

SWMS assist employers and employees to consider the hazards and risks associated with the high risk construction work and choose effective control measures.

Control measures

Erecting formwork

• Ensure a competent person produces a formwork design capable of supporting the expected dynamic and static loads.
• Where proprietary formwork systems are used, ensure they are erected in accordance with the manufacturer’s recommendations.
• Where a custom design is used, including when combining different formwork systems or using proprietary systems outside the manufacturer’s recommendations, ensure the design is completed by an engineer experienced in formwork design (note: This does not apply where there is minimal risk to the safety of persons in the event of formwork failure, such as typical slab on ground formwork).
• Inspect formwork components before use, remove defective components from service and tag them out for disposal or repair.AS 3610 – 1995: Formwork for concrete provides component inspection criteria.
• Before other trades access the formwork or the concrete is poured, ensure the erected formwork is inspected by a competent person to ensure it has been erected in accordance with the formwork design. The competent person should document the inspection and sign-off the formwork as ready for use.
• If the erected formwork does not comply with the formwork design:
  • alter the formwork so it does comply with the design, or
  • ensure the designer inspects the formwork and verifies the changes don’t compromise the structural integrity of the formwork.

Pouring concrete

• Ensure the structural integrity of the formwork has been verified before starting the concrete pour.
• Establish an appropriate exclusion zone to prevent people accessing the area under the formwork during the concrete pour and maintain the zone until the concrete reaches adequate strength.
• Monitor the formwork during the concrete pour to identify any early signs of failure. The monitors should not access areas under the formwork unless a risk assessment has been undertaken to determine it is safe to do so.
• Ensure the formwork is not overloaded during the concrete pouring operation.

Stripping formwork

Ensure the concrete has achieved minimum strength before formwork removal. This may be achieved by ensuring the minimum curing time specified in the formwork design has been achieved, or receiving appropriate certification following concrete specimen testing.

Australian standards

AS 3610-1995: Formwork for concrete