Precast Panels Collapse Crush Cars

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Construction & Utilities Program Incident Report 05: 004Precast panels collapse and crush cars

Page 1 of 3WorkSafe Victoria is a division of the Victorian WorkCover Authority

Construction & Utilities Program

Incident Report:

Precast Panels Collapse & Crush Cars

Incident

WorkSafe Inspectors attended a construction site as a result of a partial collapse of a buildingunder construction. Three of the 12 metre high pre-cast concrete panels, which were alreadyin position and secured with temporary braces, had collapsed into the adjoining propertysdriveway and public car park, destroying two cars.

No person was injured as a result of this collapse.

Category: Precast and tilt-up concrete panels

Sub-category: Design for erection

Relevant to: All construction sectors, pre-casters, rigging contractors design engineers

Date of Issue: 17 August 2005

Reference No: 05:004

Authorised by: Geoff Thomas, Director Construction & Utilities Program


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Preliminary Inquires

WorkSafes initial site inspection revealed the following:

Two of the three panels that collapsed were located on the perimeter of the building.

The third panel was located in a row of two panels standing parallel to the perimeter panelsabout 3.2 m inside the building.

The open ends between the two rows of panels were intended to be filled-in by additionalpanels to form a concrete box.

The three collapsed panels had already been positioned and each panel secured with 2braces.

The braces were connected to the 12 m panels approximately 6.5 m above their bases; theIndustry Standard recommends that braces be attached at 2/3 of the panel height.

The base dowels had yet to be grouted at the time of the collapse.

A fourth panel was being rigged into position.

This panel was intended to close one end of the boxto be formed by the two rows of panels.

The brace anchors had pulled out of the slab but thebraces remained attached to their respective panels.

At the time of the collapse it appears there was noadverse weather or wind that may have contributedto the incident.

During their initial inquiries, inspectors were not ableto confirm:

The design engineer had authorised the brandchange of M12 masonry anchors, used for the

bracing, from those initially recommended. The brace anchors had been tightened to the correct

torque.

The inner panel collapsed first and fell obliquelyoutwards impacting on the 2 outer panels.

That information detailing the sequence of panel erection was available on site.

Tests had been undertaken, prior to the anchors being installed, to verify the concretestrength of the slab.

Initial Conclusions

To date the initiating cause has not been established and no conclusions have yet beenreached as to the primary cause or any other factors which may have contributed to thecollapse.

Recommendations

WorkSafe re-states its expectation that designers, panel manufacturers, erectors and buildersfollow the guidance outlined in the Industry StandardPrecast and Tilt-up Concrete for

Buildings.

WorkSafe also expects that when planning for panel erection and during any onsite erectionof pre-cast or tilt-up panels that particular attention is paid to the following:

Perimeter wallInternal 2 panel wall

Infill panel being

installed

Erected and braced

Plan View (not to scale )

Possible Sequence of Collapse


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Panel erection should not occur unless erection drawings are available onsite and containsufficient information to clearly identify:

o The sequence of panel erection

o The slab concrete strength prior to anchor installationo The engineers recommended bracing arrangementso The brand, type and size of bracing anchors

Concrete slab strength test reports are available onsite prior to panel erection and theinstallation of brace anchors.

Any changes to the engineers design specifications are confirmed with the engineer, priorto installation, and recorded on the erection drawings.

Anchor manufacturers torque requirements are available onsite.

Correct torque of anchors is confirmed by using a torque wrench during installation.

Where braces are located at less than the recommended 2/3 height of the panel, the designengineer specifies additional positive means of securing the panel to prevent overturning.

It is essential when planning for panel erection that consideration is given to assessing andcontrolling the risk posed to adjoining properties and the public from panel collapse.

Further Information

The Industry StandardPrecast and Tilt-up Concrete for Buildings provides details of thefactors that need to be considered when:

designing for erection (see Part 4 ), or erecting precast panels (see Part 8).

More information is also available in the Australian Standard AS 3850 Tilt-up concreteConstruction.

Disclaimer:This incident report contains information following WorkSafes inquiries into the incident as at the date

of this report. The information contained in this report does not necessarily reflect the final outcome of

WorkSafes action with respect to the incident. WorkSafe does not warrant that the information in this

incident report is complete or up to date and does not accept any liability to any person for the

information contained in this incident report or as to its use.

Documents

Precast Panels Collapse Crush Cars