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Accident Alert - Precast Concrete Transport incident, panel tilted unexpectedly

Incident

A driver delivering concrete tilt-up panels suffered serious injuries when crushed between two panels. He suffered broken ribs and a punctured lung after walking between two panels on the trailer unit following the removal of the horizontal transport props. The props supported the panels back against the stanchions.

The picture shows a precast concrete slab, which is to be placed as part of a wall, on a vehicle trailer and propped up on that trailer. At the rear of the picture is another slab which has slipped over and in that position has injured a worker who was unloading the slabs. The picture also shows the crane slings which were attached to that slab.
Injured worker trapped here (follow red line on image above). Note: Rear left hand panel removed for clarity

Circumstances

It is unclear why the driver entered back between the panels after the removal of the props. This has highlighted a serious safety concern regarding the stability of the panels when left resting unrestrained against the stanchions. In this case, they were left resting 3 degrees to the vertical.

Investigation

Four panels were transported to site on a purpose-built trailer, with a central slot and stanchions sloped outwards at 3 degrees. Site investigations revealed that the truck deck was on a slope of 2.2 degrees at the front and 0.8 degrees at rear.

The drawing shows the concrete slab, the forces involved in supporting the slab and the angles at the base of the slab when it slipped over.
Click image to see larger copy

The knife-edge design of the panel base, and the base angle of the transporter meant panel 4 was left in an unstable position. When the transport horizontal props were removed, the panel become unstable, causing it to rotate about its base. This was re-enacted on site on two occasions and accurately calculated by the design engineer.

There is currently an industry working party developing a best practice document.
The previous Department of Labour guidelines  featured a requirement for tie downs or chains, this was not transferred into the current Code of Practice.

Recommendations

The current industry procedures for transportation are improved by introducing tie downs to provide restraining force at the top of the panels. Each panel is to be restrained until supported by design connection lifting points and crane. This will also ensure compliance with the Truck Load Code.

That the current Department of Labour Code of Practice includes restraining information of panels during transportation.

This photo shows the concrete slab's tie-downs in waist high position.
Tie downs positioned at waist level (follow red line on image above).

Issued by the Department of Labour, New Zealand
http://www.osh.dol.govt.nz

No. 26 - July 2007