Prosecution Details

Being a self-employed person at a construction site where concrete tilt-up panels were to be cast on the site and tilted or lifted into place, failed to ensure that the erection of the panels was in accordance with the relevant requirements of paragraph 7.6(a) of AS 3850.1 in that he failed to ensure that elements were braced in accordance with the shop drawings; contrary to regulation 3.88(1) of the Occupational Safety and Health Regulations 1996.

(Continued from Prosecution Summary Part A)
At the time of the collapse, seven panels comprising the services room had been erected. The erected panels were panels 37, 45, 46, 50-52 and 59. Each of those panels, except for panel 45, had been cut vertically in half prior to erection. This was done at the direction of the Accused without seeking any engineering advice and without consulting Tilt Lift. The panels were designed as large panels, in some circumstances greater than 50 tonnes. As a result, immediately prior to the collapse the services room comprised a series of half panels erected side by side. Panels 45 and 50-52 formed a long wall running north-south. Three large panels, panels 37, 46 and 59, were positioned at intervals running east-west and were adjacent to the wall comprising panels 45 and 50-52.

The first panel to collapse was panel 46. The eastern half of panel 46 collapsed and fell in a southerly direction into the area of the services room. Universal steel columns erected in the middle of the services room also collapsed in a southerly direction. It would appear that those steel columns made contact with the eastern half of panel 59 which in turn made contact with the eastern half of panel 37. The eastern halves of panels 59 and 37 collapsed in a southerly direction away from the area of the services room. The western half of each of those three panels, panels 46, 57 and 39, remained standing.

The shop drawing for panel 37 required seven B5 braces to be installed. The shop drawing for panel 45 required only two braces to be installed. In respect of each of the other panels identified in the charge, panels 46, 50-52 and 59, the shop drawings required five braces to be installed. The B5 braces were supplied by Tilt Lift. The B5 brace comprises a long steel piping brace running from the floor of the slab or from concrete footings to a specified point on the panel.

Following the collapse, the panels were inspected by another WorkSafe Senior Inspector. The Senior Inspector found that two braces had been attached to each half panel. Therefore, in respect of each panel except for panel 45, there were fewer braces installed than had been specified in the shop drawings.

The shop drawings also required that knee, lateral and end bracing be installed in respect of each of the panels. Lateral bracing is intended to be a continuous brace that runs adjacent to the panel at the mid point of the main brace (in this case the B5 braces). Knee bracing runs from the panel base outwards and connects with the main brace and lateral brace. End bracing connects to the end of the lateral brace to prevent lateral movement within the bracing system. The lateral and end bracing had been acquired and brought to site by the trainee site supervisor. The bracing was installed by McCracken Rigging Pty Ltd. The lateral and end bracing comprised 70 x 45 mm softwood timber. The minimum sized timber that should have been used was 100 x 50 mm timber. By using timber with smaller dimensions the lateral and end bracing had a reduced capacity. Further, the end bracing was inadequate to prevent lateral movement within the bracing system.

The importance of ensuring that panels are erected in accordance with the shop drawings was demonstrated by the collapse on 7 March 2003. By failing to ensure that the panels were braced in accordance with the shop drawings persons working at the site were exposed to a risk that a panel may collapse. The bracing installed on panel 46 was insufficient to sustain the wind loads to which the panel was exposed. The bracing system failed and the eastern half of panel 46 and nearby panels collapsed. Panel 46 was designed with a weight of 51.26 tonnes. It is fortunate that workers were not in the immediate area of the collapse at the time.