PROCEDURAL ERRORS are being blamed for the collapse last week of an 80t composite floor slab, which narrowly missed three construction workers in Sydney, Australia.
The accident happened at the 49 storey Latitude Tower, being erected by developer Multiplex at World Square in Sydney's central business district.
Australian health and safety enforcer WorkCover has confirmed that the slab fell 2.7m onto the floor beneath it when workers started dismantling temporary trusses supporting it.
The Construction, Forestry, Mining & Energy Union (CFMEU) has claimed that the trusses were being dismantled before supporting columns had been installed.
It is believed that the design, by UK consultant Hyder, is commonly used for high-rise building in Australia.
Insitu cast floor slabs 120mm deep are connected to a grillage of 610mm deep I-beams by welded shear keys.
During concrete pouring the slabs are supported on lightweight steel trusses slung from the lower flanges of the I-beams.
Structural steel tubes capable of supporting significant loads are placed before the falsework is struck. These tubes are subsequently filled with reinforced concrete.
The CFMEU believes that one of these tubes was not installed.
'We understand that a crane was parked where it was meant to go, ' said a spokesman.
'At the moment we don't know why the crane wasn't moved, but clearly a mistake caused the collapse.'