COLLAPSE OF an aircraft hangar in Canberra, Australia could have been triggered by the failure of a bolted frame used as temporary longitudinal restraint during construction, investigators believe.
'Some bolts were not tightened properly, some were missing and there were different types of bolts in the structure, ' said a source from Australian Capital Territory (ACT) Work Cover, Canberra's health and safety inspectorate.
The accident at RAAF Fairbairn in Canberra occurred last May as the structure was stress erected using patented technology by Australian structural engineering company Strarch.
Erection of the hangar involved stressing tendons fed through the bottom chord of the roof truss.
Bolted frames or gap locks are used to provide longitudinal restraint for sleeve jointed tubes during erection.
Metallurgical tests carried out as part of the ongoing investigation into the collapse revealed inconsistencies in the chemical composition of the 20mm diameter bolts used in the restraints.
Each gap-lock comprises four steel plates bolted together to make a rectangular frame.