3.3.3 Reassembling the parts
As the wreckage was pulled from the river it was examined and identified, and any failures of the metal components were recognised and tagged. This was a mammoth task, given that virtually the whole bridge had fallen into the water, including all the road decks, trusses, chains and hangers, eye bars and the two towers. The parts were then reassembled and all the failed or fractured components photographed and catalogued. Over 90 per cent of the bridge components were collected together and reorganised into their original positions in the bridge. Their position on the river bed before extraction was also an important facet of the investigation. To help reconstruct the sequence of events, the metal parts were classified into different categories:
undamaged, or minimum damage;
ductile damage, such as distortion or bending;
separation of parts by fracture.
The fractured parts were then examined in detail to identify the extent of plasticity, exposure of fracture surfaces, and their chemical state.
Distinguishing the different kinds of damage to the many different structures in the bridge was time-consuming, and often difficult. Metal surfaces exposed by fracture would have rusted both in the river and later, when exposed to the atmosphere during storage and reassembly. A selection of critical failed parts needed to be identified for shipping to the many labs involved in detailed analysis of the components.