It appears that our commenters on the original story were on the ball:
This report concludes that the main girders supporting the formwork were not braced to prevent lateral movement of the girders when subjected to the loads imposed by the concreting works. The inclination of the beams from the vertical meant that the loads in them were not carried concentrically and excessive stresses were induced through bending of the girders’ webs. Thus the cause of the falsework failure was the inability of the main longitudinal girders to carry loads arising from the 3% crossfall of the bridge deck.
Weekly NewsletterEvery Thursday afternoon, we package up the most-read and trending RiotACT stories of the past seven days and deliver straight to your inbox..
The parts of the remaining permanent works that are likely to be salvageable are limited to the central pier and abutments, but these will need to be protected during demolition and inspected for damage, distress and excessive movement when the opportunity arises.