THE TRAGEDY
Unbolting of 4-5 Splice on 10-11 North | The Collapse
The Immediate Aftermath | The Survivors | The Heroes | The Victims
Events Leading Up to the Collapse
When the two half girders on the west side, span 10-11 were brought into close proximity up in the air it was established beyond all doubt that a camber difference of about 4.5 inches existed. It was proposed by JHC that time might be saved if the vertical difference of level could be taken out by using kentledge to push down the north half span relative to its south counterpart. It so happened that ten cube-shaped concrete blocks, each weighing about 8 tons, were on site from a previous operation and it was thought that these would give about the right order of load to remove the camber difference, if positioned as a more or less concentrated load near mid-span.
Hindshaw (Jack Hindshaw, M.I.C.E, Resident Engineer, Freeman Fox and Partners for the project) discovered that the use of kentledge had caused a buckle to develop. His diary entry for Wednesday 9th September, 1970 includes the observation "Obvious overstress due to concrete kentledge." Neither in his diary nor elsewhere does Hindshaw comment that this unfortunate consequence was the result of JHC using more kentledge than the amount he had approved. There can be no doubt that the act of adding the kentledge was the precipitating cause of the buckle which, as described in the preceding section, appeared on the inner upper panel around joint 4-5 north. The buckle was a clear indication that partial failure of the structure had occurred.
On 2nd June 1970 , one span of the Milford Haven Bridge in Wales collapsed during construction. This bridge had many features in common with the West Gate Bridge including the use of a trapezoidal box girder. Following upon the Milford Haven collapse, certain steps were taken to strengthen the steel spans of the West Gate Bridge.
At the time that JHC took over Contract E, WSC had in fact, assembled the two half spans on the east side of the river between piers 14 and 15, and had successfully lifted them into position on top of the pier, but the joining of them, and the bolting together had not been completed, so that JHC had to complete the joining of those two half spans. On the west side there had been a certain amount of work done on the northern half span between piers 10 and 11, and at the time of the change-over, this partly assembled span was still on the ground.
Jacking up of this north half span between piers 10 and 11 commenced on the 15th May, 1970. After delays caused by strikes and bad weather, the rolling beam level was reached by 9th June 1970 and on the 19th June, the rolling of the north half span across the rolling beam commenced. This operation was completed on the 22nd June. The jacking of the southern half span was commenced on the 17th August. By the 28th August, it had reached the rolling beam level. On the 29th, it was rolled across, and that process was completed on the 1st September.
The situation immediately prior to the 15th October, 1970, was that on the east side, two half spans 14-15 had been joined, and cantilevering for the next span reached box 12, where it rested temporarily on a trestle specially erected for that purpose, about mid-way between piers 11 and 12. On the west side, the two half spans 10-11 had both been elevated and were resting on the rolling beams. They had been brought to their positions, but the longitudinal jointing between the two halves was less than a third completed.
