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Learning from history: why the box-girder bridge failures matter today

Ian Firth FIStructE explains why engineers can still learn from two bridge collapses that happened 50 years ago. Ian is an acclaimed bridge engineer and former President of the IStructE.

15 October marks 50 years since one of Australia’s worst accidents. 35 people were killed when the West Gate Bridge in Melbourne collapsed during construction. The tragedy came just a few months after a similar accident in Milford Haven, South Wales, when the Cleddau Bridge also collapsed during construction, killing four people.

Both bridges used a relatively new technology, steel box girders. These had developed rapidly in the 1960s and were being applied by many bridge designers. With dozens of similar bridges being planned or built in the UK alone, there was an urgent need to establish what had gone wrong.

Not long after another tragedy occurred. In November 1971 a steel box-girder bridge across the River Rhine near Koblenz in Germany collapsed killing 12 people.


Investigating the disasters


The British government responded by setting up the Merrison Committee of Inquiry. It was tasked with investigating the design and construction methods of box-girder bridges. It was also asked to make recommendations for change.

The committee was made up of some of Britain’s most respected civil and structural engineers. It quickly produced an interim report in June 1971, with a final report (Inquiry into the basis of design and method of erection of steel box-girder bridges) following in February 1973. The report set out radically new design and workmanship rules for bridges.

A similar investigation in Australia led to the publication in 1971 of the Report of the Royal Commission into the Failure of West Gate Bridge.

The two reports remain essential reading for bridge engineers. While the technical lessons have been incorporated into modern codes of practice, leading to safer designs today, the procedural lessons are still every bit as relevant.


Better procedures


When presenting the committee’s conclusions, the chairman noted:
"No amount of writing of design codes and writing of contracts can in the end be guaranteed to prevent the results of stupidity, carelessness or incompetence. But one can do a great deal to discourage these vices and that must be done."
Sir Alec Merrison
As a result, the committee recommended four key procedures to improve the safety of bridge design and construction:
  • An independent check of the engineer’s permanent design
  • An independent check of the contractor’s method of erection and temporary works design
  • Clear allocation of responsibility between the engineer and the contractor
  • Provision by both the engineer and the contractor of sufficient adequately qualified supervisory staff on site.
The system of independent checks recommended by the Merrison Report is still familiar to bridge engineers in the UK today, but should it be more widely applicable?


Relevance today


Failure, or near failures, still occur far too regularly. The collapse of a wall at Oxgangs Primary School in Edinburgh in 2016 and the collapse of a footbridge at Florida International University in 2018 are cases in point. Sadly there are still too many others.

Investigations into both examples highlighted:
  • The need for independent scrutiny of designs
  • The need for independent scrutiny of how the designs are built on site
  • The need to ensure the competence of those involved.

They go to show that the lessons of the Merrison Report apply to buildings as much as they do to bridges. They are also every bit as relevant today as they were 50 years ago.

The more complex the building or structure, the greater the need for independent scrutiny of the design and for supervision on site.

If we are to ensure the safety of buildings and structures tomorrow, we must re-learn the lessons of yesterday. It is the essential principles of care and attention, qualification and competence, responsibility and communication that matter most.


Download the Merrison Report


You can download a copy of the Merrison Report using the link below. The report is made available under the Open Government Licence.

Downloads

merrison-report.pdf (.pdf, 14.1 MB)

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