The Weekly Reflektion Week 29 / 2020

Four box girder bridges collapsed between November 1969 and November 1971, all due to deficiencies in the industry standards and practices in use at the time. Our experience indicates that it is difficult to undertake comprehensive investigations, recognize common issues and disseminate lessons throughout the industry quickly. Difficult, but imperative that we manage to learn lessons as soon as we can.

Major accidents give us opportunities for learning, but are we adaptive enough as an industry to learn quickly? Do we need a Major Accident to get our attention?

On 6th November 1969, the Fourth Danube Bridge in Vienna collapsed while under construction. The bridge was of box girder construction. Over the next 2 years there was a series of failures of box girder bridges Although no failure was exactly the same as another, the underlying cause was similar, the application of buckling theory with inadequate safety factors, and the absence of adequate fabrication tolerances.

In Vienna, the 412m long three-span bridge was in the final stages of construction when the span being installed, cantilevered from the previous span, failed, and was left hanging in the air, kinked and distorted.

Seven months later, in June 1970, the Cleddau Bridge, one of the longest bridges in Europe at 820m (0,5 miles), a box girder bridge with 7 spans, was being installed in Milford Haven, Wales. When one span was cantilevered out 61 m from the previous span, it buckled over a support and collapsed, killing 4 people.

The West Gate Bridge was under construction in Melbourne when news came through of the bridge collapse in Milford Haven. The engineering team who designed the Melbourne bridge claimed that there was no relationship between the Cleddau Bridge and the West Gate Bridge as they were using a different installation method to the free cantilevering approach. They did, however, strengthen the areas thought necessary, before continuing construction. The bridge spans were being installed in two pieces with the span being split lengthwise. This halved the weight of the lifts but doubled the number of lifts. When lifting in the first half of one span, it buckled slightly. They solved this problem by removing some of the bolts, and re-drilling the bolt holes, before replacing the bolts, this to allow for a 380mm (15”) error in position due to the buckling. The lift was then completed.

The lift of the second half of the span commenced, but when in place, a vertical gap of 115mm (4,5”) was found between the spans. Hydraulic jacks were used to try to close this gap, but this failed. In the next attempt they used 51 tons of concrete blocks to get the span in place. When one problem was solved, another arose, and the span buckled across its width. The obvious solution was one used previously, remove some bolts, re-drill the holes and replace the bolts. 37 bolts were removed, and suddenly the span collapsed killing 13 bridge workers. It was now November 1970.

In November 1971, near Koblenz in then West Germany, a box girder bridge was being built over the Rhine, when the 236m (774 feet) central span about halfway out in the cantilevering installation method buckled and collapsed with 13 fatalities.

Major disasters usually take some time to investigate, identify the causes and applicable actions including disseminations of the lessons learned. After the West Gate Bridge disaster, a Royal Commission of Inquiry was appointed to investigate the causes of the bridge failure, also using information from the Cleddau Bridge disaster. The report was published in late 1971, too late to prevent the Koblenz bridge disaster. It became apparent that the complex behaviour of the stiffeners in box girder bridges was not understood, and the design codes reflected this lack of understanding. As a result of these disasters, new design rules for box girder bridges were developed by the industry, design factors were changed, and manufacturing tolerances tightened.  

Is your industry adaptive enough, and nimble on its feet to react quickly to lessons learned? Do you wait for the final investigation report or can you be more proactive in your response? Are we observant enough to identify the incidents that we can learn from that do not end in fatalities? Do we need a Major Accident to get our attention?

Reflekt AS