A partial collapse of the Morandi bridge in Genoa, Italy has led so far to the deaths of 37 people after their vehicles fell from the wrecked structure.
An approximately 210m long section of the Morandi bridge collapsed yesterday, August 14, 2018, at 11.30, injuring a further 16 people. Members of the Italian Red Cross are using sniffer dogs to find people trapped in the wreckage.
The bridge, which is part of the Polcevera Creek Viaduct, was built in a densely crowded urban area occupied by two railroad yards and large industrial facilities. The structure, designed by Riccardo Morandi, was opened in 1967 and was said to be undergoing structural repairs at the time of collapse.
According to Dr Maria Rosaria Marsico, senior lecturer in structural engineering at Exeter University, the viaduct includes three cable-stayed spans and a series of minor spans for a total length of about 1182m. The three largest spans consist of independent cable-stayed structures, each carried by an individual reinforced concrete pier and tower 90m high.
“The cable-stayed systems were characterised by the adoption of prestressed concrete stays, a common feature of bridges designed by Morandi in the sixties,” she said. “The viaduct was subject to maintenance work since it was built, and in the nineties a complex intervention of repair was carried out involving the installation of conventional steel tendons which are flanking the existing concrete stays.”
Ian Firth, FREng, past president of The Institution of Structural Engineers, said it is too early to say what caused the collapse of Morandi bridge, but corrosion of tendons or reinforcement may be a contributory factor given the age of the bridge.
According to recent research, corrosion of reinforcement changes the long-term behaviour of ageing reinforced concrete bridges, said Dr Mehdi Kashani, associate professor in structural mechanics at Southampton University.
“In addition, bridges are constantly subjected to cyclic dynamic loading due to highway traffic, wind and/or major/minor earthquake, which will result in fatigue damage in bridge components,” said Dr Kashani. “It is reported that this bridge collapsed during a heavy storm. Therefore, dynamic wind loading, combined with additional loading due to on-going work on the bridge, and reduced capacity due to corrosion and fatigue might be the cause of failure. However, there is need for further detailed investigation to fully understand the cause of failure.”
Firth said the A-frame towers which support the concrete-encased stay cables combine with V-shaped supports below the deck of the bridge to create a stiff arrangement which is not common in cable-stayed bridges.
“This deals with potential unbalanced loads which arise due to the multi-span nature of the structure,” he said. “As yet, there is no evidence to say whether any impact occurred; it is too early to say what triggered the collapse.”
So dismayed to learn of this: the scenes of devastation looked almost like a man-inspired earthquake. All we need to read about now is of the first plane-load of ambulance chasing lawyers heading to the scene: to profit from suing whoever is responsible.
Looking at all the available photos, the concrete sections do not seem to have a lot of Rebar – appears to be on the outer edges only and some “tube” like central pipes of a Rebar-frame or Clay bricks which is hollow? https://dynaimage.cdn.cnn.com/cnn/w_1600/https%3A%2F%2Fcdn.cnn.com%2Fcnnnext%2Fdam%2Fassets%2F180814161445-38-genoa-italy-bridge-collapse-0814.jpg. also some photos show “black concrete”, what is this really and no Rebar poking from these huge chunks? https://dynaimage.cdn.cnn.com/cnn/w_1600/https%3A%2F%2Fcdn.cnn.com%2Fcnnnext%2Fdam%2Fassets%2F180814132418-18-genoa-italy-bridge-collapse-0814-restricted.jpg
Here is a clearer photo showing the lack of Rebar and the Clay-brick pipe in the middle- what does this pipe do for strength?
https://dynaimage.cdn.cnn.com/cnn/w_1600/https%3A%2F%2Fcdn.cnn.com%2Fcnnnext%2Fdam%2Fassets%2F180814125654-07-genoa-italy-bridge-collapse-0814-restricted.jpg
All ‘Man-Made’ disasters tell extremely valuable teaching lessons for engineers and designers, constructors and contractors. Sadly enough, very few engineering professionals do study those disasters seriously enough, in order to improve their knowledge and specially, their engineering criteria and judgement. Case in point: the Morandi design. After reading and re-reading numerous articles on this disaster, many of them translated from other languages, it appears to me that there are several lessons to be learned. The fact that Mr. Morandi LOVED the then novel Pre-stressed concrete construction so much that he imposed himself to use pre-stressed tendons or “stays”. He not only preferred to use the least amount of stays (only two on each side of each tower), but went so far to use pre-stressed concrete as his construction method for those stays.
One does not need to be a certified structural engineer to appreciate that a bridge stay or tendon is a comparatively slender member, so that very little pre-stressing can be applied… therefore, apart from a limited stiffness advantage, there is very little to be gained from using pre-stressed concrete stays instead of the much more conventional and universally accepted steel cables. This points to a dangerous attitude from the designer: when he/she becomes too attached to a given design type, i.e. a kind of ‘Pygmalion phenomena’ (when a creator of a work becomes too enamoured -infatuated- with his work that he ends believing it is not only the best, but the only one solution for a given design). As several academics that are well versed in concrete structures design have said,
“We were very naive believing those concrete constructions were going to last forever”, while the truth is that there are several concrete degradation mechanisms, that make those structures prone to need a lot of maintenance and close monitoring, especially after a few decades of life. Then, couple a less than acceptable design with the less than 100% perfect construction, and a general disregard by politicians and private (usually greedy) operators, and the end result is a disaster. It could have easily failed before, as there were many defects apparent from the early years, as there were many adjustments and tendon replacement required to partially correct the very notable deformations presented on the deck, that pointed out that the bridge was a partial failure from the beginning.
I paraphrase: The Engineer for the original Tay Bridge (Sir Thomas Bouch?) when asked at the Inquiry into its collapse “why did you have the cross-section of the supporting cast iron struts the same ratio as that of the webs, regardless of their length ?” replied “because I have always done so!” I take on board, as should all young Engineers and students, the well defined views that ‘time’ and ‘ambience’ and their effect(s) on all engineering structures is something we forget at our peril.
Fascinating Alfredo.
Geoff, I assume the hollow core is to improve buckling stiffness per tonne. I agree, the quantity of rebar looks small. Not clear why the weight saving was so critical if that’s the near-vertical towers.
Italy may have a tricky retrofit elsewhere, and pretty certainly on the other 2 towers: replacing the concrete “cables” with steel cables, or else creating new column supports underneath.
Tim, agree but why use regular low stress clay building blocks, which can crack and allow moisture to enter from the inside and cause corrosion of the Concrete? The bridge had a traffic flow well beyond its design, so to much loading, vibration, stress applied since the 1960’s.
A court of inquiry concluded that the bridge had been “badly designed, badly constructed and badly maintained”. All three reasons directly attributable to cost-cutting/bad workmanship:-
https://www.theengineer.co.uk/issues/january-2013-online/january-1880-the-aftermath-of-the-tay-bridge-disaster/ – Comment: 25th January 2013.
In the 1960s, 2018 and 1879, the common factor is building for (criminal?) profit, not posterity. This is negligent homicide, isn’t it? I wonder if the iconic Forth Rail Bridge is still only halfway through its working life. Engineers know how to build infrastructure to last for centuries. It’s a dereliction of duty by politicians – when will they ever learn? Do they even care enough to take responsibility?
In 1880, The Engineer wrote; “Our only comfort is that nothing of the kind has ever happened before.” – Can’t say the same now!
I free-wheeled to a rest at the bridge over a stream and the capping stone came away in my hand. It was only then I noticed that two others were missing. The mason must be proud of himself. It was only rebuilt a few years ago.
One element of the module I developed and taught at several Universities was the concept of Professional responsibilities. I used as one the example the Aberfan (coal-tip slid into the village school killing over 100 children) disaster: and also the loss of a Trident aircraft leaving London Airport (pilot retracted flaps too soon and plane literally fell out of the sky).
In the first case, everyone involved knew! that a terrible episode was in prospect, but no-one in authority did anything about it! In the second, the second pilot (there to watch and correct the pilot) was so junior in the pecking order of British Airways that he dare not say anything to his senior -who was known to be a rather crusty character. There was another episode involving an explosion in a chemical plant (Flixboro) where the fitter who had been told to connect a temporary by-pass told his senior such was unsafe and was told to mind his own business.
Invariably, there were Inquiries. I have always believed that the UK leads the world in 20/20 hindsight. In each case, there were reports, comments, advising of the potential for problems ignored. In the Aberfan episode, the only person exonerated by the Judge at the Inquiry was the site foreman: who had written to his MP, his vicar, his local Union secretary, the local press….highlighting his concerns and had been threatened with dismissal for doing so!
Sadly, I have no doubt that there will be several ‘reports’ and recommendations lying gathering dust on senior desks withing Autostrada spl to be found and acted upon when its too late.
“When will they ever learn?, when will they ever learn?”
Undoubtely, this disaster has many contributing factors, as almost ALL disasters have. But, apart from the construction and (lack of) maintenance aspects, speaking only about the engineering aspect, the basic design of this bridge (and its sister bridges in Maracaibo and other places) seems to have some fundamental weaknesses. Back in the 50’s and 60’s, the use of reinforced and pre-stressed concrete was strongly advocated and favoured, and if you read the several books and articles of that time that promoted that kind of construction, you will note that it was proclaimed as “The Way To Go”, or “The Future of (bridge) construction”…
Personally, I don’t care how “beautiful” or “ugly” a bridge appears to be, as long as it is safe and solidly built, practical and easy to inspect and maintain.
This pygmalion phenomenom is not confined to engineering. As someone who has worked for many years at a senior level interacting with career obsessed ‘business’ people I have seen this frequently. Anywhere someone has the temerity to suggest something might not be right or there may be awkward consequences is invariably ignored, disparaged or treated dismissively. It is usually the one single mindedly most vested in the intellectual concepts of whatever it is who views everyone else as an upstart, who can’t possibly know as much.
Once again, the amazing ‘value’ of our journal: to educate those of us Engineers who do not know the detail of specific areas of the Industry we all serve, by access to the thoughts and comments of those intimately involved, is demonstrated. As fellow bloggers may recall, I shared a flat at Uni with three other undergraduates, who were headed to become Civil Engineers. One (Peter Birse) became so skilled and effective as a contractor, he went Public in the 80s. I recall him describing the substantial difference(s) between that had been drawn (and presumably calculated), what had been the hope of the owner and operator to receive, and what was actually built and delivered.
I read Mechanical Sciences at Cambridge in the mid-50s as a serving officer and returned to military duty on graduation, so I am virtually an amateur in engineering matters. But even I know that concrete is strong in compression and weak to non-existent in tension. I have been impressed by bridges all over the world, especially some of the new stay-bridges but it never occurred to me that anyone had designed bridges with concrete stays, and the only mystery is that the bridge stood so long… One photograph taken after the disaster seemed to show steel cables fastened to the outside of some of the stays so clearly someone knew very well what was coming. And, sadly, it did.