#EpicFAILS 4 [Structural Engineering]

DOH!

This week I will finish the #EpicFAILS off with 3 examples of engineering malfunctions on an grand scale. The results of the mistakes vary greatly - but the underlying question is always the same.

"...Who checked these?"


Silver Bridge Collapse, Ohio , USA [1967]
#Killed [seriously injured] - 46 [9]
Designers & Contractors - The General Corporation & the American Bridge Company
Failed due to - Low redundancy in design [high tension eye-bar chains]

There were a number of reasons why this bridge was said to have failed. It did fail though, and at the height of rush hour - claiming the lives of 46 [2 of which were never found].

The system of heavily loaded eye-bar chains had been used and was being used on a number of bridge designs worldwide. One such example was the Clifton Suspension Bridge in Bristol, UK. The big difference between this design and the other examples was redundancy. Or lack of.

The eye-bar chains were a 'special' high tension steel design, and attracted more than twice the load of a simple mild steel alternative. This in itself was not a problem, as it was proven to be able to hold the load expected of them. The problem occurred when one failed due to corrosion, minute stress fractures [probably cast into the eye-bar during manufacturing] and over-loading. The disaster happened because there was no fail safe system.

Witnesses to the bridge disaster described 'a bridge collapsing like a deck of cards on a windy day'. The other bridge design examples have many eye-bar connections to fall back on incase of catastrophic failure. This bridge did not, and it was the designers choice.


Citigroup Centre, New York, USA [1978]
#Killed [seriously injured] - 0 [0]
Structural Engineering Designer - LeMessurier
Predicted Failure due to - Higher wind load than allowed for by designer. 

This building did not fail. It could have though - and was in danger of collapse.

An engineering student and a design engineer contacted the original designer, LeMessurier, to talk about certain design changes that occurred during construction, which would prove to have potentially serious effects on the strength of the braced steel connections.

The designer LeMessurier had not re-calculated all possible wind load combinations to test the theoretical model before construction was completed.

At first, it was said that LeMessurier was not overly concerned with the findings, as there was a certain level of redundancy by way of factors of safety inherent in the design. He was to later change his mind and contact the building owners about the engineering gaff.

The building was believed to be within hours of an emergency evacuation as Hurricane Ella slowly approached from Cape Hatteras.

LeMessurier managed to organise the retro modifications to the connections under cover and out of the public's eye. That was until 20 years later when the blunder was revealed to the world in the The New Yorker.


Hotel New World Disaster, Singapore [1978]
#Killed [seriously injured] - 33 [17]
Structural Engineering Designer - 'unable to locate'
Failure due to - Miscalculation of loads 

Apparently it took 60seconds for this 6-storey building to collapse, trapping 50 people, and killing 33. It still stands as Singapore's most serious civil disaster of all time.

The follow on investigations into why this building simply collapsed discovered that a great many blunders had occurred, and a substantial number of alterations had also been carried out to the building during it's life;

• In 1975, a bank added a vault weighing twenty-two tons on the ground floor.
• In 1978, the building owner added two additional cooling towers on the roof.
• In 1982 for architectural reasons, the building owner fixed heavy duty ceramic tiles on each exterior face on every floor weighing a total of fifty tons.
• In 1986 the owner installed an additional cooling tower on the roof.

All of the above extra loads were passed off as inconsequential compared to the actual reason why the design fell over. This failure represents probably the biggest engineering 'DOH!' of all time.

During the investigations, it was discovered that the original structural engineers had failed to account for any dead loads in the analysis. In effect the buildings own weight was missing from the calculations.

This error led to many similar high rise buildings being retro-fitted and strengthened due to engineering miscalculations in Singapore.

This the last of my #EpicFAILS sequence of blog posts. I hope you enjoyed reading them - and a special thank you goes out to all those who have taken the time comment too.

Again, these lists of failures are not meant to be exhaustive [have you got a few years?], nor were they meant to give you every last detail as to the reasons why failure occurred. I implore you, please take a look at the links provided and do your own research into them too. It follows that the more we learn about engineering failures, or failures during construction - the better we can prepare ourselves and help reduce the likelihood that we make similar mistakes as structural design engineers.

I will come back to these posts from time to time to refresh them as a result of new comments, and research.

Thanks again for reading, and please do not have nightmares.


Engine[er]