It's a Catastrophe

With the re-launch date of our blog looming, we are feeling confident enough to forewarn you of the up and coming opportunity to win a free gift.

The first 50 visitors to subscribe to our blog 'Starting Up an Engine[er]' will receive a 'trumps' style card game.

The game pits historic construction and engineering disasters against one another. You may well recognise the examples as some of the ones we featured on our highly successful #EpicFAILS blog posts several months ago.

Have a great weekend and watch out for our weekly blog post this weekend.

We are still trying to decide whether to first wait for the result of the England game or not.... #Euros2012


Engine[er]

#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]

#EpicFAILS 3 [Structural Engineering]

"Engineers ... are not superhuman. They make mistakes in their assumptions, in their calculations, in their conclusions. That they make mistakes is forgiveable; that they catch them is imperative. Thus it is the essence of modern engineering not only to be able to check one's own work but also to have one's work checked and to be able to check the work of others." Henry Petroski

It can be said [I hope] that all of the engineering disasters spoke of in this blog thus far are of importance, and study of them will help us to understand further the historic and modern day pitfalls of structural design. They teach us many unique lessons about the potential problems within the design process, communication of design and the coveting of too much confidence in ones abilities. If we can take any lesson from the recent blog posts, that will be to expect the unexpected, and to seek help when you are plainly out of your depth - in an engineering capacity that is.

Fame or infamy are the natural by products of people, endeavours or instances in history which have meaning or can be defined by perhaps being the first to exhibit a particular behaviour or purpose [e.g. the tallest building]. By definition they stand-out, like a beacon of light, a celebration of being the best or a warning to all others to pay heed.

This week I'd like to speak of 3 engineering disasters which had historically defining effects upon our industry, they were failures which brought about very real changes to good design practice, building codes and the regulations which we all adhere to today.

To begin us off this week I would like to introduce you to the KING of building collapse case studies:


Ronan Point Building Collapse, London, UK [1968]
#Killed [injured] - 4 [17]
Contractor - Taylor Woodrow
Building System - Larsen-Nielson [large precast concrete panels]
This disaster has been very well covered in institution presentations, and research papers - all of which are obtainable from the IStructE website. It of course such an infamous structural disaster that it deserves a prominent place on our list of historic failures. The disproportional failure of this building is what set's it apart from all others.

The disaster was caused by a gas explosion, which occurred at the south east corner, on the 18th floor of this 22 storey block of flats. The disproportionate amount of damaged which then ensued, was enabled by the construction method used, and the level of workmanship involved [allegedly].

The method of construction, which was only initially intended to be made available to the construction of buildings less than or equal to 6 storeys in height, was chosen because confidence had grown in the system.

It was made abundantly clear by the high profile expert and structural engineer - Wilem Frischmann that this method of construction could be extremely dangerous for the inhabitants if such an event [like a gas explosion] were to take place. Wilem raised his concerns before the collapse in 1968.

As a direct result of the collapse and subsequent report [written by Wilem] that 9+ blocks of flats of similar construction, which contained a piped gas supply and were found NOT to be able to withstand a simulated 5psi explosion without a disproportionate amount of damage - were demolished.

Most importantly, a change in legislation and updating of Part A - of the building regulations occurred which detailed restrictions and amendments to deal with the issue of disproportionate collapse.


Tacoma Narrows Bridge Collapse, Washington, USA [1940]
#Killed [injured] - Tubby[the dog] [0]
Lead Structural Engineer- Leon Moisseiff
The Galloping Gertie. This has been an incredibly important case study ever since it's infamous failure. As a result of the collapse [which was famously captured on video] structural engineers the world over were forced to consider a whole new dynamic effect on the design of the bridge decks - aeroelastic flutter.

Again, as one would expect, there has been a great many industry and institutional presentations which have covered the reasons behind the failure of this both famous AND infamous bridge.

So why continue to regurgitate the same evidence? Well, apart from the aforementioned aeroelastic flutter, there was another very important lesson to be learned [or resurrected]. One which is has been repeated and threatens our self stylised position as chief protector of society, and practitioner of science for the benefit of mankind... and it goes a little something like this...

"The Tacoma Narrows bridge failure has given us invaluable information...It has shown [that] every new structure [that] projects into new fields of magnitude involves new problems for the solution of which neither theory nor practical experience furnish an adequate guide. It is then that we must rely largely on judgement and if, as a result, errors, or failures occur, we must accept them as a price for human progress" Othmar Ammann

Do we really?



Alfred P. Murrah Federal Building Bombing, Oklahoma, USA [1995]
#Killed [injured] - 167 [782]
Construction Method - Insitu Concrete Frame and Shear Wall
Another saddening event which was influential in changing the way we as engineers design reinforced concrete buildings above 5 storeys, and the analysis of potential blast damage.

The A.P.Murrah Federal building was designed in the early 1970's, and a widely accepted theory for the trigger which caused the disproportional collapse of the 9 storey structure, was a terrorists home-made bomb, planted in a rental truck parked in-front of the building.

The blast resulted in a maximum 10,000 psi blast into the nearest structural column, all the way down to a minimum of 9 psi to the  upper west corner of the building.

The total of 4 columns collapsed due to the immediate blast loading, and resulted in the destruction of almost half of the floor area. Many lives were tragically lost.

Due to the effects of the upward direction of the blast wave, many of the adjacent floors were subjected to uplift. This was a load case not adequately catered for in the design and detailing of the reinforced concrete floors. Disproportionate collapse took care of the remaining upper floors.

This weeks stable of engineering disasters were once again aimed specifically at the art of structural engineering. None of the above case descriptions are meant to be extensive - a mere 'taste' of the event, with perhaps a personal opinion woven into them too.

The stand out feature of these disasters shown here on this post are to do with the journey into the unknown.

The Tacoma Narrows Bridge. Longest spanning suspension bridge in the world when completed. Ronan point, over confidence in a new building system, pushed way past it's originally intended limits for storey heights. The A.P.Murrah Federal building. Long spanning reinforced insitu concrete moment frames, with little to no redundancy incase of explosive removal of essential structural support [in this case - 4 columns].

At the time, each example above pushed structural engineering further into the unknown. An invitation to unknown loading conditions, just waiting to jump up and give the engineer a wake-up call. Again, many lives lost as a result.

Have we learned enough? Only time will tell.

Next week we will have our final 3 #EpicFAILS. Until then, please do not have nightmares.


Engine[er]