ParisAirport Terminal Collapse
May 23, 2004
At Least 6 Killed in Roof Collapse at Paris Airport
By THE ASSOCIATED PRESS
Filed at 7:14 a.m. ET
PARIS (AP) -- A section of the futuristic, cylindrical passenger terminal at Paris' Charles de Gaulle airport collapsed Sunday, killing up to six people and injuring three in a shower of concrete, glass and steel.
There was no sign that foul play was to blame for the collapse, Transport Minister Gilles de Robien said. The terminal opened 11 months ago after several construction delays, which French television station LCI said were caused by safety issues.
``Some witnesses heard cracks just before the collapse, cracks and some dust from the concrete,'' said Pierre Graff, president of the Paris airports authority.
An Air France plane coming from New York and another from Johannesburg, South Africa had just landed at Terminal 2E when the accident happened at about 7 a.m., Graff said. The identities of the dead were not immediately known.
The 450-yard-long cylinder-shaped structure sits on pylons about 20 feet off the ground. It is surrounded by glass and honeycombed with hundreds of square windows that bathe the area inside with natural light.
The collapsed area was about 50 yards long.
President Jacques Chirac said he was requesting ``that the necessary investigations be immediately started so that the causes of this accident can be determined as quickly as possible.''
Paris Fire Dept. Chief Laurent Vibert said six people were killed, while Interior Minister Dominique de Villepin said five were confirmed dead.
Search dogs indicated there were few, if any, people still under the wreckage, said Michel Sappin, prefect of the Seine-Saint-Denis region where Charles de Gaulle airport is located just north of Paris.
Hundreds of rescue workers rushed to the scene and temporary hospitals were set up on the tarmac and inside the terminal.
The terminal will eventually have the capacity for 10 million passengers per year.
Just north of Paris, Charles de Gaulle is France's largest airport, handling about 58 million passengers a year, with more than half a million arrivals and departures.
Terminal 2E of the Charles De Gaulle International Airport (Paris) collapsed unexpectedly in the early morning of Sunday, 23-May-2004. Four unsuspecting travelers died in the process, simply because they were in the wrong place at the wrong time. The $900 million (US) structure, which is designed to handle as many as 25,000 passengers in a single day, may be beyond all hope of repair. The big question: why?
Multiple investigations are currently underway to answer that question, but definitive answers are not expected for at least a year. Furthermore, investigation and cleanup efforts have been hampered by continuing failure of the structure. On Monday, personnel on the scene heard cracking noises and found new fissures in the supporting concrete pylons. Most workers were evacuated from the site at that time.
Failure Details
Available information is sketchy -- what is known is that a section of ceiling 30 metres long and 20 metres wide collapsed suddenly after standing for nearly a year without any reported problems. Based on technology adapted from tunnel-building, the terminal is essentially a long, elliptical tube formed from interlocking concrete rings. The structure itself has no internal load-bearing members, instead relying on the external walls to provide support.
The Sunday collapse occurred in a section of the terminal containing access points for three boarding walkways, a difference when compared to the rest of the structure. In addition, the Monday observations of cracking sounds and new fractures occurred in a symmetrical section of the terminal that shares this feature.
During the construction of the terminal, there were problems with hairline cracking in some of the concrete support pylons away from the area of the collapse. Measures were taken to strengthen these pylons, and the process used to build the remaining pylons was altered.
There are reports that passengers noticed cracks in the walls of the structure shortly before the accident. In addition, some observers of the collapse reported having seen puffs of dust accompanied by cracking noises just prior to the collapse.
Changes and Distinctions
Several theories have been put forth to explain the collapse, though no smoking gun has been identified. Currently, every avenue of investigation appears to be open -- design, materials, construction, quality control, etc. There is a real scarcity of useful information at this time. However, it should be possible to gain some insight by consideringchanges and distinctions suggested by the known data.
- The roof collapsed in a section of the terminal that is structurally different from the rest of the building, in that it contains access points for boarding walkways. This suggests the potential of an interface problem between structurally dissimilar portions of the building.
- Later observations of cracking noises and concrete fractures in a structurally similar area symmetric to the collapsed location,just a day later, is highly suggestive of a common design or construction flaw.
- The concrete support pylons away from the collapsed location had to be strengthened after development of early hairline cracks during construction. Later pylons (at or near the collapsed area?) were built using different techniques. Do the earlier and later pylons have different strength characteristics? If so, this is suggestive of a differential load-bearing capacity.
- By all accounts, the collapse occurred suddenly for no apparent reason. No obvious reasons exist that can explain the collapse. This suggests that perhaps some environmental factor changed which brought about the failure... the weather?
- The entire structure is built in a unique fashion that does not require internal load-bearing members. All of the building's strength and stability is provided by the thin-shelled exterior. This implies a lack of redundancy, and tight coupling of stresses through the body of the structure.
Conclusions?
If one were inclined to connect the dots, a picture might begin to emerge... speculative at best, but very, very suggestive. Could a recent change in the weather have affected the load-bearing capacity of the concrete pylons? Are some of the pylons different from the others? Did this cause some parts of the terminal structure to shift slightly relative to others? Did this introduce differential stresses in the building at an interface between structurally dissimilar sections? Was the unique design, deriving all strength from the exterior shell of the structure, able to withstand these differential stresses? Did the lack of internal load-bearing members allow a potential failure to develop into a full-blown event?
It is much too early to draw any conclusions about this accident. Everything in the previous paragraph is based on an incomplete analysis of insufficient data, done by a single person (me) while also watching television. One thing is certain however... had this event occurred in the middle of the day instead of the early morning, there would have been significantly more fatalities. Already a tragedy, this event could have been a catastrophe.
The investigation into the spontaneous collapse of an innovative terminal building at Charles de Gaulle airport in Paris on Sunday will focus on its unusual design and every aspect of its construction, say engineering experts.
A section of ceiling 30 metres long and 20 metres wide crashed to the ground at 0657 GMT on Sunday killing at least four people. Several other people were injured in the accident.
Cracks in the building's walls were noticed by passengers shortly before the collapse. The accident could have claimed many more lives had it not occurred early on a weekend morning, when the terminal was at its least busy.
Efforts to clear rubble from the remaining sections of the terminal building on Monday also had to be abandoned when more cracking noises were heard. The cause of the collapse is not yet known, although the French authorities have ruled out terrorism. Attention is now focused on the building itself.
"It's a very serious issue in either the design or the construction," says Scott Steedman, vice president of the Royal Academy of Engineers, in London, UK. "In a normal situation any normal structure should be very far away from failure."
Elliptical tube
The terminal 2E building is 450 metres long and 30 metres wide. It is shaped like a horizontal elliptical tube, and is built from rings of concrete clad in metal and glass.
The building's unusual design features no internal supports for the roof, enabling passengers to flow through it more easily. This was achieved by using technology developed for tunnel building. The outer shell of the building is made from a series of concrete rings, each of which is made of three interlocking sections.
Gordon Masterton, vice president of the UK's Institution of Civil Engineers, told New Scientist that designing a building without internal supports is particularly challenging. "It's very attractive architecturally, but it does mean you're reliant on the outer walls," he says. "Any local problem would then have an effect on the structure as a whole."
The terminal was opened on 25 June 2003 and is designed to handle between 20,000 and 25,000 passengers every day.
Steedman told New Scientist the investigators would examine "the quality of materials and their installation" as well as "the design itself and whether they have unwittingly imposed funny load combination on particular elements".
He adds that it is common to use more modern materials, which should be stronger and lighter, when building unusual structures. But these materials require much more stringent treatment and quality control, he says.
Raze to the ground
The terminal, which cost 750 million Euros, was designed by the internationally-renowned French architect Paul Andreu. He has created many other airport buildings, as well as the French terminal of the Channel Rail Tunnel, a football stadium in China and a museum in Japan.
On Monday airport officials said the entire structure may have to be demolished. "If all the (structural) rings which make up this terminal are beyond repair, we will raze everything to the ground," said Pierre Graff, President of Paris's airport authority.
"We will take no risk in terms of safety," told the newspaper Le Parisien on Monday.
One worker was killed during construction of the building and the French union CGT complained that the job was rushed, allegedly compromising safety.
Paris airport probe publishes findings
PARIS (AP) — The Paris airport collapse that killed four people in May was probably caused by metal struts piercing the building's concrete vaulted roof, an official report said Tuesday.
The French Transport Ministry said preliminary findings suggested that the "dominant cause" of the partial collapse of the new terminal 2E at Roissy Charles de Gaulle airport was "linked to the perforation of the vault by the struts."
It also blamed the poor quality of the concrete for the May 23 disaster, in which falling masonry killed four travelers — two Chinese, one Czech and one Lebanese. Three others were injured.
"It's probable that this perforation was made possible by the prior gradual deterioration of the concrete," the ministry's statement said.
A commission of inquiry into the collapse is using modeling techniques and laboratory analysis of the debris to establish the cause of the disaster.
Its final report, for which no date has yet been set, will determine whether the $920 million building will be repaired or torn down.
Completed in 2002, the new terminal was a key element in the development strategies of the airport's operator, Aeroports de Paris, and its main customer, Air France.
Metal struts blamed for airport disaster
The Paris airport terminal collapse that killed four people in May was probably caused by metal struts piercing the building’s concrete roof, an official report said today.
The French Transport Ministry said preliminary findings suggested that the “dominant cause” of the partial collapse of the new terminal 2E at Roissy Charles de Gaulle airport was “linked to the perforation of the vault by the struts”.
It also blamed the poor quality of the concrete for the May 23 disaster, in which falling masonry killed four travellers – two Chinese, one Czech and one Lebanese. Three others were injured.
“It’s probable that this perforation was made possible by the gradual deterioration of the concrete,” the ministry’s statement said.
A commission of inquiry into the collapse is using modelling techniques and laboratory analysis of the debris to establish the cause of the disaster.
Its final report, for which no date has yet been set, will determine whether the £500m (€746.4m) building will be repaired or torn down.
Completed in 2002, the new terminal was a key element in the development strategies of the airport’s operator, Aeroports de Paris, and its main customer, Air France.
Aeroports de Paris (ADP), the authority that owns and operates both the Charles de Gaulle airport and Orly airport in the French capital, has determined that the entire roof structure of Terminal 2E must be torn down and replaced.
The partial collapse of the newly constructed Terminal 2E last May, killed 4 people and injured 3. In a report, issued in February (See IJ Website Feb.16), an expert commission under the direction of Jean Berthier, engineering Professor at France's Ecole Nationale des Ponts et Chaus饳, concluded that both structural and design faults were the underlying cause of the collapse.
According to the ADP, further analysis has indicated that the roof structure itself could constitute a continuing hazard if it is simply repaired. On the other hand the ADP has concluded that the building's underlying foundation is sound. It plans to demolish the remaining roof structure and rebuild it at an estimated cost of 100 million euros ($133 million).
The new terminal originally cost 750 million euros (app. $1 billion), and up until now tearing it down completely has been a distinct possibility. The decision to replace only the roof therefore decreases the insured loss estimates considerably, although $133 million is far from negligible. In addition the Terminal 2E building will remain essentially closed - although a few flights are operating out of it - until the repairs are completed at the end of 2007.
The original coverage was placed through the broker Gras Savoye. AXA Corporate Solutions was the lead carrier with around 60 percent of the risk, followed by GAN, a division of France's Groupama, with around 40 percent. According to reports reinsurance was placed with Swiss Re, Munich Re, France's SCOR Group, General Re and Hannover Re, which has estimated its exposure at no more than 15 million euros ($20 million).
AXA has said only that its exposure would not exceed 10 million euros ($1.33 million). GAN has said that it cannot estimate the amount of the loss, while SCOR indicated that it would have no significant impact on its results
Subject: de Gaulle Aiport Collapse - Inquiry is misleading
Posted On:February 16, 2005, 5:00 am CST
Posted By: Dr. Michael Hogan. P. Eng.
Comment:
The cause of this collapse was a fundamental design error known in engineering terms as: "Structural Instability of the Euler Buckling or P-Delta Effect."
In lay terms:
The eccentricity of the load causes an increase in the bending stresses,
which causes more eccentricity of the load,
which causes more bending stresses, and so on,
until the structure collapses.
The Inquiry Commission described this mechanism clearly as progressive collapse through weakening of the structure, but failed to identify it as the overwhelming cause.
Instead, the Commission clouded the issue with a number of items that were inconsequential: cold weather (4.1C is NOT cold), under-reinforcing (the sudden collapse with a "bang" contradicts that theory) and weakened concrete (the concrete was over-stressed, not weak or weakened).
Dr. Michael Hogan, P. Eng.
Hogan & Greenfield
Toronto, Canada
Modern polymer supplemented concrete is a remarkable building material, enabling clear-span bridges hundreds of feet in length. But its strength lies in its mass. The structural design feature of strength versus aesthetic design features of light and visibility are at odds with each other. So this design approach represents a challenge, though a forced one rather than an elegant and delicate balancing act, demonstrating the human ability to successfully design and construct unlikely structural elements.
The problem is that this failure gives engineering a bad name. And why? Because the final design uses window openings with square corners! And in an airport, no less. The problem with square corners is that they create what is known as a "stress concentration" point. (This mode of failure occured in early aircraft designs using square windows as well.) The stresses in the areas near the corners of the openings can be orders of magnitude (10, 100, 1000 times or more) higher than in the rest of the structure, while the simple incorporation of radiused corners can reduce these stresses to geometric multiples (2, 4, 8 times or more) the nominal stress. Look closely at the picture and you can see cracks intersecting the corners of the windows. These cracks may have been a result of the root cause failure rather than a cause of it, but they are failures nontheless.