Posted on 05/28/2004 3:53:45 AM PDT by snopercod
Section of year-old concrete concourse at Paris airport dropped, killing at least four people
Construction problems with supports of the vaulted concrete concourse that partially collapsed early on May 23 at the year-old Terminal 2E at Paris Charles de Gaulle Airport will likely be a focus of investigations into the cause of the failure, which killed at least four people.
Roughly 30 meters of the unusual freestanding vault enclosing the 650-m- long elevated concourse dropped several meters off its bearings with little warning.
On evidence available at press time, an independent structural specialist suggested faulty concrete bents.
"It looks like the roof is an innocent victim, along with the people inside," he says, requesting anonymity. Noises emanating from nearby structures warned of continuing instability a day after the fall.
State-owned Aéroports de Paris (AdP), which was responsible for the architecture and engineering of the $900-million complex, has not ruled out demolishing the entire concourse if fundamental faults are unearthed.
Serving 22 aircraft bridges, the concourse provides waiting areas in a tubelike space on an elevated concrete slab parallel to the main terminal building. It is enclosed in a flat elliptical reinforced-concrete vault, 30 centimeters thick. The vault is heavily perforated with window openings. A nonstructural aluminum framework supports glazing above the concrete.
The vault is divided along its length into 10 sections with gaps in between to let in daylight. Halfway along the concourse, the vault is interrupted by an "isthmus" building linked to the main terminal. The failure occurred immediately next to the isthmus.
Each of the roof’s 10 sections is made of 17 precast concrete vaults, spanning more than 30 m over the concourse. Though not connected structurally to each other, the 4-m-wide vaults are fixed to previously cast edge beams running between concrete portal frames rising from the ground, much like bents.
The beams’ neoprene bearings, supplied by Paris-based Freyssinet S.A., are seated on notches at the outer corners of over 80 concrete bents, spaced along the concourse. People and vehicles circulate under the bents.
Under a $32-million contract, Paris-based GTM Construction S.A. built the roof on top of supporting frames. The frames and other substructure formed part of a separate contract by Hervé S.A., Paris. Both contracts ran between April 2000 and January 2003. A separate joint venture of two French contractors installed the external glazing.
GTM erected the 4-m-wide rings of the vaults symmetrically, with two side elements and one at the crown, explains an engineer with Vinci Group, the contractor’s owner. GTM supported the elements on a rail-mounted frame until they were stitched together with reinforcing steel and concrete into spanning shell sections. No structural connections were made between abutting shell sections.
With AdP ruling out terrorism and sabotage, construction defects are seen as a possible cause. AdP concedes that columns had to be additionally reinforced, but problems during construction appear to be more profound, says a senior contractor on a nearby job. "We know they had problems. They stopped production altogether [for weeks]," he says, speaking on terms of anonymity.
"Work stopped early during vault erection while the contractor jacked up the shells to allow repairs to columns," says the observer. "They repaired all the columns with external glass-fiber reinforcing [and] the deflection of the shell was bigger than expected," he adds.
The engineer believes AdP ordered a complete review of the design before work resumed. AdP had produced the outline design and, under normal French conditions, GTM would have taken charge of detailed work. However, GTM reportedly denies any design responsibility.
By press time, AdP was unable to provide staff to clarify several of these issues because of the pressured situation. The company could not predict when conclusions would emerge from the investigations. GTM referred questions on construction faults to AdP. Hervé declined to comment at all.
While AdP has closed Terminal 2E, the almost symmetrical twin, Terminal 2F, remains functioning. Completed in 1998, 2F introduced an internally exposed concrete vault, designed by the then chief architect Paul Andreu, now an independent practitioner. However, the older terminal’s vault is a nonstructural ceiling supported externally by long-span arching trusses.
AdP reports no problems with the 2F vault, but changed the design for its new neighbor. In 2E’s 450 x 70-m main building, lighter and easier to install timber forms the ceiling. The change was done to save time and cost, says AdP’s project architect, Anne Brison. But Andreu’s interest in the concrete vault found itself in the new terminal’s concourse, though with a significant difference. As the failure shows, the concourse vault is structural, unlike 2F’s more resilient ceiling.
* * * * * * * * * * * * * * * * * * * * * * * * * *
Moving Far Beyond
Paris airport’s evolution over the last three decades has been intricately linked with the career of Paul Andreu, until recently Aéroports de Paris’ chief architect. The collapse of his last major Paris project will be a bitter blow as he carves out a second career, which took him to Beijing, where he heard the bad news.
Andreu is an architect who stretches engineering to achieve his aesthetic goals. He admits to having little interest in molding designs to structural purity.
To achieve his goals he is known for establishing dominance over the design team. Nevertheless, he is said to be sympathetic to contrary views. “He’s an intelligent man,” says a senior engineer on a current project. “He wants to understand,” adds the engineer, but “if you are wrong or not convincing enough you don’t get what you ask for.”
Andreu left AdP last year, having reached the French civil servants’ retirement age. The architect is continuing an international career that began early on with AdP.
His current masterpiece is the elliptical steel dome that crowns China’s new national theater in Beijing. Andreu entered the design competition for that job in part to prove his range went beyond air-ports.
Sorry Andreu, the laws of physics are not French.
bump
Form over Function?
What? Mon Dieu et mon droit!!
(Which one schoolboy interpreted to mean, "My God, you're right!")
If I were Chinese, I wouldn't be buying season tickets to the new national theater!
Thanks for the bump. Interesting.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.