Steel tubular design likely cause for terminal collapse

A preliminary investigation into the collapse of a terminal at Paris’ Charles de Gaulle Airport found that steel support rods piercing the weakening concrete shell of the building probably caused the structural failure.

The report, which was conducted by a French investigative commission at the request of Transport Minister Gilles de Robien, was released July 6. The report did not state whether the collapse was the result of inadequate materials or bad design, and did not assign any responsibility for the disaster that killed four people.

According to the report, several steel support rods punched through the building’s concrete shell, which may have contributed to stresses in other parts of the building. The $900 million terminal, which was completed only a year ago, was designed and built like an elliptical tube, using construction techniques borrowed from construction of underground tunnels. To compensate for the lack of surrounding earth that keeps underground concrete tunnels intact, the architect designed steel hoops to be attached to the outside of the tunnel with short steel rods.

Investigators found that the much cooler air temperatures inside the terminal and the changing temperatures on the outside of the building might have caused the steel banding to expand and contract against the concrete. The movement might have weakened the structure, causing the steel support rods to puncture the concrete shell.

The report stated that its findings were not final. Other factors, such as the number of openings for walkways, could have played a role in the collapse. A separate criminal investigation will name who is responsible for the accident.