Anyone who watched this video of the March 11 Japan earthquake,
can only be in awe of the fact that the building is not only still standing, but preserved its structural integrity after the 9.0 earthquake. Here’s the story behind it,
Why One Remained Standing
It would be easy to call the Mediatheque’s survival a miracle, but it would be wrong. The building’s extraordinary resilience was the result of a close collaboration between a creative architect and an equally creative engineer, Mutsuro Sasaki, known for his ability to devise innovative systems that turn provocative designs into safe buildings without sacrificing their original vision. Both Mr. Ito and Mr. Sasaki were mindful of lessons learned from the Kobe earthquake of 1995 that took place during the design process. Together, they went beyond Japan’s strict earthquake codes for a new aesthetic and structural model.
Mr. Sasaki began by breaking the sketch down into its structural parts—floor, beam, column and foundation. Mr. Ito’s slender floor slabs were impossible to achieve in concrete without the conventional support of beams or walls; they would have been far too heavy and deep. Instead, Mr. Sasaki used a steel “sandwich” strengthened internally by a network of steel ribs for a slender floor plate only 15¾ inches thick. The welding technique was borrowed from shipyard building.
The stacked floor plates of a multistory building are customarily carried on solid columns. The objective here was to make the columns as light and transparent as possible. Mr. Sasaki substituted a system of hollow steel tubes in the form of open, spiraling lattices formed by smaller steel tubes. There are 13 of these lattice tubes, but only the four largest, 20 to 30 feet in diameter, placed at the corners of the floors, support the building’s main loads.
The nine smaller tubes vary in size and diameter and are placed randomly throughout the building, some straight, some angled, echoing the idea of Mr. Ito’s “floating seaweed.” These twisted, canted, open supports have a structural strength and rigidity that increases the building’s earthquake resistance. They act as light wells and contain elevators, stairs and conduits for utilities.
At the basement level, the columns are solid and firmly fastened to a below-ground framework connected by beams that can bend and deform without breaking. The large corner columns that channel the building’s major forces to the ground also conduct the seismic energy to this framework, where 60% to 70% of it is absorbed, reducing the stresses to the building above. An engineering inspection after the earthquake determined that Mr. Sasaki’s system worked.
The building’s damage was limited, and the company will reopen up the the fourth floor this month, and the other two floors in July.
A wonderful meeting of technology and art.