Rocket science steps up for quake safety

Chinese rocket engine designers have used their expertise to create a new twist on an old idea to help buildings withstand earthquakes.

The basic idea, known as seismic base isolation, is to decouple a building's superstructure from its underlying support structure, so that shock waves from an earthquake are absorbed.

While the basic concept is not new, engineers at the Academy of Aerospace Solid Propulsion Technology in Xi'an, Shaanxi province, found a way to adapt some techniques used in the production of flexible joint nozzles - key parts on rocket engines - to make seismic base isolators that perform better than others of their kind on the market.

The academy is part of the country's major space contractor, China Aerospace Science and Technology Corp, and mainly makes solid-fuel engines for Chinese carrier rockets and ballistic missiles.

You Junfeng, a chief designer of solid-propellant rocket engines at the academy, said designers developed a new type of base isolator with multiple layers of steel plates and rubber matting.

Such base isolators can help a building withstand earthquakes by mitigating about 80 percent of the seismic force, he said.

"The capabilities of our product are better than the requirements in the national standards and those of similar products in the market," he said. "This is because we used special molding and optimization methods in production. Such methods are typically employed in the production of space products rather than civilian goods, so other isolator makers don't have them."

The isolators have a service life of at least 60 years, he added.

Bai Xueshuang, a seismic analyst at the China Academy of Building Research, said deploying base isolators beneath a building is common in the construction industry, but it has not been widely used in China because it costs more for builders.

"The space engineers' design appears to be effective and reliable. If they can give it an affordable price, the product will have a lot of opportunities in the industry," Bai said.

The isolators can also be retrofitted to existing buildings, Bai said, though doing so would likely be expensive.

"China is one of the most earthquake-prone nations in the world, so it needs reliable and effective means to protect its buildings, especially the vast amount of old, low-rise residential structures," he said.

At Dali County Experimental Primary School in Shaanxi province, base isolators designed by the rocket experts have been used in three newly built buildings. There are 30 isolators laid beneath each building, with 6 meters between them, according to Tang Chunyu, an official at the academy in charge of marketing the product.

He said the academy is striving to promote the isolators to the construction industry. The market potential is large, as there are only about 3,000 buildings on the Chinese mainland that have used any kind of base isolation technology, he said.