Tennis Balls Could Protect Buildings from Earthquakes

Photo by Samuel-Elias Nadler on Unsplash

Engineers develop various methods to make buildings more earthquake resistant. Even tennis balls! Some buildings are built flexibly, so they can swing back and forth a bit without collapsing. Some very tall buildings weigh the top called a mass damper that helps to dampen the vibrations caused by the earthquake. Other buildings have insulating beds, also known as the base isolation system.

As the name suggests, these bearings insulate a building’s base from the ground, allowing it to move independently during an earthquake. That is, while the ground moves back and forth, the structure does not move. These seismic isolation systems, placed on the foundations of certain buildings in high-risk areas, use complex structures made of concrete, rubber, and metal to absorb the horizontal oscillations of the ground and reduce earthquake damage. However, such adaptations are expensive.

For example, costly seismic isolation systems can increase construction costs by up to 20%, according to engineer Jian Zhang of the University of California, Los Angeles. Although these systems save more on cost over time, builders in some earthquake-prone areas may not have enough budget.

So, to create a simpler and lower-cost alternative with readily available materials, the scientists decided to leverage the principles of “rolling physics” by using “recycled tennis balls.” The roll isolation used by the team of ETH Zurich seismic engineer Michalis Vassiliou is based on the principle of separating the building to which it is applied from the ground, transforming uneven horizontal shaking into a gentle rocking motion and using friction to reduce these vibrations further. This simple method was used even on the 5,000-year-old Peruvian pyramids that still stand, but today’s construction uses expensive and standardized insulation systems.

For a modern approach to rolling seismic isolation, detailed in Frontiers in Built Environment, researchers injected cement-like mixtures using bags of pastry cream into hundreds of rebound tennis balls from surrounding tennis clubs. They built an inexpensive prototype of four padded tennis balls sandwiched between two concrete slabs. Then, in their earthquake simulation, they found that each ball supported the equivalent of eight kilonewtons and withstood the earthquake shaking. This is about twice as much as insulation systems can withstand in single-story houses. During testing, the balls had to contain the right amount of mix to neutralize vibrations without cracking the structure.

Vassiliou said the next step is to build and test a larger prototype with hundreds of tennis balls at a research center in the seismic belt.

If you like tennis and physics, you should read “The Interesting Physics Behind Tennis.”

Ali Kaya


Ali Kaya

This is Ali. Bespectacled and mustachioed father, math blogger, and soccer player. I also do consult for global math and science startups.