How The Loma Prieta Earthquake Shook Up Seismic Standards
SAN FRANCISCO (KPIX) -- Some new Bay Area buildings may have the edge when it comes to riding out the next big earthquake, thanks to seismic-savvy building techniques inspired by hard-won lessons learned in Loma Prieta.
There is a growing interest in resilience-based design for the next generation of critical buildings and structures.
The 6.9 Loma Prieta quake was a wake-up call but not the "big one".
We're long overdue for a magnitude 8 or greater along the San Andreas or Hayward faults.
Just ask structural engineer Evan Reis. He is co-founder of the U.S. Resiliency Council.
"Earthquakes are a real problem. We can't sugarcoat the risks we face in California," noted Reis.
But inside a former naval structure on Mare Island in Vallejo, an innovative technology is shaking things up.
"Today we are building buildings all over the world that are not damaged by earthquakes," remarked Victor Zayas.
Zayas is a structural seismic engineer. He is president of Earthquake Protection Systems. He invented a system to help critical structures ride out massive earthquakes, and remain standing and functional.
"What we need functioning after an earthquake is our hospitals, our transportation systems and our electric power sources." said Zayas.
His weapon against massive quakes involves blue concave metal bowls
They're part of a technology called friction pendulum isolators. They act like very sophisticated shock absorbers for buildings.
"It absorbs the movements of the ground during an earthquake," explained Zayas.
His isolators are built on site. Each one is then tested using a monstrous seismic simulator that's equipped with jaw-dropping vertical and horizontal million pound loads.
On this day, Zayas and his team are testing a quintuple pendulum isolator which is slated to go to the new Los Angeles County Museum of Art. The requirement: that the museum's occupants, it structure, and priceless and fragile artwork all remain safe and intact following a quake.
Today's simulation will involve a magnitude 9-level earthquake.
The technician threw a switch and the ground upon which the isolator is fixed violently lurched forward. The KPIX News crew felt the factory shake.
In the isolator, you can see different pendulums begin to swing at different frequencies.
The motions lessen the quake's energy from getting transferred to the structure and thus damaging it.
"There is no limit as to how strong an earthquake our isolators can take." said Zayas.
The new Apple "spaceship" in Cupertino is resting on top of roughly 700 of EPS's massive blue isolators.
Zayas told KPIX 5 that the late Steve Jobs himself demanded them in his new building
The technology is also in use at four new Bay Area hospitals, including the new San Francisco General.
Only a small number of buildings in the U.S. use this technology. Zayas and his team have made 150 different systems for critical structures in 32 countries. He told KPIX 5 that they have all performed beautifully in huge quakes.
Three years ago, a 7.8 quake hit Ecuador, causing widespread damage. The bridge using EPS's technology continued to function
"That bridge saved many lives by being able to evacuate many people injured in it." explained Zayas.
As to why we don't see more of this technology used in the Bay Area, Zayas has an opinion: it's simply not required by code. But a growing number of seismic experts believe that may change. They point to the example being set by Japan.
While luxury condos in Bay Area advertise exclusive views, multi-million dollar condos in Japan advertise their biggest selling point: base isolators.
"I want and the U.S. Resiliency Council wants Americans to get to that same point where we value the performance of the building as much as we value the view," said Reis.
Rees remembers. He was at the 1989 World Series when the Loma Prieta quake struck. 27,000 structures were damaged at the cost of billions of dollars.
"We learned what could have been, that it could have been much worse." observed the structural engineer.
What's at stake? A lot. Last year, a federal study found a quarter of the buildings in the Bay Area would be significantly damaged by a magnitude 7.0 quake.
Links:
U.S. Resiliency Council
http://usrc.org
Earthquake Protection Systems
http://usrc.org
