Bert Hurlbut, vice president of new hospital construction at Stanford Health Care, discussed the strategies his team used to make the new Stanford Hospital earthquake-resistant.
June 12, 2019 - By Daphne Sashin
Seismologists can’t predict when, where or how severe an earthquake will be, but the probability of the Bay Area getting severely shaken by one in the next 30 years is high. Seismic safety was the No. 1 driver for construction of the new Stanford Hospital set to open in the fall, said Bert Hurlbut, vice president of new hospital construction at Stanford Health Care. Under a stringent California building code, all hospitals must be able to remain operational after a major earthquake by 2030.
The new hospital was built to withstand a magnitude 8.0 quake. Structural engineers made that calculation based on the site’s proximity to two major faults: the San Andreas and Hayward lines. The Hayward fault, which is 10 miles east of the hospital, poses the greatest danger. Scientists with the U.S. Geological Survey have described it as a “tectonic time bomb.”
Writer Daphne Sashin asked Hurlbut about the strategies his team used to make the new hospital seismically safe.
1. What did you do to make the building earthquake-resistant?
Hurlbut: We used what’s called a base isolation system. About 30 feet below ground level, we put huge steel and teflon coasters called isolators under the columns that support the building. They can slide as much as 3 feet in any direction, so that allows the building to shift up to 6 feet in an earthquake. The big isolators weigh 2.5 tons, and our humongous ones weigh 4 tons. Each one will take off a few million pounds of pressure from the weight of the building in an earthquake. The same system was used at the new Zuckerberg San Francisco General Hospital and the new Apple campus.
With Stanford providing the only Level I trauma center on the Peninsula, it’s especially critical that the hospital be up and running to receive a large number of injured people in an emergency. It was just impractical to try to renovate the current hospital.
2. How do you make sure the building doesn’t move too far?
Hurlbut: You build this big concrete bathtub, 4 feet larger all the way around your building, and that allows your building to move back and forth underground. It’s like a moat.
The tough part is your utilities. You’ve got to get water into the building, sewage out, electricity in, medical gases in, natural gas in — all kinds of stuff. So every one of those pipes is fixed at the moat wall; they’re tied to the concrete. This building’s going to potentially move 6 feet, so you have to allow that pipe to be able to move 6 feet without breaking. On some of the larger pipes, like the 12-inch sewer pipes, that pipe might have to be 60 feet long to allow that 6 feet of movement. That means nothing can get in its way for 60 feet. It’s not easy.
3. What other steps did you take to make the building earthquake-resistant?
Hurlbut: We’ve got a tremendous amount of piping above the ceiling, and all that piping has to be braced. If you just let it hang there, it’s going to swing back and forth in an earthquake and start hitting things and breaking. And as soon as a water pipe breaks, you have to shut down your hospital. The amount of braces we have to put on piping and ductwork is unbelievable. I’d bet we have 10,000 braces, and to make them all fit is not an easy task.
Another difficult element was the dome, which is made of about 11,000 square feet of glass pieces above the atrium to allow natural light in. The glass sections are probably about an inch and a half away from each other, and it’s caulked in between. That inch and a half allows the dome to deform during an earthquake. And there’s a safety film of plastic so in case that glass breaks, it will not fall down and shower down on the people below it.
4. How does the team make sure all this is going to work?
Hurlbut: You build a portion of your building — you can see the exterior wall mockups on Welch Road — and you spray it with a lot of water, and then you push and pull on it and shake it, and a lot of things crack and deform, and then you spray water again, and it can’t let water in after the earthquake. We did some minor tweaking to caulk and similar waterproofing elements to ensure a successful flood test.
All the equipment in the building has gone through a shake test. You take whatever you’re testing — whether it’s an electrical panel, a transformer or a computer-room air conditioner — and you affix it to a table, and it might be as big as a room. Then you turn a machine on and it starts shaking horizontally and vertically, vigorously. You sit back and say, “I don’t want to get too close to that.”
5. How long can the hospital operate if it’s cut off from the city utility system?
Hurlbut: We have enough provisions that we can go four days without supplies from outside the hospital. We store water, food and diesel fuel for the generators and the boilers. And if the sewer pipes break, we can store sewage in five tanks below the ground.
As a Level I trauma center, we also need to be prepared to deal with mass casualties following a major earthquake. The parking structure can be converted for additional triage space and connects directly to the emergency department. The garage has four decontamination showers which will aid the ED crew to get mass casualties ready for their entrance into the hospital in the event the victims are soiled with hazardous materials. We also have Wi-Fi to allow staff to register and admit victims into the facility during a mass casualty event.
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