‘Like a Battleship,’ Olive View Is Built to Ride Waves

When seismic shocks ripple through the San Fernando Valley in the next major earthquake, the new Olive View Medical Center is meant to ride the ground waves like a battleship on a stormy sea.

That is how the building was constructed: “Like a battleship,” according to an expert.

Officials were struck by the casual way in which the 1971 Sylmar quake wrecked the hospital’s predecessor, a month-old $27.5-million complex built to the best earthquake engineering standards then in force. So state lawmakers tightened building codes and imposed even stricter standards on new hospitals.

To meet the new standards, and taking into account the presence of an earthquake fault deep beneath the Olive View site, the hospital’s designers turned to a rarely used source of strength:

Steel walls.

Resists Side Pressure

The top four stories of the hospital not only have a steel framework, the usual support for any modern building its size, but walls of steel plate, one of a handful of such buildings in the state. Called “shear walls,” they are meant to resist the side-to-side pressures that rip buildings apart in a quake.

The walls--up to three-quarters of an inch thick--create a series of adjoining steel boxes.

“It’s built like a battleship,” said George Housner, a professor emeritus of earthquake engineering at Caltech. Housner was a member of the Los Angeles County Earthquake Commission, which studied the 1971 quake and recommended precautions against the next one.

Richard G. Troy, the structural engineer for the design of the new Olive View, said the upper floors “have 1,200 feet of steel walls--all the walls except the elevator core.”

The steel-walled upper structure rests on two lower floors that are supported by concrete-wrapped steel beams, which in turn rest on reinforced concrete foundation walls 10 to 14 inches thick.

In designing the framework, Troy said, “I was very conscious of what happened to the last hospital. It has gotten a lot of notoriety in engineering circles.”

Stronger Framework

To prevent another such collapse, he said, he designed the framework to withstand a ground acceleration of 69% of the force of gravity. That would equal an 8.6 Richter-scale reading for a quake along the San Andreas Fault or a 7.5 reading on the fault near the hospital. Either would be an extraordinarily powerful quake.

Most predictions of the “big one” that seismologists say the San Andreas will unleash some day are predicated on a top Richter magnitude of 8.3.

Under state building codes, new buildings should be able to survive a horizontal acceleration of 40% of the force of gravity, written 0.40g. But hospitals require an additional 50% safety factor.

A report by Caltech’s Earthquake Engineering Research Laboratory after the 1971 temblor estimated the peak ground acceleration at the site of the old Olive View at about 0.53g, a strong force that was still less than the power of the quake at its epicenter.

The intent of the new hospital’s steel walls is to stiffen the building to make it hum instead of sway. It is preferable that the building vibrate rapidly within a small distance rather than swing in wider, slower movements, Troy said.

Stiffness is particularly important in a hospital because so many vital systems, including anesthetic gas lines, electricity and water, are built into the walls. They could withstand short, quick movements but might snap if bent too far.

Paul Fratessa, who until October was chairman of the seismology committee of the Structural Engineering Assn. of California, and Troy said they know of only two other buildings in California with steel shear walls, including one other hospital. But neither has nearly as many steel walls as Olive View, they said.

Troy estimated that the steel walls and extra concrete added to the foundation cost about $2 million. The total construction cost for Olive View was $80 million.

Only 30 days after it opened in 1971, the former Olive View Medical Center was wrecked by the Sylmar quake, which measured 6.6 on the Richter scale. The hospital stood only three miles from the temblor’s epicenter.

Three persons were were killed at Olive View during the quake, an employee who was crushed by a collapsing ambulance shelter and two patients whose life-support systems stopped when electric power was cut. A third patient died later. Thirty persons were injured.

The concrete pillars supporting a two-story psychiatric center shattered so cleanly that the upper floor dropped neatly to the ground, almost completely intact. But the most important damage was suffered by the massive main hospital, four to six stories high.

The building failures was blamed on several factors:

Proximity to the epicenter of the quake, three miles to the east.

An irregular shape, which distributed strain unevenly.

An “open story” at the base, essentially making it a box supported on stilts instead of a unified structure from the ground up.

Support pillars in the psychiatric unit made of a lightweight concrete that shattered when twisted.

Failure by the construction code to foresee shaking as severe as occurred.

The county Earthquake Commission’s report concluded that the hospital had been constructed in accordance with the building code then in force but that there were shortcomings in the code. State laws and building codes were rewritten, based largely on what happened at Olive View.

(The collapse of the San Fernando Veteran’s Administration Hospital, a greater tragedy, took 49 lives. That building was completed in 1925, before the codes were written.)

In the case of hospitals, state law was amended to require that they be designed to remain not only standing but functional after “the most severe earthquake that seismologists estimated could happen in the vicinity,” Housner said.

Although there is an earthquake fault beneath the Olive View site, it was not a factor in the 1971 damage, a geological investigation of the site determined.

The fault is buried about two miles deep, said Edward G. Heath, who was the project geologist for a firm hired to determine whether it was possible to build anything at Olive View without running the risk of another quake tragedy.

Heath said he found that the 45-degree angled fault does not reach the surface of the earth. A vertical fault is more dangerous because it could rip apart buildings above it if its two sides move in different directions, he said.

“There are faults all over this area,” he said. “You’re going to be beside one or between two of them almost anyplace you are.”

His report concluded that, in a strong earthquake, a new hospital might receive the same amount of shaking as did the previous one.

The report failed to convince some members of the county Board of Supervisors when it was delivered in 1971.

Supervisor Kenneth Hahn called it “extremely foolish, no matter what these engineers say” to rebuild the hospital in the same place. Then-Supervisor Ernest Debs declared: “If we rebuilt Olive View where it was and another mistake occurred and it fell down, the people are going to say, ‘We’ve got a stupid bunch of supervisors.’ ”

However, patients should be safer in Olive View, or any other hospital built since the Hospital Seismic Safety Act was strengthened, said L. Thomas Tobin, executive director of the California Seismic Safety Commission.

“The vast majority of hospitals in California have not been constructed to this higher standard,” he said.