'Restrain, Respect and Rehabilitate'
Engineer examines earthquake retrofits of campus buildings
Memorial Church was severely damaged after the 1989 Loma Prieta earthquake. This 1992 photo shows workers restoring the church skylight. Most of the structural work was done inside the dome, hidden from public view.
Engineers used reinforced steel and concrete to rebuild Memorial Church after the 1906 earthquake, but the arched crossing area was left untouched and was never attached to the main structure. As a result, the crossing walls moved just enough during the 1989 Loma Prieta quake to seriously damage the arch.
Today marks the 103rd anniversary of the dedication of Memorial Church, the architectural centerpiece of the Stanford campus. The event took place on Jan. 25, 1903. But just three years later, the building lay in ruins, one of many campus structures destroyed in the Great Earthquake of April 18, 1906.
Workers began renovating the church in 1907, this time using steel-frame construction instead of unreinforced stone masonry. The new building remained intact until Oct. 17, 1989, when it was severely damaged in the Loma Prieta earthquake. The refurbished church might have fared better in that quake had engineers in 1906 known what we know about earthquakes today, said Chris D. Poland, chair, president and chief executive officer of Degenkolb Engineers in San Francisco.
"In 1906, it was still a puzzle," said Poland, who earned a master's degree in civil engineering at Stanford in 1974. "[Today] we're beginning to understand what's going on, what works well and what doesn't work well. It really comes out of our experience in paying close attention to how buildings perform in earthquakes. ... I think we have a lot to learn."
Poland's company was instrumental in the restoration of Memorial Church and the Stanford Museum (now the Cantor Center for Visual Arts) following the Loma Prieta quake, as well as the earthquake retrofit of the Mitchell Earth Sciences Building. His remarks came during a Jan. 17 speech at Kresge Auditorium titled "Restrain, Respect and Rehabilitate: A Tale of Three Seismic Projects at Stanford," part of the 1906 Earthquake Centennial Lecture Series sponsored by the Stanford Quake '06 Alliance and the University of California-Berkeley.
"We have gone from a point back at the turn of the last century, the 1900s, of denying that earthquakes were a problem in California ... to realizing in the last round of earthquakes that we've had—Loma Prieta and other earthquakes around the world—that we really have to talk about actual performance," he said. "The benchmark is not what the computer evaluation says [or] the intuition of the engineer that's doing the evaluation. The benchmark is how the building behaves in the earthquake."
According to Poland, earthquake engineers have four main concerns: safety, cost, time and the importance of the building to the community. Heritage structures, such as Memorial Church, which are "near and dear to the heart of a university," need to be rehabilitated despite the cost. "This was a very expensive project in dollars per square foot," Poland said. "But it doesn't matter. It's the kind of facility that deserves that."
Poland said that the 1906 disaster taught engineers that steel and concrete can reduce earthquake damage, so when they rebuilt Memorial Church, they erected a new steel frame and concrete structure around the crossing—the domed central area where religious services are held. However, the walls and dome in the original crossing area were left untouched.
During the 1989 quake, keystones in the crossing slipped down about 3 inches, causing severe structural damage. "I remember thinking, How in the world are we ever going to push that stone back?" Poland recalled. Mosaic tile from one of the angel's wings also fell.
Poland spent several weeks crawling through church attics to find out what went wrong. "This building is amazing," he said. "You can get way up in the catacombs in the attics and see all sorts of things."
His conclusion: The pillars and unreinforced masonry walls in the upper portion of the crossing were unbraced and, in fact, had never been connected to the refurbished steel-and- concrete sections of the building. As a result, when the Loma Prieta earthquake struck, the walls moved freely in and out, because there was nothing holding them in place—"like a shoebox with no top or bottom," he said. Unfortunately, walls moved just enough so that the arch opened up and the keystones slipped down, he explained.
To prevent the crossing area from moving independently again, Poland and his team recommended reinforcing the walls with concrete and steel and connecting them to the rest of the structure at a cost of about $6 million.
"Everyone was worried about how we were going to pay for this," he said, noting that the federal government had refused to pay any money for a church. "That $6 million price tag looked absolutely insurmountable. [Alumni] Mel Lane of Sunset magazine and David Packard of Hewlett-Packard got together and formed a little fundraising committee. I'll never forget the day they came into our team meeting and said, 'Guys, we've raised $10 million. Do you think you can figure out how to spend it?' True story. Of course everybody said, 'Sure, no problem!'"
The final cost for the engineering retrofit was about $6.5 million, Poland said, noting that most of the structural work was actually done above the angels inside the dome, hidden from view. "I really felt like people never quite understood what we did, because you can't tell when you go in there," Poland said. "You walk into Memorial Church right now and you can't see a speck of anything we've done, and that's good news, because that's what you want to do with your historic structures."
Restoration of the angel's wing was "an extraordinary job," Poland noted, and restoring the Fisk-Nanney pipe organ required close collaboration with very territorial organ masters. The architects wanted dirt left on the interior finish to reflect "the maturity of the building," he said, so workers spent a lot of time "dirtying up" the original stones before replacing them in the arch. To repair the balcony area damaged during the Loma Prieta quake, workers surgically drilled through each stone railing, installed dowels and put a steel channel across the top to tie them all together.
"This was not just about life safety," Poland told the audience. "This was about building integrity, this was about preserving the heritage of the church for future generations. ... The church, I don't think, is going to be damaged anymore. I bet the guys that put the concrete walls in 1907 figured the same thing, so we'll see what they say in 100 years."
Poland also discussed the minimalist approach he used to retrofit the Mitchell Earth Sciences Building to withstand major earthquakes—a sharp contrast with the elaborate restoration of the Cantor Arts Center, which was originally built as a museum in 1891 and suffered serious damage in 1906 and again in 1989. The building was redesigned and reopened in 1999. Like Memorial Church, the new arts center needed to be tied together so that the central main lobby would not be pulled apart by the two adjacent side wings, which is apparently what happened in the Loma Prieta earthquake, Poland said.
"Stanford has been a leader in taking care of its facilities and in developing earthquake technology. I am proud to have been a part of this, as a student, as a participant in research and as an engineer working on the buildings," he said.
The next lecture in the 1906 Earthquake Centennial series will be presented by Mary Lou Zoback, senior research scientist at the U.S. Geological Survey, who will discuss lessons learned and forgotten since the '06 quake and future directions in earthquake hazard prevention. Her lecture will be held at 7:30 p.m. Tuesday, Jan. 31, in Kresge Auditorium and again at 7:30 p.m. on Wednesday, Feb. 1, at UC-Berkeley's Sibley Auditorium. For more information, contact Racquel Hagen at 723-4150 or firstname.lastname@example.org