Arts Plaza Can Survive 6.5 Quake, Engineer Says : Thousand Oaks: The designer tells residents that the complex exceeds state codes. ‘These buildings are not going to come apart.’

The Civic Arts Plaza is strong.

So strong, in fact, that it could stand tall even if a 6.5-magnitude earthquake tore through the bedrock under its foundation.

That’s what structural engineer John A. Martin Jr. believes. And he’s willing to bet his life on it.

Martin, who designed the Civic Arts Plaza’s seismic braces, said he would “have no concern at all being in the office building or the auditorium during an earthquake.” If he were in the City Hall side of the complex during a quake, he said, “the biggest damage would probably be from falling stacks of books.”

In a half-hour presentation designed to quell residents’ concerns about the Civic Arts Plaza’s quake-worthiness, Martin said he had designed the complex to be even sturdier than state codes mandate.

“These buildings,” he told the council, “are not going to come apart.”

Martin praised the garage design as well, because the concrete was poured on the site itself, rather than precast and trucked over in pieces. The Northridge quake revealed that prefabricated garage pieces can split apart during intense shaking.

“From what I’ve heard,” Councilwoman Elois Zeanah said, “it’s as structurally sound as a building can get.”

City officials invited Martin to discuss the Civic Arts Plaza’s seismic safeguards after several residents expressed fear that a violent quake could crumple the 10-story tower and its five-level parking garage.

After January’s 6.8-magnitude earthquake flattened many buildings in Northridge, some Thousand Oaks residents worried aloud about the faults that crisscross the Conejo Valley. If a quake were centered in Thousand Oaks, they asked, how would local buildings fare?

In response, Civic Arts Plaza engineers said they had designed the complex to stand up to a 6.5-magnitude quake centered in Thousand Oaks--a seismic event that geologists think could happen only once in about 475 years. Scientists recommended that he design the building for a quake of that magnitude based on their analysis of the area’s geology. The building’s performance in a larger quake would depend on the location of the fault and the magnitude of the quake, he said.

The building sits on solid bedrock, which holds up much better in a quake than shifting sandy soil, Martin said. But engineers faced other challenges.

Because of an auditorium’s physical layout and acoustical requirements, structural engineers often have a tough time shoring up a theater to meet seismic standards. They cannot plop concrete pillars in spots that would block the audience’s view of the stage, for example, and they cannot brace balconies with bulky supports.

“If we structural engineers had our way,” Martin said, “we’d have all buildings be boxes with no windows.”

But to accommodate theater design, Martin and his colleagues tinkered with stress points and incorporated the most up-to-date seismic safeguards. They then tested their theories with a computer-simulated quake.

“We realize that God can mobilize more force than we can (mobilize) steel,” Martin said. “A building’s performance (during a quake) depends not so much on strength as on how it’s designed and where (supports) are placed.”