Engineers warn that a weak building makes damage from a powerful earthquake even worse    ALSO: In U.S., Turkey quake brings frustration, action VIDEO CNN's Don Knapp reports on engineering techniques that could have lessened the devastation from the earthquake in Turkey (August 19). Windows Media 28K 80K

August 19, 1999
Web posted at: 12:13 p.m. EDT (1613 GMT)

In this story: Learning from Northridge RELATED STORIES, SITES

By Correspondent Don Knapp

SAN FRANCISCO (CNN) -- Reviewing the massive devastation caused by the earthquake that ripped through Turkey, American structural engineers say that employing design and construction techniques currently being used in the United States might have mitigated the damage and saved lives.

"The most common form of multistory building in Turkey (is) what we call a concrete frame," structural engineer Jim Malley of Degenkolb Engineers says. That's where concrete beams are walled in with bricks and mortar.

Malley studied damaged buildings in Turkey after a 6.2 magnitude earthquake in 1992 left more than 600 people dead.

"These are very heavy buildings, and it's not uncommon for them to collapse in earthquakes because of the extra mass," Malley said.

He says the risk of a building collapse increases when the first floor is a shop, and glass windows replace brick walls.

Malley points out that Turkey's concrete frame buildings often lack reinforcing steel, use too little of it or use a smooth steel bar that fails to grip the concrete.

A different construction method is used in the United States.

"We use what's called deformed bars, where little bumps on the steel help to tie the reinforcing steel to the concrete," Malley said.

Learning from Northridge

In California, where each big quake teaches engineers another way of coping with the forces of nature, steel frames reduce the weight of new buildings. Strong joints keep them agile.

"The building is designed to move and to sway," said structural engineer Janiele Maffei, "and the connections to stay together."

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Maffei says the 1994 Northridge, California, earthquake revealed the weaknesses of rigid joints. Engineers found a simple solution by tapering the area of the beam near the connection into a "dog bone" configuration.

"It will take the stresses away from the connection and concentrate them in that smaller section of the beam," Maffei said.

Cross-bracing upward through the elevator shaft gives a building additional strength.

"Steel bracing ... connects the various floors and keeps them from moving relative to each other in an earthquake," Maffei said.

Surveying the destruction in Turkey, Maffei said Turkish engineers do know how to build for earthquakes. She said that Turkey's building codes are good -- at least on paper. But the images of collapsed structures are clear evidence that somehow the system failed to produce earthquake-resistant buildings.

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