Seismic safety of steel-frame buildings

Re “Big Buildings Go Unchecked After Quake,” Sept. 17

Immediately after the 1994 Northridge earthquake, the Los Angeles Department of Building and Safety mobilized its entire staff to respond to all requests for inspections of damaged properties.

After the inspections, recommendations were forwarded to the City Council and resulted in different mandatory and voluntary retrofit ordinances. One of those ordinances dealt with steel-frame buildings.

The ordinance required owners of the 242 steel-frame buildings within specific geographical areas (highly earthquake-damaged areas of the San Fernando Valley and parts of the city’s Westside) to undergo detailed structural engineering evaluations and that repairs be made to those buildings when necessary. As of today, 241 of 242 buildings have completed the repair work.

It is important to note that the Department of Building and Safety has been instrumental in developing, implementing and enforcing some of the most restrictive seismic-safety ordinances in the world. However, in the case of steel-frame buildings, the department’s authority to require engineering evaluations was limited by the ordinance to specific geographic areas of the city.

NICK DELLI QUADRI

Chief of Engineering Bureau

Department of Building and Safety

Los Angeles

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The Times’ article was well reported, accurate and timely. Had the Northridge earthquake lasted a few seconds longer, it is believed that some of the high-rise steel-frame buildings near the epicenter would have suffered partial or total collapse.

Steel-frame buildings using connection technology similar to that existing before the Northridge earthquake continue to be designed and constructed, even though cost-effective technology using steel-side plates largely eliminates threats.

This new technology has been effectively adopted in buildings of high importance, such as hospitals, courthouses and strategic military and aviation facilities, and can easily be implemented in commercial and residential structures.

The prospect of terrorist threats to buildings and the accompanying scenario of progressive collapse of these structures, in addition to the ever-present seismic threat, make continuing business as usual in the design and construction of steel-frame buildings unacceptable.

GARRY D. MYERS

Structural Engineer

Long Beach