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Engineers Announce Results of Second Northridge Shake of 7-Story Building

real.media.shake
CBS Evening News story on 7-story Northridge shake test.
San Diego, CA, January 20, 2006 -- University of California, San Diego (UCSD) structural  engineers today announced that the most violent ear thquake shake of a seven-story structure at the UCSD Jacobs School of Engineerin g's Englekirk Structural Engineering Center resulted in only minor cosmetic dama ge to the building.

The test was conducted Jan. 14 under tight safety precautions with powerful m echanical jolts delivered by a 25 ft. by 40 ft. shake table. The experiment dupl icated ground motions from the Jan. 17, 1994, Northridge earthquake that were re corded at the Olive View Hospital in Sylmar, CA.

The goal of the Jan. 14 experiment and earlier shakes was to test a revolutio nary new theory that mid-rise concrete apartments, condominiums and hotels can b e built to survive powerful earthquakes with less steel reinforcement than curre ntly required by California building codes. UCSD structural engineers said the b uilding held up as well as the theory.

cbs news video
An Earthquake-Proof Building?
"What we found is fairly simple; if we use an intelligent design strategy that r educes the demands required by the current California building standards, and us e about half the reinforcing steel that's required, mid-rise buildings will surv ive powerful earthquakes with only minor damage," said José Restrepo, profe ssor of structural engineering at the UCSD Jacobs School of Engineering's Depart ment of Structural Engineering and co-principal investigator of the project.

After the Shake
After the 'big shake' (l -r): NEES @ UCSD principal investigator José Restrepo;industry pa rtner Robert Bachman; Ph.D. candidate Marios Panagiotou;  Jacobs School Dean Frieder Seible; and co-PI and center namesake Robert Englekirk.
The 275-ton, 65-foot-tall building was also tested on Nov. 22, 2005, with ground motions that were recorded during the Northridge earthquake farther from the ep icenter at a seven-story hotel in Van Nuys, CA. The November 2005 test produced horizontal accelerations that were 30 percent of the force of gravity, and maxim um accelerations in the Jan. 14 test were 82 percent of gravity.

The Northridge earthquake resulted in 60 deaths, more than 7,000 injured, 20, 000 homeless, and more than 40,000 buildings damaged in Los Angeles, Ventura, Or ange, and San Bernardino Counties. The death toll and roughly $40 billion in pro perty damage prompted professional structural engineers to call for more scienti fic testing of mid-rise residential buildings.

"Many people don't realize that excessive building strength can actually prom ote poor structural performance and non-structural damage during an earthquake," said Robert Englekirk, adjunct professor of structural engineering at UCSD and co-principal investigator of the project. "The structural engineering community wants to develop regional design procedures that allow for the development of mo re suitable buildings in Southern California."

detail shots
Video close-ups of cracking at the base of the 7-story structure during a Northridge simulation on Jan. 14, 2006.
Construction of the seven-story structure was led by Highrise Concrete Systems, Inc. of Dallas, TX, America's largest sub-contractor using cast-in-place tunnelf orm technology to build multi-story reinforced concrete buildings throughout the U.S.  Additional financial support, donated equipment and labor was provid ed by: Baumann Engineering; Dywidag Systems International, USA, Inc (DSI); HILTI ; Associated Ready Mix; California Field Ironworkers; Cemex; Concrete Reinforcin g Steel Institute; Douglas E. Barnhart, Inc.; Englekirk & Sabol, Inc.; Fonta na, Grace, Hanson Aggregates, Morley Builders; Pacific Southwest Structures; Sch uff Steel-Pacific Inc.; Southern California Ready Mix Concrete Association; the Portland Cement Association; and Carpenters/Contractors Cooperation Committee, a nonprofit labor and management group. 

Restrepo said the performance of the seven-story building was even better tha n the sponsors of the project had expected. "The professional engineers we have talked to were thrilled," he said.

real image widenagle
Video of the Nov. 22, 2005, and Jan. 14, 2006, tests of the 7-story st ructure.
Full-scale tests of such large buildings have previously not been possible becau se of weight, space, and technical limitations of smaller indoor shake tables. U CSD's shake table can actually support a building roughly 10 times heavier than the one currently being tested.

The $9 million shake table is one of 15 earthquake testing facilities in the National Science Foundation's Network for Earthquake Engineering Simulation (NEE S). The UCSD-NEES shake table, the largest in the U.S. and the only outdoor shak e table in the world, is ideally suited for testing tall, full-scale buildings.

Restrepo said the seven-story building may be put through additional tests to provide further scientific confirmation that less reinforcing steel than curren tly required could improve the performance of similar buildings in densely popul ated and seismically active regions in Los Angeles and Southern California.

Big Shake
Engineers check out the aftermath of a Northridge-scale 'earthquake' on the world's first outd oor shake table. 
The Englekirk Structural Engineering Center, part of UCSD's Powell Structural Re search Laboratories, is named in recognition of Robert and Natalie Englekirk's s upport of structural engineering research and education at UCSD Jacobs School of Engineering's Department of Structural Engineering. Construction of the center and operation of the earthquake research program there are supported by the Engl ekirk Center Industry Advisory Board, a group of 43 structural engineering firms and associations in Southern California. Patron members include the Carpenters/ Contractors Cooperation Committee, Englekirk Systems Development, Inc., and High rise Concrete Systems, Inc.  Other partners include: American Segmental Bri dge Institute; Anderson Drilling; Baumann Engineering; Brandow & Johnston As sociates; Burkett and Wong Engineers; Charles Pankow Builders, Ltd.; Clark Pacif ic; Douglas E. Barnhart, Inc.; Dywidag Systems International, USA, Inc. (DSI); E nglekirk and Sabol Consulting Structural Engineers, Inc.; EsGil Corporation; GEO CON; Gordon Forward; HILTI; Hope Engineering, Inc.; John A. Martin and Associate s; Josephson Werdowatz & Associates Incorporated; JVI, Inc.; KPFF Consulting Engineers; Matt Construction Corporation; Morley Builders; Nabih Youssef and As sociates; Oak Creek Energy Systems; Occidental Petroleum Corporation; Pacific So uthwest Structures; PCL Construction Services, Inc.; Portland Cement Association ; Precast/Prestressed Concrete Manufacturers Association of California (PCMAC); Saiful/Bouquet Consulting Structural Engineers, Inc.; Schuff Steel-Pacific, Inc. ; Structural Engineering Association of Southern California (SEAOSC); Simon Wong Engineering, Simpson Manufacturing Co., Inc.; Smith-Emery Company; Stedman & ; Dyson Structural Engineers; The Eli & Edythe L. Broad Foundation; Twining Laboratories; UC San Diego Design and Construction; Verco Manufacturing Co.; Wei dlinger Associates, Inc.; and the Structural Engineering Association of San Dieg o (SEAOSD).

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Media Contacts

Rex Graham
Jacobs School of Engineering
Phone: 858-822-3075
rgraham@soe.ucsd.edu

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