The shake table tests showed that a 7-story concrete building could withstand powerful earthquakes using less steel reinforcement than required by California building codes, suffering only minor cosmetic damage. The tests duplicated motions from the 1994 Northridge earthquake, showing the building performed better than expected when using about half the reinforcing steel. The tests proved a new design approach could improve earthquake resistance of mid-rise buildings while using less steel.

1. SHAKE TEST
Shake Table Tests Prove Structures Can Be Seismically Sound With Less Steel
Than Called for by Current California Code - San Diego, View CBS coverage of testing in Real
Player University of California, San Diego (UCSD) structural engineers have announced that a
violent simulated reproduction of the Northridge earthquake shook a seven-story structure at the
UCSD Jacobs School of Engineering's Englekirk Structural Engineering Center, and resulted in
only minor cosmetic damage to the building. The experiment, (Click to view Video 1 from angle
in photo above) along with earlier shakes, was conducted to test a revolutionary new theory that
mid-rise concrete apartment, condominium and hotel structures can be built to survive powerful
earthquakes using less steel reinforcement than currently required by California building codes.
"Many people don't realize that excessive building strength can actually promote poor structural
performance and non-structural damage during an earthquake," said Robert Englekirk, founder
of the Englekirk Companies and a co-principal investigator of the project. "The structural
engineering community wants to develop regional design procedures that allow for the
development of more suitable buildings in Southern California." UCSD structural engineers said
the building held up as well as the theory.
The test (click to view Video 2 of the southeast corner of the structure, links to
more videos can be found at the bottom of the middle column) was conducted under tight safety
precautions with the powerful mechanical jolts delivered by a 25 ft. by 40 ft. shake table. The
experiment duplicated ground motions from the Jan. 17, 1994, Northridge earthquake that were
recorded at the Olive View Hospital in Sylmar, CA. 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 epicenter, 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 the
Jan. 14 test simulated the earthquake closer to its epicenter, with horizontal accelerations of 82
percent of gravity.
"What we found is fairly simple; if we use an intelligent design strategy that
reduces the demands required by the current California building standards, and use about half the

2. reinforcing steel that's required, mid-rise buildings will survive powerful earthquakes with only
minor damage," said Jose Restrepo, professor of structural engineering at the UCSD Jacobs
School of Engineering Department of Structural Engineering and co-principal investigator of the
project. Prof. Restrepo likened the design to that of a car, where upon impact, a large amount of
the force is dissipated at the bumper, prior to spreading through the car to the passenger area. So
to in this design, the intent was to have the brunt of the impact absorbed in an energy absorbing
“plastic hinge” located at the ground floor, causing a dissipation of the earthquake forces prior to
their spreading throughout the building. Restrepo said the performance of the seven-story
building was even better than the sponsors of the project had expected. "The professional
engineers we have talked to were thrilled," said Restrepo.
“I can’t tell you how satisfying it is to see the BauGrid Welded Reinforcement
Grids (WRG) withstand such tremendous large tension and compression forces,” said Hanns U.
Baumann, S.E., president of BauTech, Inc., which donated the WRG that were used as the
confinement reinforcement in the walls of the 7-story test structure. “This design is one that Bob
Englekirk has espoused for some time, and I’m glad to see that Prof. Restrepo’s test program has
done such an excellent job of showing that he was absolutely right.” said Baumann. Baumann
added that “Because of public safety concerns, it is quite important that design engineers
understand that the WRG used in this structure is not the same as the much weaker Welded Wire
Reinforcement (WWR). WRG is manufactured with high strength welds at every location where
the steel rods intersect, which provides the unique and valuable inter-cell confinement that was
exhibited during the test.”
Restrepo said the seven-story building may be put through additional tests to provide further
scientific confirmation that less reinforcing steel than currently required could improve the
performance of mid-rise concrete buildings in densely populated and seismically active regions
in California.
Sixty people were killed and 7,000 injured during the Northridge earthquake
which left 20,000 homeless, and damaged more than 40,000 buildings in Los Angeles, Ventura,
Orange, and San Bernardino Counties. The death toll and roughly $40 billion in property damage

3. prompted professional structural engineers to call for more scientific testing of mid-rise
residential buildings.
When asked how soon new design procedures such as this could be incorporated
into Southern California buildings, in that implementation of new ideas into building codes is a
process that is notoriously slow moving, Englekirk stated that the current code already allows
use of this “performance-based” design. “The code allows engineers two ways to design
structures. There are prescriptive designs, as spelled out in the codes, and there are performance-
based designs, where through the use of testing and proven scientific methods, it is shown that a
design is safe.”
Full-scale tests of such large buildings have previously not been possible because of weight,
space, and technical limitations of smaller indoor shake tables. UCSD's shake table can actually
support a building roughly 10 times heavier than the seven-story structure it currently holds.
The $9 million shake table at the Jacobs School's Englekirk Center is one of 15 earthquake
testing facilities in the National Science Foundation's Network for Earthquake Engineering
Simulation. The UCSD-NEES shake table, the largest in the U.S. and the only outdoor shake
table in the world, is ideally suited for testing tall, full-scale buildings. Click here to take an
animated tour of the facility.
Construction of the seven-story test building was led by Highrise Concrete
Systems, Inc. of Dallas, TX, a company which specializes in the construction of multi-story
concrete buildings using the latest formwork technology. Additional financial support donated
equipment and labor was provided by Tech, Inc.; Dywidag Systems International, USA;, Inc.
(DSI); HILTI; Associated Ready Mix; California Field Ironworkers; Cemex: Concrete Steel
Reinforcing Institute (CRSI); Douglas E. Barnhart, Inc.; Englekirk & Sabol, Inc.; Fontana,
Grace, Hanson Aggregates; Morley Builders; Pacific Southwest Structures; Schuff Steel-Pacific
Inc.; Southern California Ready Mix Concrete Association; the Portland Cement
Association(PCA); and Carpenters/Contractors Cooperation Committee, a nonprofit labor and
management group.

4. The Englekirk Structural Engineering Center, part of UCSD's renowned Powell
Structural Research Laboratories, is named in recognition of Robert and Natalie Englekirk's
support of structural engineering research and education at UCSD Jacobs School of Engineering
Department of Structural Engineering. Construction of the Englekirk Center and the earthquake
research program there are supported by the Englekirk Center Industry Advisory Board, a group
of 43 structural engineering firms and associations in Southern California. Patron members
include Carpenters/Contractors Cooperation Committee, Englekirk Systems Development, Inc.,
and Highrise Concrete Systems, Inc. Other partners include: American Segmental Bridge
Institute; Anderson Drilling; Baumann Engineering; Brandow & Johnston Associates; Burkett
and Wong Engineers; Charles Pankow Builders, Ltd.; Clark Pacific; Douglas E. Barnhart, Inc.;
Dywidag Systems International, USA, Inc. (DSI); Englekirk and Sabol Consulting Structural
Engineers, Inc.; EsGil Corporation; GEOCON; Gordon Forward; HILTI; Hope Engineering,
Inc.; John A. Martin and Associates; Josephson Werdowatz & Associates Incorporated; JVI,
Inc.; KPFF Consulting Engineers; Matt Construction Corporation; Morley Builders; Nabih
Youssef and Associates; Oak Creek Energy Systems; Occidental Petroleum Corporation; Pacific
Southwest 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.; Weidlinger Associates, Inc.; and the Structural
Engineering Association of San Diego (SEAOSD).