SHAKE TEST Shake Table Tests Prove Structures Can Be Seismically Sound With Less SteelThan Called for by Current California Code - San Diego, View CBS coverage of testing in RealPlayer University of California, San Diego (UCSD) structural engineers have announced that aviolent simulated reproduction of the Northridge earthquake shook a seven-story structure at theUCSD Jacobs School of Engineerings Englekirk Structural Engineering Center, and resulted inonly minor cosmetic damage to the building. The experiment, (Click to view Video 1 from anglein photo above) along with earlier shakes, was conducted to test a revolutionary new theory thatmid-rise concrete apartment, condominium and hotel structures can be built to survive powerfulearthquakes using less steel reinforcement than currently required by California building codes."Many people dont realize that excessive building strength can actually promote poor structuralperformance and non-structural damage during an earthquake," said Robert Englekirk, founderof the Englekirk Companies and a co-principal investigator of the project. "The structuralengineering community wants to develop regional design procedures that allow for thedevelopment of more suitable buildings in Southern California." UCSD structural engineers saidthe building held up as well as the theory. The test (click to view Video 2 of the southeast corner of the structure, links tomore videos can be found at the bottom of the middle column) was conducted under tight safetyprecautions with the powerful mechanical jolts delivered by a 25 ft. by 40 ft. shake table. Theexperiment duplicated ground motions from the Jan. 17, 1994, Northridge earthquake that wererecorded at the Olive View Hospital in Sylmar, CA. The 275-ton, 65-foot-tall building was alsotested on Nov. 22, 2005, with ground motions that were recorded during the Northridgeearthquake 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 theJan. 14 test simulated the earthquake closer to its epicenter, with horizontal accelerations of 82percent of gravity. "What we found is fairly simple; if we use an intelligent design strategy thatreduces the demands required by the current California building standards, and use about half the
reinforcing steel thats required, mid-rise buildings will survive powerful earthquakes with onlyminor damage," said Jose Restrepo, professor of structural engineering at the UCSD JacobsSchool of Engineering Department of Structural Engineering and co-principal investigator of theproject. Prof. Restrepo likened the design to that of a car, where upon impact, a large amount ofthe force is dissipated at the bumper, prior to spreading through the car to the passenger area. Soto 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 totheir spreading throughout the building. Restrepo said the performance of the seven-storybuilding was even better than the sponsors of the project had expected. "The professionalengineers we have talked to were thrilled," said Restrepo. “I can’t tell you how satisfying it is to see the BauGrid Welded ReinforcementGrids (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 theconfinement reinforcement in the walls of the 7-story test structure. “This design is one that BobEnglekirk has espoused for some time, and I’m glad to see that Prof. Restrepo’s test program hasdone such an excellent job of showing that he was absolutely right.” said Baumann. Baumannadded that “Because of public safety concerns, it is quite important that design engineersunderstand that the WRG used in this structure is not the same as the much weaker Welded WireReinforcement (WWR). WRG is manufactured with high strength welds at every location wherethe steel rods intersect, which provides the unique and valuable inter-cell confinement that wasexhibited during the test.”Restrepo said the seven-story building may be put through additional tests to provide furtherscientific confirmation that less reinforcing steel than currently required could improve theperformance of mid-rise concrete buildings in densely populated and seismically active regionsin California. Sixty people were killed and 7,000 injured during the Northridge earthquakewhich 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
prompted professional structural engineers to call for more scientific testing of mid-riseresidential buildings. When asked how soon new design procedures such as this could be incorporatedinto Southern California buildings, in that implementation of new ideas into building codes is aprocess that is notoriously slow moving, Englekirk stated that the current code already allowsuse of this “performance-based” design. “The code allows engineers two ways to designstructures. 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 adesign 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. UCSDs shake table can actuallysupport a building roughly 10 times heavier than the seven-story structure it currently holds.The $9 million shake table at the Jacobs Schools Englekirk Center is one of 15 earthquaketesting facilities in the National Science Foundations Network for Earthquake EngineeringSimulation. The UCSD-NEES shake table, the largest in the U.S. and the only outdoor shaketable in the world, is ideally suited for testing tall, full-scale buildings. Click here to take ananimated tour of the facility. Construction of the seven-story test building was led by Highrise ConcreteSystems, Inc. of Dallas, TX, a company which specializes in the construction of multi-storyconcrete buildings using the latest formwork technology. Additional financial support donatedequipment and labor was provided by Tech, Inc.; Dywidag Systems International, USA;, Inc.(DSI); HILTI; Associated Ready Mix; California Field Ironworkers; Cemex: Concrete SteelReinforcing Institute (CRSI); Douglas E. Barnhart, Inc.; Englekirk & Sabol, Inc.; Fontana,Grace, Hanson Aggregates; Morley Builders; Pacific Southwest Structures; Schuff Steel-PacificInc.; Southern California Ready Mix Concrete Association; the Portland CementAssociation(PCA); and Carpenters/Contractors Cooperation Committee, a nonprofit labor andmanagement group.
The Englekirk Structural Engineering Center, part of UCSDs renowned PowellStructural Research Laboratories, is named in recognition of Robert and Natalie Englekirkssupport of structural engineering research and education at UCSD Jacobs School of EngineeringDepartment of Structural Engineering. Construction of the Englekirk Center and the earthquakeresearch program there are supported by the Englekirk Center Industry Advisory Board, a groupof 43 structural engineering firms and associations in Southern California. Patron membersinclude Carpenters/Contractors Cooperation Committee, Englekirk Systems Development, Inc.,and Highrise Concrete Systems, Inc. Other partners include: American Segmental BridgeInstitute; Anderson Drilling; Baumann Engineering; Brandow & Johnston Associates; Burkettand Wong Engineers; Charles Pankow Builders, Ltd.; Clark Pacific; Douglas E. Barnhart, Inc.;Dywidag Systems International, USA, Inc. (DSI); Englekirk and Sabol Consulting StructuralEngineers, 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; NabihYoussef and Associates; Oak Creek Energy Systems; Occidental Petroleum Corporation; PacificSouthwest Structures; PCL Construction Services, Inc.; Portland Cement Association;Precast/Prestressed Concrete Manufacturers Association of California (PCMAC); Saiful/BouquetConsulting Structural Engineers, Inc.; Schuff Steel-Pacific, Inc.; Structural EngineeringAssociation of Southern California (SEAOSC); Simon Wong Engineering, SimpsonManufacturing Co., Inc.; Smith-Emery Company; Stedman & Dyson Structural Engineers; TheEli & Edythe L. Broad Foundation; Twining Laboratories; UC San Diego Design andConstruction; Verco Manufacturing Co.; Weidlinger Associates, Inc.; and the StructuralEngineering Association of San Diego (SEAOSD).