FEBRUARY 2007 Contents:

Oregon State University Wins 2007 Seismic Design Competition

Of the 14 competing student teams, Oregon State University took first place in the 4th Annual Seismic Design Competition for Undergraduates, jointly sponsored by the Pacific Earthquake Engineering Research Center (PEER), Earthquake Engineering Research Institute (EERI), Mid-America Earthquake (MAE) Center and MCEER. The event, held during the EERI Annual Meeting, February 7-10, in Los Angeles, was an opportunity to demonstrate performance-based, cost-effective seismic design. Read more.

Strong Future for PEER Announced at Annual Meeting

Reflecting NSF's vision that "competitiveness is 'key' for the future," PEER director Jack Moehle emphasized his center's commitment to continue as a national research center with funding from the federal government, State of California, and private industry. Partnership with industry will be a key element for PEER beyond its tenth and final year of funding by the NSF. Speaking before nearly 200 attendees at PEER's Annual Meeting, held Jan. 19-20 at Hotel Nikko in San Francisco, a panel of Moehle, Tom Shantz of Caltrans, Jacqueline Meszaros of NSF, and in-coming EERI President Thalia Anagnos of San Jose State University, addressed the value of PEER's accomplishments and need for the center to continue its operation well into the future.

According to NSF's Meszaros, PEER "transformed the culture" of how an NSF center functioned and operated, and performed well beyond its expectations. "PEER gleaned so much from collaboration with other universities, including student interaction with a worldwide research community, by sharing labs and research findings. PEER brings a dialogue between practitioners and researchers, applicable to problems that need to be solved." One significant end result of PEER's efforts, she added, is the transition of PEER-supported education programs to community-supported programs.

Tom Shantz emphasized that "Caltrans's support for PEER will continue to be strong, extending through 2010," and it is likely that other DOTs will participate, given the transformation to LRFD design. He added that there is increased support by Caltrans on the structural/geotech side and growing support for PEER's research specializations. "Working with PEER," he said, "is superior to CalTrans's hiring of separate individuals to acquire the latest research findings."

Jack Moehle also noted PEER's commitment to collaboration with other research organizations such as SCEC, and discussed their combined efforts in nuclear powerplant engineering, OpenSees and Open Seismic Hazard projects, and international collaboration. The hope is for both centers to grow together and sustain research in key areas related to earthquake engineering.

DECEMBER 2006 Contents:

Pacific Earthquake Engineering Research Center (PEER) Receives $3.6 Million NSF NEES Grand Challenge Grant

The Pacific Earthquake Engineering Research Center (PEER) has been awarded a five-year, $3.6 million NEES Grand Challenge grant from the National Science Foundation (NSF) to study the collapse potential of older nonductile concrete buildings during earthquakes. These buildings are pervasive throughout the U.S. and other countries, and are considered a high risk. The project will fully utilize the George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES).

Nonductile concrete buildings were a prevalent construction type in highly seismic zones of the U.S. prior to enforcement of codes for ductile concrete in the mid-1970s, and are widespread in many countries. In California, alone, it is estimated there are 40,000 of these buildings, including residential, commercial and critical service facilities. The poor seismic performance of nonductile concrete buildings was evident in recent earthquakes including Northridge (1994); Kobe, Japan (1995); Chi Chi, Taiwan (1999); Kocaeli, Duzce, and Bingol, Turkey (1999, 1999, 2003); Sumatra (2005); and Pakistan (2005).

For this project, PEER will study the vulnerability and toughening of nonductile concrete infrastructure against earthquake effects. Specifically, PEER's research will develop procedures to identify the truly /dangerous/ buildings from among the large building population, thereby turning an intractable problem into one that can be addressed with available resources. Mitigation strategies developed here also can inform strategies to mitigate for other natural and manmade hazards such as hurricanes and explosions.

"Existing vulnerable buildings are the number one seismic safety problem in the world, and nonductile reinforced concrete buildings are a noteworthy percentage of these that have yet to be addressed in a systematic way," said Jack Moehle, PEER's director. "This project will tackle this issue in a comprehensive way, leading to solutions that can save thousands of lives."

According to Joy Pauschke, Program Director of NEES at NSF, "We have learned the lesson over and over again in past earthquakes in the U.S. and abroad – many of our nation's older concrete buildings, where many of us live and work, are not safe during an earthquake. This project will use the NSF-funded NEES laboratories around the U.S. to provide building owners, occupants, and public officials with solutions to make these buildings safer."

In order to improve understanding of earthquakes and their effects, the National Science Foundation created the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES), managed by NEES Consortium, Inc. in Davis, CA, under NSF award number CMMI-0402490. NEES is a shared network of fifteen experimental facilities, collaborative tools, a centralized data repository, and earthquake simulation software, all linked by the ultra high-speed Internet2 connections of NEESgrid. The University of California, Berkeley, is one of the NEES laboratories in this consortium. Altogether, these resources provide the means for collaboration and discovery in the form of more advanced research based on experimentation and computational simulations of the ways buildings, bridges, utility systems, coastal regions, and geomaterials perform during seismic events.

The PEER project team will include these institutions and their respective departments: University of California (UC) at Berkeley–Architecture Dept. and Civil Engineering Dept., UC Irvine–Civil Engineering Dept., UC Los Angeles–Civil Engineering Dept., San Jose State University–Civil Engineering Dept., University of Puerto Rico at Mayaguez–Civil Engineering Dept., University of Kansas at Lawrence–Civil Engineering Dept., University of Washington–Political Science Dept., Purdue University—Civil Engineering Dept., University of Southern California–School of Policy, Planning and Development.

The project team is partnering with the Earthquake Engineering Research Institute (EERI) to form the Concrete Coalition, an alliance of concerned engineers, planners, policy experts, and other stakeholders who will work with the project team to develop and implement effective mitigation strategies.

The research will consist of four areas: 1) Exposure—An inventory of older-type concrete buildings will be developed for one urban region to serve as a testbed for regional loss studies.; 2) Component and System Performance—Laboratory and field experiments will be conducted on concrete components and soil-foundation-structure systems to improve understanding of conditions that lead to collapse; 3) Building and Regional Simulation—Computer models and simulations will be developed and used to study regional distribution of building collapses in a major earthquake; and 4) Mitigation Strategies—Effective mitigation strategies will be developed to promote action for risk reduction.

Expected outcomes of PEER's study include improved inventory, data and models for components and subsystems, single building simulation capabilities, improved fragilities/regional simulations, public policy, improved engineering assessment and retrofit tools, increased diversity in earthquake engineering, and active rehabilitation of truly vulnerable buildings nationwide initiated through public policy and professional encouragement.

The Pacific Earthquake Engineering Research Center (PEER) develops, validates and disseminates performance-based seismic design technologies for buildings and infrastructure to meet the diverse economic and safety needs of owners and society. PEER is supported by funds from the U.S. National Science Foundation, the State of California, participating universities, private industry and business partners. It is administered under the National Science Foundation's Engineering Research Centers Program.

Register Today for PEER's Annual Meeting, January 19-29, 2007

PEER will hold its Annual Meeting on January 19-20, 2007, at the Hotel Nikko in San Francisco. The theme is "The Practice of Performance-Based Earthquake Engineering." This meeting will provide opportunities for PEER researchers and partners to engage in discussions on research accomplishments, important research needs, and strategies to address those needs.

Day 1, Friday, January 19, will feature plenary sessions to examine the ways in which PEER's research has influenced earthquake engineering practice and seismic hazard mitigation. The day will conclude with a student poster session, reception and banquet for all participants.

Day 2, Saturday, January 20, will feature small working groups, organized around thrust areas, along with select presentations by student and faculty researchers on current projects and opportunities.

Expected attendees include all individuals working on PEER-funded Core and Lifelines projects inYears 8 and/or 9, such as principal investigators, students and post-doctoral researchers, and anyone else supported by the project; PEER business and industry partners; active PEER committee members (SAC, IAB, SLC); and other students or industry members interested in learning more about PEER's research programs.

The venue for the 2007 PEER Annual Meeting is the stylish Hotel Nikko San Francisco, www.hotelnikkosf.com , located two blocks from Union Square and within easy walking distance of many shops, restaurants and city attractions. Hotel Nikko is easily accessible by BART, MUNI and other transportation. On-site parking is available. Register On-line.

For more information: Please direct any questions about this event to the PEER Outreach Office, or call (510) 642-3462.

OCTOBER 2006 Contents:

PEER Signs 5-Year Contract With PG&E

PEER has signed a five-year research contract with the Pacific Gas and Electric Company (PG&E) to study extreme ground motion at the proposed nuclear waste repository site at Yucca Mountain, Nevada. The project is about $1 million and the original source of funding is the U.S. Department of Energy. In the last nine years, PEER and PG&E have been partners on various earthquake research projects related to seismic performance of lifelines. For more information, please contact Prof. Jack Moehle, PEER Director, or Dr. Yousef Bozorgnia, PEER Associate Director.

COSMOS 2006 Technical Session, Co-Sponsored by PEER, Scheduled for Nov. 17th

The Consortium of Organization for Strong Motion Observation Systems (COSMOS) will be holding its Annual Meeting and Technical Session at the Doubletree Hotel in Berkeley, California, on Friday, November 17th. The day-long technical session, which begins at 10 a.m., will focus on "An Evaluation of Methods for the Selection and Modification of Ground Motions Time Histories for Code and PBEE Applications." The Technical Session is being co-sponsored by the Pacific Earthquake Engineering Research Center (PEER).

The session program builds upon last year's program that discussed current procedures found in building codes and seismic guidelines. This year's technical session will focus on objectively evaluating various building code procedures and the most current Performance-Based Earthquake Engineer procedures considering the performance they are trying to achieve. The goal of the session is to identify the subjective issues that may be present in current procedures and to provide suggestions for improving the procedures so that they are more objective and, hopefully, result in less variation between ground motion providers.

The technical session will include presentations by Norm Abrahamson, Charles Kircher, Andrew Whittaker, and Jack Baker, and members of PEER Working Group. The PEER Working Group on Ground Motion Selection and Modification is evaluating various procedures for nonlinear response of building models. The Working Group presentations will be made by Yousef Bozorgnia, Nicolas Luco, Curt Haselton and Jennie Watson-Lamprey. Procedures found in current building codes and those being developed for the ATC-58 and ATC-63 projects will be discussed and objectively evaluated. The presenters will also serve on a panel that will discuss (along with session participants) concerns and issues with the current procedures, and suggestions for their improvements in future codes and guidelines.

REGISTER TODAY!
Early registration fees before Oct. 15th are $80 for COMOS and PEER members and $120 for nonmembers, including lunch and refreshments. After Oct 15th, fees are $100 for COSMOS members and $140 for nonmembers. There is also a special reduced student rate. For complete program and registration details for the COSMOS Annual Meeting and Technical Session, visit the COSMOS website at www.cosmos-eq.org.

PEER Leads Tall Building Initiative

Several west coast cities are seeing an upsurge in the construction of high rise buildings. This tall buildings boom has created a demand for performance-based approaches that will enable construction using new framing systems rising to heights outside the range of building code prescriptive provisions. The Pacific Earthquake Engineering Research Center (PEER) is responding to this need by leading an initiative to develop design criteria that will ensure safe and usable tall buildings following future earthquakes.

Collectively known as the Tall Building Initiative, this project involves the Applied Technology Council, Los Angeles Department of Building and Safety, Los Angeles Tall Buildings Structural Design Council, San Francisco Department of Building Inspection, Southern California Earthquake Center, Structural Engineers Association of California, U.S. Geological Survey, PEER, and several practicing professionals.

The initiative is funding a range of short to intermediate-term projects over the next 24 months. One early task will bring together appropriate professionals and stakeholders to achieve a consensus on appropriate seismic performance objectives for tall buildings, including consideration of safety and serviceability. Another task will develop guidelines on selection and modification of ground motions suitable for tall building designs, including generation of synthetic motions for large magnitude earthquakes at short distances. Still another major task will develop engineering procedures for modeling, analysis, and design to meet the target performance objectives.

The initiative is guided by a Project Advisory Committee comprising EERI members Norm Abrahamson, Yousef Bozorgnia, Ron Hamburger, Helmut Krawinkler, Marshall Lew, Ray Lui, Jack Moehle, Mark Moore, Farzad Naeim, and Paul Somerville. Broader community engagement will be achieved through a series of regular workshops and other outreach activities. For more information, including information on how to participate in upcoming workshops, go to http://peer.berkeley.edu.

PEER-Sponsored Lifelines Researcher, Brian Chiou, Receives Roberts Best Paper Award

The James Roberts Best Paper Award was presented to Brian Chiou of the California Department of Transportation at the Fifth National Seismic Conference on Bridges & Highways, in San Mateo, in September. The paper, "An Overview of the Project of Next Generation of Ground Motion Attenuation Models (NGA) for Shallow Crustal Earthquakes in Active Tectonic Regions," was co-authored by Maurice Power of Geomatrix Consultants, Norman Abrahamson of Pacific Gas and Electric Company, and Clifford Roblee of NEES Consortium Inc. The project is a partnered research program conducted by PEER , USGS and SCEC. The award was granted in recognition of a Caltrans employee whose paper discusses a deployable research innovation that is expected to have a significant impact on the practice of the bridge engineering profession.

Mahin Receives Best Paper Award at Seismic Conference on Bridges & Highways

Stephen Mahin, PEER researcher and Byron and Elvira Nishkian Professor of Structural Engineering at UC Berkeley, was awarded the James D. Cooper Best Paper Award at the Fifth National Seismic Conference on Bridges & Highways, in San Mateo. The paper, "Use of Partially Prestressed Reinforced Concrete Columns to Reduce Post-Earthquake Residual Displacements of Bridges," co-authored by Junichi Sakai and Hyungil Jeong, was presented on Wednesday, September 20, 2006. This work was funded by the State of California and the National Science Foundation through the Pacific Earthquake Engineering Research Center. The award was bestowed in recognition of an exemplary contribution to the profession for a paper with great potential impact, contribution to society and high overall quality. This is the first year the award has been given. The full paper can be found at: http://peer.berkeley.edu/mahin/Mahin_Best_Paper_Award.pdf

Register Today for PEER's Annual Meeting, January 19-29, 2007

Register on-line!

PEER will hold its Annual Meeting on January 19-20, 2007, at the Hotel Nikko in San Francisco. The theme is "The Practice of Performance-Based Earthquake Engineering." This meeting will provide opportunities for PEER researchers and partners to engage in discussions on research accomplishments, important research needs, and strategies to address those needs.

Day 1, Friday, January 19, will feature plenary sessions to examine the ways in which PEER's research has influenced earthquake engineering practice and seismic hazard mitigation. The day will conclude with a student poster session, reception and banquet for all participants.

Day 2, Saturday, January 20, will feature small working groups, organized around thrust areas, along with select presentations by student and faculty researchers on current projects and opportunities.

Expected attendees include all individuals working on PEER-funded Core and Lifelines projects inYears 8 and/or 9, such as principal investigators, students and post-doctoral researchers, and anyone else supported by the project; PEER business and industry partners; active PEER committee members (SAC, IAB, SLC); and other students or industry members interested in learning more about PEER's research programs.

The venue for the 2007 PEER Annual Meeting is the stylish Hotel Nikko San Francisco, www.hotelnikkosf.com , located two blocks from Union Square and within easy walking distance of many shops, restaurants and city attractions. Hotel Nikko is easily accessible by BART, MUNI and other transportation. On-site parking is available. Register On-line.

For more information: Please direct any questions about this event to the PEER Outreach Office, or call (510) 642-3462.

Better Than the Real Thing: Virtual Earthquakes in Berkeley

by Bart Eisenberg, Pacific Connection, Software Design magazine

Professor Gregory Fenves could hardly have picked a better location to study earthquakes. His office on the University of California, Berkeley campus sits almost on the Hayward Fault, which runs just east of Davis Hall, where Fenves is the chairman of the Department of Civil and Environmental Engineering. From there, the Hayward slices right through Memorial Stadium where, each fall, crowds of 70,000 come to watch Cal football. Relative to each other, half the stadium is poised to lurch slightly towards Canada, while the other half aims for Mexico.

Fenves's research interest is in using computers to predict how structures of various designs will hold up in earthquakes with varying vector forces. Where some earthquake researchers employ shake tables, centrifuges, and reaction wall systems, Fenves and his graduate students stage virtual quakes on computers. "Physical and software simulation have developed somewhat in parallel," he says. Software simulation relies on algorithms and data models, as well as the kind of number crunching that has accelerated over the years with Moore's Law. Meanwhile, physical simulation "is important for understanding what happens in the real world under controlled conditions. We use the data to validate and calibrate our software models."

Both the physical test equipment and software analysis comprise the research conducted by the Pacific Earthquake Engineering Research Center, a 10-year project funded principally by the National Science Foundation. PEER's website gives much detail about the actuators, controllers, and pounds of force used to re-create earthquake conditions, but the over-arching message is this: when it comes to designing structures for earthquakes, simulation is much preferable to the real thing. Software simulation involves the use of finite element analysis, which is also employed for virtual product stress testing—the kind used to analyze, say, aircraft designs. That is what Berkeley's Ray Clough was doing when he first coined the phrase "finite element method" back in 1959. "He called it that because the technique turns a continuum into discrete elements that have simple mathematical properties, which can lead to an understanding of larger systems," Fenves says. Researchers have used FEA software in analyzing structural design for earthquakes since the early 1970s, "but the software was incredibly crude compared to what we are now doing. FEA programs now accommodate far larger models and deliver more precise results. But to push the technology even further, at least two essentials are needed: a coordinated software development effort with common tools, as well as a few smart civil engineering students who can also program. Both these non-linear problems have occupied Fenves for the last 10 years or so.

"We want to build upon each person's research accomplishments without every person having a different version of the code," Fenves says. "And when someone develops a model or equation solver or a time integration scheme, we want a common software framework to ensure they all work together." He is of course describing the methods found in the open source development model. That may seem like old news, but in the structural engineering field, the idea is relatively new. And for good reason: the open source movement was created by full-time programmers who think a lot about software development, whereas engineers prefer to spend their time doing engineering. "In the Unix/Linux/Apache world, people are very literate in modern computing," Fenves says. "In structural engineering, that's not usually the case because the core instruction is on the design and behavior of structural systems. So our goal here has been to see if open source can be pushed into a technical field whose focus is not computing, but engineering."

In the mid-1990s, Fenves's graduate students developed an object-oriented development framework called Open System for Earthquake Simulation. The framework is written in C++, with a unified modeling language to define a set of extensible classes in the areas of modeling, analysis, and structural reliability. It is platform-neutral, running mostly on Windows, but also on Linux and MacOS. It includes wrappers for Fortran, a language still in wide use in among civil engineers. The framework's creators admit they have freely "swiped" ideas from the Open Source Initiative, reflecting that philosophy in the short version of the name: OpenSees.

The second challenge for Fenves has been in finding civil engineering students who know enough about computing to take a few courses outside the department and learn about object-oriented design, APIs, and C++. To paraphrase the U.S. Marine tagline: Fenves is looking for a few good programmers. Typically, about half them have come from outside the United States, including Yoshikazu Takahashi, now at Kyoto University, who maintains the Japanese version of the OpenSees website at http://opensees.kuciv.kyoto-u.ac.jp.

"This problem extends through much of science," Fenves says. In the big computational science projects, the software people and the science people come from different planets, and they have to figure out how to work together. Occasionally, someone enters the field with both skills, which, after 25 years, describes Fenves himself. "I like to work at the boundaries between computing and structural engineering—to bring the two together."

Fenves says that C++ is especially daunting for students, but remains the overall best option for software design. At Berkeley's civil engineering department, Matlab is the teaching language of choice. "It's a powerful package put out by The MathWorks, an interpreter set up for mathematical processing. The interpreter makes it a great teaching language but it's too slow for large research programs." Fenves thinks the department should also be teaching Java because of its object-oriented structure. "It's a pretty clean language compared with C++, but others think it will be too confusing for students to learn two languages: Matlab and Java."

OpenSees also uses Tcl, a pre-Java scripting language created by a former Berkeley computer science professor, John Ousterhout that enables engineers to program their models without having to dive into the intricacies of C++. "Tcl executes all the OpenSees constructors. It's a first-class programming language, with objects, lists, data structures and control structures," Fenves says. For OpenSees, Tcl has thus become the research group's interface of choice. Some students have also experimented with GUIs, but Fenves says that this is really the domain of the commercial vendors. "GUI technology changes very rapidly, and students don't have the skills or time to keep up." GUIs are also very OS-specific—making the code difficult to maintain. He hopes that, long-term, that the commercial world will "package" the research models and algorithms by adding a GUI, support, documentation and quality assurance.

Surprisingly, OpenSees lacks a conventional output file with pre-formatted rows and columns showing the analysis results. Fenves had expected to hear a lot of complaints about that (he didn't), but argues that output files don't scale well to bigger models. "Instead, we make use of recorder objects, which are usually just interfaces to a MySQL database. If you are shaking something and want to know the strain, you put in a recorder object and query the data. We are now working on another database repository that is part of a national effort, with recorders that output XML metadata."

OpenSees has now been around long enough for Fenves to assess its influence. "Twice a year, I do a ‘Google metric' to see how many hits we get compared to the commercial networks. Interest has been growing."

Off-The-Shelf vs. Roll-Your-Own

Fenves says that the codes used for earthquake simulation have come either from the commercial sector or have emerged from a haphazard development process within academia. Commercial applications like Ansys, Abacus, Adina, and the structural engineering program SAP200 have some advantages: they are tested, documented and supported. "For design engineers with a job to do, these are good solutions, but they are not adequate for cutting-edge research because the modeling capability is not enough. Large models are at the core of our research and the commercial packages aren't equipped to handle them. The same is true for the testing of new algorithms—commercial code, being closed source, can't be modified to include them."

Researcher-developed code is more accommodating of experimentation, but in the past, it has run into a different sort of problem: a lack of coordinated development and no code repository. "Structurally, development has too often branched at the root, never to re-converge. With some widely used applications, there could be 200 versions out there, with some unable to interoperate with others. With the open source model, there's a whole process involved. People communicate about who is working on what, and someone takes responsibility for the repository." The OpenSees website has linked some of the basics and culture of open source, creating a primer for interested students. There are links to Eric Raymond's seminal essay "The Cathedral and the Bazaar," the Apache project, GNU, Red Hat Linux, and the Open Source Initiative—the non-profit corporation behind the movement.

When PEER was established in 1997, OpenSees fit right in to the project's overall goal of "performance-based" earthquake engineering. The term defines broader criteria for designing structures to withstand earthquakes. Today, earthquake design is prescriptive—you design structures to meet the building codes, and if they pass, you have done your job. "Building codes are there to save lives, but they don't say anything about whether the building can be used afterward, the damage it might sustain, or the cost of repair," Fenves says. "Nor do the codes say whether there will be loss of life due to non-structural components: ceilings falling, pipes breaking. Performance-based engineering looks into all of this. It means identifying performance goals—not just building codes—then designing a structure to meet those goals. The key to performance-based engineering is the ability to predict what will happen to a given structural design given a certain type of earthquake."

An inevitable byproduct of performance-based engineering is that it puts more "stress" on the simulation software. The creators of commercial packages don't worry about performance-based goals, "because an engineer is not going to use a model that is more sophisticated than is needed to satisfy the code Right now, if a commercial firm actually added sophisticated models, I don't think anyone would use them. The design process needs to change, first." That means not just crunching numbers with existing software, but writing entirely new code. "The fidelity of our models far exceeds what's available commercially, with the ability to replicate experimental data throughout a full range of loads. Whether we are looking at soil models, reinforced concrete models, or non-linear solution methods—our solvers are much more capable than what's available commercially."

When combined, these various software models can lead to surprising results. That was the case for the analysis of a bridge near the California-Oregon border, conducted by a research group at the University of California, San Diego. Fenves thinks it may be the most advanced model of a bridge ever created. When researchers ran the simulation, the results predicted that soil on the hill could slump and liquefy, squeezing the bridge together. "People have talked about that happening, but the model actually showed us that if the earthquake is big enough, with the right site conditions, the soil slides in and the bridge follows. You couldn't model this on a shake table." Nor could you do so in commercial software, because the building codes don't require it.

The Shake Table in Richmond

After leaving Professor Fenves's office, I drove a few miles west to the university's Richmond Field Station, home to the Pacific Earthquake Engineering Research Center, itself. The site is near the Interstate 80 freeway, which runs alongside the muddy shoreline of the San Francisco Bay. Except for the nearby traffic, the place was quiet—unlike in 1860 when the California Blasting Cap Company did business here.

On the day I visited, a group of researchers wearing hard hats had gathered around PEER's shake table—one of the largest in the United States. Stephen Mahin, professor of structural engineering, explained that the group was testing seismic isolators—a kind of structural shock absorber. The technology is expensive and is more commonly used in Japan than in the United States. Above the table, the isolators were mounted on a simple structure that resembled the scaled-down skeletal base of a skyscraper. "Here, we are looking at putting isolators at the top of the first floor columns, Mahin said. "This configuration would make them more palatable for construction in the U.S."

I asked Mahin about the relationship between this kind of physical simulation and the software counterpart. "We integrate the two," he said. "We can model some parts quite well analytically, often because we have lots of data. But in other cases, we are looking at new concepts, so that only experimental testing will do. Many of the things we test here are scale-dependent—scaled down structures don't necessarily deliver results we can believe. At the same time, even a detailed finite element analysis doesn't convince everybody that it is reflecting the real world. Physical simulation is an exercise in humility."

Sometimes, the two types of simulation are combined into a single hybrid analysis. "Say you have a big structure like a suspension bridge, and you want to analyze one of the bridge piers. So you use an actual pier, then model the rest of it in software: the tower, deck, cables, foundations, sea bed, and wave propagation." The FEA application operates as it always does, but every time data is needed on the base pier, an actual physical structure gets moved the specified distance and the actual resulting force is returned to the program. "So on this component, instead of having finite elements, we have physical elements." Mahin said that this day's physical simulation was, itself, a preliminary test for later hybrid testing. "The shake table test represents what the structure would do in an earthquake. We are then going to move the specimen to another building and hook it up to large, computer-controlled hydraulic actuator that see if we can replicate what we saw here." Inside the control room, a technician had his eyes on a computer screen and his hand, over his shoulder, poised on a dial. A flick of that dial would trigger a set of 75,000-pound hydraulic actuators, eight horizontal and four vertical, built into a pit below the table—creating an "earthquake" on demand. As if opening a safe, he pulsed the dial, and it took me a split second before I realized the obvious: that the shaking would not be confined to the table. For a few nanoseconds, my native California brain, with its first-hand knowledge of earthquakes, insisted that this was the real thing.

Japan and the U.S.: Neighbors on the Ring of Fire.

The largest quake in United States history took place not in California, but 1,500 miles to the east, in Missouri. The year was 1811. Professor Gregory Fenves points out that some 30 U.S. states are affected—a fact most Americans tend to forget. But the Pacific Ring of Fire is where most earthquakes take place, and so it is not surprising that for PEER researchers, Japan is right next door. "Our biggest research collaborators are in Japan," Fenves says. "Japan has the largest shake table now, at the E-Defense facility in Miki City just outside Kobe, inaugurated a year and a half ago on the anniversary of the Kobe earthquake. The research director, Dr. Masayoshi Nakashima of Kyoto University is a close friend. I go to Japan once or twice a year, and Japanese researchers often come to Berkeley. The collaboration between our two countries has been ongoing for 25 years." (To see the shake table in action, check out the E-Defense website: www.bosai.go.jp/hyogo) Fenves says that similar circumstances bind both locations. Both Japan and California have major cities residing on earthquake faults. Both have similar types of dense urban construction, with many pre-1975 reinforced concrete buildings that were not designed to deform during an earthquake. "We both have the soft soils that can liquefy in earthquakes, and while we have use different structural systems for our residential wood construction—they have similar vulnerabilities."

The earthquake codes are also similar. "Japan legislates building codes on the Federal level while in the U.S., it's done through municipalities," Fenves says. "Usually, the U.S. building code is a little bit ahead of Japan's, while Japan is a bit ahead of us on bridges. Design philosophies are somewhat different. We make our buildings more flexible to dissipate energy during an earthquake. They make theirs a little bit stiffer and stronger."

Hybrid testing techniques have also brought the two locations together. The "hardware in the loop" of a software simulation can be located anywhere within reach of a data network, even across the Pacific. This November, for example, portions of a bridge will be physically tested at PEER and in Kyoto, with software analysis done at the Tokyo Institute of Technology. That project will lead to a larger one: a very large, full-size shaking table test at the Miki city facility.

E-Defense/NEES Testing

The fourth and last test in a series of experiments on rectangular columns were performed on the shaking table at the UC Berkeley Richmond Field Station. This test is part of the E-Defense/NEES Collaborative Research Program on Earthquake Engineering and focuses on a comparison of U.S. and Japanese design practices for constructing reinforced concrete bridges, and on developing test models for subsequent tests on the E-Defense Shaking Table in Japan. (http://www.bosai.go.jp/hyogo/ehyogo/index.html)

The first two columns in the program had transverse reinforcement provided by interlocking spirals as commonly employed by Caltrans, and the second two have traditional hoops supplemented with a limited number of cross ties, as utilized in Japan. In each set of columns, the aspect ratio of column thickness to width is altered.

The fourth specimen is similar to the first three, and will be subjected to the same ground motions, except it uses the larger aspect ratio. The ground motion utilized consists of three components from the Takatori record from the 1995 Kobe (Hyogo-ken Nanbu earthquake). The tests consist of low level runs, a design level run (nominal displacement ductility of about 4), a maximum considered run (scaled to about the predicted displacement capacity of the column), a repeat of the design level event, followed by a succession of runs where the intensity of the motion is increased up to about 1.8 times the nominal design level event. Tests continue until the specimen appears to be unsafe to test further (due to excessive local damage or residual tilt).

The tests are co-supervised by Prof. Kawashima of the Tokyo Institute of Technology and Prof. Mahin of UC Berkeley. The tests are performed by a team of students from Tokyo Tech and UC Berkeley. Funds are provided by the U.S. National Science Foundation though institutional support by NEES Consortium, Inc. of the NEES@berkeley facility and the Japan Ministry of Education, Sports, Culture, Science and Technology through the National Research Institute for Earth Science and Disaster Prevention.

The next series of tests will involve a hybrid simulation where we will mimic the behavior of a shaking table test of one of these columns with seismic isolators placed on top of the columns to limit damage. The column will be tested at Kyoto University and the seismic isolators will be tested in Berkeley in the nees@berkeley laboratory.

The remainder of the bridge and its supports will be simulated numerically. The tests will involve embedding the two test specimens within the overall structural dynamic analysis model, and carrying out the tests simultaneously with the analysis via the internet. The hybrid simulation will be carried out using OpenFresco, a framework for experimentation and control developed by Profs. Fenves and Mahin of UC Berkeley and Prof. Takahashi at Kyoto University. The simulation will be carried out using OpenSees, developed by Prof. Fenves. More information on these tests will be available at a later date.

Faculty Positions Available

The Department of Civil & Environmental Engineering at UC Berkeley is conducting a tenure-track faculty search in the area of High-Performance Structural Engineering.

Please circulate the announcement to individuals who are interested in pursuing an academic career in structural engineering at UC Berkeley.

http://www.ce.berkeley.edu/news/hpse_position_july06.html

The closing date for applications is November 9, 2006.

Call For Papers

The Call for Papers for the Sixth International Conference on Case Histories in Geotechnical Engineering and Symposium in Honor of Professor James K. Mitchell, in the Washington, DC area, August 11-16, 2008 is now available at http://campus.umr.edu/6icchge/.