Projects
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Pathways Project: Experimental Determination of Performance of Drift-Sensitive Nonstructural Systems under Seismic Loading
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Funding: NEESR-SG
PIs: Kurt McMullin (San Jose State University),
Winncy Du (San Jose State University),
Thuy Le (San Jose State University),
Bozidar Stojidinovic (UC Berkeley),
Kathi Rai (SensiBuild)
Test Time: July 2011 – Feb 2012
Test Laboratories: nees@berkeley Laboratory
Participants: San Jose State University, UC Berkeley
Data Repository: NEES Project Warehouse
Detailed Information: website “http://www.engr.sjsu.edu/~pathway/”
This project investigates the damage events of nonstructural building components due to lateral story movement due to an earthquake. The project is led by Professor Kurt McMullin (San Jose State University). The project explores seismic damage to three different nonstructural systems: precast concrete cladding, inset windows, and vertical plumbing risers. A series of six full-scale experiments are to be conducted. The primary experimental test objectives include defining component and system force-deformation relationships, quantifying damage events with applied drift, evaluation of a robotic plumbing inspection system, and qualitative understanding of the behavior of façade systems. The testing involved several students including doctoral candidates from U.C. Berkeley, masters-level students from both San Jose State University and U.C. Berkeley, and undergraduate students from San Jose State University. Experimental test results will be correlated with both pre-test and post-test analytical models.
Performance-Based Design of Squat Reinforced Concrete Shear Walls
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Funding: NSF NEES-R Grant CMMI-0829978
PIs: Andrew Whittaker (University at Buffalo), Bozidar Stojadinovic (University of California, Berkeley), Laura Lowes (University of Washington), Abraham Lynn (California Polytechnic State University, San Luis Obispo)
Students: Catherine Whyte (University of California, Berkeley), Joshua Rocks (University at Buffalo), Bismarck Luna (University at Buffalo), Joshua Pugh (University of Washington)
Test Laboratories: UB-NEES (Buffalo), nees@berkeley Laboratory
Participants: University at Buffalo, University of California, Berkeley, University of Washington, California Polytechnic State University, San Luis Obispo
Data Repository: NEES Project Warehouse
Detailed Information: webpage
This project will investigate the earthquake response of large-scale reinforced concrete walls through hybrid simulation tests conducted at the nees@Berkeley laboratory site. Squat structural walls with aspect ratio (wall height/wall length) of approximately 0.5 are often the primary seismic lateral-force-resisting components in nuclear and industrial facilities. In nuclear structures, the walls are very thick for radiation shielding and blast and fire protection. Similarly thick walls are also found in industrial structures. This combination of a thick and squat wall results in a high wall stiffness. The goals of this project are to develop hybrid testing methods suited to this problem of a very stiff specimen and to better understand the earthquake response behavior. With a very stiff specimen, a small increment in displacement causes a large increment in force. This is difficult to manage in a typical displacement control hybrid simulation since very small displacements must be commanded to the specimen to achieve reasonable size force increments. We are considering using either a high precision displacement encoder in displacement control or force control. These types of walls have not been previously studied dynamically in large scale because of the difficult nature of performing these tests. Most previous studies have used predefined monotonic or cyclic loading patterns. The relatively few dynamic tests were performed on small scale models on a shaking table.
NEES Base Isolation Studies
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Funding: NEES
PIs: Stephen Mahin (UC Berkeley), Keri Ryan (?)
Students: Tracy Becker (UC Berkeley)
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley
Data Repository: NEES Project Warehouse
In the design of seismically isolated buildings in the US, response modification factors (R-values) greater than one are permitted in the design of the superstructures of non-critical facilities. These R-values may lead to yielding under the Design Basis Earthquake, and will certainly result in yielding in structures designed to be compliant with minimum code provisions during the Maximum Considered Earthquake. Using the NEES Reconfigurable Platform for Earthquake Testing (REPEAT) frame, we are testing multiple superstructure configurations to determine, in the event of superstructure yielding, what is the best design approach to achieve acceptable post-yield performance. The experimental setup consists of a 1/3-scale two-story, two-bay by one-bay frame supported on six triple friction pendulum bearings. At critical plastic hinge locations, the frame uses pinned clevis connections with steel coupons installed to resist moment. The coupons will yield during testing to produce plastic hinge action, but can easily be replaced to test a new configuration. The experimental goal is to better understand the behavior of isolated buildings when yielding occurs in the superstructure, and to find a recommendation for equivalent linear design procedures that will avoid concentrated yielding in the story immediately above the isolation plane. To test the frame, we assembled a 19x7 ft one-dimensional hybrid shake platform with +/- 20 in displacement capacity in the NEES lab at UC Berkeley. The shake platform can perform a wide variety of tests, including ones where the isolation plane is located at the top of columns or over several stories to eliminate the need for a moat at a the base of a building. The portion of the building below the isolation plane is numerically simulated during these hybrid shaking table tests.
Seismic Performance of Reinforced Concrete Corner Beam-Column Joints without Transverse Reinforcement Experiencing Axial Collapse — Phase II
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Funding: NEES Grand Challenge
PIs: Jack P. Moehle (UC Berkeley)
Students: Wael Hassan (UC Berkeley)
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley
Data Repository: NEES Project Warehouse
Detailed Information: webpage
The axial collapse potential of existing gravity load designed RC buildings is a great concern during intense seismic events.
Testing of four full scale corner beam-column joint subassemblies, including floor slabs, is under way. The goal is to evaluate non-ductile corner joints shear strength and axial residual capacity under high axial load reversals varying with lateral loads; and representing intense ground motion overturning moment effects. Gravity axial load is 0.20f’ c Ag, while the overturning axial loads vary with displacement reversals to range the joint axial load from tension to high compression (0.45f’ c Ag). A sophisticated test setup was constructed to simulate realistic boundary conditions of actual buildings. A drift based history is used to simulate lateral loading. The main test parameters are axial load level, joint aspect ratio, beam reinforcement ratio, and loading history (unidirectional vs. bidirectional displacement reversals).
The results of this investigation will provide essential input to update strength and ductility provisions of existing buildings assessment documents (ASCE/SEI 41-06). Test results also will help quantify and prioritize the axial collapse vulnerability of shear damaged unreinforced beam-column joints. Throughout the analytical stage of the current research, a simplified shear strength model was developed and verified using test results. In addition, test and analytical model outcomes will be implemented in nonlinear dynamic analysis simulations of existing RC buildings aiming to assess collapse risk during seismic events.
Two specimens have been tested so far, while the remaining two specimens will be tested by the end of September 2010.
Design, Evaluation and Testing of a Ductile Fiber-Reinforced Concrete Infill Panel System for Seismic Retrofitting of Existing Steel Structures
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Funding: NEESR-SG
PIs: Professor James Wight (University of Michigan), Sarah L. Billington (Stanford University)
Postdoctoral Researcher: Dimitrios G. Lignos (Stanford University, Kyoto University)
Students: Daniel Mauricio Moreno-Luna (Stanford University)
Test Laboratories: nees@berkeley Laboratory
Participants: University of Michigan, Stanford University
Data Repository: NEEScentral
Detailed Information: webpage
This project is part of a larger project titled “NEESR-SG: Innovative Applications of Damage Tolerant Fiber-Reinforced Cementitious Materials for New Earthquake-Resistant Structural Systems and Retrofit of Existing Structures” funded by the National Science Foundation under award number CMS-0530383 to Prof. James Wight (PI) at The University of Michigan Ann Arbor.
Large-scale hybrid testing will be conducted at the NEES facility at the University of California at Berkeley (UCB) to evaluate the performance of full-bay and partial bay infills in steel frame structures. Two testing phases are scheduled of a 2/3 scale of a 2-story steel moment frame designed in 1980s in United States. Global performance (e.g. building energy dissipation, story drift ratios) as well as local performance, such as the response of the existing frame at its own connections and where the panels connect to the existing frame, will be evaluated. The main objectives of the experimental program are as follows:
Develop and evaluate an easily-installed and rapidly-repairable system for steel frames that can be used for both retrofits and new design
Evaluate the hysteretic response and connection performance of precast HPFRC panels connected to each other and to steel frame components, subjected to cyclic loading
Seismic Performance of Reinforced Concrete Corner Beam-Column Joints without Transverse Reinforcement — Phase I
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Funding: NEES Grand Challenge
PIs: Jack P. Moehle (UC Berkeley)
and Khalid M. Mosalam (UC Berkeley)
Students: Sangjoon Park (UC Berkeley)
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley
Data Repository: NEEScentral
Detailed Information: webpage
Four full-scale reinforced concrete corner beam-column joints without transverse reinforcement are constructed with floor slabs between two orthogonal beams to assess the vulnerability of old existing reinforced concrete buildings. The specimens are designed by two main parameters: (1) beam longitudinal reinforcement ratio and (2) joint aspect ratio expressed by beam depth to column depth. Testing is conducted under quasi-static reverse cyclic alternating uni-directional loading. During test, column axial load varies linearly with respect to beam shear by the pre-defined relationship in order to consider the fluctuation of column axial load due to overturning moment within reasonable range. The objectives are to assess the seismic performance of corner joints in old existing reinforced concrete buildings, and to provide the information for analytical joint shear strength model and progressive collapse analysis of old existing RC buildings.
International Hybrid Simulation
of Tomorrow's Steel Braced Frames
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Funding: NEESR
PIs: Charles Roeder (University of Washington)
and Dawn Lehman (University of Washington)
NEES-ES Investigator: Stephen Mahin (UC Berkeley)
Students: Jiun-Wei Lai (UC Berkeley)
Test Time: ongoing since July 2008 (test preparation)
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley; University of Minnesota; University of Washington; NCREE Taiwan
Data Repository: NEEScentral
Detailed Information: webpage
These experimental research tests at Berkeley are part of the NEES small group project “International Hybrid Simulation of Tomorrow's Steel Braced Frames.” The overall project team includes researchers from the US, Japan and Taiwan, as well as affiliated researchers from Canada. The research utilizes the NEES facilities at the University of California, Berkeley, the University of Minnesota and the NCREE Laboratory in Taiwan. The major objective is to use advanced hybrid simulation research methods and international, cooperative investigation to develop performance-based tools and techniques for advanced seismic engineering of steel braced frame systems. The research work at the Berkeley site is directly supervised by Professor Stephen Mahin. The test program consists of:
Testing nearly full-scale planar specimens of steel concentrically braced frames (including SCBF, BRBF, and innovative braced frame systems). At least five experiments are planned.
Testing full-scale bracing components.
Developing and validating hybrid simulation techniques for geographically distributed hybrid simulations of steel braced frame building structures.
Seismic Response
of Column Base Connections:
Flexural Limit States
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Funding: AISC, NEESR
PIs: Amit M. Kanvinde (UC Davis)
and
Gregory G. Deierlein (Stanford University)
Students: Ivan R. Gomez (UC Davis)
Test Time: December, 2008 - March, 2009
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley; UC Davis; Stanford University
Data Repository: NEEScentral
Detailed Information: webpage
Notes. This project corresponds to Phase 4 of the overarching ULCF project (Large Scale Tests and Micromechanics-Based Simulation of Ultra-Low Cycle Fatigue and Fracture in Steel Structures).
This NEESR-SG project will run its AISC-NEES Phase 2 tests on a number of column base plate specimens. The research team is led by Professor Amit Kanvinde (UC Davis). The main objective of this phase of testing is to develop an improved understanding of flexural limit states in base plate details under seismic loading. The emphasis is on the force and deformation patterns and on the capacities of various components (i.e. base plate, anchor rods, concrete and grout) to resist the imposed force and deformation demands. The work is being carried out collaboratively between UC Davis and Stanford with students from each University participating. The key issues examined during the testing (which will include a total of 7 tests), will be the effects of anchor rod placement and strength, base plate thickness as well as gravity loads. The test data will be complemented by an extensive simulation component to inform and improve design considerations.
Fundamentals of Column Bases
and Exposed Seismic Base Design
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click here for panorama movie of the setup |
Funding: NEESR (CMS 0421492)
PIs: Amit M. Kanvinde (UC Davis)
and
Gregory G. Deierlein (Stanford University)
Students: Ivan R. Gomez (UC Davis)
Test Time: December, 2007 - January, 2008
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley; UC Davis; Stanford University
Data Repository: NEEScentral
Detailed Information: webpage
Notes. This project corresponds to Phase 3 of the overarching ULCF project (Large Scale Tests and Micromechanics-Based Simulation of Ultra-Low Cycle Fatigue and Fracture in Steel Structures).
The main aim of this phase of testing is to develop a better understanding and design considerations for shear transfer in base plate connections. A number of issues regarding shear transfer mechanisms will be addressed:
- friction as an initial load bearing mechanism,
- anchor rod shear as the limit mechanism, and
- use of shear keys for larger shear loads.
Determining the Live Load Capacity of Bridges Designed to Caltrans Seismic Design Criteria Following a Major Seismic (Design) Event
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click here for wmv movie of lateral test |
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click here for panorama movie of compression setup |
Funding: Caltrans
PI: Bozidar Stojadinovic (UC Berkeley)
Students: Vesna Terzic (UC Berkeley),
Nicola Tondini (U.of Trento, Italy)
Test Time: September, 2007 - January, 2008
Test Laboratories: nees@berkeley Laboratory,
Participants: UC Berkeley
Data Repository: local
Detailed Information: Paper presented at the
5th National Seismic Bridge Conference
The aim of this project is to evaluate the remaining traffic load capacity of a bridge after an earthquake event. A combination of experimental and analytical methods is used to achieve this goal. Five scaled models of typical circular bridge columns are tested using a two-stage procedure: the columns will be damaged by applying lateral displacement up to a desired level of displacement ductility, and then tested to capacity by applying axial load. The amount of axial load capacity remaining after a controlled amount of lateral load induced damage is measured. These tests will be used to develop the evaluation procedure and modeling guidelines. Two additional hybrid simulation tests, where column specimens will be subjected to earthquake ground motion their prototype counterparts would experience in a bridge, followed by axial load tests, are used to validate the proposed procedure and recommendations. Work on this project is leveraged by the results of past and ongoing research on bridges conducted within the PEER Center.
Fragility Testing of 230-kV Porcelain Insulators
under Cyclic Loading
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Funding: PEER
PI: Yousef Bozorgnia (UC Berkeley)
Staff Researcher : Shakhzod Takhirov (UC Berkeley)
Test Time: August, 2007 - January, 2008
Test Laboratories: nees@berkeley Laboratory
Data Repository: local
The project studies the degradation and fragility of porcelain insulator sections commonly used by utilities in installation of 230-kV disconnect switches. The experimental program investigates common failure modes of the insulator posts and determines ultimate loads under cyclic loading. Free-vibration and pull-back tests are conducted after each increment of cyclic loading amplitude to detect any degradation of the insulator sections.
Hybrid Simulation of Base Isolated Structures
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click here for wmv movie of a shaking table run |
Funding: NEES
PI: Stephen Mahin (UC Berkeley)
Students: Andreas Schellenberg (UC Berkeley)
Test Time: December, 2006 - May, 2007
Test Laboratories: nees@berkeley Laboratory; PEER Shaking Table Laboratory
Participants: UC Berkeley
Data Repository: NEEScentral
The goal of this Equipment Enhancement and Improvement (EEI) project is to develop a hybrid simulation algorithm for a 6 degrees of freedom system that produces results well correlated to shaking table tests.
International Distributed Hybrid Experiments
on Bridge Systems
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Funding: NEES/E-Defense
PIs: Yoshikazu Takahashi (Kyoto University), Stephen Mahin (UC Berkeley) and Gregory L. Fenves (UC Berkeley)
Students: Andreas Schellenberg (UC Berkeley), Hong Kim (UC Berkeley) and Yosuke Nakano (Kyoto University)
Test Time: February-March, 2007
Test Laboratories: nees@berkeley Laboratory, Kyoto University
Participants: nees@berkeley Laboratory, Kyoto University
Data Repository: local
Detailed Information: presentation
This project investigates the seismic response of a continuous bridge planned to be tested at the E-Defense shaking table by a distiributed hybrid simulation with OpenFresco and OpenSees. The bridge consists of a RC C-bent column, a RC single column, a steel single column, a steel girder and elastomeric bearings. The C-bent RC column and the steel column were tested at Kyoto University and nees@berkeley Laboratory, respectively.
NEES TITech and UCB Joint Research on Seismic Performance of Bridge Columns Based on NEES and E-Defense Collaboration
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Funding: NEES, Tokyo Institute of Technology (TITech)
PIs: Stephen Mahin (UC Berkeley) and Kazuhiko Kawashima (TITech)
Students: Erik Okstad (UC Berkeley), Gakuho Watanabe (TITech), Seiji Nagata (TITech), Takashi Matsumoto (TITech)
Test Time: September-October, 2006
Test Laboratories: nees@berkeley Laboratory; PEER Shaking Table Laboratory
Participants: UC Berkeley; E-Defense; Tokyo Institute of Technology
Data Repository: NEEScentral
Detailed Information: webpage
This project performed a series of shaking table experiments on reinforced concrete bridge columns. Four columns were tested, comparing bridge construction details commonly used in Japan and California.
Large Scale Tests and Micromechanics-Based Simulation of Ultra-Low Cycle Fatigue (ULCF) and Fracture in Steel Structures: Phase 2
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Funding: NEESR (CMS 0421492)
PIs: Amit M. Kanvinde (UC Davis) and Gregory G. Deierlein (Stanford University)
Students: Andy T. Myers (Stanford University)
Test Time: August-September, 2006
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley; UC Davis; Stanford University
Data Repository: NEEScentral
Detailed Information: webpage
This project investigate Ultra-Low Cycle Fatigue (ULCF) in large-scale welded steel columns. The extensive experimental study was complemented by detailed continuum-based FEM and micromechanics-based models that capture the fundamental processes of void growth, collapse, and damage responsible for ULCF
Investigation of Welded Reinforcement Grids
in Compression
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Funding: PEER (REU)
PI: Jack P. Moehle (UC Berkeley)
Student: Matthew Rood (University of Florida)
Test Time: August 2006
Test Laboratories: nees@berkeley Laboratory
Data Repository: local
Detailed Information: report
A monotonic uniaxial compression test was performed on a high-strength concrete (7.5 ksi) column with welded grids for transverse reinforcement. The column reached design compressive strength around 2100 kips, but failed prematurely (strain in test region = 0.01) owing to fracture of the welds in the welded grids. Axial load dropped effectively instantly from 2100 kips to 100 kips, suggesting complete failure.
2006 National Student Leadership Conference (NSLC)
Engineering Program at UC Berkeley
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Funding: NEES
PIs: Khalid Mosalam (UC Berkeley)
Students: Tran Ngoc Le, Timmy Siauw, Matias Hube, Tarek Elkhoraibi (all UC Berkeley)
Test Time: June-July, 2006
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley, National Student Leadership Conference (NSLC)
Data Repository: local
The nees@berkeley experimental facility hosted an engineering program for the National Student Leadership Conference (NSLC). High school students from across the US particiated in a hands-on introduction to earthquake engineering. The program included in numerous full-scale hybrid simulations and conventional tests of wood frame panels.
Large Scale Tests and Micromechanics-Based Simulation of Ultra-Low Cycle Fatigue (ULCF) and Fracture in Steel Structures: Phase 1
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click here for mpeg movie |
Funding: NEESR (CMS 0421492)
PIs: Amit M. Kanvinde (UC Davis)
and Gregory G. Deierlein (Stanford University)
Students: Benjamin V. Fell (UC Davis)
Test Time: October-December, 2005
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley; UC Davis; Stanford University
Data Repository: NEEScentral
Detailed Information: webpage
This project investigates Ultra-Low Cycle Fatigue (ULCF) in large-scale steel bracing members. The experimental findings are complemented by detailed continuum-based FEM and micromechanics-based models that capture the fundamental processes of void growth, collapse, and damage responsible for ULCF.
Reinforced Concrete Frame Validation Tests: Single Columns
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Funding: PEER
PI: Jack P. Moehle (UC Berkeley)
Student: Yoon Bong Shin (UC Berkeley)
Test Time: October 2005
Test Laboratories: PEER Shaking Table Laboratory
Data Repository: local
Detailed Information: webpage
The goal of the project was to develop validation data and nonlinear models for nonlinear response, component failure mechanisms, and internal force redistribution as collapse occurs in a building frame representative of older concrete construction.
Collaborative Research Behavior of Braced Steel Frames with Innovative Bracing Schemes – A NEES Collaboratory Project
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Funding: pre-NEESR (CMS 032462)
PIs: B. Stojadinovic and J. Moehle (UC Berkeley); B. Shing (UC San Diego); A. Reinhorn and M. Bruneau (University at Buffalo, SUNY); R. Leon and R. DesRoches (Georgia Institute of Technology)
Students: T. Y. Yang (UC Berkeley); A. Stavridis (UC San Diego); M. Chachter (University at Buffalo); W. Yang (Georgia Institute of Technology)
Test Time: April-May, 2005
Test Laboratories: nees@berkeley Laboratory; University of Colorado, Boulder (distributed hybrid simulation); University at Buffalo, SUNY (shaking table tests); Georgia Institute of Technology (quasi-static tests)
Participants: UC Berkeley; UC San Diego; University at Buffalo, SUNY; Georgia Institute of Technology; University of Colorado, Boulder
Data Repository: NEEScentral
Detailed Information: webpage
The project studied the behavior of braced steel frames under seismic loading with emphasis on a novel configuration called a zipper frame. In addition to its innovative technical content, the project was a successful showcase of the capabilities and potential of some of the newly installed NEES facilities to demonstrate the advantages of integrating new advanced control algorithms for testing and analysis.
Hybrid On-Line Experiments and Monitoring of Structural Systems
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Funding: pre-NEESR (CMS 0115006)
PIs: Khalid M. Mosalam (UC Berkeley)
Students: Alidad Hashemi and Tarek Elkhoraibi (UC Berkeley)
Test Time: February-March, 2005
Test Laboratories: nees@berkeley Laboratory; PEER Shaking Table Laboratory
Participants: UC Berkeley
Data Repository: NEEScentral
An extensive experimental research of reinforced concrete frames infilled with masonry walls was conducted. Both shaking table and hybrid simulation tests were conducted to study the complex behavior of the test models with the quasi-brittle component. A hybrid simulation methodology based on mixed-variable control of a structure with multiple physical and computational substructures was developed.
Grand Opening of nees@berkeley Facility
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Funding: NEES (outreach)
Test Time: November, 2004
Test Laboratories: nees@berkeley Laboratory
Participants: UC Berkeley; SEAONC
Data Repository: local
Detailed Information: webpage
The grand opening of nees@berkeley was coordinated with the Structural Engineers Association of Northern California (SEAONC) Dinner Program. The evening featured brief statements by invited dignitaries, a laboratory tour including exciting demonstration experiments, refreshments and a catered dinner. This was followed by a presentation by Professors Mahin, Stojadinovic, and Moehle, who were responsible for the development of the new facility. The presentation introduced NEES, described the special capabilities of nees@berkeley, including the new hybrid simulation capability, and through an open dialogue with attendees, explored ways that SEAONC engineers can join in to utilize this unique new facility to advance earthquake engineering practice.
