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NEESR: Near Collapse Performance
of Existing Reinforced Concrete Frame Buildings
Project
duration:
01/2012~12/2014
Funding
agency:
National Science Foundation
Research
assistant:
Adam Mueller
Principal
investigator:
Mehrdad Sasani, Ph.D. Northeastern University
Co-Principal
investigators:
Xiaoyun Shao, Ph.D. Western
Michigan University
Description:
This project
utilizes the unique hybrid simulation
capability provided by the NEES facilities to integrate the physical
experiments on four sets of three columns of four buildings and the
numerical
simulation of the remaining reinforced concrete frame structure. The
goals of
the project are to determine the effects and important characteristics
of
triaxial as opposed to unidirectional seismic ground motions on column
failure
and collapse mechanisms, to develop reliable analytical modeling tools
and
methods for collapse analysis and to develop system level acceptance
criteria
and procedures for collapse analysis of reinforced concrete structures.
NEESsoft:
Seismic Risk Reduction for Soft-Story Woodframe Buildings
Project
duration:
7/2011~7/2013
Funding
agency:
National Science Foundation
Research
assistant:
Chelsea Griffith
Principal
investigator:
John W. van de
Lindt,
Ph.D. University of Alabama
Co-Principal
investigators:
Xiaoyun Shao, Ph.D. Western
Michigan University
WeiChiang Pang, Ph.D.
Clemson
University
Michael D. Symans,
Ph.D.
Rensselaer
Polytechnic Institute (RPI)
Mikhail Gershfeld, S.E. California
State
Polytechnic University – Pomona
Description:
The vision for the NEESsoft project is twofold: To
provide a methodology to retrofit soft story woodframe buildings to (1)
protect
life, safety, and property by avoiding soft story collapse and
excessive
upper
story accelerations, and (2) provide a mechanism by which soft story
woodframe
buildings can be retrofitted using performance-based seismic design
(PBSD) to
achieve a level of performance commensurate with
stakeholders’
target. This
vision will be accomplished through a comprehensive combination of new
numerical modeling procedures, hybrid testing for validation of two
levels of
soft story woodframe retrofit and system level validation to better
understand
the mechanisms of woodframe collapse and the effect of these two levels
of
retrofit on system performance.
Western
Michigan University is leading the hybrid testing task essential in
gaining a
full understanding of soft story collapse mechanisms. Hybrid testing
allows
seismic evaluation of complex structural systems through substructure
system/component testing. Simulation techniques employed in this
project will
evaluate a full scale wood frame structure with and without various
retrofitting options, measuring the margin against collapse, focusing
on the
effects of a first story retrofit on the upper stories. Experimental
methodology is to be developed at WMU’s LESS facility and
ultimately carried
out on a full-scale model at University of Buffalo’s SEESL
facility, where
large scale servo-hydraulic actuators will simulate earthquake ground
motion
and the structure’s dynamic response is recorded.
Pseudo-Dynamic Testing of a Scaled
Specimen Using General Similitude Laws
Researcher:
Kevin Phillips
Description: Pseudo-dynamic
testing is increasingly being used for testing structures that are
subject to
seismic loadings. Due to the limited
capacity of available testing facilities and also due to economic
reasons,
testing is often carried out on scaled down models, rather than full
scale
structures. The various aspects that are
considered, when selecting scale factors for the similitude laws
chosen, are explained. The question of the practicality of scaled
down testing on structures is examined using both open and closed loop
pseudo-dynamic testing procedures. It was found that the results
obtained from
pseudo-dynamic testing of scaled models can be considered identical to
full
scale responses, when used for practical purposes.
Incremental Dynamic Analysis of a Steel
Moment Frame
Researcher:
Roger A. Sanchez M.
Description: Incremental
Dynamic Analysis (IDA) is an analysis procedure by which can be
obtained the
dynamic response of a structural model exited by several seismic loads
where
increasing intensities are applied to analyze the structure performance
from
its elastic behavior to inelastic response until collapse. After the
execution
of several IDA analyses the results can be summarized on IDA curves to
have a
graphical representation of the structure’s performance. On this
project the
procedure to perform IDA analysis is detailed step by step using the
software
SAP2000 where it is explained how to create the model of a 2D steel
frame,
define load and masses, assign section properties, define nonlinear
properties,
add earthquake record data to the model, define time history dynamic
analysis
case with the required configuration to get the nonlinear response of
the model
and how to display and export the results. The procedure to perform IDA
analysis is executed using time history analysis showing how to scale
the
earthquake data and run the analysis for several scale factors to get
the
response of the structure from its linear behavior to dynamic
instability. IDA
curves are then generated with the data obtained from the sets of
dynamic
analysis using Microsoft Excel.
Health
Monitoring System of a Bridge Structure Using Wireless Sensor Network
Project
duration:
02/2011~01/2012
Funding
agency: Western
Michigan University
Research
assistant: Chee Kian Teng
Description: The
objective
of this project is to identify an reliable structural
health monitoring method of civil
infrastructural systems, mainly a bridge system, by utilizing
a wireless
sensor
network .
The structural vibration data measured by the wireless sensors will be
analyzed
and investigated to identify the dynamic properties change in the
structural
system due to aging and real time traffic load, thus structural health
condition can be determined.
Development of Versatile Hybrid
Testing
System
for Seismic Evaluation
Project
duration: 08/2009~06/2011
Funding
agency: Western
Michigan University
Research
assistant: Griffin Enyart
Description: The
hybrid
testing method
was developed to evaluate the seismic performance of a structural
system
by physically testing part of the structure, called a
physical
substructure, while numerically simulating the rest of the structure
using a
computer model, named as computational substructure. Instead of
building full
sized structural specimen, hybrid testing allows researchers to build a
complex
substructure to be tested experimentally while the relatively simple
part of
the structure being numerically simulated. Recently versatile hybrid
testing
system was built at Western Michigan University including a seismic
simulator
(often called shake table), a reaction/loading system and an advanced
controller. Such testing system was used to evaluate the seismic
performance of
a three story structure whose top story installed with motion
mitigation
devices (i.e. dampers). The physical substructure is the top story with
damper
that was installed on the shake table and the numerical substructure is
the
bottom two story simulated in the computer. The boundary motions
between the
physical and numerical substructure were numerically simulated and
applied to
the top story using the shake table. Test results as well as the
development of
the test system is presented.
The
Effect of Varying Mass and Stiffness on a Structure's Displacement,
Velocity, and Acceleration
During an Earthquake
Project duration:
02/2011~04/2011
Research assistants:
Kelsey Wiers, Annalin Davis (Kalamazoo Area Math and
Science
Center)
Investigation
of Damage
Detection
Methods with a Wireless Sensor Network
Project
duration: 08/2009~01/2010
Funding
agencies: Western
Michigan University
Research
assistant: Mark
Humiecki
Description: This
study
evaluates three damage detection
methods with a wireless sensor network based on accuracy and
efficiency. The
three methods assessed are: Modal Assurance Criterion (MAC); Damage
Location
Assurance Criterion (DLAC); and a method which utilizes the change of
the
structures flexibility. The concept of each method is discussed and
demonstrated with a numerical example of a three story shear type
structural
model that was designed and constructed as the benchmark structure used
in this
study. The wireless sensor network adopted here utilizes the Intel Mote
2
pre-configured with the latest tool suite released by the Illinois
Structural
Health Monitoring Program (ISHMP). The establishment of the wireless
sensing
network, from software installation to data analysis, is presented. The
three
damage detection methods are then experimentally validated by using the
wireless sensor network to monitor the benchmark structure model.
Experimental
results are presented and compared to demonstrate the performance of
these
three methods. The MAC method, with this simple benchmark structure,
was
determined to be the most accurate and efficient. The flexibility-based
method
was found to be the least accurate.
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