Structural Engineering
and Mechanics
Research Project Abstracts: 2003
- 2004
Efficient Computational Methods
for Accurate Simulation of Wave Propagation
M.N. Guddati
National Science Foundation
08/16/01 to 08/15/04
Wave propagation is encountered in countless problems of practical importance
such as nondestructive evaluation, earthquake engineering, seismology and medical
imaging. In spite of its immense importance and extensive research performed,
the current approaches to modeling of wave phenomenon still suffer from several
shortcomings related computational efficiency and accuracy. This project is
aimed at devising new and efficient modeling techniques that would result in
highly accurate solutions with relatively low computational cost. Most recent
results from this research are related to dispersion reducing finite element
methods and absorbing boundaries.
Numerical Simulation of Bridging and Tip-Screenout in Hydraulic Fractures
M. N. Guddati
Schlumberger Oilfield Services
08/01/02 to 12/31/03
Bridging of proppant particles in a hydraulic fracture can lead to the phenomena
of tip-screenout that results in reduced productivity of oil and gas wells.
This project is aimed at accurate modeling of rock fracturing, slurry flow in
the fracture, along with the complicated nonlinear coupling. Such modeling will
be performed by innovative mixture theory based formulation developed by the
PI, along with some semi-analytical modeling of hydraulic fracture tip. At the
end, it is expected that the modeling procedure would be able to accurately
predict the bridging process and eventually tip-screenout.
Development of Specification Testing to Promote Fracture Fatigue Resistance
and to Optimize Microdamage Healing
Y.R. Kim and M.N. Guddati
FHWA/WRI/Texas A&M Research Foundation
07/99 to 12/03
The ultimate goal of this project is "to be able to classify/ specify/
improve asphalts by their healing rates and efficiencies using chemical data
that can be acquired more rapidly than by mechanical methods." To accomplish
this goal, the viscoelastic, continuum damage model developed by the PI will
be tied to the micro-mechanical properties of component materials using DM2,
a discrete element code developed by the Co-PI. Various test methods will be
explored for binder specification testing using the viscoelastic, continuum
damage formulation and DM2 simulation with an objective to promote fatigue resistance
and to optimize the microdamage healing potential.
Characterization of ALF Mixtures Using the Viscoelastoplastic Continuum
Damage Model
Y.R. Kim and M.N. Guddati
Federal Highway Administration
08/15/03 to 08/14/05
The primary objectives of the proposed research are: (1) to verify the time-temperature
superposition principle in damaged states for various asphalt mixtures used
in the current ALF study; (2) to characterize the ALF mixtures using the viscoelastoplastic
continuum damage model; and (3) to predict the performance of various ALF pavements
using finite element analysis and the VEPCD model.
Inverse Wave Propagation Algorithms
M.N. Guddati
Unsponsored
09/01 to current
Wave-based inversion is used in many fields of engineering including nondestructive
evaluation, seismic imaging, seismology and medical imaging. In many cases,
the extensive experimental data is processed by the inverse solution of the
wave propagation problem to predict the underlying domain properties. These
existing solution methods are either very approximate or extremely expensive.
This project attempts to devise a method that will provide an efficient and
accurate alternative to the existing data processing algorithms.
Semi-Analytical Modeling of Fractures in Layered Media
M.N. Guddati
Unsponsored
10/03 to current
Proper understanding of fracture growth in layered media is of significant importance
in various engineering problems of economic significance (cracking of laminated
composites, hydraulic fracturing in the context of petroleum engineering and
geophysics, to name a few applications). This project aims to develop an extremely
efficient alternative to the existing numerical methods such as finite element
and boundary element methods. An appealing feature of the resulting method is
expected to be an approximate modeling procedure of slippage between un-bounded
layers, a phenomenon that can have considerable effect on fracture growth.
Multi-level Computational Modeling of Damage and Failure
M.N. Guddati
Unsponsored
02/00 to 08/03
The phenomena of failure and damage of engineering materials span a wide range
of spatial and temporal scales. Recent advances in computing power and micro-mechanical
modeling research make it feasible to investigate the local behavior of failure
and damage of heterogeneous materials with the use of computational models.
However, simulating global mechanisms using micro-mechanics-based models is
not efficient, even when it becomes feasible. This project involves exploratory
investigation of multi-level algorithms to simulate failure and damage of large
heterogeneous systems. On one extreme, these algorithms are expected to emulate
homogenized continuum models, and on the other extreme, they emulate detailed
micro-mechanical models.
Remote Observation and Control of a Shake Table Experiment
Abhinav Gupta, V.C. Matzen, and M. Gabr
NC State University, DELTA IDEAS Grant
07/03 to 06/04
This project supports tasks that are needed in addition to those being conducted
in the development of a prototype for remote observation and control of a shake
table experiment under an NSF sponsored project. These tasks are needed to integrate
the prototype with the University computing network for incorporation in distance
education courses. The tasks need to be implemented in a manner that would maintain
real-time safety as well as security features built into the prototype. While
the tasks being undertaken are specific to the shake table experiment, the outcome
of this work can be extended to other experiments either directly or with only
minor modifications.
Computer Programs CREST and INCABS
Abhinav Gupta
Center for Nuclear Power Plant Structures, Equipment and Piping
01/02 to 12/03
This project continues to study the effects of uncertainties in the various
primary and secondary system parameters on the coupled primary-secondary system
response. A method is being developed to account for these uncertainties in
CREST as well as INCABS. The purpose is to facilitate the use of CREST and INCABS
in a risk-informed environment for design and operability. It is anticipated
that such an implementation would be helpful in identifying minor structural
modifications of cabinets and control panels that may significantly reduce cabinet
amplifications and facilitate the use of commercial grade equipment.
Decision Support for Seismic Performance Evaluation
Abhinav Gupta, J, Baugh, and G. Mahinthakumar
National Science Foundation
09/00 to 08/03
Overall goal of this research is to develop formal computational approaches
that support comprehensive decision making in structural engineering. Specifically,
these approaches are being realized in a prototype decision support system that
draws on complementary strengths of the engineer and the computer in a joint-cognitive
system. Its design is based on three major concepts: (1) optimization for evaluating
alternatives and supporting what-if analyses; (2) sub-component approach to
address structural model synthesis, scalability, model updating, and uncertainty
propagation; and (3) implementation in an object-oriented framework of high
performance distributed computing. A series of simple and real-life test cases
are being used to evaluate the proposed prototype.
Optimizing Moment Connections in Steel Frame Buildings Subjected to Dynamic
Loads
Abhinav Gupta and Debra Laefer
Unsponsored
Ongoing
This research focuses on optimizing the number of moment connections in steel
frame buildings. High performance computational tools will support an iterative
decision process by finding not only an optimal solution but also meaningful
alternatives to allow better consideration of uncertainty and tradeoffs among
objectives. Alternatives will be assessed with respect to margins associated
with design and serviceability requirements, redundancy, assembly depth, and
schedule related constraints. Advisory board members will comment on constructability,
field welding, compatibility with floor framing work, sensitivity to field modifications,
OSHA regulations for erection, and other "intangibles" that may depend
upon schedule and site related constraints.
Failure Mechanisms of Elbow Piping and Welded Components: Experiments and
Analysis
T. Hassan
Center for Nuclear Power Plant Structures, Equipment & Piping
01/03-12/03
Failure mechanisms of elbow piping and welded piping joints subjected to various
cyclic loads are studied in this research. When ratcheting is involved in a
low-cycle fatigue failure mechanism it is not well understood. Several experiments
conducted so far demonstrated the ratcheting damage accumulation and resulting
failure. In order to understand the ratcheting-fatigue failure mechanism observed,
this research is performing, i) a series of experiments, and ii) implementing
a new cyclic plasticity model into the finite element program ANSYS. Analyses
will be performed to determine the implication of the ratcheting failure mechanism
on design methodologies.
Behavior of Shear Dominated Reinforced Lightweight Concrete Members under
Seismic Conditions
M. J. Kowalsky
Expanded Shale, Clay, and Slate Institute
01/04 to 12/05
The objective of this research is to develop a process by which the characteristic
shear resistance under cyclic loading of various lightweight aggregates concretes
can be assessed. Motivation for the research stems from the small dataset and
large scatter of past tests which has resulted in a lack of consensus among
major worldwide concrete codes on lightweight concrete shear performance. The
research consists large scale reversed cyclic structural testing of 24 shear
critical members where the primary variables are aggregate properties and concrete
compression strength, 3D Laser-based mapping of cracked concrete surfaces, analysis
correlating the above tasks.
The Dynamic Seismic Performance and the Structural Seismic Design of Residential
Post-tensioned Concrete Masonry
M. J. Kowalsky and J. M. Ingham
National Concrete Masonry Association
04/03 to 06/04
The behavior of post-tensioned concrete masonry for residential housing is considered
in this project. A series of 7 large scale shake table tests on a variety of
wall configurations will be conducted which are aimed at assessing the influence
of grout, pre-stress levels, and wall openings on seismic behavior. A review
of existing post-tensioned masonry construction and development of design recommendations
is also part of the proposed research program. Analytical studies aimed at assessing
the response of rocking systems will also be considered.
Influence of Low Temperature on the Behavior of Reinforced Concrete Members
in Seismic Conditions
M. J. Kowalsky and T. Hassan (with MS Student John Sloan)
Unsponsored
08/02 to 07/03
This research represents a pilot study on the effects of low temperature on
the ductility of reinforced concrete structures. Currently, there is no consideration
for the possible effects of low temperatures on design of concrete structures,
however, limited research has indicated that steel ductility is greatly reduced
as temperatures reduce. This investigation consists of the design, construction,
testing, and analysis of four large scale reinforced concrete columns. The columns
will be subjected to reversed cyclic loads in the NCSU CFL Environmental Chamber.
Performance-Based Earthquake Engineering of Structural Systems
M. J. Kowalsky (with MS Student Jay Harris and PhD student Hazim Dwairi)
Unsponsored
Ongoing
The objective of the research is to develop comprehensive methods for achieving
performance-based design of structural systems with a specific emphasis on concrete
and masonry structures. This requires characterization of limit states at various
levels of performance, evaluation of inelastic deformation patterns, as well
as development of rational deformation-based seismic design procedures. Current
activities in this area consist of: (1) Parametric study of inelastic displacement
patterns for multi-span concrete bridges; (2) Investigation of limitations of
equivalent viscous damping for displacement-based design (with J. Nau); (3)
Displacement-based design of strength degrading systems; (4) Displacement-based
design of steel moment frames.
Internet-Enable Laboratory Experiences for Undergraduate Civil Engineering
Students
V.C. Matzen, M. Gabr, and Abhinav Gupta
National Science Foundation
07/03 to 06/05
This study is aimed at adaptation of recent developments in information technology
for incorporation of internet-enabled civil engineering laboratory experiments
in undergraduate structures and geotechnical courses. Faculty and students will
be able to remotely access, run, and control these experiments either independently
or in a classroom setting. Such a capability would facilitate the offering of
these courses via distance learning program to provide opportunities for "non-traditional"
students (e.g., part-time student, working parent, and career-changing adult)
seeking careers in Civil Engineering. Implementation of this work will lead
to enhancing the quality of undergraduate Civil Engineering courses and making
laboratory curriculum widely accessible.
B2 Stress Index for Cyclic Loading
V.C. Matzen
Center for Nuclear Power Plant Structures, Equipment and Piping
01/03 to 12/03
Piping design in nuclear power plants is normally carried out using linear elastic
analysis and simplified equations to ensure that the piping system and components
don't fail under normal or sever loadings. One of the failure modes considered
is low-cycle fatigue that might occur during an earthquake. The ASME Boiler
and Pressure Vessel Code committees have recently modified the design equation
related to this failure mode. Our research will help define one of the parameters,
B2', that occurs in that equation. The research will involve shake table experiments
and nonlinear finite element analysis.
Hybrid Columns of Concrete and FRP
A. Mirmiran
National Science Foundation (CAREER)
08/96 to 08/04
This project has focused on development of a new structural system made of concrete
and fiber composites for use as bridge pier columns and piles. The study includes
short-term static behavior under axial, flexural, and combined axial-flexural
loading, long-term creep and shrinkage, as well as cyclic loading at the member
level and connection level. Both experimental and analytical components are
included.
Construction Specs for Bonded Repair and Retrofit of Concrete Structures
using FRP Composites
A. Mirmiran (Co-PIs: Dr. Shahawy at SDR Engineering, Dr. Nanni at the University
of Missouri-Rolla, and Dr. Karbhari at the University of California, San Diego)
National Academy of Sciences (National Cooperative Highway Research Program)
10/01 to 08/04
This project has focused on developing construction specifications and process
control manual for concrete bridges repaired with FRP composites. For the first
time, detailed specifications and inspector checklists have been developed for
use by state departments of transportation. A pilot workshop is planned for
early summer to train construction inspectors. Phase II of the project focuses
on developing experimental data for construction thresholds in the bonded repair
practice using FRP.
Control of Plastic Shrinkage Cracking of Concrete with Carbon FRP Grids
A. Mirmiran
TechFab Industry in South Carolina
08/03 to 05/04
This project focused on evaluating the performance of carbon composite grids
for the control of plastic shrinkage cracking of concrete in a side-by-side
comparison of several reinforcement alternatives, including welded wire fabric,
FRP bars, and fiber reinforced concrete. Fiver different types of grids were
included in the evaluation.
Traffic Control Design for Portable Concrete Barriers
A. Mirmiran and S. Rahman
North Carolina Department of Transportation
07/04 to 06/05
This newly funded project will focus on developing design aids and charts for
portable concrete barriers in the state of North Carolina. Safe back distance
behind these free standing barriers will be evaluated using finite element and
impact analysis software for different boundary conditions and traffic configurations.
The findings will be incorporated into the state's traffic control manual.
Application of the LRFD Bridge Design Specifications to High-Strength Structural
Concrete Flexure and Compression Provisions
A. Mirmiran, S. Rizkalla and P. Zia
Cooperative Research Programs, Transportation Research Board (NCHRP)
05/03 to 03/06
The objective of this research is to develop recommended revisions to the AASHTO
LRFD Bridge Design Specifications to extend the applicability of the flexural
and compression design provisions to concrete up to 18 ksi. The research results
will allow full utilization of the material characteristics and greater use
of high-strength concrete, since the current LRFD limits the design strength
of the ultimate compressive strength of concrete to 69 MPa (10 ksi). The results
will have great economical advantages by allowing bridge design engineers to
design AASHTO girders more effectively in terms of the thickness of the web
and larger beam spacing.
Corrosion Inhibitors for Concrete Bridges
A. Mirmiran and S. Rizkalla
NC Department of Transportation
07/02 to 06/04
This project evaluates the effectiveness of commercially available corrosion
inhibitors for remediation purposes in delaying, slowing, stopping or reversing
the corrosion process in existing concrete under laboratory conditions of wet-dry
cycles and salt water spray, simulating severe field conditions. The results
will be used to compare the effectiveness of corrosion inhibitors at different
levels of chloride contamination and establish the threshold beyond which surface
application does not provide any significant improvement.
I/UCRC Center, "Repair of Buildings and Bridges with Composites (RB2C)"
S. Rizkalla
National Science Foundation
07/01/02 to 06/30/07
The NSF Industry/University Cooperative Research Center entitled "Repair
of Buildings and Bridges with Composites" (RB2C) is located
at the Constructed Facilities Laboratory. The Center focuses on the needs of
the construction industry in development of new and innovative structural components
as well as strengthening/repair methods for existing structures using advanced
composite materials. The current projects in progress are:
1. Development of Repair Systems for Steel Structures and Bridges.
2. Evaluation of New Generation of Adhesives for Marine Structures.
3. An Innovative Deck System for highway bridge decks and trailer walls using
the Z-technology.
Wireless Sensor Networks for Structural Health Monitoring of Bridges
S. Rizkalla
National Science Foundation
06/03 to 06/05
The research project deals with structural health monitoring of bridges and
civil engineering buildings. The first part addresses sensing/data interpretation,
the second part addresses the transfer of data from sensors to the location
interpretation occurs. The proposal ties together the expertise of the two NSF-I/UCRC
Centers at NC State, RB2C in the Department of Civil Engineering
and CACC in the Electrical and Computer Engineering Department. The specific
issue is the wireless communication of data for structural health monitoring
of civil engineering structures.
Supplement Funding to Support Undergraduate Student
S. Rizkalla
National Science Foundation
07/03 to 06/04
Efforts at repair of steel bridges with FRP have not been very successful because
of low modulus of most FRP materials as compared to steel. The new carbon fibers
have high modulus of elasticity that is about 3 times that of steel in fiber
form and twice that of steel in laminate form. The student will be involved
in an experimental plan consisting of testing the fibers with a variety of resins
to identify the most effective and compatible resin for the repair of steel.
Tests will include laminates as well as bond with steel plates.
Innovative Textile Technology for Modular Bridge Decks
S. Rizkalla and A. Mirmiran
National Science Foundation
07/03 to 06/05
The main objective of the proposed research is to adapt the 3-D weaving process
to develop innovative FRP bridge decks. This requires a thorough understanding
of the weaving process on the structural behavior of bridge decks. The experimental
work consists of testing scale models of FRP decks as well as coupon testing
under static and fatigue loading. The analytical work includes finite element
modeling of the FRP decks using micro- and macro-models. Once the models are
calibrated using the experimental results of Part I, a parametric study will
be carried out to optimize the shape and configuration of the deck.
Value Engineering and Cost Effectiveness of Various FRP Repair Systems
S. Rizkalla and A. Mirmiran
North Carolina Department of Transportation
07/03 to 06/05
This research program investigate the feasibility of using the most efficient
externally bonded Fiber Reinforced Polymer (FRP) repair/strengthening system
to rehabilitate prestressed concrete bridge girders damaged due to accident
or collision impact causing loss of prestressing and/or spalling of concrete.
The research will investigate the efficiency and cost-effectiveness of externally
bonded FRP sheet and strip repair/strengthening systems using prestressed channel
beams to be supplied by NCDOT from existing bridges. It will also investigate
the use of Near-Surface-Mounted FRP bars and strips to strengthen the same prestressed
channel beams. The experimental program will examine the flexural behavior under
the effect of static and fatigue loadings.
Nacromolecular Science and Infrastructure Engineering
S. Rizkalla (Co-PI with Virginia Tech)
National Science Foundation
07/01 to 06/06
The Integrated Graduate Education Research and Traineeship (IGERT) Program provides
the opportunity for our graduate students to conduct an interdisciplinary research
focused on polymeric adhesives and composites in civil engineering structures.
The program allows collaboration between the following seven departments: Chemistry,
Engineering Science, Civil Engineering, Electrical Engineering, Computer Engineering,
Wood Science and Marketing from four colleges, including NC State University.
It will include exchange of students and faculty members, as well as development
of new courses in the field of infrastructures. The first student this year
was Mr. Taylor Norton, who spent one semester at Virginia Tech and is currently
working on his M.S. research.
Evaluation of MMFX Steel for NCDOT Concrete Bridges
S. Rizkalla and P. Zia
NC Department of Transportation
07/04 to 06/05
This research project investigates the effectiveness of highly corrosive, resistant,
high strength steel reinforcements, recently patented as MMFX Steel, for use
in highway concrete bridge applications. The experimental program consists of
multi-phases to examine the mechanical properties, effect of bend and corrosion
resistance claimed by the manufacturer. The structural performance includes
full-scale concrete bridge decks. The analysis will be based on non-linear-finite
elements to determine the influence of other parameters, which could affect
the design. The research will provide design guidelines for the use of this
new tool.
Structural Load Tests of Light Gauge Steel Connection Clips
E. Sumner
The Steel Network, Inc.
06/03 to 02/04
Numerous types of steel metal-to-metal connection clips manufactured by The
Steel Network, Inc. were tested to determine the structural load capacity and
the serviceability performance limits. The service load capacity and design
strength were determined in accordance with the AISI design specification. The
results of this testing will be submitted as evidence for OSHPD certification
of these components.
Determination of Bolt Eccentricity in Single-Plate Shear Connections with
Rigid and Flexible Supports
E. Sumner
W&W Steel Company, Oklahoma City (donation of materials and load frames)
03/03 to 05/04
The eccentricity assumptions in the design of structural steel single-plate
connections have been a long-standing topic of debate among connection designers.
As a part of this project, ten full-scale shear tab connection tests will be
performed to investigate the eccentricity in the connection bolts. Current analytical
procedures will be evaluated and new provisions developed as necessary. The
experimental and analytical results of this project will provide the additional
experimental data needed to evaluate the current design methods.
Analysis and Design of Extended Single-Plate Shear Connections
E. Sumner
W&W Steel Company, Oklahoma City (donation of materials and possible partial
student funding)
05/04 to 08/04
Many of the assumptions commonly made in the analysis and design of extended
single-plate connections result in overly conservative and costly connection
designs. This research will focus on the validation of four connection details
and the development of reasonable design procedures.
Review of NCDOT Practices for Analyzing Overhang Falsework
E. Sumner and A. Mirmiran
NC Department of Transportation
07/03 to 06/04
To ensure the safety of the construction workers and personnel in bridge construction
areas, the proper design of bridge overhang falsework is essential. An effort
by the NCDOT to produce standardized details for bridge overhang falsework has
identified a need to review the current analysis and design procedures adopted
by the department. The purpose of this research is to provide a comprehensive
review to ensure that the analysis procedures and the design assumptions integrated
into the current guidelines are not too restrictive and that they are in compliance
with the latest ACI and AASHTO specifications.
Full Scale Testing of Overhang Falsework Hangers on NCDOT Modified Bulb
Tee (MBT) Girders
NC Department of Transportation
E. Sumner and A. Mirmiran
07/04 to 06/05
In the design of the overhang falsework systems, the ultimate strength and safe
working load capacity of falsework hangers on modified bulb tee (MBT) prestressed
concrete girders is not wholly known. The analysis procedures used by the manufactures
and NCDOT to predict the strength of the hangers on MBT girders are not consistent
and may have resulted in conservative and more costly falsework designs. The
focus of this research is to determine the ultimate strength and safe working
load capacity of falsework hangers on MBT girders through full scale testing
and analytical investigation.
Developing a Simplified Method for Predicting Deflection in Steel Plate
Girder Under Non-Composite Dead Load for State-Constructed Bridges
E. Sumner and S. Rizkalla
North Carolina Department of Transportation
07/03 to 06/05
Matching the final bridge deck elevations in stage constructed steel girder
bridges has created numerous problems during construction. Misaligned deck elevations
between two stages may require grinding of the deck surface or result in reduced
concrete cover leading to early deterioration of the bridge deck. The objective
of this research is to develop an empirically based method to predict the non-composite
deflection of steel plate girders in staged-constructed bridges. The formulation
of the simplified method will require a combination of field measured data and
extensive three-dimensional analytical simulation.
ICC Evaluation of Metal-To-Metal Connection Clips
E. Sumner and S. Rizkalla
The Steel Network, Inc.
11/02 to 02/04
This purpose of this project is to evaluate the performance of several types
of steel metal-to-metal connection clips manufactured by The Steel Network,
Inc. The clips are used in light gauge (cold-formed) steel construction to connect
framing members to one another or to a supporting structure. The testing was
conduced to determine the design load rating for lateral, horizontal, vertical,
and rotational load components as applicable. A methodology to determine the
service and ultimate load ratings was also developed. The results of this testing
will be submitted as evidence for ICC accreditation of these components.
| 