Structural Engineering and Mechanics

Research Project Abstracts: 2002 - 2003

Efficient Computational Methods for Accurate Simulation of Wave Propagation
M. N. Guddati
National Science Foundation
08/01 to 08/04
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, current approaches to modeling wave phenomenon still suffer from several shortcomings related to 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 Fracture
M. N. Guddati
Schlumberger Oilfield Services
08/02 to 12/03
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 AandM Research Foundation
07/07 to 6/03
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.

Inverse Wave Propagation Algorithms
M. N. Guddati
Unsponsored
ongoing
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.

Multi-level Computational Modeling of Damage and Failure
M. N. Guddati
Unsponsored
ongoing
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.

Decision Support for Seismic Performance Evaluation
A. Gupta, J. Baugh Jr. and G. Mahinthakumar
National Science Foundation
09/00 to 08/03
The overall goal of this research is to develop formal computational approaches that support comprehensive decision making in structural engineering. Specifically, these approaches will be 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 will be 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 will be used to evaluate the proposed prototype.

Risk Informed Assessment of Regulatory and Design Requirements for Future Nuclear Power Plants
A. Gupta and A. K. Gupta
Department of Energy, Sub-award from ABB Combustion Engineering, Windsor, CT
08/99 to 12/02
Risk-consistent design of structural systems constitutes two important tasks: allocation of system risk to individual components; and development of risk-based design procedures. In practice, a mixed approach is needed in which certain structural members are designed within a risk-based framework whereas the others in a deterministic framework. However, it requires identification of interacting components to evaluate critical failure modes and their interdependencies. These interactions are incorrectly ignored in current practice leading to excessive conservatism and high costs. Proposed research will develop methods for (1) identification of interacting components, (2) optimized allocation of system risk among components, and (3) seismic risk assessment and design.

Development of Advanced Technologies to Reduce Design, Fabrication and Construction Costs for Future Nuclear Power Plants
A. Gupta and A. K. Gupta
Department of Energy, Sub-award from Duke Engineering and Services, Marlborough, MA
08/99 to 10/02
Numerical and practical difficulties in modeling systems with heterogeneous structures like building, equipment and piping by conventional analysis tools have resulted in excessive conservatism and cost intensive requirements for construction, procurement, installation and maintenance. Computational and numerical techniques will be developed for synthesizing system models using heterogeneous sub-system models with varying degree of refinements without sacrificing solution efficiency needed in analytical simulations. These methods will account for sub-system interactions and provide flexibility to evaluate effects of structural changes at design, construction, and operation stages on qualification requirements for mechanical and electrical equipment. Uncertainty propagation and model updating will also be studied.

Computer Programs CREST and INCABS
A. Gupta
Center for Nuclear Power Plant Structures, Equipment and Piping, NC State University
01/02 to 12/03
It is proposed to continue work on studying the effects of uncertainties in the various primary and secondary system parameters on the coupled primary-secondary system response. A method will be 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 also proposed to explore the development of a web-based version of INCABS to facilitate its integration with the procurement process. It is also 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.

Failure Mechanisms of Elbow Piping and Welded Components: Experiments and Analysis
T. Hassan
Center for Nuclear Power Plant Structures, Equipment and Piping, NC State University
01/02 to 12/03
An improved constitutive model is incorporated into ANSYS and ABAQUS finite element programs to improve their cyclic response simulation. The improved analysis responses from these programs along with the experimental data will be critically reviewed to understand the fatigue failure mechanisms and its implication to design. In addition, a series of residual stresses measurements at piping welded joints will be carried out, before fatigue tests and at an intermediate life, using x-ray diffraction technique at Oak Ridge National Laboratory. These measurements will demonstrate the effect of residual stress on fatigue failure which is not well understood.

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
04/04 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.

Behavior of A New High Performance Concrete Bridge on US 401 Over Neuse River in Wake County
M. J. Kowalsky and P. Zia
NC Department of Transportation
08/01 to 07/03
High performance concrete (HPC) is one of the major products of the national Strategic Highway Research Program conducted nearly a decade ago. By using HPC, designers can take advantage of not only its structural efficiency but also its enhanced durability. To encourage the use of HPC for bridge construction, the Federal Highway Administration (FHWA) has provided funding for many state departments of transportation to implement the HPC technology. The implementation program allows the state DOT's to install instrumentation and monitor the behavior of HPC bridges of various designs and exposed to different environments so as to gain the necessary knowledge and confidence of using the technology. In this research project, an HPC bridge located in Raleigh, NC will be instrumented to investigate its performance in regards to (1) Girder stiffness and deflection calculations, (2) Creep effects, and (3) Thermal effects. The research program includes analytical predictions of bridge performance, controlled live-load testing, and long-term monitoring.

Precast Post-Tensioned Clay Masonry Walls for High Performance Modular Housing
M. J. Kowalsky
National Science Foundation
08/00 to 07/03
This research is geared towards development of a housing construction technique that utilizes pre-cast masonry elements to achieve modular housing. A significant portion of the research is dedicated towards understanding the behavior of the primary load bearing elements in this system: Pre-cast, post-tensioned clay masonry walls. Through the use of reversed cyclic testing, shake table testing, and analytical studies, the effect of confinement, grouting, and bonding on pre-cast post-tensioned walls is explored. The research aims to reduce the risk of life, injury, and property destruction from natural hazards while improving durability and reducing maintenance costs of affordable modular housing.

Analysis of an Instrumented Jointless Bridge
M. J. Kowalsky
NC Department of Transportation
08/00 to 07/02
Through the use of remote data acquisition, the behavior of an instrumented jointless bridge is explored. The bridge structure, located in Haywood County North Carolina, was recently rehabilitated by the North Carolina Department of Transportation. As part of the rehabilitation, the superstructure was widened and a jointless link-slab deck employed. The goals of the research are to validate analysis and design assumptions, investigate limit-states design methods, and develop a strategy and guide for long-term monitoring of jointless link-slab bridges.

Performance-Based Earthquake Engineering of Structural Systems' Ongoing Research
M. J. Kowalsky
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.

Internet-Enabled Laboratory Experiences for Undergraduate Civil Engineering Students
V.C. Matzen, M.A. Gabr and A. Gupta
National Science Foundation CCLI program
06/01/03 to 05/31/05
This proposal 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.

NSF-CAREER: Hybrid Columns of Concrete and FRP," National Science Foundation
A. Mirmiran
National Science Foundation
08/1/96 to 08/31/04
This is a career grant. The research plan will focus on hybrid construction with concrete and fiber composites in systems with pseudo-ductile behavior with high stiffness and strength. The plan will include analytical and experimental components. The education plan will synergize the research results into the classroom teaching which will allow to the students and the faculty person to be at the peaks of knowledge in a specific topic.

Hybrid FRP-Concrete Columns
A. Mirmiran
Florida Department of Transportation
08/01/01 to 08/31/03
The project focuses on precast and cast-in-place construction of bridge substructure with concrete-filled FRP tubes. A number of innovative ideas for piling and bridge pier columns have been evaluated as part of this project.

Construction Specs for Bonded Repair and Retrofit of Concrete Structures using FRP Composites
A. Mirmiran (Co-PIs: Shahawy at SDR Engineering, Nanni at the University of Missouri-Rolla, and Karbhari at the University of California, San Diego)
National Academy of Sciences (National Cooperative Highway Research Program)
10/19/01 to 10/18/03
The objective of this research is to develop recommended construction specifications and a construction process control manual for bonded FRP repair and retrofit of concrete structures to assure performance as designed. These documents will be prepared in a format suitable for consideration for adoption by the AASHTO Highway Subcommittee on Bridges and Structures.

Application of the LRFD Bridge Design Specifications to High-Strength Structural Concrete Flexure and Compression Provisions
A. Mirmiran and S. Rizkalla
Cooperative Research Programs, Transportation Research Board (NCHRP)
05/03 to 03/06
The FHWA has sponsored many showcase projects to encourage the application of high performance concrete due to its great economical advantages. 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 limit 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
07/01/02 to 06/30/04
The proposed study will provide accelerated test data to compare the effectiveness of six surface-applied corrosion inhibitors on concrete specimens with different levels of chloride contamination, and subjected to different environmental conditions. The study will establish threshold chloride content, beyond which surface treatments are not useful. The products will be evaluated for potential application problems or detrimental effect on concrete. The study will recommend guidelines and specifications for incorporating corrosion inhibitor surface treatments within the state bridge inspection and maintenance program.

Introduction of Fiber Composite Technology into Design and Construction Curriculum of Developing Countries as a Technical Tool for Disaster Mitigation and Recovery
A. Mirmiran and R. Nunez
NC State University Office of International Programs in Provost
07/01/02 to 06/30/03
The proposed research is a collaboration between NC State researchers and those in Ecuador on emerging technology in the area of FRP.

Ultrasonic Pulse Velocity Monitoring of Concrete: Undergraduate Research Award
A. Mirmiran (Co-PI: R. Billingley (student) at NC State University)
NC State University Office of Vice Provost for Undergraduate Affairs
11/01/02 to 05/31/03
The proposed research is provides means for damage detection using non-destructive testing with ultrasonic pulse velocity.

Evaluation of the Equivalent Lateral Force Procedure for Seismic Design of Irregular Buildings
J. Nau
Unsponsored
ongoing
The objective of this research is to examine the limitations of the equivalent lateral force procedure for the seismic design of buildings with structural discontinuities. This study formed the basis of the thesis for one M.S. student (Eggert Valmundsson), and a journal article based upon this work was published in January 1997. One Ph.D. student (Satrajit Das) completed his degree in 2000. A paper based upon his doctoral dissertation is in press.

Performance of Coped and Uncoped Framed Beam Connections
J. Nau and D. W. Johnston
Unsponsored
ongoing
This largely experimental study is nearing completion. The test fixture and twenty four specimens were fabricated (and donated) by Steel-Fab, a structural steel fabricator in Charlotte, NC. The study formed the basis of the MS thesis for one student (Jennifer Moffitt). A second MS thesis (Kyle Reece) continues and is expected to complete his degree in 2003.

Equivalent Viscous Damping for Inelastic Systems Subjected to Earthquakes
J. Nau, M. J. Kowalsky, and S. Das
Unsponsored
ongoing
Work has begun to evaluate different definitions of equivalent viscous damping to be used in performance-based earthquake engineering design.

Under Construction Bridge Deflection Measurements of Eno River
S. Rizkalla and E. Sumner
North Carolina Department of Transportation
02/03 to 04/03
NCDOT Structure Design Unit is currently investigating alternate means to accurately predict girder deflection due to the casting of the concrete decks. The accurate prediction of this deflection becomes increasingly important as the high performance steel and the associated long span structures increases. In addition, the prediction of deflection for adjacent girders of two different stages of construction is important to ensure that the adjacent cast results in an even deck and that the ultimate deck thickness matches that used in the design of the girders. The primary objective of the project is to provide NCDOT a field measurement of the steel girders of the Eno River Bridge in Durham, NC. The measurement will be compared to the predicted deflections.

I/UCRC Center, Repair of Buildings and Bridges with Composites (RB2C)
S. Rizkalla
National Science Foundation and Industrial Partners
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, North Carolina State University (NCSU). The Center is an extension to the Center located at the University of Missouri-Rolla (UMR). The Center at NCSU focuses on the needs of the 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 Bridge Deck System

Nacromolecular Science and Infrastructure Engineering
S. Rizkalla (Joint with Virginia Tech)
National Science Foundation
07/01 to 06/06
The Integrated Graduate Education Research and Training (IGERT) Program provides opportunity for our graduate students to conduct an interdisciplinary research in Macromolecular Science and Infrastructure Engineering, focused on polymeric adhesives and composites in civil engineering structures. The program allows collaboration between 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 will start, in the summer of 2003, to work on his M.Sc. research in the new development of bridge decks with the industrial partners.

Performance of Sandwich Panels Under Axial, Flexural and Shear Loads Bally Refrigerated Box Inc.
S. Rizkalla and R. Nunez
Bally Refrigerated Box Inc.
2002
The objective of this investigation is to evaluate the structural performance of Bally's sandwich panels in accordance with ICBO AC04 "Acceptance Criteria for Sandwich Panels." The panels are examined under the effect of axial compression load, transverse load and racking shear loads. End condition and panel sizes are randomly selected for typical products line.

Mechanical Properties of MMFX Steel Rebars
S. Rizkalla
MMFX Steel Corporation of America
2002
The project provides the fundamental mechanical material properties ofthe new high performance steel reinforcing bars commercially known as MMFX. The investigation included the tensile strength, shear strength, bend effect, bond strength and behavior of the bars in concrete compression members. Currently, the work extended to examine the flexural behavior including deflection, cracking and mode failure. Large scale specimens are currently used to examine the development length for different sizes of MMFX bars.

Shear Strength of FRP Anchors
S. Rizkalla
Fyfe Co., LLC
2002
The project evaluates the strength and mode of failure of typical joints for aluminum trusses used for highway sign structures and strengthened by carbon fiber-reinforced polymer materials (CFRP). Typical joints have been subjected to membrane tension forces to examine the behavior. The CFRP is wrapped to correct the diagonal member with the bottom chrod members. This phase includes static loading conditions only.

Concept Paper for Establishment of Industry/University Cooperative Research Center, Repair of Buildings and Bridges with Composites (RB2C)
S. Rizkalla
National Science Foundation
04/01 to 07/02
The "Repair of Bridges and Buildings Center" (RB2C) is an industry/university/ government cooperative research center sponsored jointly by North Carolina State University, the University of Missouri - Rolla, the National Science Foundation, and participating industrial corporations and government agencies. Faculty members from the Department of Civil Engineering are involved in unique research programs with industrial relevance. Center programs provide research assistants (MS and PhD candidates) with pertinent research topics, the means for carrying out their research, and valuable career-oriented experiences.

Determination of Bolt Eccentricity in Shear Tab Connections
E. A.Sumner
Unsponsored (materials and load frames donated by Wand W Steel Co.
03/03 to 08/03
The eccentricity assumptions in the design of structural steel shear tab connections have been a long-standing topic of debate among connection designers. As a part of this project, eight 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.