Structural Engineering and Mechanics

Research Project Abstracts: 2001 - 2002

Efficient Computational Methods for Accurate Simulation of Wave Propagation
M. N. Guddati
National Science Foundation
8/01 to 8/04
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.

Investigation of Tip-Screenout Mechanisms in Hydraulic Fracturing
M. N. Guddati
Schlumberger Oilfield Services
8/00 to 12/01
Hydraulic fracturing has been widely used in increasing the productivity of oil and gas wells over the last century and continues to be the most effective technique for production enhancement. In spite of the extensive experience, the hydraulic fracturing process is still a mystery, with several critical aspects not properly understood. One of such important phenomena is tip-screenout, defined as the arrest of the fracture resulting from dehydration of the slurry. This has a tremendous impact on the final propped fracture geometry, and thus on production enhancement. This project is expected to result in an enhanced qualitative and quantitative understanding of tip-screenout mechanisms.

Multi-Level Computational Modeling of Damage and Failure
M. N. Guddati
Unsponsored
02/00, 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.

Inverse Wave Propagation Algorithms
M. N. Guddati
Unsponsored
09/01, 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.

Development of Advanced Technologies to Reduce Design, Fabrication and Construction Costs for Future Nuclear Power Plants
Abhinav Gupta and Ajaya Kumar Gupta
US Department of Energy, Sub-award from Duke Engineering & Services, Marlborough, MA.
8/99 to 7/02
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.

Risk Informed Assessment of Regulatory and Design Requirements for Future Nuclear Power Plants
Abhinav Gupta and Ajaya Kumar Gupta
US Department of Energy, Sub-award from ABB Combustion Engineering, Windsor, CT
8/99 to 7/02
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 are designed 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.

Decision Support for Seismic Performance Evaluation
Abhinav Gupta, John Baugh Jr., and G. Mahinthakumar
National Science Foundation
9/00 to 8/02
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.

ASME Code and Ratcheting in Piping Components: Experiments and Analyses
T. Hassan and V. C. Matzen
Center for Nuclear Power Plant Structures, Equipment and Piping, NC State University
1/01 to 12/01
The main goal of this project is to develop an analysis tool for ratcheting simulation of piping components. This analysis tool can be used to incorporate ratcheting into the ASME Code in a rational manner. To understand the ratcheting failure mechanism and incorporate it into the design methodology, a systematic set of ratcheting data and an improved finite element analysis program for ratcheting simulation will be developed.

Fatigue Failure of Socket Welded Joints
T. Hassan
Center for Nuclear Power Plant Structures, Equipment and Piping, NC State University
1/01 to 12/01
This research is making efforts to understand the influence of residual stresses on fatigue crack initiation in socket welds. Residual stresses at welds because of welding sequence will be estimated through detailed finite element analyses. Influence of residual stresses on the initiation of fatigue cracks will be studied. Computed fatigue life will be verified by comparing with experimental data.

A Unified Approach to Predicting Long Term Performance of Asphalt-Aggregate Mixtures
Y. R. Kim, R. H. Borden, and Y. Horie
National Science Foundation
9/98 to 8/01
The research objective is to develop test methods and models for predicting long term performance of asphalt concrete that can account for viscoelasticity, damage, volumetric/deviatoric coupling, temperature, and aging. The objective will be accomplished by applying the elastic-viscoelastic correspondence principle and the continuum damage theory. The constitutive model will be incorporated into the ABAQUS finite element code and used to predict the response and performance of laboratory pavements loaded by the Model Mobile Load Simulator. Nondestructive surface wave tests will be performed to determine the change in material properties due to fatigue damage growth.

Development of Specification Testing to Promote Fracture Fatigue Resistance and to Optimize Microdamage Healing
Y. R. Kim and M. N. Guddati
Texas A&M Research Foundation/Western Research Institute/Federal Highway Administration
7/99 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 micromechanical properties of component materials using microscopic lattice modeling. Various test methods will be explored for binder specification testing using the viscoelastic, continuum damage formulation and micromechanical simulation with an objective to promote fatigue resistance and to optimize the microdamage healing potential.

Analysis of an Instrumented Jointless Bridge
M. J. Kowalsky
NC Department of Transportation (NCDOT)
8/00 to 7/02
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 NCDOT. 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.

Precast Post-Tensioned Clay Masonry Walls for High Performance Modular Housing
M. J. Kowalsky
National Science Foundation
8/00 to 7/03
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.

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 (NCDOT)
8/01 to 7/03
To encourage the use of High Performance Concrete (HPC) for bridge construction, the Federal Highway Administration (FHWA) has provided funding for many state departments of transportation to implement HPC technology. The implementation program allows the state DOTs to install instrumentation and monitor the behavior of HPC bridges of various designs exposed to different environments so as to gain the necessary knowledge and confidence of using the technology. In this project, an HPC bridge located in Raleigh, NC, will be instrumented to investigate its performance regarding (1) girder stiffness and deflection calculations, (2) creep effects, and (3) thermal effects.

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.

B Stress Index: Monotonic and Cyclic Loading
V. C. Matzen and T. Hassan
Center for Nuclear Power Plant Structures, Equipment and Piping,
1/01 to 12/01
Conduct experiments on piping elbows by subjecting them to cyclic loading, both in-plane and out-of-plane. Verify that nonlinear FEA can accurately simulate the experimental results. Using FEA, determine failure loads for a variety of elbow sizes and schedules. Propose a new definition for B2 for cyclic loading.

Markl Bending and Torsion Tests of 4-Inch Straight Pipes
V. C. Matzen and J. M. Nau
Ed Wais and Associates, Inc.
Spring 2002
The objective of this project is to determine fatigue strengths of piping components.

NSF-CAREER: Hybrid Columns of Concrete and FRP
A. Mirmiran
National Science Foundation
1996 to 2003
This project involves an integration of research and education plans for the advancement of hybrid construction with fiber reinforced polymer (FRP) composites and concrete. Hybrid construction results in systems with pseudo-ductile characteristics and high stiffness and strength. It also makes optimum use of materials based on their mechanical properties and resistance to corrosive environments. The research component includes long-term and time-dependent behavior of concrete-filled FRP tubes, with emphasis on creep, shrinkage, fatigue, shear, and performance under cyclic loading. The educational plan includes innovative teaching and evaluation techniques, as well as integrating composites in civil engineering.

NCHRP 12-53: Connection between Simple-Span Precast Concrete Girders made Continuous
R. Miller, A. Mirmiran, M. Hastak, and B. Shahrooz
National Academy of Sciences, Transportation Research Board
1999 to 2002
The objective of this project is to recommend details and specifications for the design of durable and constructible connections that achieve structural continuity between simple-span precast, prestressed concrete girders that will be adopted by AASHTO. This project is housed at the University of Cincinnati, and Dr. Mirmiran is responsible for the analytical component, which involves finite element analysis of the connection and developing a new analytical tool for time dependent analysis of this type of bridges. The final report is due by the end of summer.

Field Test and Analysis of Existing Steel Truss Bridge before and after Deck Replacement with FRP Panels
A. Mirmiran and J. Swanson
Delaware County, Ohio
2000 to 2002
This project involves field and laboratory testing and analysis for rehabilitating an existing steel bridge on Tyler Road in Delaware County, OH, with a span of 113 feet and twin steel trusses supporting a wooden deck. The rehabilitation plan includes replacement of the existing deck with an FRP deck. This project is housed at the University of Cincinnati, and Dr. Mirmiran is involved in the field testing and rating of the bridge.

Tyler Road Bridge in Delaware County, Ohio, Supplement Funding
A. Mirmiran and J. Swanson
Fiber Reinforced Systems
2000 to 2002
This project is a supplement of the Delaware County project, housed at the University of Cincinnati.

Hybrid FRP-Concrete Columns: 4th year match of NSF CAREER
A. Mirmiran
National Science Foundation
2001 to 2003
This is a 4th year matching and part of the NSF-CAREER project.

Low-cycle Fatigue of Plastic Piles at Connections: Non-Federal 4th Year Match for NSF-CAREER
A. Mirmiran
Florida Department of Transportation
2001 to 2003
This is the last phase of a multi-year project with the Florida Department of Transportation for the development and implementation of concrete-filled FRP piles and pier columns. The primary objective of this phase is to evaluate the performance of concrete-filled FRP tubes, with and without internal reinforcement, under low-cycle fatigue, both at the member level and at the connection level. This project complements the NSF-CAREER project of Dr. Mirmiran.

NCHRP 10-59: Construction Specs for Bonded Repair and Retrofit of Concrete Structures using FRP Composites
A. Mirmiran
National Academy of Sciences, Transportation Research Board
2001 to 2003
FRP systems can be used to rehabilitate a weakened structural member or to retrofit a sound structural member to resist higher loads. Typical applications include compensation for increased traffic volumes on bridges, dampening of vibration, corrosion rehabilitation, stress reduction in internal reinforcement, and repair of collision-damaged structures. The quality of construction is an important factor that affects long-term performance of FRP repair applications. The objective of this project is to develop specifications and process control manual in a format suitable for consideration for adoption by the AASHTO Highway Subcommittee on Bridges and Structures.

NCDOT 2003-14: Corrosion Inhibitors for Concrete Bridges
A. Mirmiran and S. Rizkalla
North Carolina Department of Transportation (NCDOT)
2002 to 2004
Deterioration of concrete bridges is a continuing problem facing NCDOT. 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.

Evaluation of the Equivalent Lateral Force Procedure for Seismic Design of Irregular Buildings
J. Nau
Unsponsored
1998, 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. One journal article was published in January 1997; one Ph.D. student completed his degree in 2000. A paper based upon his doctoral dissertation is currently under review.

Determination of the Modulus of Elasticity of Concrete from Dynamic Tests
J. Nau and M. L. Leming
Unsponsored
1998, ongoing
The objective of this project is to evaluate the modulus of elasticity of concrete from dynamic tests on thick cylindrical samples. This study formed the basis of the independent study project for one MCE student. One journal article has been published. Work continues to relate the modulus of elasticity and other dynamic properties including damping to permeability and other measures of deterioration.

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 24 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. A second MS thesis continues and is expected to complete his degree in 2002.

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.

Experimental Testing of DuraSpanTM Fiber-Reinforced Polymer (FRP) Bridge Deck
S. H. Rizkalla and A. Z. Fam
Martin Marietta Composites
9/01
Reinforced concrete bridge decks suffer from rapid deterioration, especially in the northeast of the United States and Canada, due to severe temperature effects and use of salt for deicing the roads, which result in an accelerated corrosion process of the steel reinforcement. A new Glass-FRP bridge deck is introduced to overcome the serious durability issues. This project provides structural testing of the new deck using AASHTO specifications to simulate truck loads. The two profiles considered are the 7.66-in.-thick and the 5-in.-thick decks.