Structural Engineering and Mechanics

Research Project Abstracts: 2006 - 2007

Efficient Computational Methods for Accurate Simulation of Wave Propagation
M.N. Guddati
National Science Foundation
01/01 to 09/06
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 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.

SST: Polymer Fiber and Waveguide Sensors for Performance-Based Assessment and Health Monitoring of Civil Infrastructure Systems
T. Hassan, M.J. Kowalsky, and K. Peters
National Science Foundation
08/04 to 07/07
The goal of the project is to develop polymer sensors for health monitoring of civil infrastructure systems. Of specific interest is to develop a sensor that can measure strains in excess of 6% under high strain rates. Although the sensors to be developed can be utilized under a variety of load conditions and structural materials, this research program will focus on application of the sensors to concrete and steel structures subjected to earthquakes loads. The research will develop a data acquisition system that can be utilized in health monitoring and techniques for bonding the polymer sensors to concrete structures.

A Multiscale Study of Ratcheting Failure Mechanisms in Austenitic and Ferritic Steel Welded Joints
T. Hassan and K.L. Murty
National Science Foundation
08/04 to 07/07
The goal of the project is to study multiscale failure mechanisms of austenitic and ferritic steel welded joints subjected to low-cycle fatigue loading. The progressive accumulation of strain with cycle known as ratcheting is believed to result in unexpected failures of defect-free joints. This project will perform low-cycle fatigue tests of welded joints and transmission and scanning electronic microscopy studies of dislocation substructures of the heat affected zone and base metals at various stages of fatigue life. Efforts will be made to develop a model for simulating ratcheting responses of welded joints using both macroscale and multiscale based constitutive models.

Evaluation of a New High Corrosive Resistant Steel Reinforcement for Concrete Structures in the Miditerian Salt Environments
T. Hassan and S. Rizkalla
National Science Foundation
09/05 to 08/07
MMFX is a high strength, highly corrosion resistant steel, ideal for use in civil engineering applications for salt environments such as the miditerian environment in Egypt and high humidity climate such as in North Carolina and many other ocean exposed states. The research will introduce the MMFX steel as a new material has a high corrosion resistance to the engineering community in Egypt for the first time. The proposed research project consists of three major tasks: (1) experimental work, (2) analytical phase, (3) development of design guidelines.

Calibration of Rutting Models for HMA Structural and Mix Design
R. Kim and M.N. Guddati
NCHRP 9-30A, Subcontract from Applied Research Associates, Inc.
11/05 to 10/08
The objective of this research effort is to recommend revisions to the HMA rut depth prediction model in the mechanistic-empirical pavement design guide and software developed in NCHRP Project 1-37A for consideration by the NCHRP Project 1-40 panel and the AASHTO Joint Task Force on Pavements. The recommended revisions will be based on the calibration and validation of distress models with measured materials properties and performance data from existing field and other full-scale pavement sections that incorporate modified as well as unmodified asphalt binders.

Development of Multi-axial VEPCD-FEP++ and its Extension to Indirect Tension Test
Y.R. Kim and M.N. Guddati
Federal Highway Administration
09/05 to 08/07
Over the past decade, the NCSU research team has been successful in developing HMA models that can accurately capture various critical phenomena such as microcrack induced damage, strain rate - temperature interdependence, and viscoplastic flow that is critical for high temperature modeling; the resulting model is termed the viscoelastoplastic continuum damage (VEPCD) model. The primary objectives of this research are to (1) extend the VEPCD model to multiaxial state of stress; (2) develop a three-dimensional finite element program with the multiaxial VEPCD model; and (3) extend the principles used in the VEPCD modeling to the indirect tension mode.

Development of the Asphalt Pavement Performance Prediction Methodology Based on the Viscoelastoplastic Continuum Damage Theory
Y.R. Kim and M.N. Guddati
Korea Highway Corp.
10/04 to 12/06
The primary objectives of this research are (1) standardization of test and analysis methods for the determination of viscoelastic properties and performance of asphalt mixtures; (2) development of the multiaxial viscoelastoplastic continuum damage (VEPCD) models using the indirect tension test and triaxial permanent deformation test; (3) development of the VEPCD finite element program (VEPCD-FEP++); (4) calibration of the VECPD-FEP++ using the data measured from the KHC Test Road pavements; (5) development of transfer functions for the 33 asphalt pavements in the Test Road; and (6) development of a user-friendly graphic interface for pre- and post-processing of the VEPCD-FEP++.

Behavior of Shear Dominated Reinforced Lightweight Concrete Members under Seismic Conditions
M.J. Kowalsky
Expanded Shale, Clay, and Slate Institute
01/04 to 12/06
The objective of the research described in this proposal is to develop a process by which the characteristic shear resistance under cyclic loading of various lightweight aggregates concretes can be assessed. The need for this research stems from the following reasons: (1) small dataset of past reversed cyclic shear critical tests, (2) relatively large scatter in experimental data that has been observed for monotonic shear critical tests, (3) lack of consensus among major worldwide concrete codes on lightweight concrete shear performance, and (4) potential economic impact if it is shown that existing shear strength reductions are overly conservative.

Design Criteria for Post and Beam Bents with Drilled Shafts and Other Structures
M.J. Kowalsky and M. Gabr
NC Department of Transportation
07/05 to 06/07
The research described in this proposal aims to expand upon work currently underway for Pile-Bent bridge structures to all sub-structure systems employed by the NC Department of Transportation, including spread footings and columns supported on drilled shaft foundations. The research tasks encompass identifying issues specific to drilled shaft bent design and selection of a series of sample structures for analysis and design, as well as structural testing of bridge sub-structure to superstructure connections.

Pile Bent Design Criteria
M.J. Kowalsky and M.A. Gabr
NC Department of Transportation
07/05 to 07/07
Detailed 3D analysis models will be used to provide a better understanding of the actual performance of NC Department of Transportation sub-structure systems (depth to fixity; connection performance, effective length factors). In addition, the proposed work aims at providing a rational basis for identification of key performance limit states (drift and strength limits) as well as design examples comparing LFD and LRFD criteria for bridge sub-structures.

Influence of Low Temperatures on the Ductility of Bridge Structures in High Seismic Regions
M. Kowalsky and T. Hassan
Alaska Department of Transportation
08/05 to 07/07
Through a series of cyclic experiments on reinforced concrete circular columns at 20°C, 0°C, -20°C, -40°C and -50°C, this research will study the seismic responses of concrete structures at low temperatures. Based on the experimental results at the structural and material levels at various temperatures, ductility and seismic failure mechanisms of reinforced concrete members will be determined and design issues at low temperatures will be addressed.

The Sounds of Concrete: Utilizing a Sound Acquisition System (SAQS) to Record Sound Waves Generated During Extreme Loading Events to Assess the Condition of Concrete Structural Systems
M. J. Kowalsky
NCSU Faculty Research & Professional Development Fund
07/06 to 06/07
The objective of the research involves the recording and analysis of sound waves that are generated by the structure during the extreme events. The goals of the research described in this proposal are: (1) Development of a Sound Acquisition System (SAQS) suitable for the recording of sound waves generated during the large scale testing of concrete bridges and buildings. (2) Application of the SAQS to a series of large scale (3) Correlate audible sound waves to events observed during testing, with a specific focus on identifying events that initiate failure of structural components in the test.

Modeling the Impact and Blast Performance of Fiber Reinforced Concrete
V.C. Matzen and Abhinav Gupta
Idaho National Laboratory
2006 to 2009
This study is aimed at providing an experiment-based application for the blast/impact software investigation to be carried out at INL. An active research collaboration between INL and the Center for Nuclear Power Plant Structures, Equipment and Piping at NCSU is proposed. The collaboration will provide NCSU personnel an access to the advanced finite element software available at INL to model the structural performance of FRC. Simple experiments on FRC structural members will be conducted at NCSU for reconciliation of analytical and experimental results. The purpose would be to help in the development of new FRC material to withstand impact and blast loads.

Testing of Glulam to Steel Connection for RDU Terminal C Renovation and Expansion
R. Nunez, D. Johnston, and E. Sumner
Western-Archer Construction
Fall 2006
Test and evaluate the performance of glue-laminated girder to steel girder connections for the new terminal building at the Raleigh-Durham International Airport.

I/UCRC Center, Repair of Buildings and Bridges with Composites (RB2C)
S. Rizkalla
National Science Foundation
07/02 to 06/07
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 working in collaboration with the Center located at the University of Missouri-Rolla (UMR). The Center at NCSU 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.

Shear Behavior of MMFX Stirrups
S. Rizkalla
MMFX Technologies Corporation
07/06 TO 06/07
The objective of this test program is to determine the feasibility of using MMFX reinforcing bars as shear reinforcement for reinforced concrete structures. To achieve this objective, comparative tests will be conducted for shear critical reinforced concrete beams using both conventional steel and MMFX steel reinforcements. The experimental program consists of nine reinforced concrete beams of each series are further divided into 3 groups of 3 beams each. Within each group, the variable would be the amount of shear reinforcement - the minimum, the intermediate, and the maximum amounts.

Evaluation of Bond Characteristics of MMFX Steel
S. Rizkalla
MMFX Technologies Corporation
07/05 to 06/07
The high-strength steel commercially known as Micro-composite Multi-structural formable (MMFX) steel could lead to potential savings through the use of lower reinforcement ratios due to its higher strength. However, a critical evaluation of the bond characteristics of MMFX steel with concrete is of paramount importance, especially if high strength is to be utilized. The proposed research will deeply investigate the bond behavior of MMFX steel to concrete. The first phase of the proposed research program will include the parameters believed to significantly affect the bond strength: concrete compressive strength, bar size, concrete clear cover, and confinement level.

Structural Behavior of Grancrete Material
Grancrete
S. Rizkalla
01/07 to 06/08
The proposed research program is designed to examine a new type of concrete as material for construction of buildings, bridges and special infrastructural applications. The initial phase of the evaluation includes tests to determine the basic material characteristics of Grancrete including compressive strength, elastic modulus, tensile strength, creep, shrinkage, and toughness of materials. The second phase will include examining the behavior of Grancrete mixed with small aggregate to enhance the overall behavior as construction materials. Based on the findings, the research will be extended to include the behavior of Grancrete reinforced with steel reinforcements and fiber reinforced polymer materials.

Bond Behavior of SAS High Performance Steel
S. Rizkalla
SAS Stressteel, Inc.
04/04 to 07/07
To evaluate the bond characteristics of the SAS high tensile strength steel using end-block and splice beam test specimens according to the ICC specifications.

Debonding Failure in CFRP Strengthened Steel Structures
X. Zhao (Monash University), S. Rizkalla and R. Al-Mahaidi (Monash University)
Australian Research Council
01/05 to 12/07
The research will make a breakthrough in understanding the bond characteristics between CFRP and steel. It will enhance the capacity of Australian researchers to participate in a new cutting-edge research area, and help create a vibrant new industry for strengthening steel structures. The project will contribute to improved cost efficiency and safety of steel structures thereby contributing to the socio-economic well being of Australia and the USA including road, offshore, building and mining industries.

RC Beams Strengthened with Near Surface Mounted FRP
Jin-Guang Teng, S. Rizkalla and B. Taljsten (Sweden)
Hong Kong National Research Council
01/05 to 12/07
The project investigates the use of fiber reinforced polymer (FRP) material to strengthen reinforced concrete (RC) beams to increase their flexural and shear capacity. The project at Hong Kong will focus on installing these materials into the tension zones of the flexural members using the near surface mounted technique. The project complements the research in progress at North Carolina State University sponsored by the North Carolina Department of Transportation using 43-year old prestressed c-channels and AASHTO girders. The research findings will be greatly enhanced by the collaboration with the University of Technology, Sweden.

Development of Repair Systems for Steel Structures and Bridges
S. Rizkalla
Mitsubishi Chemical America
07/02 to 06/07
The project investigates the use of high modulus carbon fiber polymer (CFRP) material for strengthening steel structures and bridges. The material in use now is in the form of sheets and strips bonded to the tension surface of steel structures. The first phase includes selection of the appropriate resin and bond characteristics of the material. The second phase is to test large-scale steel monopoles strengthening with different materials, configurations and subjected to static and fatigue loading conditions. The study will be continued to include the environmental effect on the strengthening system.

An Innovative Bridge Deck System
S. Rizkalla
Martin Marietta Composites
07/02 to 06/07
The research includes development of an innovative system for highway bridge decks. The system is also suitable for manufacturing trailer walls using small thicknesses. The innovative concept consists of two layers of 2-D fiber pultruded sheets and styrofoam layers in between to provide the required thickness. At a later stage, bundled fibers are inserted in the third direction to increase the strength through-thickness properties of the panels. The system is a modified process for the Z-technology used for the aerospace industry. The test program consists of different tests to examine the material characteristics as well as the behavior of the panel.

Lateral Flange Bending in Heavily Skewed Bridges
Emmett A. Sumner
NC Department of Transportation
01/07 to 12/08
Today's steel plate girder bridges are more commonly constructed with long spans and a heavy skew. As a result, an increase in problems with lateral flange bending of the steel plate girders during construction has been observed by the NCDOT. Lateral flange bending induces additional stresses into the flanges of the girders, the end-bent diaphragms, the intermediate cross-frames, and the support bearings. The focus of this research is to quantify the effects of lateral flange bending, establish a method to predict the effects, and develop strategies to mitigate the effects of heavy skew on lateral flange bending. A combination of field monitoring and finite element analysis will be utilized to accomplish these objectives.

Shear Bond, Web Crippling and Flexural Strength of Composite and Non-composite 'DeepDek' Steel Deck Systems
Emmett A. Sumner
Consolidated Systems, Inc. (CSI)
06/07 to 12/07
Full-scale experimental tests to determine the shear bond, web crippling and flexural behavior of an innovative composite and non-composite corrugated steel deck product. The testing will be conducted in accordance with ICC standards to investigate the strength and behavior of the new products.

Evaluation of the Strength and Behavior of Stiff Wall Tie-downs For Use in Light-gauge Sheer Wall Systems
Emmett A. Sumner
The Steel Network, Inc.
01/07 to 05/07
The use of light-gauge shear wall systems to resist lateral forces in commercial and residential structures is a growing industry. The focus of this investigation is to determine the strength and behavior of an innovative tie-down system manufactured by The Steel Network Inc.

Structural Load Tests of Movement Allowing Light Gauge Steel Connection Clips
Emmett A. Sumner
The Steel Network, Inc.
06/06 to 12/06
The need for movement allowing connections in the construction of light gauge structural components is a growing industry. The innovative DriftClip products manufactured by The Steel Network Inc. were investigated to determine the service and ultimate behavior and strength. The results of these tests were submitted for ICC certification.

Digital Recording of Large Scale Structural Testing for use in Undergraduate and Graduate Civil Engineering Classrooms
Emmett A. Sumner
NCSU-LITRE
01/06 to 06/07
Laboratory demonstrations are an essential aspect of many engineering classes that improve a student's understanding of fundamental concepts by allowing them to associate theoretical concepts and calculations with observed behavior. The objective of this project is to develop a system to record still images, video, sound, and test data into a format that can be played back in real time or at an accelerated rate. The system will be used to document numerous full-scale structural tests conducted at the NCSU Constructed Facilities Laboratory. These recordings will be stored on the web for use in civil engineering courses.