<p>YANG, JIANFENG. Ritz Vector Approach for Evaluating the Dynamic Properties of Structural Systems and Incabinet Spectra. (Under the direction of Abhinav Gupta)The earthquake input needed in a shake table test for the seismic qualification of safety related electrical instruments, typically mounted on electrical cabinets or control panels, is defined in terms of incabinet response spectrum. This dissertation presents modifications to the originally proposed Ritz vector approach developed by Rustogi et al. (1998) for evaluating the dynamic properties of the cabinets and the incabinet spectra. Modifications are needed to overcome the limitations encountered in the application to actual cabinets. The accuracy of the modified formulations is evaluated by comparison of results for actual cabinets with the corresponding results obtained from detailed finite element analyses. The modified Ritz vector approach can account for actual rotational constraints imparted by supporting structural members such as stiffeners. It can also be applied to bench board type cabinets in which instruments are mounted on plates or frames that are inclined to the global axes as well as to frames in which parallel frame members can vibrate in different vibration shapes.In this dissertation, detailed finite element analyses are used to study the rocking behavior of cabinets and to show that accurate representation of the boundary conditions at the cabinet base is essential in the evaluation of cabinet rocking mode. Simple formulations are developed for evaluating the rocking stiffness in three different types of cabinet mounting arrangements. These formulations enable incorporation of a cabinet rocking mode in the Ritz vector approach.The Ritz vector approach is also used to develop new formulations for evaluating static and dynamic characteristics of rectangular slabs with edge beams. The effect of elastic edge restraints is considered by including appropriate integrals for edge beams in the expressions for total kinetic and potential energies in a Rayleigh-Ritz approach. The effect of various types of boundary conditions at the beam ends is accounted for by considering the corresponding Ritz vectors. The contribution of beam mass to the total kinetic energy is also considered in the proposed approach.<P>

<p>ABSTRACT BARI, MD. SHAFIQUL Constitutive Modeling for Cyclic Plasticity and Ratcheting. (under the supervision of Dr. Tasnim Hassan)This study critically evaluates the performance of a number of constitutive models in predicting ratcheting responses of carbon steel for a set of uniaxial and biaxial loading histories. Two types of modeling schemes, coupled and uncoupled, are evaluated. The coupled models from Prager, Armstrong-Frederick, Chaboche, Ohno-Wang, and Guionnet are examined. The Prager and the Armstrong-Frederick models perform inadequately. The Chaboche and Ohno-Wang models perform well for uniaxial ratcheting responses, but overpredict the biaxial ratcheting. The Guionnet model simulates one set of biaxial ratcheting response well, but fails in others. Performances of several kinematic hardening rules, when used with the uncoupled Dafalias-Popov model are also evaluated. The Armstrong-Frederick rule simulates one set of biaxial response reasonably. The Voyiadjis-Sivakumar, Phillips, Tseng-Lee, Kaneko and Xia-Ellyin rules fail to simulate the biaxial ratcheting responses. The Chaboche rule, with three decomposed terms, performs reasonably for the whole set of responses. The Ohno-Wang rule also performs reasonably, except for one biaxial response. This study indicates a strong influence of the kinematic hardening rule and its parameter determination scheme on multiaxial ratcheting simulations. The coupled models by McDowell, Jiang-Sehitoglu, Voyiadjis-Basuroychowdhury and AbdelKarim-Ohno, where additional multiaxial parameters are included in the hardening rules, are also investigated. None of these models perform consistently for the whole set of experiments. A modified kinematic hardening rule using the idea of Delobelle and his co-workers in the framework of the Chaboche model is proposed. This new rule performs impressively for all of the ratcheting responses considered. Several models for anisotropic deformation of the yield surface are scrutinized. Most of these models use complex and numerically extensive higher order tensors for the yield surface formulations and thus become less attractive for implementation with a cyclic plasticity model. This study demonstrates the methodology and promise in incorporating the equi-plastic-strain surface proposed by Shiratori and his co-workers into the Dafalias-Popov model for general multiaxial ratcheting simulations.<P>

<p>This thesis presents a methodology for estimating saturation flow rates at signalized intersections by traffic subgroups. A subgroup is defined as a group of vehicles of a specific vehicle classification that make a single directional movement from one lane. The subgroup method is founded on the procedures described in the 1997 Highway Capacity Manual (HCM) (Transportation Research Board, 1997) but extends beyond the HCM's lane group model to provide results that can be aggregated at multiple levels. Rather than assuming homogeneous conditions within each lane or lane group as is the case with many capacity guides, the subgroup method decomposes a traffic stream into individual components, each of which have unique saturation headways. Comparisons with the HCM show that under similar assumptions, the subgroup method produces similar saturation flow rates when aggregated at the lane group level. This gives confidence for applying the subgroup approach to estimate individual lane performance.The most critical element of the subgroup model is the estimation of lane volumes. Lane volume field data were gathered at four sites. Results of an evaluation of lane distribution strategies for estimating lane volumes when a choice is present indicate that the equal back of queue strategy best reflects driver behavior. Based on the observed field data, the equal back of queue strategy outperforms the equal delay strategy and the equal flow ratio strategy which are widely used in various international capacity guides. <P>

<p>To evaluate the risks and potential pay-offs of a new technology, a systematic approach for assessment must be developed. Characterization of the performance and emissions of the technology must be made comparable to conventional and other advanced alternatives. This study deals with the design and implementation of a performance and emission model for a gasification based power system fueled with municipal solid waste (MSW) and coal in ASPEN PLUS ¨C a chemical process simulation software package. The power system modeled is an integrated gasification combined cycle (IGCC) and has several advantages over conventional combustion plants including lower pollutant emissions; higher thermal efficiencies; and the ability to co-produce several products aside from electricity. The model was developed to analyze and quantify the expected benefits associated with MSW gasification. This research models a British Gas/Lurgi (BGL) Slagging gasifer-based IGCC power and methanol production facility firing coal and MSW. The ASPEN PLUS IGCC model consists of 153 unit operation blocks, 24 FORTRAN blocks and 32 design specifications. The performance model calculates mass and energy balances for the entire IGCC system. For validation, the model was calibrated to a design study by the Electric Power Research Institute (EPRI) of a BGL gasifier based IGCC system (Pechtl et al., 1992). First developed and calibrated for a coal fueled IGCC system, the model was then converted to process MSW. Three fuels are used in this study: a Pittsburgh No. 8 bituminous coal; a German waste blend; and an American 75/25 percent mixture of Refuse Derived Fuel (RDF) and Pittsburgh No. 8 Bituminous coal. Methanol plant sizes of 10,000, 20,000 and 40,000 lb methanol/hr, each with and without recycling the methanol plant purge gas to the gas turbine, were modeled for each fuel. Regardless of the type of fuel fired, all systems were more efficient when the purge gas from the methanol plant was recycled for combustion in the gas turbine. Another trend observed between the fuels is that as a system produces more methanol, the overall thermal efficiency of the plant decreases. Systems fueled with German waste performed most efficiently, followed by the Pittsburgh coal and American waste.Compared to conventional combustion power plants, Integrated Gasification Combined Cycles are relatively new technologies promising decreased pollutant emissions and increased thermal efficiencies. Additionally, IGCC systems can co-produce chemicals, further increasing the marketability of the plant. The ASPEN PLUS model can be used with several other analysis tools and techniques. The model can be used in conjunction with life cycle analysis to quantify the benefits associated with the avoided (prevented) emissions and avoided use of virgin feedstock. Probabilistic analysis can be utilized in the model to identify which model parameters most affect performance and to quantify the uncertainty and variability associated with the system.<P>

<p>COLYAR, JAMES DANIEL. An Empirical Study of the Relationships between Macroscopic Traffic Parameters and Vehicle Emissions. (Under the direction of Dr. Nagui Rouphail.)Understanding the relation between traffic parameters and vehicle emissions is an important step toward reducing the potential for global warming, smog, ozone depletion, and respiratory illness. Traffic engineers, through improved roadway design and traffic control, have the ability to reduce vehicle emissions. However, current vehicle emissions models do not allow traffic analysts to easily and accurately predict vehicle emissions based on commonly used macroscopic traffic parameters (i.e., control delay, corridor stops, average speed).The primary purpose of this thesis is to develop a corridor-level methodology for quantifying the individual effects of delay and stops on hydrocarbon (HC), nitric oxide (NO), and carbon monoxide (CO) vehicle emissions. A secondary, but equally important, purpose is to evaluate the impact of signal coordination on vehicle emissions through a before and after study. This is an important funding issue because signal coordination projects currently receive CMAQ funding with the expectation of a reduction in vehicle emissions.The study focused on three signalized arterials in Research Triangle Park and Cary, North Carolina. The data collection procedure differed from the majority of past emissions research in focusing on the collection of real-world, on-road data from instrumented vehicles. Sixteen different vehicles and ten drivers were tested, resulting in a total of approximately 825 corridor runs, 140 vehicle-hours, and 3,060 vehicle-miles of simultaneous vehicle emissions and engine diagnostic data. The latter were manipulated to produce macroscopic traffic parameters such as free flow speed, delays, and stops.An important result from this thesis is that vehicle emissions are generally highest while vehicles are accelerating and lowest while idling. In addition, control delay and corridor stops have a quantifiable effect on vehicle emissions, as an increase in control delay and corridor stops produces an increase in emissions. HC emissions show the strongest dependence on delay and stops, while NO and CO emissions show a weaker dependence.For the most part, the results of the before and after study showed no statistically significant changes in traffic parameters (speed, delay, and stops). As a result, no statistically significant changes occurred in the vehicle emissions. However, when arranging the data into groups of congested and uncongested runs, a significant direct relationship was found between HC emissions and traffic congestion. NO and CO emissions did not change significantly, even with significant changes in traffic congestion.Overall, this thesis presents a first-of-a-kind investigation into the trends between traffic parameters and real-world, on-road vehicle emissions.<P>

<p>BOSE, MRINAL KANTI. Non-Classical Damping Properties and Modal Correlation Coefficient for Dynamic Analysis of Structures. (Under the direction of Abhinav Gupta and Ajaya Gupta.)The seismic response of secondary systems depends, in addition to their uncoupled dynamic characteristics, on the interaction with primary structures supporting them. This dissertation presents a verification study of the formulations to evaluate the seismic response of non-classically damped building-piping systems by modal synthesis approach. The existing studies consider only simple representative primary-secondary systems. No real-life like coupled system such as building-piping was used in these studies. Further, the majority of simple systems considered in these studies do not represent realistic coupled systems with significant effect of non-classical damping as they have either high values of mass ratios or systems with detuned modes.In this dissertation, different configurations of simple representative systems as well as real-life like building-piping systems are considered. Responses obtained from modal superposition time history analyses as well as response spectrum analyses are compared with the corresponding responses obtained by Brookhaven National Laboratory from the direct integration time history analyses. Modal superposition time history analyses results and direct integration time history analyses results are almost identical. The mean and standard deviation of responses from response spectrum analyses are close to the corresponding values evaluated using direct integration time history analysis. In addition to the verification results, a detailed discussion is also presented on the significance of non-classical damping. It is shown that the effect of non-classical damping is significant in systems that have nearly tuned modes and sufficiently small values of modal mass ratios. It is also illustrated that composite modal damping is an alternate form of classical damping that can result in incorrect responses in non-classically damped systems. Possible reasons for numerical and modeling differences that can occur in real-life like building-piping system are identified and their effect on the dynamic characteristics of the coupled system is illustrated.In the response spectrum method, the maximum modal responses are combined using an appropriate formulation for the modal correlation coefficient. This dissertation presents a new formulation which is based on the observation that the response spectrum method is a design method such that the statistical values of responses evaluated from multiple time history analyses should be close to the corresponding values obtained from the response spectrum method. Results from a numerical study using several real earthquake records are used to develop the new formulation. Different expressions are proposed for combining modal responses that have same algebraic sign and for those that have opposite algebraic signs.<P>

<p>Wood, Bryan Thane. Use of Slurry Infiltrated Fiber Concrete in Hinge Regions of Earthquake Resistant Structures. (Under the direction of Dr. John Hanson, Distinguished Emeritus Professor of Civil Engineering)This dissertation reports on an experimental and analytical study of the use of precast slurry infiltrated fiber concrete (SIFCON) flexural hinges to improve the seismic resistance of reinforced concrete moment frames. The main thrust of the research was to investigate how different variables effect the nonlinear, cyclic, flexural behavior of reinforced SIFCON hinges, and to determine how to optimize hinge performance. In addition, a conceptual analysis was performed to evaluate the improvement in seismic resistance from using SIFCON hinges in concrete structures. Seven 10? wide, 16? deep, and 26? long reinforced SIFCON hinges were designedand fabricated, then tested under quasi-static loading. All specimens were fabricated using between 9 and 11%, by volume, Dramix 30/50 fibers, made by the Bekaert Corporation. Grade 60, Grade 75, and ASTM A722 (Dywidag) bars were used, in combination with three different SIFCON compression strengths. Additionally, various end connection details were used in testing three different reinforcing arrangements. It was shown that precast SIFCON hinges can exhibit better performance than reinforced concrete hinges. The maximum curvature ductility achieved was 26.4 over a 4? inch long interior region of a specimen. The curvature ductility of this hinge specimen, when taken over the full 26 inch hinge length, was 10.5. SIFCON hinges absorb approximately 30% more energy than fiber-reinforced concrete hinges. SIFCON hinge ductility is limited by the ultimate tensile strain of the reinforcing steel. Grade 60 reinforcing resulted in the best hinge behavior seen in testing. Transverse ties may be required to prevent buckling of compression reinforcing. SIFCON flexural stiffness is approximately half that of comparable strength reinforced concrete beams.It was found that SIFCON material behavior is highly variable. Fiber orientation and size effects are the main variables that affect SIFCON behavior. Fabrication technique and skill of workmanship greatly affects fiber orientation, while size effects make it difficult to predict insitu SIFCON properties. State-of-the-art models are not accurate enough to facilitate using SIFCON hinges to build more earthquake resistant structures. With present models, the weakest region of a beam may actually be the strongest region. <P>

<p>This document discusses an investigation into the relationship between stopped and control delay for through lane groups at actuated signalized intersections. The research was motivated by potential inconsistencies in the level-of-service thresholds between the 1994 and 1997 Highway Capacity Manuals. The research identified four existing analytical models that describe the stopped to control delay relationship, Reilly-Gardner, Akcelik, Teply, and Quigora-Bullock. <p>The research also identified five variables as having an impact on the stopped to control delay relationship, namely the delay magnitude, controller type, number of lanes, percent split, and approach speed. Focusing on actuated controllers, a comprehensive simulation-based dataset was developed using CORSIM that allowed for direct comparison of the existing analytical models noted above. None of the four models proved capable of describing all the factors that affect the stopped to control delay relationship. The CORSIM dataset was also used to test the consistency of the 1994 and 1997 level-of-service thresholds, which were found to be inconsistent. Using control delay and the 1997 thresholds tended toward a worse level-of-service than using stopped delay with the 1994 thresholds. <p>Using the same CORSIM dataset, three new analytical models describing the stopped to control delay relationship were developed. Both the existing and the newly developed analytical models were validated using field data. The validation steps showed that one of the newly developed models, called the Multivariate-Linear Model, provided the best overall description of the stopped to control delay relationship. This model was used to develop a new set of level-of-service thresholds for use with control delay. This new set of thresholds was shown to be more consistent with the 1994 Highway Capacity Manual stopped delay thresholds than the 1997 Highway Capacity Manual control delay thresholds.<P>

<p>Activated carbon adsorption is the best available treatment technology for thecontrol of many objectionable trace organic compounds. Activated carbons are frequentlycharacterized by the iodine number and BET surface area, but these parameters do notcorrelate well with trace organic compound removal from natural water. Therefore, theobjective of this research was to develop activated carbon selection criteria that assure theeffective removal of trace organic contaminants from natural water and to base theselection criteria on the adsorbent?s pore structure and surface chemistry. Tosystematically evaluate pore structure and surface chemistry effects, a matrix of activatedcarbon fibers (ACFs) with three activation levels and four surface chemistry levels wasstudied. To evaluate whether adsorption trends established for ACFs were also valid forgranular activated carbon (GAC), ACF results were compared with those obtained forthree commercially available GACs. Adsorption capacities were determined for naturalorganic matter (NOM), for relatively hydrophilic methyl tertiary-butyl ether (MTBE) andrelatively hydrophobic trichloroethene (TCE) in organic-free water, and for MTBE andTCE in the presence of NOM. NOM isotherms showed that DOC adsorption occurredprimarily in pores with diameters in the 11 to 500 Å range and that electrostaticinteractions between NOM and the carbon surface played a role in NOM adsorption.According to both single-solute isotherms and micropollutant isotherms in the presence of NOM, hydrophobic adsorbents more effectively removed TCE and MTBE thanhydrophilic adsorbents. Effective adsorbents for drinking water treatment shouldtherefore contain little oxygen and nitrogen whose presence increases the polarity of theadsorbent surface. Based on the elemental composition of the low-ash carbons evaluatedin this study, activated carbons should have oxygen and nitrogen contents that sum to nomore than 2 to 3 mmol/g to assure sufficient hydrophobicity. In addition, both single-soluteisotherms and isotherms in the presence of NOM indicated that adsorbents shouldexhibit a large pore volume in micropores with widths that are about 1.5 times larger thanthe kinetic diameter of the target adsorbate. Furthermore, based on the micropollutantisotherms in the presence of NOM, an effective adsorbent should possess a microporesize distribution that extends to widths that are approximately twice the kinetic diameterof the target adsorbate to prevent pore blockage or restriction as a result of NOMadsorption.<P>

<p>Kuterdem, Can Ali. Integrated Watershed Management Using a Genetic Algorithm-Based Approach (Under the direction of Dr. Ranji S. Ranjithan)Watershed management requires consideration of a multitude of factors affecting water quality at the watershed-scale while integrating point and non-point sources of pollution and control. While the existing water quality modeling systems and associated quantitative tools can assist in some aspects of Total Maximum Daily Load (TMDL) development for a watershed, their abilities to assist in determining efficient management strategies are limited. Typically, the best a user can do is employ these tools manually to explore the solution space via a trial-and-error process, which is inefficient for finding management strategies that consider water quality as well as a multitude of other design issues simultaneously. Recent implementation of the STAR (STrategy, Analysis, and Reporting) system incorporates a set of systems analytic tools to assist decisions-makers explore and identify alternative management strategies. The main engine of the STAR system is a genetic algorithm-based optimization technique, which is coupled with additional tools such as an uncertainty propagation tool, a solution reporting system, and an incremental strategy development system to form a decision support framework. This paper describes some of the capabilities of this framework through several illustrative scenarios for the Yellow River watershed in Gwinnett County, Georgia, which conducted a comprehensive, countywide TMDL investigation to assess the current water quality conditions. The STAR system?s capabilities are employed to identify ways to achieve minimum total phosphorous (TP) levels via point and nonpoint source controls, as well as characterize the implications of future urban development on TP levels. Noninferior tradeoffs between urban development and TP levels at different degrees of point source controls are generated. The range of uses of the STAR system in considering the integrated effect of point and non-point sources in watershed management is demonstrated throughout these illustrative scenarios.<P>