The use of probabilistic analysis methods for dealing with variability and uncertainty is being more widely recognized and recommended in the development of emission factor and emission inventory. Probabilistic analysis provides decision-makers with quantitative information about the confidence with which an emission factor may be used. Variability refers to the heterogeneity of a quantity with respect to time, space, or different members of a population. Uncertainty refers to the lack of knowledge regarding the true value of an empirical quantity. Ignorance of the distinction between variability and uncertainty may lead to erroneous conclusions regarding emission factor and emission inventory. This dissertation extensively and systematically discusses methodologies associated with quantification of variability and uncertainty in the development of emission factors and emission inventory, including the method based upon use of mixture distribution and the method for accounting for the effect of measurement error on variability and uncertainty analysis. A general approach for developing a probabilistic emission inventory is presented. A few example case studies were conducted to demonstrate the methodologies. The case studies range from utility power plant emission source to highway vehicle emission sources. A prototype software tool, AUVEE, was developed to demonstrate the general approach in developing a probabilistic emission inventory based upon an example utility power plant emission source. A general software tool, AuvTool, was developed to implement all methodologies and algorithms presented in this dissertation for variability and uncertainty analysis. The tool can be used in any quantitative analysis fields where variability and uncertainty analysis are needed in model inputs.

The objective of this research is to develop and implement some numerical models to analyze pavement responses under vehicle loading. Firstly, to study the pavement delamination problem, the pavement structure is modeled as an elastic finite layer system subjected to vertical and horizontal loadings over circular areas. By using the finite layer method, the maximum interface shear stress are determined; the maximum interface shear stress can be used to compare with the interface shear strength obtained through simple shear testing to determine reasonable pavement design parameters to prevent delamination failure. Secondly, the responses of a linear viscoelastic pavement system, with asphalt concrete layer of viscoelastic properties, subjected to vertical circular loadings, are analyzed by finite element method using three algorithms: (i) direct time integration; (ii) Fourier transform; (iii) Laplace transform. The inverse Fast Fourier Transform algorithm and the numerical inversion of Laplace transform method of Honig and Hirdes are used. The numerical results of the quasi-static responses by the three algorithms are presented and compared with respect to their accuracy and computational efficiency. To use the viscoelastic model in the pavement analysis, the parameters of the generalized Maxwell model based on the frequency sweep test results are determined by using the software IRIS, which is then assigned as the property of the asphalt concrete layer in a typical pavement structure subjected to a standard dual tire axle loading. Results for the distributions of stress and strain at various times are presented. In the last part of the research, a preliminary study is presented for permanent deformation of asphalt concrete. A simplified one-dimensional elasto-visco-plastic model is implemented and used to analyze the visco-plastic deformation of a cylindrical asphalt concrete sample under one-dimensional loading.

"Decision-making under uncertainty" is an important area of study in numerous disciplines. The variety of quantitative methods that have been proposed to address environmental and water resources problems reflects the importance of this subject. In a review of the literature, methods were compared and contrasted and promising areas for future research were identified. Conclusions drawn from the review were that 1) large gains may be realized from cross-disciplinary research, 2) significant benefits may be realized from considering uncertainty, 3) advanced algorithms?probabilistic search methods and efficient methods for Bayesian analysis?and increased computing power should greatly extend the applicability of existing methods, and 4) in particular, decision-theoretic methods that have wide application for sequential decision-making. A new decision-theoretic method, Bayesian programming (BP), was developed that takes advantage of the increased computing power and improvements in Bayesian analysis methods. The method has wide applicability, suitable for problems in which there is 1) uncertainty in the modeling, 2) stochastic behavior in the systems that are modeled, 3) the possibility to reduce uncertainty through data collection, and 4) the opportunity for a recourse decision after a period of data collection. The approach combines systematic search methods (mathematical programming) and Bayesian statistical analysis techniques (Markov chain Monte Carlo) in a decision analysis framework. The BP method is tested with application to a hypothetical, but realistic river basin management problem, using real data from the much-studied Athabasca River in Alberta, Canada. The management problem involves balancing the objectives of pulp mill development and water quality protection (dissolved oxygen). Results from application of the BP method were compared with those applying other methodologies. Examination of the results indicated that the BP method is a practical method worthy of additional research. Ultimately, it is hoped, this research will lead to computer-based tools that will improve environmental and water resources decision-making.

A study was performed to investigate the impact of turbulent heterogeneity on aggregation and breakup in a flocculation reactor. The influence of the average characteristic velocity gradient (G), particle concentration, and coagulation mechanism on the flocculation performance was also investigated. Experiments were performed in a bench-scale reactor with a low-shear axial-flow impeller using a photometric dispersion analyzer (PDA) to examine the state of aggregation. Results indicated that floc growth increased while the floc size and variance in the floc size distribution decreased as G increased. In addition, floc growth, size, and floc size variance increased when the particle concentration of the water was increased and when moving from a charge neutralization mechanism to a sweep floc mechanism. Lastly, floc growth, size, and variance were found to vary spatially at low G values in the reactor with floc size and growth larger in the bulk region and the variance larger in the impeller discharge region.

Transportation departments and the telecommunications industry are currently demanding cost-effective rehabilitation and/or strengthening techniques for steel structures, including bridges and monopole towers. Rehabilitation is often required due to cross-section losses resulting from corrosion damage and strengthening may be required due to changes in the use of a structure. Current strengthening techniques, have several disadvantages including their cost, need to match the surface configuration of the existing structure, poor fatigue performance and the need for ongoing maintenance due to continued corrosion attack. The current research program makes use of new high modulus types of carbon fiber for strengthening steel structures. The experimental program was developed in four phases. These phases included the selection of suitable resins and adhesives for bonding the CFRP sheets and strips to the steel, characterization the bond to the steel through testing of the development length, performing large-scale tests on strengthened steel monopole towers and also determining the behavior of strengthened steel-concrete composite beams that are typical of bridge structures. The result of the experimental program was the demonstration of sizeable strength and stiffness increases for the steel structures, strengthened with the developed system. Analytical work has also been completed to predict these strength and stiffness increases as well as to determine the bond stresses to ensure the avoidance of a debonding failure, which is detrimental to the effective use of the high modulus CFRP material.

This study investigates the behavior of stainless steel, butt welded elbows under a variety of loading conditions. The out-of-plane performance of 2 inch, schedule 10 elbows was examined and compared with analyses obtained from ANSYS using element SHELL181. The correlations between measured and simulated curves for load vs. displacement and strains were excellent. Also, the in-plane experimental behavior of 4 inch, schedule 10 elbows was examined and compared with SHELL181 analysis results for both opening and closing modes. In general, the correlation was quite good for both the global behavior and the local strain measures. The cyclic behavior of 2 inch, schedule 10 elbows was also measured. A one and three-fourths cycle test on a 2 inch, schedule 10 elbow was performed and compared with SHELL181 using both kinematic and isotropic hardening rules. The first quarter cycle performance of both analyses was quite good, but as deformation continued the isotropic results deviated significantly while the kinematic results remained quite good. Finally, the effect of loading rate on 4 inch, schedule 10 elbows was examined for the in-plane closing. The specimens were loaded at 0.5 mm/sec, 5 mm/sec and 50 mm/sec. With an increase in closure rate, an increased deviation from the analytical results was observed. By taking strain rate hardening effect into account the correlation improved greatly. The initial conclusion from these tests is that SHELL181 can provide excellent correlation under quasi-static loading, but at faster rates the effect of strain rate hardening may need to be implemented in the FEA.

Load-bearing light steel framing (LSF) systems have gained good acceptance to the low to mid-rise construction market in the U.S. in recent years. This construction market covers a wide range of building usage, including apartment and office buildings, hotels, and schools. For years, standard C-shaped metal studs have been the only option for designers and contractors when selecting a cross-section for load bearing studs. As design loads for the studs get larger with heavier floor systems or at lower levels of mid-rise buildings, designers have been required to either use multiple (built-up) C-shaped studs or switch to structural steel members. An alternative to the standard shapes, although seldom found in the U.S., is the sigma-shaped section, but this shape is primarily used as a roof purlin in Europe. The Steel Network, Inc. of Raleigh, North Carolina recognized the potential of this section for use within a LSF system and developed the SigmaStud?. A testing program was developed for the SigmaStud? and testing was conducted at North Carolina State University?s Constructed Facilities Laboratory (CFL). Presented are the results of a series of tests to evaluate the web crippling behavior of a new sigma-shaped metal stud when subjected to lateral load in addition to axial load. Also presented is an analytical study that results in proposed modifications to the AISI web crippling equation to account for sigma-shaped sections with or without axial load.

There is a growing need for a cost-effective, durable repair system that can be used for the repair and strengthening of steel bridges. Recently, high modulus carbon fiber reinforced polymers (CFRP) have been developed with a modulus of elasticity approximately two times greater than that of steel. Externally bonded high modulus CFRP materials have successfully been used to increase the elastic stiffness and ultimate capacity of steel-concrete composite beams However, since the technology is relatively new, the detailed behavior of steel bridge members strengthened with high modulus CFRP is not yet well understood. The current research investigates three aspects of the behavior of steel-concrete composite beams in detail. An experimental program was conducted to investigate the behavior of steel-concrete composite beams strengthened with high modulus CFRP materials. In the first phase of the study the behavior under overloading conditions was investigated. In the second phase of the research, the fatigue durability of the system was examined. In the third phase, the possible presence of shear-lag between the steel beam and the CFRP materials was investigated in detail. An analytical model was developed which can be used to determine the ultimate capacity and elastic stiffness increase for steel beams strengthened with high modulus CFRP materials. Additionally, a set of criteria are proposed which can be used to determine the allowable increase in the live load level for steel beams strengthened with high modulus CFRP materials.

While reinforced concrete structures depend on ductility for acceptable seismic performance, research on the material behavior of concrete and steel has indicated that the loss of ductility may occur under low temperatures. The current research program investigates the behavior of reinforced concrete column-type members under low temperatures (-20 degrees Celsius, -30 degrees Celsius, and -40 degrees Celsius, approximately) and compares the results to an identical specimen tested at ambient laboratory temperature (23 degrees Celsius). The columns are lightly reinforced, and were loaded in a reversed cyclic manner while inside of an environmental chamber. The results of the experimentation indicate moderate increases in column strength as the temperature decreases, as well as moderate decreases in ultimate displacement capacity as the temperature decreases. The hysteretic damping properties of the columns were not significantly affected by low temperatures, and the specimen tested at -40 degrees Celsius exhibited a shortening of the extent of plasticity.

The end plate moment connection has been studied with various design concepts. However the low cycle fatigue (LCF) analysis was focused after 1994 the Northridge earthquake because the connection failure mode of structure was not matched with the current design concept. This concept has been applied to the design of moment resisting frames and several research studies on the LCF behavior of various connections under cyclic loading have been conducted. While the research on the behavior of end plate moment connections (EPMC) under cyclic loading has been conducted very little information on the LCF behavior is available. To evaluate the accumulation of LCF damage, the LCF life prediction, three phases of experimental tests were conducted. In order to investigate critical geometric parameters for 4E EPMCs in the LCF behavior, parametric study was conducted with pre-qualified FEM model. In the first phase of the experimental test, total 4 reduced EPMCs, T-stub, was tested to verify the elastic range of the connection system and general behavior of the connection. Three different levels of constant peak displacement loadings were applied to three full scale EPMCs for developing a LCF model in second phase of the experimental test. In the last phase, an accumulated damage model was evaluated by one full scale end plate moment connection test using random loading. All of phases were adopted three-dimensional finite element numerical analysis, and theoretical analysis to predict the experimental behavior and it successfully anticipated the behavior of connection. The results of the experimental test developed the LCF model for 4E EPMC and it predicted the LCF life of connection. The parametric study determined the three critical geometry parameters.