<p>Continuous hydrology packages such as Hydrologic Simulation Program--Fortran (HSPF) and Version 3 of the Storm Water Management Model (SWMM3) require extensive computing time even for certain cases of event modelling. In their original sequential, time-sharing, computing schemes, continuous modelling applications required a prohibitively expensive overall turn-around time and an overwhelming amount of manual Input/Output (I/O) time series (TS) data management effort. By decentralizing the processing, avoiding a time-sharing computing environment, and finding ways to keep track of I/O TS data as part of the processing, these problems can be overcome.</p> <p>Computational Hydraulics Group Time Series Manager (CHGTSM), a Database Management System (DBMS), was developed by the present author to provide easy access to TS data, independent of details of storage. CHGTSM is based on an unconventional data access technique, also developed by the author, that handles variable resolution continuous TS records. The CHG Time Series Store (CHGTSS) is prepared by the CHGTSM. CHGTSM is applied succesfully. In a case study, CHGTSM saved 88% in hard disk storage compared to the raw database. CHGTSM serves event as well as continuous modelling applications. A manual for CHGTSM is also written by the present author.</p> <p>CHGTSM can be used to distribute the database to the nodes of a linked configuration of microcomputers. Distributed processing (DISP) of centralized data is made possible by CHG Distributed Data Processing Software (CHGDPS). CHGDPS, developed by the present author, is a shell around CHGTSM which includes security provisions and node synchronization assistance. The simulation of a DISP application for continuous hydrologic modelling in a Local Area Network (LAN) improved the computing efficiency by 54% compared to sequential processing. CHGDPS will allow true concurrency only through a batch application.</p> <p>CHGDPS synchronization assistance relies on timing relations of the computational modules that are accessing the system. A program measurement (PM) technique was adopted, enhanced and applied by the present author to obtain the timing relations. Such DISP control helps the user to optimize overall system processing. For example, CHGDPS may decide (or help decide) a shift from one computational approach to another for considerations of time, space, numerical stability, and accuracy.</p> <p>The DISP scheme is flexible and can be implemented on any linked configuration of computers e.g. LAN' s, distributed data gathering and real time control (RTC) devices. The whole system, called the Computational Hydrology Work Group System (CHWGS) is assessed as an environment for continuous (or event) hydrologic modelling, distributed data gathering and distributed RTC.</p> / Doctor of Philosophy (PhD)

<p>In order to assess the structural charateristics of a pavement-subgrade system, non-destructive, in-situ tests together with backcalculation procedures are widely used. Traditionally, the analytical models adopted for this proccess are deterministic, however, in reality, the quantities involved in the problem may be random variables. Neglecting the variable nature of the system parameters, e.g., highway material properties, may affect the reliability of the pavement response prediction. On the other hand, inverse solutions to pavement problems are often ill-conditioned and sensitive to the input parameters. Past experience has shown that the estimated values of a blackcalculated parameter by different agencies may vary by several orders of magnitude, representing a high level of uncertainty in the estimated paramter. Unless the uncertainty is quantified, practitioners are forced to resort to higher safety factors, which is neither economical nor always conservative. The present study investigates, rigorously, the behavior of a pavement-subgrade system from a stochastic point of view, and addresses the sensitivity of response variation to variations in layer properties. The results of a forward analysis are utilized to establish a relation between input and output statistical moments in order to interpret the pavement deflection data stochastically. The proposed framework in this research allows one to quantify the uncertainty level in backcalculated system parameters. It also provides a tool to infer the accuracy of the pavement performance prediction based on mechanistic models. For the purpose of introducing the stochastic approach, the perturbation technique is applied to an idealized, two-layered, pavement-subgrade system for the case of: (a) a static solution based on Odemark definition of equivalent layer thickness; and (b) a frequency domain solution to a single degree of freedom (SDOF) system using an impedance function. The methodology is then extended to a stochastic finite element framework in order to analyze boundary-valued problems of more complex geometry and distribution of material properties. The perturbation method is a mean-based, second-moment analysis for the second-order accurate expected value, and first-order accurate cross-covariance function. For the dynamic analysis, viscoelastic response of the pavement is obtained by using the periodic-load analysis approach and Fourier synthesis. Based on the results of the simulations, it is demonstrated that, the sensitivity of surface deflections is significantly higher to the subgrade properties than those of the surface and base layers, both in a static and a dynamic analysis. Consequently, it is concluded that, the low dominant frequency of the falling weight deflectometer (FWD) load limits the capability of this test in characterizing surface layer properties. Using the concept of coefficient matrix, it is illustrated that, the low sensitivity of deflections to surface layer properties can be interpreted as a high level of uncertainty in the estimated pavement moduli in a backcalculation exercise. It is indicated that uncertainties in backcalculated parameters often result in an unacceptable pavement performance prediction. Moreover, the physical behavior of the layers are identified by finding the contribution of each layer to the total deflection of the system using the notation of contribution ratio.</p> / Doctor of Philosophy (PhD)

<p>A waste form can be prepared by mixing a hydraulic cement and, if needed, a bulking agent with an aqueous waste to cause it to solidify. A mechanistic leaching model was developed based on describing the chemistry of the waste form-Ieachant system and the flow regime of the leachant and assuming that transport takes place via diffusive exchanges through the waste form-Ieachant Interface. This model was successful in predicting Ieaching from simpIe waste matrices and in identifying important containment mechanisms effective in the more complex matrices.</p> <p>The cement-based waste forms studied had porosities ranging from 40 to 60%. Portland cement provided acid neutralization capacity to maintain the high pH environment where the waste form is stable; a typical waste form contains enough cement to neutralize between 2000 to 3000 times its volume of a pH 3 leachant.</p> <p>In a mild environment, leaching was controlled by the diffusion of the soluble fraction of a contaminant present in the connected pores of the matrices. Immobile species instantaneously solubilized to maintain chemical equilibrium between the soluble and insoluble fractions. In tests conducted over a period of almost 2 years, less than 1% of the initial amount of cadmium, chromium and lead contained in a specimen leached out.</p> <p>In an acidic environment, the leaching rates were limited by the availability of acid to dissolve the matrix. The leaching process was similar to a surface corrosion process. However, since waste matrices are not completely soluble in a mild acid, a leached layer develops, eventually protecting the core of the waste form from direct contact with aggressive groundwaters. Contaminants solubilized at the leaching front are subjected to concentration gradients that force them to diffuse both inward and outward. Only a fraction of the total concentration therefore leaches out.</p> <p>The mechanistic knowledge developed through the experimental programme and the modelling effort was used to develop eight long term leaching scenarios covering a wide range of waste form and groundwater conditions. In addition to allowing the prediction of leaching rates for periods of up to 100 years, these scenarios were useful in developing recommendations to prepare more efficient waste forms and design better landfills.</p> / Doctor of Philosophy (PhD)

<p>Pollution in the coastal zones of the Great Lakes has become more serious in recent years. This is due to increased use of coastal water as a result of population and industrial growth. A substantial portion of the contaminants that enters a lake do so from the shoreline via discharges from sewer overflows, industrial outfaIIs and runoff. Such discharges contain particulates and other materials of density greater than that of lake water. Many heavy metals with toxic components are present in these fractions. The dynamic behavior of these particIes in the coastal and offshore waters is thus of great importance. The principal removal processes for these materials are transport and particle settling. An understanding of the characteristics of nearshore currents, diffusion and temperature patterns is essentiaI to determine their effect on removal processes, and in turn, on coastal biological and chemical processes. This study is limited to the physical fluid mechanics of coastal zones.</p> <p>The structure of the nearshore flow in the vicinity of Cleveland, Ohio is analyzed in detaiI in this study. The impact of Cleveland, one of the largest urban and industrial agglomerations on the shoreline of Lake Erie, in terms of additional loading is thought to be considerable. A computer program (ADVDIFF) was developed to calculate the mean flow, horizontal turbulent length and time scales, horizontal diffusivities and kinetic energy. ADVDIFF uses filtering techniques, spectral analyses and statistical analyses. Five episodes representing three different flow regimes which may exist in the coastal zone were chosen for special analyses.</p> <p>To generate the coastal currents, a rigid-lid, channel-type model with fine grid size in the coastal zone was used. A model originally developed by Simons (1983) was modified to incIude nonlinear acceIeration terms and two different forms of the vertical eddy viscosity. Also, a two dimensional x-y model developed by Simons and Lam (1982) was modified and used to expIain some of the observations. Both new modeIs (ERCH, ONELAY) were verified, calibrated and applied to Lake Erie.</p> <p>A computer program (SEDTRAN) was developed to predict the inflow sediment concentration distribution within the coastaI zone. SEDTRAN soIves numericaIIy the three dimensionaI time-dependent mass transport equation including the settIing term. The modeI uses the currents and diffusivities computed by ERCH and ONELAY and the statistical analyses, respectively. SEDTRAN was verified using several test examples, and partiaIIy vaIidated using the avaiIable data set. The modeI was applied to many cases of settIing activity that may take place in the coastaI zone. The results were used to define a representative influence zone for a pollutant source at CIeveIand.</p> / Doctor of Philosophy (PhD)

<p>The objective is the development of two reIated mathematical models to provide minimum cost designs of water distribution and waste-water collection networks.</p> <p>This wealth of literature is classified in terms of problems formation and method of solution. This places individual contributions in perspective and serves to identify the major shortcomings of existing techniques. These are:-</p> <p>1- Inability to handle large network systems efficiently. 2- lnadequate treatment of the hydraulics of the system. 3- Absence of a satisfactory discrete solution.</p> <p>The results presented are considered to be more comprehensive than any other technique reported in the literature to the author's knowledge. The major contributions presented are:-</p> <p>(i) Both problems are formulated in the form of a nonlinear programming problem and in terms of practical engineering variables and solved by application of the MINOS package.</p> <p>(ii) A standard data format is suggested which allows user input to be defined in a very compact and logical form.</p> <p>(iii) Pre-and Post-processors are developed which free the user from the complicated and extremely error-prone tasks of creating the necessary input data and interpreting the resultant output files of the MINOS package.</p> <p>(iv) For distribution networks, a comparison is presented between the explicit use of a network analyser (coupled with an efficient optimization package) and the implicit incorporation of the analysis stage within the linear and nonlinear constraints of a comprehensive nonlinear model. The latter method is shown to have significant advantages.</p> <p>(v) For collection networks, a model formulation is presented which properly represents the hydraulics of part full flow in circular sewers. The problem size is reduced by the introduction of an equality constraint which correlates velocity and discharge under these conditions. The accuracy of the method is checked by comparison with a more rigorous but significantly more expensive problem formulation.</p> <p>(vi) Methods are suggested whereby pumps, reservoirs, pressure reducing valves and minor loss devices can be easily and correctly incorporated in a distribution network design.</p> <p>(vii) Techniques involving variable transformation and the partitioning of basic, nonbasic and superbasic variables are developed which greatly increase the efficiency of solution.</p> <p>(viii) For both types of network, the models are augmented to allow a very good discrete solution to be obtained in terms of pipe diameter. A heuristic argument is presented which suggests that the solution for distribution networks must be very close to optimal although optimality cannot be rigorously proven. For collection networks it is shown that discretization may frequently be infeasible unless at least one of the constraints is relaxed in the form of a 'soft' constraint.</p> <p>(ix) Both types of network design are demonstrated using problems of substantial size. For distribution networks a method is demonstrated whereby the analysis or design problem can be solved as special cases of the more general optimization problem.</p> / Doctor of Philosophy (PhD)

<p>When new construction projects are postponed or cancelled because of socio-economic concerns, greater emphasis is placed on enhanced operational planning -- to get the most at the least cost, from the existing projects. Of the approaches that made significant improvement in the operation of energy production systems is the co-ordination between hydro and thermal power plants. In this research, the problem of "Long-term Optimal Operation of Hydro-Thermal Power Systems" is addressed. Considering the uncertainty in reservoir in flows, the problem is defined as a "two-stage stochastic linear network programming with recourse". To avoid dimensionality problem generally associated with the employment of dynamic programming in large scale applications, Bender's decomposition approach is employed as the solution algorithm basis for the defined problem. Using the "General Algebraic Modelling System", a modelling code, the "Hydro-Thermal Co-ordinating Model (HTCOM)" is developed. In HTCOM, each sequence of hydrologic inflows generates a subproblem which is solved deterministically. The solutions of all subproblems are next co-ordinated by a master problem to determine a single feasible optimal policy for the original problem. This policy includes optimal reservoirs releases as well as allocation of energy generation at different power plants in the subsequent time period. The objective minimizes the expected total cost of meeting the energy demands while satisfying the system constraints over the long-term horizon of one to three years. To demonstrate the applicability of HTCOM, a real world case study named the "Khozestan Water and Power Authority (KWPA)" in Iran is employed as a system of two multipurpose reservoirs with five hydro-thermal power plants and transactions of energy. The KWPA system components are operating policies are stimulated as the network flow model and an integrated solution procedure is planned to determine the optimal operation policies. This procedure included the development of three specialized models: - HTCOM-I: to investigate the potential improvements of the current system; -HTCOM-II: to provide the required confidence in using the model in future simulations by evaluating the actual savings; and -HTCOM-III: to simulate the system operation under uncertainty, and determining the optimal operation policies for the next month. The results of employing all three cods in the KWPA system conclude that the selected approach for formulating the problem, the adopted algorithm based on Benders' decomposition technique, and the models (developed in the GAMS environment) are suitable, capable to handle stochasticity of inflows, and considerably cost-efficient.</p> / Doctor of Philosophy (PhD)

<p>In cold climates, temperatures higher than the ambient have been observed near the bottom of water lakes in the vicinity of thermal discharges. Concern has been expressed about the adverse effects of such abnormally warm water on the winter ecology of lake bottoms. It is expected that the existence of a density extremum in water at 4° C and the resulting nonlinear relation between density and temperature gives rise to densimetric flows which are markedly different from those in the linear range.</p> <p>This thesis presents experimental and numerical investigations that give some insight into the phenomenon of the thermal bar and the manner in which it may infIuence nearshore transport processes in the vicinity of a thermal outfalI in a cold climate. The investigations are restricted to an idealized model where the lock exchange mechanism is selected due to the fact that its behaviour is close to that expected in the prototype situation.</p> <p>The experimental investigation provides dramatic proof that the existence of an extremum in the density-temperature relation has a profound influence on the behaviour of densimetric flows in general and lock exchange behaviour in particular. Three zones in the vicinity of a thermal bar are clearly demonstrated viz. (i) the thermal overflow region. (ii) the thermal bar, and (iii) the thermal underflow region. The experiments provide data on the horizontal scale at which sinking takes place.</p> <p>A numerical model has been constructed to develop a means of modelling the behaviour of a thermal bar at the outfall of a steam electric generating station cooling water system. The numerical model employs a finite-difference scheme where the resulting algebraic finite difference equations are soIved using an alternating direction implicit method and a sparse-matrix package. The numericaI modeI has been verified by comparing it to numerical solutions of four different cases of the idealized problem of steady laminar flow in an enclosed rectangular cavity with differentially heated end walIs. Moreover, additional acceleration techniques are introduced to improve the numerical solution procedure. The numerical model is employed to solve the actual problem of simulating lock exchange flows created between two water bodies having different temperatures around the temperature of maximum density (i .e. having temperatures above and below 4° C). The general behaviour which has been observed experimentally is also confirmed numerically. The sensitivity of the associated parameters is examined. The relative extension of the thermal bar is correlated with relevant system parameters. Difficulty was experienced in obtaining numerical results for the same (high) Rayleigh numbers as were used for the physical experiments. Despite this, an encouraging degree of consistency was observed between simulated and observed behaviour.</p> <p>The important aspect of the study is to draw attention to the adverse effects of the sinking phenomenon (thermal bar), which may occur in the vicinity of man-made warm effluents as well as in natural bodies of water during the spring warming period. The study is significant in terms of the horizontaI scaIe at which sinking takes place, for the design of power station once-through-cooling water systems that must operate in cold climate winter conditions.</p> / Doctor of Philosophy (PhD)

<p>The fact that considerable quantities of solids, toxic metals and hazardous contaminants are washed off urban surfaces has been well documented in recent literature.</p> <p>It is generally recognised that urban runoff models predict runoff quantity quite well. However, due to lack of understanding of the various processes involved in pollutant buildup, washoff and routing and insufficient, and faulty data collection, urban runoff models depict runoff quality poorly. This research therefore attempts to introduce new concepts and algorithms, based on the physical processes involved, to improve runoff quality prediction. The problem has been segmented into three broad areas: a) pollutant buildup, b) pollutant washoff and, c) routing and fate of pollutants.</p> <p>The interaction of addition and removal processes in pollutant buildup has been further disaggregated. Estimates are made of the daily mass balance of pollutants over a dry period, considering meteorological and geographical effects. Additions from atmospheric dustfall, vehicles, population and special activities; removal due to biological decay, vehicle and wind created eddies and intentional removals (street sweeping) are formulated individually. Scavenging of aerosols and gases and washoff from canopies during precipitation are also modelled and added to conventional washoff. Expressions for the impact of raindrops, shear due to overland flow, and vehicle-induced eddies are used to develop a new washoff equation which is compared to conventional washoff equations. An established pollutant routing algorithm is modified to minimise summation error. All these pollutant concentration prediction algorithms are interfaced with one of the most comprehensive models, the Storm Water Management Model Version 3 (SWMM3), preserving the runoff quantity prediction algorithms. Provision has been made for variable time steps for both runoff quantity and quality. The modified SWMM3 is called CHGQUAL in the present work. CHGQUAL was applied to the Chedoke Creek Catchment in Hamilton, Canada, for verification, calibration and validation. The pollutional parameters used in the study are suspended solids(SS), biochemical oxygen demand (BOD), total nitrogen (TKN) and total phosphorous (TP). The CHGQUAL computed pollutant concentration results were statistically compared to both SWMM3 results and observed data.</p> <p>The new runoff water quality algorithms showed improved predictability for the test catchment. The CHGQUAL model can readily be applied to other catchments.</p> / Doctor of Philosophy (PhD)

<p>Coagulation is a common water treatment step primarily designed to aggregate and thereby help remove true particulate (turbidity causing) matter. Organic compounds of natural origin (i.e. humic and fulvic acids) have also been observed to be removed by Coagulation. This research was designed primarily to identify the limiting mechanisms responsible for the removal of natural organics by the coagulation process. This identification is thought to be crucial in the optimization of this important water treatment step as it may help to maximize the benefits obtained from coagulants.</p> <p>The examination of the literature related to this topic suggests two possible removal routes:</p> <p>(i) a reaction whereby the fulvic acids form an original compound with the coagulating ion Al³⁺ or one of its hydroxy complexes.</p> <p>(ii) the adsorption of the fulvic acid molecules or jons onto the surface of a solid precipitating independently of these compounds.</p> <p>These two possibilities are examined in detail on theoretical grounds, and two following pieces of information are defined as being discriminatory with respect to the two removal routes:</p> <p>(i) The shape of the isotherm, as defined in typical adsorption studies.</p> <p>(ii) The ligand number or OH/Al ratio of the precipitate, accessible by processing the dissolved Aluminum data with respect to pH.</p> <p>These considerations lead to an experimental design allowing the convenient evaluation of these characteristics. An array of nine treatment dosages and four operating pH is applied on two raw waters, using four Aluminum based coagulants.</p> <p>The results suggest that under these experimental conditions (dosage between .1 and 1 mM Al/L pH between 5 and 8.5), the Fulvic acids are removed by Adsorption onto Al(OH)₃, regardless of the type of coagulant. Increasing pH and the presence of SuIfate in the coagulant were found detrimental to this adsorption. Increasing OH/Al ratio in the coagulant is detrimental at low pH, low dosage, and becomes beneficial at neutral to mildly alkaline pH conditions. A two stage treatment scheme was found efficient at neutral to mildly alkaline pH, using Alum.</p> / Doctor of Philosophy (PhD)

<p>A research program is presented to investigate the behaviour of rectangular hollow section (RHS) T-joints in the elasto-plastic range of loading. The study includes the determination of both rotational and punching shear stiffnesses and strengths of the RHS T-joints due to branch moment or punching shear or a combination of both. The determined joint characteristics are then incorporated into an elasto-plastic analysis of Vierendeel trusses composed of RHS members.</p> <p>Two different joint types have been analyzed, the double chord T-joint and the single chord type. In both cases, the joint is modelled by the chord top flange treated as a thin plate loaded on the perimeter of a rigid inclusion and restrained by coupled translational and rotational springs along its longitudinal edges. These springs simulate the restraining effect of the side walls and connecting bottom flange. Transverse edges, some distance from the joint, are taken as simply supported.</p> <p>The proposed finite element formulation incorporates rectangular plate, beam and boundary spring elements. The formulation considers both bending and in-plane actions. Material nonlinearities of the joint are assumed to be adequately represented by the Von-Mises yield criterion and the associated flow rule. While geometric nonlinearities have been neglected, this assumption is reasonable for the range of deformations deemed important in this study.</p> <p>A parametric analysis has been undertaken for each of the double chord and single chord joints under either branch moment or punching shear. Each analysis considers the effect of each of five non-dimensiononal geometric parameters. One of the parameters, considered, is used to study the stiffening effect of a reinforcing flange plate. Results of the analysis are presented in the form of non-dimensionalized load-deformation (M-Φ and P-δ) curves.</p> <p>A standardization procedure has been used to develop generalized (M-Φ and P-δ) formulae, based on the parametric analyses. In addition, formulae for the joint stiffness and strength, in terms of its geometry, are presented for each case.</p> <p>When the joints are analyzed under combined loading, the branch moment and punching shear are applied in different ratios. The results are presented in the form of interaction equations.</p> <p>Next, the joint characteristics have been incorporated in an elasto-plastic finite element analysis of Vierendeel trusses. The effect of the joint flexibility on the truss behaviour is investigated. Also considered is a comparison between trusses possessing single chords and those possessing double chords.</p> <p>Another aspect of this investigation is to predict upper bound capacities for the double chord joints due to branch moment or punching shear. The yield line theory has been utilized for this purpose.</p> <p>The experimental part of the study involves the testing of ten double chord joints. Results of these tests along vith other available experimental data are used in examining the validity of the analytical models that have been developed.</p> / Doctor of Philosophy (PhD)