Master of Science in Civil Engineering

Permanent URI for this collectionhttp://192.248.9.226/handle/123/742

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item: Thesis-Abstract
A New test for the evaluation of air classifier performance
McNabb, MB
sciency of mechanically extracting valuable resources from municipal solid waste (MSW). With today's techniques, resources such as combustibles, aluminum, glass, and ferrous materials can be extracted from ordinary refuse, processed, and returned to society for further use. This thesis examines one aspect of resource recovery engineering, namely the separation of MSW combustibles from noncombustibles by air classification. The combustible or organic fraction of MSW is valuable to society because it can be processed into refuse derived fuel (RDF) which power companies can mix with coal and burn in their combustion chanbers to create the steam that operates electric generators. Recovered combustibles are of greatest value when they are of high "purity" or rather are free from the contamination of noncombustibles, have a high energy value per unit mass, and require minimal processing. Problems caused by contaminants in RDF include glass slagging on the combustion chamber grates, increased residue left after burning, and a lowering of the RDF energy value.
item: Thesis-Abstract
Laboratory evaluation and modelling of shear strength of infilled joints under constant normal stiffness (CNS) condition
Welideniya, HS
Infill materials found in natural rock joints may cause a reduction in joint shear strength, influencing rock mass stability. The shear strength of rock mass, already reduced by these discontinuities, will further diminish if they are filled with sediments, thereby posing significant concerns for any construction or excavation carried out in rock. These concerns invite accurate quantification of the shear strength of infilled joints and proper understanding of the basic mechanics of discontinua and the principles involved in their shear deformation. The practical application of any models developed through such studies will be of immense help to mining, tunnelling, and all other underground construction works. The geotechnical research work carried out by the University of Wollongong in the late 90's included infilled joint modelling using hyperbolic techniques. A new shear strength model was developed in these studies for predicting unfilled and infilled joint strength based on the Fourier transform method, energy balance principle and the hyperbolic stress-strain simulation. Taking into account the field conditions frequently encountered, the diversity observed in joint shear response and the occasional inadequacy of data (for the estimation of Fourier coefficients and the hyperbolic constants), this study was undertaken to develop a semi-empirical methodology for predicting the shear strength of infilled joints. In this research study joint shear behaviour was studied under CNS and CNL conditions and also the effect of joint orientation and confinement. The study aimed to develop a methodology which includes joint surface characteristics, joint properties, and infill materials. A new model for predicting the shear strength of infilled joints based on a series of tests carried out on two types of model joint surfaces (with asperity angles of 9.5° and 18.5°) is presented. Graphite, bentonite and clayey sand were used as infill materials. All tests were carried out in a large-scale shear apparatus under constant normal stiffness (eNS) conditions. The results indicate that at low infill thickness to asperity height ratio (t/a), the combined effect of the basic friction angle (
item: Thesis-Full-text
Rationalization of prestressed concrete spine beam design philosophy for expert systems
Jayasinghe, MTR
The most important aim of expert systems is to emulate the expert. The majority of existing expert systems for design try to achieve this by integrating the phases of the design process within one software environment thus achieving an overall automation. These integrated systems tend to support design by numerous repeated analysis due to their inability to suggest good preliminary solutions. The feedback from numerical analyses is needed to modify the preliminary solutions. It is argued here that human experts have a different approach to design problems. They try to minimize the iterative nature of design by suggesting preliminary solutions which have a higher chance of succeeding at the subsequent detailed design stage. Expert systems should be able to do the same. Ideally, good preliminary solutions should be tailored to the requirements; this means that they should take account of the majority of constraints and structural behaviors quantitatively while selecting the values for key design parameters. It is suggested here that the numerical processing power of the computer should be used to obtain good preliminary solutions by developing design algorithms, which can take account of governing factors at an early stage of the design process. These in turn can be used to encapsulate knowledge in the expert systems instead of the 'heuristics' which are used to incorporate past experience in existing expert systems. In order to develop these design algorithms, it is necessary to unravel the rationale behind each decision made during the preliminary design stage. In this thesis, the work carried out to rationalize the philosophy of the design process of prestressed concrete spine beams is explained in detail. The main advantage of this approach is that the expert system is compact and fast in execution. It is also capable of guiding the designer in a consultation session either by suggesting appropriate values or allowable ranges for key design parameters, as is done by a human expert. Keywords: Prestressed Concrete, Spine Beams, Bridges (structures), Expert Systems, Prolog, Deep Knowledge
item: Thesis-Abstract
Some problems in time series analysis and forecasting
Peiris, MS
This thesis is concerned with various investigations relating to time series analysis and forecasting. Particular attention is given to fractional differencing and its applications to long memory time series models. Chapter 1 entitled "Introduction", contains the summary of the basic time series theory required for the work carried out in the remaining six chapters. In addition to the general theory, the notion of fractional differencing, time reversibility and optimal experimental designs are included as special aspects of the thesis. In Chapter 2, the general class of univariate ARMA models with time dependent coefficients is considered. Existence and uniqueness of a second-order solution to the model is established using certain AR and MA regularity conditions. A simple form of the solution~ the covariance structure and the associated model building problem are considered from the theoretical point of view. The prediction problem is solved using alternative approaches. Some recursive relations to the optimum linear predictors are obtained by the orthogonal projection in Hilbert spaces. Few examples are added in support of the general results derived in this chapter. Chapter 3 considers the multivariate generalization of the results obtained in Chapter 2. The condition for the asymptotic stationary of the associated process is obtained in terms of the spectral radii of the corresponding matrices. It is shown that the recursive relations of the predictors satisfy a matricial equation as in the univariate case. Assuming the predictive distribution to be multivariate normal, a simultaneous confidence interval for the predictors is derived. The family of ARMA models with constant coefficients and nonstationary innovations is considered in Chapter4. A particular form of the model is considered for further analysis. It is shown that the usual regularity conditions are necessary and sufficient to ensure the existence and uniqueness of second-order solutions. The covariance structure of the associated process is obtained. The prediction problem is solved using the same procedures as in the stationary innovation case. The effect of nonstationarity in noise is shown to be insignificant in the parameter estimation. In Chapter 5 the theoretical autocorrelation function of an ARIMA (0,d,q) process is obtained. An asymptotically unbiased estimator of the sample spectrum is given. The various relations of the predictors are obtained. In particular, the attention is paid to the minimum mean squared error prediction and it is shown that this predictor is not optimal from the theoretical point of view. Finally, a direct basic form of the predictors of ARIMA (0,d,q) ; d .1 model is obtained. Fractional differencing and its applications to long memory time series are discussed in Chapter 6. This new class of ARIMA models aroused the interest of many time series since it has numerous applications in several scientific A proof for the stationarity and invertibility conditions ARIMA(p,d,q) ; d . R is given. Persistence in time series the Hurst phenomenon are examined for some actual situations. For the predictors of ARIMA (p,d,q) ; are given and it is shown that the minimum mean squared optimum properties when |d| < 1/2 . Numerical examples are added. In particular the long memory characteristic of some Australian rivers are demonstrated a suitable model is fitted in each case. Chapter 7 addresses itself to some miscellaneous problems in time series analysis. The first section is devoted to the discussion of some functions of ARMA models and generalizes the existing results for the multivariate case. Some contributions to bilinear time series models are considered in Section 7.2. Various new results regarding BL(p,q,p,s) and BL(p,q,r,l) are given. Section 7.3 considers the notion of time reversibility of a stochastic process and non Gaussian ARMA models from the theoretical point of view. The last section i.e. Section 7.4 discusses the optimal experimental design problems of time series regression model, when the coefficients are stochastic. It is shown that under certain conditions the effect of randomness of the coefficients is insignificant in the optimal design problem.
item: Thesis-Abstract
The in-plane failure of brickwork
Samarasinghe, W
This thesis presents the results of an experimental investigation into the strength of brickwork under biaxial tension-compression. Since there is insufficient experimental evidence available on the strength of brickwork under biaxial stress to explain the behavior of brick masonry walls under in-plane loads, experiments were carried out on one-sixth scale model brickwork panels under uniform stress conditions. An idealized failure surface is suggested based on experimental results and the effect of shear bond strength and tensile bond strength on the results is discussed. An iterative plane stress finite element computer programme incorporating the above information is used to simulate the in-plane behavior of brickwork. Brickwork is treated as an elastic, isotropic material with limited capacity when stressed in a state of biaxial tension-compression. The model reproduces the non-linear behavior of masonry produced by progressive cracking. Shear wall tests have been used to test the validity of the analytical model. Sensitivity analysis of the elastic constants used in the model are performed to illustrate their influence on the calculated stresses. The influence of the stress distribution on shear wall behaviour, and the derivation of a failure criterion for local failure in masonry shear walls, are described. This criterion, in terms of the vertical stress and shear stress at a point, has been derived for particular values of horizontal stress from the three dimensional surface mentioned above. The effect of the shape of the specimen, testing technique, and boundary conditions on the shear strength of masonry panels is discussed.
item: Thesis-Abstract
The University of Calgary airport terminals - optimum configurations and gate position requirement
Bandara, JMSJ
Passenger walking distance is a major consideration in determining the geometry of an airport terminal configuration. The number of aircraft gate positions and the expected passenger mix are the significant elements to be considered in planning new terminal buildings. Two different methods: 1) level of service method, 2) minimum cost method, are reported to determine the gate position requirement. The level of service method is used to calculate the number of gate positions that are required to provide a given level of reliability. The randomness of the relevant parameters; aircraft arrival rate at the gate positions, gate occupancy time and the aircraft separation time at gates, is taken into account in the analysis. The gate requirement at Calgary International Airport is analyzed for common and preferential gate use policies. In the minimum cost method, an optimum number of gate positions that will minimize the sum of the cost of gates and the cost of delay to aircraft is obtained. An approximate procedure to determine the deterministic delay to aircraft, based on the information regarding the peaking of the aircraft arrival rate and the number of peaks per day is presented. Closed-form solutions are obtained for the cases of one peak and several identical non- overlapping peaks respectively. The optimum number of gates required for the Calgary International Airport, based on a common gate use policy, is reported. Given the size of a terminal in terms of the number of aircraft gates, an analytical expression is obtained for the mean passenger walking distance based on: the fraction of arriving, departing and transferring (hub and non-hub) passengers; gate spacing; spacing requirement for aircraft maneuvering; and the terminal block dimensions. Commonly used configurations of pier, satellite and pier-satellite terminals are considered for the analysis. It is assumed that all aircraft parking positions are capable of handling any type of aircraft and arriving, departing and non-hub transferring passengers are equally distributed among all the gate positions. Two groups of hub transfers are defined to accommodate different levels of hub and spoke operations. A continuum approximation is used to model passenger walking within the piers or the satellites. Walking distance between the piers or the satellites are modeled using discrete methods. The optimum geometry in terms of the number of piers or satellites and their sizes, is obtained by minimizing the mean walking distance for all the passengers. When there is no closed-form solution for the optimum number of piers or satellites, lower and upper bounds of the optimum number of piers or satellites is obtained so that the optimum geometry can be obtained using numerical methods. The optimum number of piers or satellites is proportional to the square root of the total number of gates for some of the configurations. The probability distribution of the walking distance of a passenger is generated by simulation. Given an acceptable maximum walking distance, several statistical parameters that are suitable to choose the best configuration from among several optimum geometries are suggested. A numerical example to illustrate the selection of the best terminal geometry for the LaGuardia main terminal, Atlanta Hartsfield terminal and for a hypothetical terminal is presented. Examples to illustrate the effect of people mover systems on walking distance and the use of the suggested technique for a terminal expansion situation arc also given.

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