<p>Many of the existing reinforced concrete (RC) structures performed poorly during recent earthquakes. Most of these structures were designed for gravity loads only with inadequate lateral load resistance. Several of the construction details in existing gravity load designed buildings do not conform to current code requirements for seismic design and may lead to nonductile inelastic behaviour. The objective of this research program is to investigate the use of steel systems for the rehabilitation of existing nonductile RC buildings. The study is limited to low-and mediumrise frame buildings. A beam-column element capable of representing the behaviour of nonductile RC frame members is developed. The model is capable of representing the strength decay of nonductile RC members and the effects of the axial force on the yield moment and the deformation capacities of the member at peak strength. A procedure for evaluating the damage to nonductile RC structures following an earthquake is developed. The damage procedure depends on calculating the deterioration of the building stiffness and lateral load carrying capacity due to the application of the earthquake loading. The building stiffness and lateral load carrying capacity before and after the application of the earthquake loading were determined by conducting a pushover analysis. Two nonductile RC buildings, three- and nine-stories, representing low-and mediumrise existing nonductile structures, were analyzed using various ground motion records. The seismic behaviour of the nonductile buildings when rehabilitated using various structural steel systems was determined. The investigated steel systems include the addition of concentric X-bracing, eccentric bracing and attached steel frames. The effectiveness of the various steel systems in rehabilitating the three- and nine-story buildings were examined. The effect of the distribution of the steel bracing along the height and along the bays of the RC frames on the seismic performance of the rehabilitated building was studied. A simplified approach was proposed for selecting the proper brace distribution. The seismic performance of the nonductile three-story budding when using well designed eccentric bracing rehabilitation was compared with the performance of the building when using concentric bracing. The relationship between the deformation capacity of the rehabilitated building and the link deformation angle was evaluated. The distribution of the link strength along the building height was investigated. The seismic performance of the rehabilitated nine-story building was evaluated when using both flexible and stiff steel frames.</p> / Doctor of Philosophy (PhD)

<p>This research set out to investigate reported anomalies in the calculation of COD balances in biological nutrient (nitrogen and phosphorus) removal (BNR) activated sludge systems. For non-BNR systems, accurate COD balances are consistently attainable from experimental measurements. That is, influent COD can be accounted for in the effluent flow, waste sludge stream, and mass of oxygen utilised for carbonaceous oxidation. For BNR systems, in a number of instances where COD balances have been performed, the balances do not close. That is, the sum of the COD leaving the system is as much as 20% less than the COD entering the system, and thus there is an apparent COD 'loss'. In attempting to explain the problem, a laboratory based experimental program was developed which isolated specific areas of interest within BNR systems. The study involved two main experimental phases. In the first experimental phase, a closed denitrification assay technique was developed. This assay technique allowed specific aspects which have relevance to be evaluated: the nitrate-to-oxygen conversion factor, and the yield of activated sludge organisms under anoxic conditions. The advantages of the closed assay were that all of the needed COD balance terms were independently measurable, and the denitrification system was sealed which isolated the assay environment from the surrounding environment and minimised the effects of external inputs (i.e. oxygen transfer from the air to the liquid). In the second experimental phase, an excess biological phosphorus removal (EBPR) system was operated to investigate the influence of the influent COD to phosphorus ratio on EBPR biological activity and COD balance calculations. The EBPR system was a laboratory - scale sequenching batch reactor (SBR) which was extensively monitored over an eight month period. This allowed for the investigation of several factors such as, the rate of anaerobic phosphorus release and COD uptake, the ratio of anaerobic phosphorus released to COD taken up, and the rate of aerobic phosphorus uptake. The system also allowed for the calculation of COD balances. The main body of this thesis is presented as a series of five papers. The first aper (Chapter 3) presents a study on the nitrate-to-oxygen conversion factor for denitrification which theoretically is 2.86 gO₂/gNO₃-N. That is, when nitrate replaces oxygen as electron acceptor, the mass of nitrate reduced can be converted to oxygen equivalence - for purposes of COD balancing - through the use of this conversion factor. Calculations from a series of denitrifying experiments resulted in an observed conversion factor of 2.96 gO₂/gNO₃-N. However, the observed factor could not be distinguised statistically from the theoretical value, hence confirming the theoretical factor. The second paper presents a study of sludge production under anoxic (denitrifying) and aerobic conditions. Decreased sludge production and COD 'losses' are confounded in nutrient removal activated sludge systems. Hence this portion of the investigation was initiated to separate these two influences. Batch tests were performed under anoxic (denitrifying) and aerobic conditions using various organisms. The results show that COD balances were achieved, but differences in sludge production under the two conditions indicate a difference in true yield between the environments. An anoxic yield of 0.402 mg particulate COD/mg consumed COD was determined and compared with an observed aerobic yield of 0.645 mg particulate COD/mg consumed COD. These results dispel the assertion that less sludge production results because of COD 'losses'. That is, decreased sludge production in BNR systems can at least in part be explained by a lower yield during unaerated periods. The third and fourth papers (Chapters 5 & 6) present the results from the EBPR system. The third paper conccentrates on the results from the SBR and the influence of the various influent COD to phosphorus ratios. Five different influent ratios were investigated ranging from 8 to 98 (mgCOD/mgP) using a synthetic feed with acetate as the sole carbon source. The phosphorus content of the waste sludge increased from 4 to 17 per cent of the total solids as the influent COD:P ratio decreased. However, complete anaerobic COD uptake was observed irrespective of the phosphorus content of the sludge. Also, COD balances on the reactor averaged 1.04 indicating no apparent COD 'loss' in the system. The fourth paper presents the results of batch tests performed on the waste sludge from the SBR. Anaerobic batch tests were designed to determine the influence of the SBR steady state influent COD to phosphorus ratio on the kinetics and stoichiometry of the system's microbial community. In particular, the rate of substrate uptake increased from 104 to 211 mgCOD/gVSS/hr as the influent ratio decreased. Similarly, the rate of phosphorus release increased from 17 to 166 mgP/gVSS/hr as the influent ratio decreased. The batch test results showed that the ratio of COD taken up to phosphorus released under anaerobic conditions varies with the phosphorus content of the sludge. The observed release ratio increased from 0.17 to 0.79 mgP/mgCOD as the phosphorus content increased. The final paper (Chapter 7) presents a theoretical biochemical model for EBPR systems. The proposed model makes a distinction between glycogen accumulating organisms (GAOs) and polyphosphate accumulating organisms (PAOs) but suggests that significant populations of both types of organisms exist in most EBPR systems. That is, it is proposed that only in systems that are stressed does one type of organism dominate the mixed community. The biochemical models of Comeau et al. (1986) and Wentzel et al. (1986) were merged with the biochemical model of Satoh et al. (1994) to form a comprehensive model for EBPR system activity. The two-organism model provides several advantages over single organism models including the ability to predict variable rates of reaction and a variable anaerobic COD uptake to phosphorus release ratio.</p> / Doctor of Philosophy (PhD)

<p>The overall objective of this study is to obtain characteristics of seismic floor motions in a nuclear reactor structure in order to examine current procedures used in seismic qualification of nuclear power plant equipment. The study incorporates seismic data from real earthquake events and uses these records as inputs to a mathematical model of a CANDU nuclear reactor building. Seismic floor responses at typical equipment locations are calculated by standard techniques of structural dynamic analysis. Six mathematical techniques are applied to develop characterizations of each seismic floor response record. From this data a set of parameters are evolved to qualitatively and quantitatively describe the characteristics of the ensemble of floor motions. Results of a theoretical study on sine beat, limited-duration sine, and decaying sinusoidal motions are compared to the characteristics of the seismic floor motions to evaluate the realism afforded by current single frequency seismic qualification test procedures. It is concluded that single frequency test motions have a valid application in seismic qualification test programs and can realistically simulate many seismic floor motion characteristics provided that the specific type of test motion and the test procedures are well defined. Recommendations are presented for the selection of single frequency test motions and for developing the test procedures.</p> / Master of Engineering (ME)

<p>A study has been made for the ineslastic response of a thirty story frame tube structure subjected to static loading as well as dynamic excitation. The intent of this study was (i) to develop a simplified model for frame tube structures in order to compute both elactic and inelastic responses of such structures when subjected to lateral loadings, (ii) to identify the parameters that govern the behavior of frame tube structures, (iii) to assess the significance of the tube action on the elastic as well as inelastic responses, and (iv) to provide guidelines to estimate the structural responses when subjected to multiple components of earthquake ground motions.</p> <p>The simplified model reduces the 3-D frame tube system into sets of plane frame, interconnected by 3-D beam column elements. It is shown that this model gives good accuracy for each of the static and dynamic loading cases when compared with the results based on a 3-D model. The computer time involved with the planar model is at least one third that for the 3-D model. Therefore, it is beleived that the proposed model is a viable tool for the inelastic analysis of frame tube structures.</p> <p>The tube action if referred to as the forces developed in the two frames that are orthogonal to the direction of loading and which provide partial resistance to the applied loading. In order for this tube action to be effective, it is found that the frame tube should deflect like a cantilever with linear variation of axial force in the columns of the longitudinal frames and almost uniform axial force in the columns of the transversal frames. The key parameter that governs the inelastic dynamic response of frame tube structure was found to be the change of the post elastic story stiffness from the elastic story stiffness. For a large change of story stiffness, the bottom stories suffered large interstory drift. However, by decreasing such changes, the interstory drift became more evenly distributed along the height of the structure.</p> <p>The inelastic response when the frame tube is subjected to a bidirectional excitation is finally presented. It is found that the approximate estimates suggested by design codes underestimate the response. An alternative was proposed to give a more realistic estimate. Such scheme is the simple summation rule.</p> / Doctor of Philosophy (PhD)

<p>Over the years, rapidly varying channel flow and discontinuities in the solution of fluid mechanics problems have provided stimulation and challenge to numerical modelers. Traditional finite difference and finite element methods produce accurate but oscillatory solutions. Attempts to selectively eliminate these parasitic waves have been only partially successful in that the cost of a smoother profile was a lower accuracy solution. It is common to employ either internal and external dissipation parameters or a provision of dispersive interface.</p> <p>In this thesis, the problem of rapidly varying open channel flow is represented by a pair of nonlinear partial differential equations which are solved by a powerful moving finite element technique. The method developed in this research is based on the linking of a novel Lagrangian mode solution with the convenience of the Eularian grid at each time step. This second order scheme was employed in solving a variety of devised and reported open channel flow problems with near discontinuities.</p> <p>Comparisons with solutions obtained using the finite difference and finite element methods with Crank-Nicholson centred weightings demonstrates the quality improvements which have been achieved by this moving element scheme. The basic scheme was further generalized in both spatial and temporal dimensions. Sensitivity analysis of these generalized parameters established the grid size relaxations for a variety of problems. The moving element technique solved near discontinuous and gradually varied flow problems both in supercritical and subcritical regimes.</p> <p>An alternate form of Petrov-Galerkin weighting function was tested and found to give promising results. Further experimentation and testing are required before implementation.</p> <p>The robustness of the solution procedure is indicated by the adaptation of the model from the numerical and laboratory experiment stage to field problems. The model was successfully applied to the Teton Dam break flood and flood routing problem in the (Ontario) Grand River basin. Sensitivity analysis with very mild sloped channels with topographical features such as sudden expansions and offchannel storage suggest that the Eulerian-Lagrangian mode algorithm provides the missing link between the fluid mechanics of discontinuities and a practical tool for the modelling of rapidly varying open channel flow.</p> / Doctor of Philosophy (PhD)

<p>A variable source area model called TOPMODEL was modified to incorporate urban areas in both the topographic index and the mechanism of surface runoff generation. The revised model was applied to a small catchment in the Hamilton-Wentworth area. A Geographic Information System was utilized to delineate the Ancaster Creek Catchment and produce Digital Elevation Models (DEM). FORTRAN programs in conjunction with the DEM were used to compute topographic indiced that explicitly accounted for urban areas. Additional FORTRAN programs were modified to determine flow rates from this semi-urbanized catchment. Model testing was conducted in three phases: 1)a study of aggregation and scale effects using a partially revised model (TOPURBAN v.1) on three separate time periods; 2) a fully revised model (TOPURBAN v. 2) tested on six time periods; 3) comparisons between a conventional Hortonian flow model and TOPURBAN v. 2. Ten different DEM sizes were used to compute topographic indiced and TOPURBAN v. 1 was applied during the snow-free period of a wet, dry and median year. Four separate parameters were optimized. The results indicated that three of the four calibrated parameters varied only slightly with DEM size but the hydraulic conductivity increased with increasing grid cell size. Twenty-one statistics were compute to evaluate TOPURBAN v. 1's performance for predicting flow with regard to DEM size. The statistics indicated that the DEM size of 50m produces the most optimum conditions for the best TOPURBAN v. 1 performance. TOPURBAN v. 1 was later modified to create TOPURBAN v. 2 which better accounted for the storage in urban areas that was not considered in version 1. The new version added an additional calibration parameter and was tested on 6 data series in total. TOPURBAN v. 2 increased Nash and Sutcliffe Efficiency by anywhere from 2% to 8%. This increase proves that TOPURBAN v. 2 is a suitable model for combining urban areas into a hillslope hydrology scheme. TOPURBAN v. 2 was compared to the conventional Hortonian-Flow model QualHYMO, on all 6 continuous series, on two single events, and on the regional storm. TOPURBAN v. 2 out-performed QualHYMO in the single event tests and in the continuous series simulations by anywhere from 20% - 80% in Nash and Stutcliffe Efficiency. Estimates of peak flow rate for the regional storm were within roughly 35% of the estimate provided by MacLaren Plansearch Ltd. in the Spencer Creek Watershed Study that included the Ancaster Creek Catchment.</p> / Doctor of Philosophy (PhD)

<p>Seismic torsional response has always been a principal cause of structural failure in every major earthquake. There are numerous observations of damages caused by excessive torsional response in buildings, bridges, and lifeline structures. The torsion-induced failures have been especially catastrophic for multi-storey buildings because torsional response changes the uniform translational seismic floor displacements and causes concentration of demand in elements at the perimeter of the building. This often leads to failure of the over-loaded elements, which in turn initiates progressive collapse of the building. This study provides a conceptual explanation for the poor seismic performance of torsionally flexible asymmetric structures. These are buildings with a low level of torsional stiffness. Post-earthquake observations and also studies on single storey buildings have shown the vulnerability of these buildings to seismic damages. The study reported in this thesis extends the findings of previous research to multi-storey buildings and provides a theoretical foundation for understanding their seismic performance. Guidelines are developed and formulated to enable designers to identify torsionally flexible asymmetric buildings. This is of prime importance, as it is shown here that corrective measures taken by building codes in the form of statically applied torsional provisions are not effective for this type of structure. The future generation of codes for designing new structures and retrofitting existing structures will be performance based. A structure designed with such an approach has to meet a specific set of seismic performance criteria for a specific level of seismic hazard. Dynamic analyses of the building will be needed to assess the performance of the building at the many levels of seismic hazard. Preparation of input and interpretation of the large amount of output, resulting from an inelastic response analysis of multi-storey buildings is not practical, even for symmetric buildings. To overcome this, several simplified procedures based on inelastic static analyses are formulated in this thesis. Application of these procedures to some example multi-storey asymmetric buildings has shown that they are sufficiently simple and yet accurate for use in design offices. It is believed that a combination of these methods with sound engineering judgement will provide a practical and economical tool for the earthquake-resistant design profession to implement the performance-based design codes, currently being prepared by many countries, to protect life and property in urban centres in the event of an earthquake.</p> / Doctor of Philosophy (PhD)

<p>A computer model is developed for the solution of regional sanitary sewerage systems on a minimum cost basis. The regional system is considered to consist of a substantial number of alternative transportation (collection) routes, several potential treatment facilities and a receiving body of water which is able to accept the effluents from these facilities. The model, using a steady state analysis, facilitates the selection of a good collection network from the large number of possible networks, the selection of good depth-diameter combinations for each link in this final network and the selection of the size and number of treatment facilities which should be involved in the regional system. In addition, the required treatment efficiency of each facility will be determined so that a specified water quality goal may be satisfied.</p> <p>A major point to be considered in attempting to select a least cost system is the tradeoff in costs between constructing a few, large, centralized treatment facilities (thereby benefitting from the economies of scale which generally exist) and the extra cost associated with transporting the wastes an extra distance to these centralized plants. The possibility of higher treatment efficiencies being required at these centralized treatment facilities (due to a greater stress being exerted on the water quality of the receiving body of water) should also be considered. The piping costs are a function of the wasteflow. Fixed costs may be included in the cost function. The treatment plant costs are a function of both wasteflow and treatment efficiency. Fixed costs may also be included when determining the treatment plant costs.</p> <p>Linear programming and dynamic programming techniques are used as a basis for the computer model. Additional subroutines were requires to ensure that the technical constraints (for example, the minimum and maximum velocity constraints) were satisfied and to provide the missing components which are necessary to develop a complete computer package.</p> / Master of Engineering (ME)

<p>This thesis studies the behaviour of multi-storey wall-frame structures subjected to lateral and/or torsional loads. A planar structure with rotational and vertical restraints imposed between the wall and the frame is analysed. Parametric studies of a nominal structure are presented to examine the general effects of such restraints and structure height on wall-frame interaction. In the light of the understanding acquired from this two-dimensional analysis, a more general method of analysis for three-dimensional wall-frame structures is developed. For both methods, the variation of structural properties along the structure height is considered. A more flexible method of analysis for general three-dimensional building structures analogous to the stiffness matrix method is also presented. Applying this method to determine the structure stiffness matrix and using the lumped-mass approach, an attempt is made to study the free-vibration dynamic responses of the Banco de America Building both before and after damage was sustained by the building during the Managua earthquake of December 23, 1972. Lastly, conclusions regrading the behaviour and design of wall-frame structures are drawn, and the applicabilities and limitations of the three-dimensional analytical methods developed in this thesis discussed.</p> / Master of Engineering (ME)

<p>Reinforced concrete beam column joints are critical members in frame structures they can be subjected to high shear forces under earthquake loading. As a consequence, they can experience high shear and bond slip deformations that contribute significantly to the story drift. Moreover, the joint capacity may be exceeded leading to a joint shear failure that can have a major impact on the overall stability of the entire structure. This condition is particularly pronounced in lightly reinforced concrete structures where the beam column joints are typically the weakest link in the lateral load resistant frame. There is a persistent need to develop an analytical model that accounts for their shear and bond slip deformations in order to predict realistically their response and assess their safety. A finite element based analytical model is developed in this thesis for the beam column connection region. The model overcomes the need of using refined meshes of simple elements by using high power elements in the critical regions of the joint panel and the plastic hinge zones in the beams and the columns. The proposed model takes into account the shear and bond slip deformations in the joint panel as well as flexural and shear deformations in the plastic hinge zones in the beams and the columns. Material non-linearities associated with the concrete and steel behaviour are taken into account. Bond slip relationship between the beam reinforcement and concrete in the joint panel is considered. The material models developed in this thesis are verified at the element level before the verification is made to the entire beam column connection model. The predicitions of the model are compared with experimental data for beam column subassemblies experiencing high shear and/or bond slip deformations. The success of the proposed model is demonstrated by the good correlation achieved with the experimental data. The model is then used in the analysis of a three story reinforced concrete frame structure designed without consideration of earthquake loads. The structure is analyzed using different joint detailing schemes using pushover and time history analyses to investigate the effect of the joint detailing on the response of the structure. It is concluded that the proposed beam column connection model can be used successfully for the dynamic analyses of a complete multistory structure.</p> / Doctor of Philosophy (PhD)