bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental considerations for ocean outfalls and land-based treatment plants
Authors: Allen J. H. , Sharp J. J.
Published: January 2010

When planning for the treatment and disposal of domestic wastes, coastal communities have a number of options. Like inland towns, they may utilize full treatment allied with traditional methods of disposing of the treated liquid and solid end products. At the other extreme, it would be possible to consider discharge of untreated wastes directly to the ocean through a submerged outfall. As a compromise, some combination might be used with the final design incorporating a degree of on-land treatment together with a submerged outfall.In this paper, the environmental problems and benefits of discharging domestic wastes through a submerged ocean outfall after minimal on-land treatment are compared with those of a totally land-based treatment plant. Water-quality standards attainable by both systems are enumerated, and other environmental problems are taken into account. Consideration is also given to biological, chemical, and bacterial effects; and aspects of aesthetics and health are discussed. Financial and economic viewpoints merit considerable discussion but are generally outside the scope of this paper and are mentioned only briefly. Regulations governing discharges in Canada, the United States, and Europe are discussed and considered in light of the evidence presented. Key words: outfall, dilution, pollution, treatment, sewage.
Ice action on fixed offshore structures: a state-of-the-art review
Authors: Nessim M. A. , Cheung M. S. , Jordaan I. J.
Published: January 2010

The methods and approaches for calculating global ice loads on fixed offshore structures are critically reviewed. The review covers both the mechanical approaches used in load calculation and the probabilistic methods used to deal with the uncertainties involved. The paper gives a brief review of background information related to ice conditions, ice-load characterization, and ice mechanics. Load calculation methods for different types of ice behaviour are reviewed for vertical structures, as well as sloping-sided structures. Size effects are discussed, and the effects of rubble piles on ice loads are briefly reviewed. The emphasis of the review is on summarizing the different models and approaches reported in the literature, and making evaluations, comments, and suggestions for further research from the viewpoint of choosing design criteria. Key words: ice-structure interaction, design criteria, ice indentation, probabilistic load assessment, Arctic structures, size effects.
Cross-section strength of concrete-filled HSS columns at simple beam connections
Authors: Dunberry E. , Leblanc D. , Redwood R. G.
Published: January 2010

Tests are described in which short, rectangular steel columns filled with concrete are loaded to failure under axial load. Part of the load is applied at typical beam connections within the column length; and part is applied at the top, representing the load from upper stories of a building. The length of the column near the connection over which slip takes place is examined, and the ultimate strength of the columns is compared with that of stub columns loaded uniformly over their length. A small reduction in strength is found to occur, which depends upon the proportion of total load applied at the connection. An empirical means of accounting for this strength reduction is given. Key words: columns, composite construction, connections, tubular columns, axial compression.
Limit states design of concrete slender columns
Authors: Mirza S. A. , MacGregor J. G.
Published: January 2010

The limit states design requires the use of load factors and resistance factors to consider the probability of overloading, understrength, or both. Research has been underway in Canada to introduce the probability-based limit states design for concrete structures. Based on the current knowledge of building load statistics, the National Building Code of Canada adopted a set of load factors which are different from those used in the Canadian Standards Association Standard A23.3-M77. This required the development of resistance factors that would be compatible with the load factors specified in the National Building Code of Canada. The research reported herein discusses the development of such resistance factors for use in computing the moment magnification of concrete slender columns. Key words: building codes, load factors, loads (forces), moment magnification, reinforced concrete, resistance, resistance factors, slender columns, stability, structural design.
Evaluation of signal timing and parking strategies on a signalized urban arterial
Authors: Easa Said M. , Strelesky Raymond H.
Published: January 2010

A computer model for traffic signal coordination, TRANSYT-7F, was applied to a signalized urban arterial in the city of Thunder Bay. The purpose of this application was to develop an optimal coordinated signal timing for the arterial. The study arterial consisted of five intersections and extended over a distance of 1.2 km. Observed traffic volumes and their direction of movement were collected during an afternoon peak period (4:00 p.m. to 5:00 p.m.) in September 1983. Data on existing physical configuration and signal system characteristics were also collected and modelled for input to TRANSYT-7F. Seven improvement strategies concerning changes in the existing signal system and regulatory conditions were evaluated and compared to existing conditions (do-nothing). Several measures of effectiveness generated by TRANSYT-7F were used as the basis for evaluation, which included travel time in the system, delay, fuel consumption, and a performance index, which is a function of delay encountered in the system and the number of stops.The results showed that the best strategy was to implement a common cycle of 52 s for the entire system. This is opposed to the existing 80 s network-wide cycle length. This strategy optimized the corridor with parking prohibitions on both sides of the arterial, and two phases per cycle at all intersections. The best strategy improved all measures of effectiveness. In particular, a reduction in the magnitude of 36% in the performance index was observed, along with a predicted decrease in fuel consumption of 21%. Key words: signal timing, coordination, arterial, traffic, management, parking, evaluation, computer model, delay, fuel consumption.
Improvement in aerobic sludge digestion through pH control: initial assessment of pilot-scale studies
Authors: Anderson B. C. , Mavinic D. S.
Published: January 2010

Waste-activated sludges from an extended-aeration, pilot-scale wastewater treatment facility and a high-rate, full-scale system were aerobically digested in 150 L pilot-scale digesters, operated in a semicontinuous (daily fill-and-draw) mode, at a standard 15-day solids retention time (SRT). To offset the mixed-liquor pH (MLpH) decrease normally encountered in these digesters (as a result of nitrification), hydrated lime and sodium bicarbonate were used in separate experiments to control MLpH in the series pH 6, 7, 8, and 9. Digester performance in the first stage of this work was assessed solely on the basis of reduction in total volatile suspended solids.The extended-aeration type sludge exhibited the greatest improvement in process performance under all pH-controlled conditions. Improvements in digestion efficiency of up to 80% over the uncontrolled reactors were noted. The use of lime resulted in greater digestion enhancement than did sodium bicarbonate with this sludge, without a significant increase in sludge solids production (owing to the low chemical doses required). Digestion efficiency of the high-rate type sludge was little improved (on a relative basis) with either chemical; however, absolute efficiencies in the individual digesters were, in some cases, nearly double those of the comparative extended-aeration sludge digesters. This difference appears to be a function of the process from which the digesting sludge originated, and seems to be influenced by the amount of easily oxidizable, endogenous substrate contained in the biomass. It was concluded that the extended-aeration type sludge was most amenable to enhanced digestion through pH control; as well, cost and process considerations made lime the chemical of choice. Key words: activated sludge, aerobic digestion, hydrated lime, mixed-liquor pH control, nitrification, process enhancement, pilot-scale, sodium bicarbonate.
A foundation factor for earthquake design using the Canadian code of practice
Authors: Balendra Thambirajah , Heidebrecht Arthur C.
Published: January 2010

A new foundation factor is proposed to account for the soil amplification effects in the calculation of seismic base shear, as specified in the 1985 edition of the National Building Code of Canada. Three types of soil conditions are considered, viz., stiff soil, deep cohesionless soil, and soft clay deposits. In order to capture the resonance effect at the site–structure period, the foundation factor is expressed as a function of the ratio between fixed base period of the building and site period. The proposed foundation factor takes into account both the site–structure period coincidence effect and soil–structure interaction. The application of the proposed foundation factor is illustrated for three particular sites that have been subjected to an actual recorded earthquake. Key words: foundation factor, site effect, soil–structure interaction, buildings, seismic, shear, design, code of practice.
Thermal pressure due to an ice cap in an elevated water tank
Authors: Kong W. L. , Campbell T. I.
Published: January 2010

Ice formations have contributed to the deterioration observed in elevated reinforced concrete water tanks in Ontario. Pressures exerted by an ice cap contained within a circular tank and subjected to an increase in temperature are studied in this paper. A mathematical model for simulation of ice is used to determine hoop and flexural stresses induced in the wall of the tank by an expanding ice cap. These predictions are validated by comparison with test data, and charts have been developed by means of which hoop and flexural stresses in the wall of a tank may be determined for any particular thermal conditions in the ice cap. Key words: thermal pressure, water tank, ice cap, mathematical model, design charts, hoop stress, flexural stress.
Design recommendations for reinforced concrete cylindrical storage structures for aqueous materials
Authors: Jofriet J. C. , Green R. , Campbell T. I.
Published: January 2010

The design of cylindrical non-prestressed concrete storage structures in Ontario does not appear governed by any standard or building code. Many aboveground water storage reservoirs in Ontario have deteriorated badly in a relatively short period of use. Many farm silos suffer from problems similar to those of the water storage reservoirs. This paper is concerned with the selection of the wall thickness and the hoop reinforcement for cylindrical storage tanks and silos for liquids or wet materials where tensile cracking of the concrete is to be limited.Three design criteria are presented. The first limits the circumferential tensile stress in the concrete from lateral wall pressure, shrinkage, and temperature gradients in the wall. The second is concerned with the tension in the hoop reinforcement and guards against collapse. The third limits the crack widths of the cracked concrete section. The most important design loads are discussed. Maximum values for hoop tension are provided for liquid pressures. A design temperature gradient of 15 °C is recommended for design in southern Ontario. As well, appropriate values of shrinkage tensile stress are suggested. The collapse limit state criterion must be evaluated for the hoop steel stresses due to the lateral wall loads. The limit state criterion related to the hoop tensile stress in the concrete must be investigated for all possible load combinations of lateral wall load, shrinkage, and temperature gradients. Reasonable load combination factors have been recommended. Recommendations on the tensile strength of concrete and on appropriate strength factors have been made. Key words: cylindrical tank, design criteria, hoop stresses, reinforced concrete, silo, standpipe, storage of liquids, storage of saturated bulk materials.
Verification of a numerical beach water quality model
Authors: Palmer Merv D. , Dewey Ray J.
Published: January 2010

A dynamic two-dimensional finite difference water quality model was developed to predict the fecal coliform densities at the Toronto, Ontario, Eastern Beaches resulting from storm-water discharges. There are 10 storm-water and 2 combined sewer overflows discharging to the beach. Site-specific data were collected for use in the model. This data included local bathymetry, currents, dispersion, fecal coliform mortality rates, winds, receiving water fecal coliform densities, and discharge pollutographs. Specially designed field fecal coliform surveys were required to calibrate and verify the model since the storm effects are very dynamic in both time and space. The verified model was then used to estimate the reduction in fecal coliform densities at the beaches for different intensity storms for different remedial works. The improvements resulting from the different remedial works were quantified as the number of hours when the fecal coliform densities exceeded 100 counts/dL. Key words: beach fecal coliform predictions, storm runoff, water quality, numerical modelling, verification.
Problems in calculating the flexure of beams on elastic foundation
Authors: Ding Dajun
Published: January 2010

This paper deals with some problems concerning the flexure of beams on an elastic half space. Based on the link method of Zemochkin, the author gives an improved method by which the number of simultaneous algebraic equations can be reduced by 2. Following the author's proposal, the universal tables of reaction coefficients for any loading case are compiled. The author has obtained dimensionless coefficients of reaction, shear, and moment between the infinite and semi-infinite beams subjected to concentrated loads and those under moments, so the coefficient tables of long beams under concentrated loads can be used for calculating those under moments. Key words: elastic foundation, settlement, half-plane and half-space, link method, pressure, segment, typical equation, matrix, dimensionless coefficient, long (infinite and semi-infinite) beam, finite beam (beam with finite length), elastic characteristic value.
A reevaluation of the Canadian provisions pertaining to steel beam–column design and frame stability
Authors: Beaulieu D. , Picard A.
Published: January 2010

The actual recommendations of the Canadian standard for steel construction pertaining to beam–column design are reviewed and discussed. The major shortcomings of both the traditional and the P–Δ methods are described. Some recent developments on beam–column design and frame stability are reviewed and are used to suggest improvements to the P–Δ method. Simplified second-order analysis procedures are finally suggested for use in the P–Δ method. Key words: analysis, beam–column, bending, buckling, compression, design, interaction equation, resistance, stability, sway.
Rigid latticed steel frames: two large-scale tests and failure predictions
Authors: Ellis John S.
Published: January 2010

This work is concerned with the predictions of failure under static load for two identical free-standing latticed cantilever frames. Each structure was 3 m high and consisted of three storeys with panel points 1 m apart; in plan it was 1 m2; its diagonals were at 45° in the form of St. Andrew's cross; all joints were welded and were considered rigid. The four bases were bolted to the laboratory floor and the static load was applied at the top as two compressive horizontal forces parallel to the sides of the structure. The individual members were all solid mild steel round rods; the verticals were of uniform cross section of 25.4 mm in diameter with a slenderness of 157; the horizontal cross-arms were of uniform cross section of 19 mm in diameter; and the diagonals were of uniform cross section of 15.9 mm in diameter. The diagonals were cut at their mid-lengths and welded to give a flush joint.The total horizontal loads that caused failure of the two structures were 79.6 and 79.2 kN. In both cases failure occurred by the sudden buckling of one of the bottom-storey vertical legs, inwards towards the centre of the structure. Also upon failure, the diagonals in the bottom storey of the compression face buckled inwards and the compression diagonal of the side contiguous to the buckled leg also buckled.Three elastic stiffness matrices were used to predict the failure loads: (1) linear with yield criterion, 116 kN; (2) stability with change in sign of the total potential energy, 66 kN; and (3) bowing with the criterion of maximum curvature of the load–deflection curve, 80 kN. The failure loads of the two structures were thus accurately predicted by the bowing matrix. Key words: latticed rigid frames, large-scale tests, bowing matrix, steel.
Diffusional limitations of anaerobic biofilms
Authors: Kennedy K. J. , Droste R. L.
Published: January 2010

Using an empirical determination of apparent kinetic parameters in the bulk mixed liquor, the intrinsic kinetic parameters of anaerobic biofilms developed at 35 °C during start-up and steady-state downflow stationary fixed film reactor operation were estimated. The apparent kinetic parameters of anaerobic biofilms are not significantly influenced by internal diffusion limitations. The apparent kinetic parameters of mature biofilms showed no significant trends with increased biofilm thickness up to 2.6 mm and increased apparent Thiele modulus up to 3.1. Key words: anaerobic, biofilm kinetics, Thiele modulus, wastewater, filter.
Effects of time-dependent concrete properties on prestress losses
Authors: Shiu Kwok-Nam , Russell Henry G.
Published: January 2010

Prestress losses were calculated for a segmental concrete box-girder bridge. Results were based on the time-dependent investigation of the Kishwaukee River Bridge constructed by the balanced cantilever method. Instruments were installed in the bridge during construction to measure the time-dependent deformations. Short- and long-term properties of concrete used in the instrumented segments were measured. With the actual construction schedule and the measured concrete properties, time-dependent nonlinear analyses were performed. Prestress losses were calculated for each construction step. Time-dependent variations of prestress losses during and after construction are presented. Comparisons between design concrete properties and measured values and between analytical prestress losses and design values were made. Key words: mechanical properties, creep properties, shrinkage, prestressing, losses, prestressed concrete bridges, measurement, analysis.
Characterization of Canadian fly ashes and their relative performance in concrete
Authors: Carette G. G. , Malhotra V. M.
Published: January 2010

Eleven Canadian fly ashes were characterized and evaluated for their relative performance in concrete. Characterization included the determination of mineralogical composition, chemical composition, physical characteristics, and pozzolanic properties. The relative performance of each fly ash in concrete was evaluated through determination of the following properties of fresh and hardened concrete: slump, air content, bleeding, setting time, strength, modulus of elasticity, drying shrinkage, creep, and freezing-and-thawing resistance.The results indicate a wide range of chemical, physical, and pozzolanic properties for the fly ashes investigated. In spite of this, all the fly ashes studied are shown to be suitable for use in concrete. They affect, however, the properties of fresh and hardened concrete in different ways, and this should be taken into account when proportioning concrete containing these fly ashes. Key words: fly ash, concrete, pozzolanic activity index, bleeding, setting time, air-entrainment, strength, creep, shrinkage, freezing and thawing.
Injection d'ancrages à base de ciment Portland dans l'arctique
Authors: Benmokrane Brahim , Aïtcin Pierre-Claude , Ballivy Gérard
Published: January 2010

During summer, it is possible to inject Portland cement grout in the Arctic because there is a layer of unfrozen rock surface which is approximately 2 m deep. During the month of August, the temperature of the unfrozen rock layer reaches +5 °C at a depth of 1 m, which allows the Portland cement to harden in good conditions and to acquire its full strength.After 7 days, the mean shear strength to failure at the rod–group contact, determined when the anchorages were pulled out, was 10 MPa. After 1 year, this strength was close to 20 MPa. These results are similar to those recorded in Sherbrooke for the same grout formulas. Key words: anchorage, cement grout, rock, Arctic, tearing off. [Journal translation]
Canada's urban infrastructure: rehabilitation needs and approaches
Authors: Adams B. J. , Heinke G. W.
Published: January 2010

This paper reports on the results of a survey conducted for the Federation of Canadian Municipalities on the condition of urban infrastructure in Canadian cities and towns. The major emphasis was on roads, bridges, sewage collection and treatment, and water distribution and treatment systems. The Canadian findings are also compared with the reported U.S. situation. Although not as serious as in the U.S. cities, the survey shows that a significant decline has occurred in the condition of some infrastructure systems in Canadian urban areas. Costs to bring the most seriously deteriorated components of infrastructure (roads, bridges, sewer and water systems) back to acceptable levels are high. Even when spread over a 10-year recovery period, these costs will require an increase in current public works budgets of about 25%.Following the discussion of the state of urban infrastructure in Canada, the paper addresses approaches necessary to obtain optimum value for funds spent on rehabilitation of infrastructure. The need for rehabilitation must distinguish between structural and capacity inadequacies. Alternatives for rehabilitation must include both the engineering alternatives through repair, renovation, and replacement of systems and the management alternatives obtained through operational changes in the system and through changes in system demands. It is both desirable and possible to select engineering and (or) management alternatives on the basis of economic evaluations which trade off the cost of rehabilitation alternatives against the benefits from performance improvements, including the time staging or sequencing of alternatives. Key words: urban infrastructure, infrastructure deterioration, rehabilitation, alternatives, alternative evaluation.
Adfreezing of insulated residential basements: an hypothesis
Authors: Pressnail K. D. , Timusk J.
Published: January 2010

Concern has been expressed that recent increases in thermal insulation levels of residential basements in areas of seasonal frost may increase the risk of damage to foundations due to frost heave and adfreezing of the soil to the foundation wall. An hypothesis is presented which states that the adfreezing bond strength is affected by the direction of soil moisture movement in response to thermal gradients. This hypothesis may be used to explain why there have been no reported adfreezing problems associated with heated, insulated residential basements. Key words: adfreezing, basement, frost heave, insulation, moisture.
Explicit infiltration equations based on the Green–Ampt model
Authors: Thooyamani K. P. , Norum D. I.
Published: January 2010

The Green–Ampt infiltration equations are based on physical parameters of the soil that can be either measured or calculated reasonably easily. However, neither the infiltration rate equation nor the cumulative depth of infiltration equation is in a form that can be used easily in hydrologic modeling, as both equations are in an implicit form when time is the independent variable. Therefore iterative procedures must be used to find either the infiltration rate or cumulative depth at a specific time.Explicit infiltration equations have been developed, based on the Green–Ampt infiltration model. These equations describe the infiltration rate and the cumulative depth of infiltration with a maximum deviation from the Green–Ampt equations of 2.5% for any time. The derived equations have been put in dimensionless form by choosing appropriate length and time scales. Approximate values for the length and time scales for 11 different soil textures, ranging from sand to clay, are given. Key words: infiltration, Green–Ampt explicit equations, hydrology, hydrologic models, surface irrigation, surface irrigation models.
Structural analysis of pipeline stresses created by line lowering
Authors: Czinkota Sid
Published: January 2010

To increase the depth of soil which covers a buried steel pipeline, the line can be lowered without cutting and welding. The degree of curvature in the new profile is the critical factor for controlling the resultant strains. Presented are two methods of calculating the required profile for a line containing high-pressure natural gas. One of the two is selected as being more efficient than the other and is compared with other known methods. Finally, a case history using the new method is presented. Key words: pipelines, gas pipelines, structural analysis, stress analysis, axial stress, axial strain, deflection, curvature, profiles.
Ultimate load distribution characteristics of a model slab-on-girder bridge
Authors: Cheung M. S. , Gardner N. J. , Ng S. F.
Published: January 2010

The introduction of limit states design philosophy and the ever growing demand for higher permissible loads for overload vehicles or special permit vehicles necessitates a thorough investigation of the behaviour and live load distribution characteristics of bridges beyond the working stress range. Evaluation of the live load moment capacity at ultimate utilizing elastic load distribution factors is neither realistic nor logical, as the distribution factors should reflect the ultimate structural/load responses including nonlinear behaviour, load redistribution due to yielding, etc.The purpose of this paper is to study load distribution characteristics of a slab-on-girder bridge model at ultimate loads and to develop load distribution factors for the ultimate limit state which include load redistribution, nonlinear behaviour, and other effects. Key words: load distribution factor, ultimate limit state, load redistribution, nonlinear behaviour, slab-on-girder bridge, OHBD truck.
Review of advantages and applications of disaggregate mode choice models in intercity passenger travel
Authors: Ghoneim N. S. , Sargious M.
Published: January 2010

The use of disaggregate models in modelling intercity passengers mode choice behaviour has emerged over the past 20 years. In an attempt to encourage this use, the present paper addresses the advantages and disadvantages of the disaggregate approach as opposed to the conventional aggregate techniques. The results of a literature review in this regard indicate that disaggregation is statistically and behaviourally necessary to model human travel behaviour while being sensitive in selecting the unit of analysis. The paper also compares the logit analysis with other modelling techniques available for application in order to identify the most suitable one. A critical review of previous modelling efforts in the U.S. and Canada, based on the disaggregate logit analysis is presented to demonstrate the applicability of this technique to modelling intercity passengers mode choice behaviour. Some modelling drawbacks and the general findings of the studies are emphasized to provide useful insight for future modelling considerations. Key words: behavioural, disaggregate, logit analysis, mode choice, models, passenger travel.
Nonlinear analysis of planar reinforced concrete structures
Authors: Bahlis Jihad B. , Saeedmirza M.
Published: January 2010

A new, simple, hypoelastic, and anisotropic stress–strain relationship is proposed for modeling the behaviour of concrete subjected to a general state of monotonic loading. The proposed model reduces to an incremental orthotropic model if the direction of the principal stress axes remains constant. It also eliminates the inability of the orthotropic constitutive relationships to model the behaviour of concrete under a general state of monotonic loading when the principal stress axes rotate during the loading process.The capability and reliability of the proposed model for the analysis of structures in which the principal stress direction does not rotate is verified. A finite element computer program is formulated and used for the nonlinear analysis of planar concrete specimens tested by Kupfer, Hilsdorf, and Rusch and by Tasuji and reinforced concrete panels tested by Vecchio and Collins. The results obtained from the analytical models are in good agreement with the corresponding experimental results. Key words: biaxial stresses, constitutive relationships and failure criteria, cracking and postcracking response, finite element analysis, hypoelastic model, orthotropic model, plain and reinforced concrete.
Calibration basis for structural glass design
Authors: Lind Niels C.
Published: January 2010

A design standard for structural glass in the limit state design format is currently being developed under the auspices of the Canadian General Standards Board. The standard will be calibrated to a target level of reliability expressed in terms of a reliability index. The selection of this reliability level presents some special problems because the loading is dynamic, the structural response is geometrically nonlinear, and the strength is highly dependent on time, size, and loading history. Selection of safety level so as to achieve a social and economic optimum is described. The optimum reliability index is 3.0, corresponding to a lifetime failure probability of 0.0014, when the social and economic cost of failure is between 15 and 70 times the initial cost. Optimal ranges of applicability over cost for a pair of importance factors (0.8 and 1.25) are also determined. Key words: glass, design, standard, code, calibration, reliability, optimization, importance factor.
Génération de séries synthétiques de débit
Authors: Llamas J. , Fernandez R. , Calvache A.
Published: January 2010

The main objective of this research is to find a simple and precise methodology for the stochastic generation of flow series having statistical behaviour similar to the registered or reconstituted historical series. The common statistical parameters are the mean, the variance, the auto- and cross-correlations, and, under particular conditions, the skewness coefficient. A procedure to disaggregate annual series to lower levels (monthly or seasonal) is also presented. Finally, the article describes the general computer model utilized for the synthetic generation. Key words: synthetic generation, flow series, disaggregation, computer model.
Approximate method of analysis for braced barrel vaults
Authors: Anekwe C. M.
Published: January 2010

The analysis of very dense barrel vaults on a computer poses problems of storage and increased computation time to the extent of pushing the cost of analysis to an unacceptable level. In most cases, refinements of the results of analysis are not necessary for the economic design of barrel vaults. The concept of structural factoring is proposed and discussed as an approximate method for the analysis of very dense barrel vaults. The concept provides a method which can be used systematically to predict the behaviour of very dense barrel vaults within the confines of the available computer resources. It proposes a simple relationship between forces and displacements in dense barrel vaults and those in a less dense barrel vault of similar interconnection pattern. There is an appreciable saving in computer resources with the loss of accuracy in the results lying within a range acceptable for the design of barrel vaults. Key words: braced barrel vaults, computer resources, design, shell structures, space structures, structural factoring, stiffness matrix.
Seismic behaviour of highway bridges with base isolation
Authors: Ghobarah A.
Published: January 2010

A study is made on the seismic behaviour of highway bridges with lead–rubber base isolation. The system of base isolation is considered as a bilinear spring. Single- and two-span highway bridges subjected to representative strong earthquake ground motion records were analyzed. The effect of various parameters such as the isolator's stiffness, pier stiffness, and pier eccentricity on the system response was evaluated.It was found that the use of base isolation shifts the fundamental frequency of the bridge system towards the longer period. Proper design of the base isolation tends to reduce the design forces on the bridge piers and is accompanied by larger displacements. Simplified design guidelines are adequate as long as the bridge system can be represented by a single degree of freedom model. The reduction in pier stiffness of a two-span bridge may increase the displacement and the force transmitted to the abutment. The increased forces at the abutments are accompanied by reduction in the shear force transmitted to the pier. Increased displacements and forces may also result when the location of the pier departs from the centre and unequal spans are created. In this case, the maximum displacements and forces occur at the abutment adjacent to the long span. Key words: dynamic, seismic, response, highway, bridges, earthquake, base isolation, design.
The effect of pH adjustment on the internal corrosion rate of residential cast-iron and copper water distribution pipes
Authors: Millette Louise , Mavinic Donald S.
Published: January 2010

The Greater Vancouver Regional District distributes drinking water that displays several attributes of an aggressive water: low pH, low alkalinity, and high dissolved oxygen. A study, consisting of two experimental sessions, was conducted at the University of British Columbia to examine the effects of pH adjustment on internal corrosion of residential cast-iron and copper water distribution pipes.Because of its aggressive nature, this water accelerates the corrosion of water pipes, which not only increases maintenance costs, but also encourages high levels of metal in the water. This last finding was confirmed by a preliminary survey wherein, after one month's sampling of six dwellings, it was found that the recommended maximum level of 1.0 mg/L was exceeded in 67% of the morning cold water first-flush samples.Adjustment of pH with hydrated lime, Ca(OH)2, was used for corrosion control. Cast-iron and copper samples were exposed to pH-adjusted water for varying lengths of time, in two flow-through experimental systems (gravity-fed and system-pressure-fed).Although the corrosion rates were different for the two experimental sessions, analysis of the pH-related corrosion rates variation led to the same two findings. The corrosion rates of cast iron were 10 times those of copper; the increased pH enhanced these cast-iron corrosion rates by approximately 15%. However, a pH increase reduced copper corrosion by as much as 68%. The effects of increased pressure on corrosion were different for both metals; a higher pressure greatly enhanced cast-iron corrosion but had little effect on copper corrosion. Key words: aggressive water, cast iron, corrosion, copper, lime, pH adjustment, water pipes.
The rotational behaviour of clipped end plate connections
Authors: Dalen Karl Van , MacIntyre John
Published: January 2010

The rotational behaviour of clipped end plate connections was studied by subjecting nine clipped and three conventional or “unclipped” specimens with varying connection geometry to combined shear and moment and obtaining the corresponding moment–rotation characteristics. It was found that the clipped end plate connections in this investigation had more than adequate rotation capacity to permit an interior beam connected to a supporting member by this type of connection to achieve its full plastic moment, provided the length-to-depth ratio of the beam does not exceed 20. For the range of rotations that would be experienced by clipped end plate connections in a practical structure, a model originally developed to predict the moment–rotation behaviour of conventional shear end plate connections was modified so as to be applicable to clipped end plate connections. Good agreement was obtained between the test values and those predicted by the modified model. No adverse effect on the rotational behaviour of the connections was observed to result from the asymmetry caused by clipping the end plate. Key words: beams, bolts, columns, connections, fillet welds, limit states design, moment, rotation, shear tests, steel construction.
Effect of diaphragms on stress reduction in box girder bridge sections
Authors: Siddiqui A. H. , Ng S. F.
Published: January 2010

The purpose of this study is to examine the effect of rigid diaphragms in reducing warping and distortion stresses developed in box girders due to deformation of the cross section. Tests were conducted for two Plexiglas box girder models to determine effect of diaphragms on the behaviour of box girder sections. The results of the tests were compared with values obtained from the so-called “beam on elastic foundation (BEF) analogy,” an analytical procedure that permits the calculation of warping and distortion stresses in box sections due to deformation of the cross section.Each box girder model was tested as a simply supported beam with a 1168.4 mm (46 in.) span. Six separate loading positions were used for each of the three predesigned diaphragm spacings. Thus, 18 separate loading tests were conducted for each model in order to obtain sufficient data to determine the amount of reduction in both warping and distortion stresses. Test measurements included the applied load, deflections, and strains at various locations on the webs and bottom flanges.The results indicate that deformation of a box girder cross section due to eccentric loading may cause substantial warping and distortion stresses, and that these stresses can be effectively controlled by judicious installation of rigid diaphragms along the span of the girder. Also, experimental warping and distortion stresses obtained from both tests compare reasonably well with those predicted by the BEF analogy. Key words: warping, torsional, stresses, deformations, box girder bridges, diaphragms.
Hydrologic design methodologies for prefeasibility studies of small-scale hydro at ungauged sites
Authors: Judge David G. , Anderson James E. , McClennan Bruce I. , Park Eon T.
Published: January 2010

Hydrologic variables such as available flow for electrical generation and its time distribution, together with flood magnitudes, represent the basis for evaluation of potential hydro sites. Economic viability, especially for small-scale hydro sites is very sensitive to these basic hydrologic variables. Unfortunately, many potential small-scale hydro sites are located on ungauged streams and often the cost of deriving the necessary site specific hydrologic information for design is prohibitive in relation to overall project costs. Therefore, regional techniques have been developed for evaluating the necessary hydrologic variables at a prefeasibility level for small-scale ungauged sites anywhere in Canada. Studies concerned with developing regional techniques for application to feasibility level evaluations have been completed for Atlantic Canada, British Columbia, and Ontario.The methodology can be used to estimate the flow duration curve and the turbinable flow curve for ungauged streams. Equations relating characteristics of the curves to physiographic and climatic parameters have been derived for eleven regions across Canada. An example demonstrating application of the new methodology is included. Key words: hydroelectric power, small-hydro, regional hydrology, ungauged streams, flow duration curves, turbinable flow curves.
Computer-assisted resource access road route location
Authors: Douglas Robert A. , Henderson Bruce S.
Published: January 2010

The development of resource access road route location methods is outlined, leading to the conclusion that there is a need for an access road route location system which uses an overall optimization scheme, facilitates sensitivity analyses, can be implemented on widely available microcomputers, and can be easily integrated into geographic information systems. The algorithm for a microcomputer program, which is designed to fit this specification, is presented and tested with atypical route location problem. Key words: access roads, resource roads, route location, dynamic programming, microcomputers, optimization.
Modélisation de l'azote total en rivière à l'aide du modèle quantité–qualité CEQUEAU
Authors: Morin Guy , Cluis Daniel , Couillard Denis , Jones H. Gérald , Gauthier Jean-Maurice
Published: January 2010

A model for nitrogen concentrations in running waters has been developed and associated with the hydrological model CEQUEAU. The model allows the simulation of total nitrogen concentrations at any point in a watershed during various hydrological event. The catchment area is first subdivided into discrete elements; each element is associated with a production function which quantifies the accumulation of nitrogen at the soil–atmosphere interface. Supplementary functions describe the transformations of nitrogen species in the soil and the transfer of the nitrogen load towards the hydrographic system by runoff (caused by rain and (or) snowmelt), and the transport of the different nitrogen compounds downstream. Another function is used to represent the in-stream transformation. Nitrogen data inputs to be modeled are those from precipitation dry deposition, diffuse sources due to agricultural practices, and industrial point sources. The model was applied to the Sainte-Anne River, Québec (catchment area, 2700 km2) in order to reproduce the observed nitrogen concentrations for 1978, 1979, and 1980. Model performance was judged to be promising and it is proposed to validate the model by the simulation of nitrogen concentration on the other rivers for which land use and industrial activity are well documented. Key words: modeling, river, nitrogen, supply, runoff, seepage, drainage.
Le rôle des glaces dans le régime morpho-sédimentologique d'un estran de l'estuaire moyen du Saint-Laurent
Authors: Troude J. P. , Sérodes J. B.
Published: January 2010

Not Available
Evaluation of the seismic response factor introduced in the 1985 edition of the National Building Code of Canada
Authors: Heidebrecht A. C. , Lu Chee Yuen
Published: January 2010

The seismic loading provisions included in the 1985 edition of the National Building Code of Canada simulate the dynamic response of structures using a seismic response factor, which has three branches depending upon the relationship between the velocity-related seismic zone Zv and the acceleration-related zone Za. This paper utilizes three ensembles of actual seismic strong motion records to evaluate the seismic response factor; each ensemble has acceleration/velocity ratios corresponding to one of the three branches of the seismic response factor. These strong motion time histories are used as input to relatively simple elastic models of frame and wall structures in order to obtain dynamic seismic response factors. The comparison of these dynamic factors with those specified in the NBCC 1985 indicates that the code factors are generally quite satisfactory, with the exception of the case of frame structures with low fundamental periods located such that Za is two zones higher than Zv. The paper references several other investigations that produce similar results. In that instance, it is recommended that the seismic response factor should be increased, particularly if the structure is located on stiff soil rather than on rock. Key words: structures, loading, seismic, code, earthquake, dynamic, elastic, acceleration, velocity, spectra.
Analysis of truck accident rates using loglinear models
Authors: Buyco C. , Saccomanno F. F.
Published: January 2010

Alternative approaches for the analysis of factors affecting truck accident rates are assessed. The scope of the discussion is methodological in nature, with emphasis on exploring the limitations of each approach. Several important statistical concerns associated with the weighted least squares algorithm for calibrating loglinear models are addressed, including reduced cell membership in the contingency tables of accidents, scaling factors for measuring truck exposure, incompatibility between continuous exposure variables and categorical accident data, and sensitivity of calibrated coefficients to changes in accident characteristics for different data sets. An alternative approach for fitting loglinear models is proposed, which makes use of the generalized linear interactive models (GLIM) package. This approach assumes that the dependent variables in the contingency table of accidents behave in a Poisson-like process with values ranging from 0 to infinity. The calibration of the beta parameters in the loglinear expressions uses maximum likelihood techniques. Continuous exposure variates are incorporated into these models as offsets. As in the classical weighted least squares algorithm, this approach permits a stepwise statistical analysis of higher-order interactions for categorical accident frequency data, while adjusting directly for continuous measures of exposure. The results of a calibration of loglinear expressions for Ontario truck accident data are presented. Key words: truck accident rate, exposure, loglinear calibration, causal interaction.
Geometric imperfections and tolerances for steel box girder bridges
Authors: Thimmhardy Eugene G. , Korol Robert M.
Published: January 2010

An investigation to determine the magnitude of geometric imperfections induced during the fabrication of welded steel box girders is reported for nine highway bridges constructed in Canada. Measurement data were collected to compare the significance of dead load on initial imperfections obtained following fabrication. Existing bridges were found to have out-of-plane deviations of plate panels about 10% higher than unloaded bridge values. A statistical interpretation of measurements of initial plate imperfections and out-of-straightness of stiffeners culminates in tolerance levels, deemed to be appropriate for Canadian-built box girders, and well within the capability of the fabricating industry to achieve. Key words: box girder, bridges, field measurements, geometric imperfections, plate panels, stiffeners, structural steel, tolerances.
Bacterial loadings from resuspended sediments in recreational beaches
Authors: Palmer Merv
Published: January 2010

Bacterial loadings from the resuspension of contaminated sediments were measured in situ at three Toronto waterfront beaches and the increase in water bacterial densities due to sediment resuspension was determined. The loadings due to sediment resuspension varied from 0 to 1410 fecal coliforms/(m2∙s). Sediment loadings in excess of 100 fecal coliforms/(m2∙s) caused significant increases in the water fecal coliform densities in shallow beach areas. Over 2970 water samples were analyzed for both fecal coliforms and E.coli and it was found that fecal coliforms and E.coli were statistically correlated. Over 1770 water samples were analyzed for both fecal coliforms and Pseudomonas aeruginosa and these bacteria were found to be statistically correlated. Key words: beach bacterial contamination, sediment resuspension loadings, fecal coliforms, E.coli and Pseudomonas aeruginosa.