bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave–current effects on large offshore structures
Authors: Isaacson Michael , Baldwin John
Published: January 2010

The various effects that influence loads acting on a large offshore structure due to the combination of waves and currents are reviewed. These may be broadly associated with potential flow effects and viscous effects. The potential flow effects are nonlinear and may generally be investigated by perturbation or time-stepping methods. Viscous effects include the onset of flow separation, which affects the validity of the assumed potential flow, as well as steady and oscillatory forces. The fluid mechanics of the complete wave–current–structure interaction problem are not yet well understood and areas in need of additional research are identified. Key words: currents, drag, drift forces, hydrodynamics, ocean engineering, offshore structures, waves, wave forces.
Calculation of stress in prestressing steel at ultimate conditions
Authors: Batchelor B. deV. , Srinivasan Jayanth
Published: January 2010

This paper reviews different methods available for the calculation of stress in prestressing steel at ultimate, ƒps, and the methods are evaluated using a nonlinear analysis computer program. The development of a nonlinear model for the analysis of partially prestressed concrete flexural members is described. The model takes the material nonlinearities into account by the use of appropriate stress–strain relationships for steel and concrete. A parametric study of partially prestressed beams was conducted to study the effect of various parameters on stress in prestressing steel at ultimate conditions. Two types of sections, rectangular and T sections, were studied. The prediction equation, recommended in the Canadian Code Can3-A23.3-M84, for calculating the stress in prestressing steel at ultimate is found to be very conservative for all the cases studied, which covered all possible ranges of partial prestressing ratio. The present restriction in the Canadian Code, for the use of their prediction equation only when the ratio of the neutral axis depth, Cu, to the depth of the centroid of prestressing steel, dps, is less than or equal to 0.3, is found to be too restrictive. An alternative equation for ƒps, suggested by Loov, is found to be more suitable than the present equation in the Canadian Code; however, a more practical upper limit for cu/dps ratio is suggested in the paper. It is shown that the proposed equation can be used conservatively over the complete range of partially prestressed concrete. Key words: analysis, concrete (prestress), flexure, partial prestressing, prestressing, strain, stress, steel.
Buckling of longitudinally stiffened plates in bending and compression
Authors: Bradford Mark A.
Published: January 2010

The nonlinear stiffness equations that predict local and post-local buckling of plates and plate assemblies are given. These equations are validated by accurate predictions of independent test results. The elastic local buckling of longitudinally stiffened web plates in combined bending and compression is considered. Graphs which may be used to predict the optimum position of a stiffener are presented. The relationship between the area and second moment of area of a stiffener of finite dimensions that optimizes the local buckling coefficient is given for various eccentricities of end load. The post-local buckling of a longitudinally stiffened plate in uniform compression and pure bending is also considered. It is shown that the provision of a longitudinal stiffener, of proportions to enforce a node at the plate–stiffener junction, enhances significantly the postbuckling response of the plate with regard to the serviceability limit state, particularly for the case of pure bending. Key words: bending, compression, finite strips, local buckling, plates, postbuckling, stiffeners, webs.
Brooks Aqueduct
Authors: Manz David H. , Loov Robert E. , Webber Jim
Published: January 2010

The Brooks Aqueduct is a very large elevated flume commissioned in 1914 by the Canadian Pacific Railway (CPR) to carry water at the rate of 25.5 m3/s over a valley 3.2 km wide and 20 m deep. Construction of the aqueduct permitted the irrigation of a 50 000 ha block of land within a region now known as the Eastern Irrigation District in southern Alberta. The flume is 6.5 m wide and 2.5 m deep with a curved cross section. It is supported by 1030 columns. A 3000 mm diameter inverted syphon near the outlet of the flume permitted the crossing of the CPR main line through the valley. All components of the aqueduct, including the shell of the flume, columns, syphon, and inlet and outlet structures, were constructed of reinforced concrete. The Brooks Aqueduct was abandoned in 1979 with the completion of its earth-fill replacement. Except for a 122 m section, removed to permit the construction of a county road, the old aqueduct still stands. It serves to remind us of the significant engineering accomplishments of the pioneer civil engineers who helped to realize ambitions to irrigate the vast plains of southern Alberta at the turn of the century. On May 28, 1988, the Brooks Aqueduct was named a National Historic Civil Engineering Site by the Canadian Society for Civil Engineering. Key words: Brooks Aqueduct, history.
Pavement damage implications of Ontario Bridge Formula axle group weight limits
Authors: Hutchinson B. G.
Published: January 2010

The Ontario Bridge Formula (OBF) is the basis for the regulation of highway truck weights in Ontario. Allowable loads on tandem and tridem axle groups increase with increasing axle group spread. Analyses of the moments induced in simple-span bridges by the allowable axle group loads show that the moments increase with the increasing loads allowed on wider axle spreads. Pavement damage load equivalency functions developed from the Canroad pavement test series are used to estimate the. pavement damage impacts of these allowable axle loads. Relative pavement damage is shown to increase by 50% for the range of loads allowed on tandem axle groups and by 125 % for the load range allowed on tridems. If equal pavement damage were used for regulating axle group loads, then the range allowed for tandems would be 15 400–16 500 kg, instead of the OBF-allowed 15 400–19 000 kg; and 19 100–20 000 kg, instead of the OBF-allowed 19 500–28 600 kg, for tridems. Key words: highway bridges, highway pavements, bridge loads, trucks, load equivalencies.
Longitudinal girder moments in simply supported bridges by the finite strip method
Authors: Ho S. , Cheung M. S. , Ng S. F. , Yu Tonghua
Published: January 2010

The finite strip method is used to analyze three different kinds of simply supported highway bridges: slab-on-girder, two-cell box-girder, and rectangular voided slab bridges. Deck width from two lanes to four lanes are considered. The Ontario highway bridge design (OHBD) truck load is applied at the most critical location of the bridge. A total of 12 design curves are developed, corresponding to different bridge sections and deck widths. From these design curves, one can obtain the ratio of the maximum longitudinal bending moment to the equivalent beam moment. Key words: bridge decks, design curves, concrete, steel, finite strip, OHBD truck load.
Evolution of design standards and recorded failures of guyed towers in Canada
Authors: Magued Mohammed H. , Bruneau Michel , Dryburgh Robert B.
Published: January 2010

The information contained herein constitutes the foundations for a companion paper in which a set of guidelines for the upgrading of existing guyed towers is developed, following a rational approach. Large increases in strength requirements for guyed towers have been introduced by successive revisions of the CAN-CSA-S37 Standard "Antennas, Towers and Antenna-Supporting Structures" (S37). Up to now, there has been a perception among tower owners that tower failures were few and, in consequence, that the added strength requirements are not needed, and further, that existing towers should not be forced to comply with the latest edition of the S37 standard. This paper demonstrates that the failure rate for guyed towers designed to earlier versions of S37 is generally unacceptably high. General comments on standard developments and various design philosophies are presented. The evolution of the Canadian standard for the design of guyed towers is also examined, as deficiencies in earlier versions of S37 are partly accountable for the high observed failure rate. Other international standards for the design and analysis of guyed towers are also reviewed for their approach towards the upgrading of existing towers. Since guyed telecommunication towers are often reviewed for addition of new antennas, upgrading to the strength levels of the most recent edition of the standard — as required in many cases — can be very expensive. Yet, in many cases, much of this expense is unjustified for a variety of reasons. This paper proposes the need for the development of upgrading guidelines and further development work on S37. Key words: guyed towers, failure, failure rate, working stress design, limit state design, environmental loading, existing structures, strength upgrading.
Recommended guidelines for upgrading existing towers
Authors: Bruneau Michel , Magued Mohammed H. , Dryburgh Robert B.
Published: January 2010

A companion paper reviewed the history of the development of the Canadian standard for towers, and demonstrated that the failure rate for guyed telecommunications towers designed to earlier editions of the CAN-CS A-S37 Standard "Antennas, Towers and Antenna-Supporting Structures" (S37) is generally unacceptably high. These towers are often reviewed for addition of new antennas, and upgrading to the strength levels of the most recent edition of the standard — as required in many cases — can be very expensive, due to the sizeable increases in strength requirements for guyed towers which have been introduced by successive revisions of S37. Clearly, there is a need to match strength requirements to the significance of the structure and the economic consequences of its failure. Uniformly high strength requirements will occasionally result in reinforcement costs that exceed the costs of the risk of failure. In answer to this, a rational approach has been used to develop a set of guidelines for the upgrading of existing towers. This methodology relies on the classification of towers in various reliability classes, having increased probabilities of failure attached, and correspondingly lower load factors for use in the analysis. Results from this research are presented herein, together with the recommended proposed guidelines. Key words: guyed towers, reliability classes, probability of failure, safety index, upgrading cost, failure rate, environmental loads, guidelines.
Powdered activated carbon selection for water treatment
Authors: Troxler S. , Smith D. W. , Knettig E.
Published: January 2010

Increasing concern with colour, taste, and odour in municipal water supplies has led to the use of a variety of coagulants, oxidants, and adsorbents for improving water quality. Powdered activated carbon (PAC) is a good adsorbent of many organic materials in water. This paper presents a protocol for evaluating various PACs, taking into account the objective of the unit process. Using a series of decision criteria, more weight can be placed on the test parameters which relate to the cause of the quality problem. An example of the procedure is demonstrated. Key words: adsorption, powdered activated carbon, taste and odour, iodine number, modified phenol value, tannin value.
Parameters influencing the design of friction damped structures
Authors: Filiatrault A. , Cherry S.
Published: January 2010

This paper is concerned with a study of the parameters influencing the seismic design of structures fitted with friction dampers. For the efficient design of such systems, the slip load distribution which minimizes structural response during a major earthquake must be determined for the dampers; this distribution is referred to herein as the optimum slip load distribution. A simple procedure is presented for establishing this basic design parameter. An analogy is first made between a single-storey friction damped structure and a simple nonlinear mechanical system. The response of this system to sinusoidal base excitation is then computed using an existing analytical solution. The solution clearly shows that the optimum slip load of the analogous friction damped structure depends on the amplitude and frequency of the ground motion and is not strictly a structural property. By extension, the optimum slip load distribution of a multistorey friction damped structure will be influenced by the characteristics of the earthquake ground motion anticipated at the construction site. Using this information, numerical sensitivity and parametric studies are performed on multistorey friction damped structures excited by a large number of artificial accelerograms generated from an existing stochastic earthquake model. The results of the study lead to the construction of a design slip load spectrum for the rapid evaluation of the optimum slip load distribution in a multistorey friction damped structure. The spectrum takes into account the properties of the structure and of the ground motion anticipated at the construction site and greatly simplifies the seismic design of this new structural system. Key words: braced frames, brake lining, design, damping, dynamics, earthquakes, energy, friction, slip load spectrum.
Pool-orifice and pool-orifice-weir fishways
Authors: Rajaratnam N. , Katopodis C. , Mainali A.
Published: January 2010

This technical note presents a method of analyzing the flow in pool-orifice fishways by dividing it into vertical slot and submerged orifice flow regimes. For a pool-orifice-weir fishway, with flow through the orifice as well as over the weir, a method has been suggested for predicting the total flow rate in the fishway. Experimental observations are presented in support of these methods. Key words: open-channel flow, hydraulics, fishways, turbulent flow.
Structural analysis of old stone arch bridges
Authors: McNeely D. K. , Archer G. C. , Smith K. N.
Published: January 2010

The use of stone arches for bridge construction has generally ceased, but since these structures still exist in modern road systems, their structural integrity is of current concern. This paper presents an analysis technique suited for the thick jointed heritage stone arch bridges found in Canada. The effect of increased mortar joint size on structural response is investigated. The response of a section to eccentric thrust is postulated and the effective section properties are derived. Structural behaviour proceeds from a fixed arch to a two-hinge, a three-hinge, and finally a five-hinge failure mode for a symmetrical arch with midspan loading. A typical load–deflection curve is developed, suitably adjusted for secondary effects due to changes in geometry and material nonlinearity. Stone arch bridges in Canada were constructed with thick mortar joints, which exhibit significant deterioration of stiffness with load eccentricity and, therefore, significant secondary effects; as thickness increases, ultimate strength decreases. A suitable limit states prediction for the load capacity of old stone arches is proposed. Key words: arch, bridge, heritage, limit states, stone, structural analysis.
Adsorption and desorption of perchloroethylene in soils, peat moss, and granular activated carbon
Authors: Zytner Richard , Biswas Nihar , Bewtra Jatinder K.
Published: January 2010

Studies were conducted to evaluate the adsorption–desorption isotherms of a common dry cleaning solvent, perchloroethylene (PCE), in soils, peat moss, and granular activated carbon. The results obtained followed the Freundlich Isotherm, and the organic carbon content of the media was the most significant controlling factor in the adsorption–desorption process. The peat moss exhibited the highest residual saturation concentration for pure PCE amongst all the media tested. The desorption studies indicated that PCE had medium mobility in soil and was not significantly affected by moderate changes in pH. Key words: adsorption, desorption, Freundlich Isotherm, granular activated carbon, peat moss, perchloroethylene, soils.
Modélisation tridimensionnelle de l'écoulement au voisinage d'un aménagement portuaire
Authors: Soulaïmani A. , Ouellet Y. , Dhatt G. , Blanchet R.
Published: January 2010

This paper is devoted to the computational analysis of three-dimensional free surface flows. The model solves the Navier-Stokes equations without any a priori restriction on the pressure distribution. The variational formulation along with the solution algorithm are presented. Finally, the model is used to study the hydrodynamic regime in the vicinity of a projected harbor installation. Key words: free surface flows, three-dimensional flows, finite element method.
Out-of-plane resistance of concrete masonry infilled panels
Authors: Dawe J. L. , Seah C. K.
Published: January 2010

Nine large-scale concrete masonry infilled panels (3.6 × 2.8 m) were tested to destruction under uniformly distributed lateral pressure applied in small increments. Load–deformation curves of the infills and the enclosing steel frame showed linear elastic behaviour prior to first cracking. Nonlinear behaviour due to cracking and arching action of infill was prominent in the postcracking range. Parameters investigated experimentally included the effects of boundary supports, joint reinforcement, panel thicknesses, panel opening, and characteristics of construction. In parallel with the testing program, computer-aided analytical techniques were developed to predict the first crack and ultimate loads. First crack prediction was based on a finite element analysis for bending of thick plates, while ultimate load prediction was based on a yield-line technique modified to account for the arching action of infill confined within a flexible frame. Having been verified by comparison with test results, the postcracking analysis program was used to conduct a parametric study. It was found that infill compressive strength, panel dimensions, and frame rigidity have significant effect on ultimate loads. While central openings do not affect the ultimate strength, they do, however, reduce postcracking ductility. Key words: masonry, infill panel, steel frame, experimental, out-of-plane, behaviour, strength, arching, yield-line technique, cracking.
A device for measuring forces in a rubble-mound breakwater
Authors: Scott R. D. , Turcke D. J. , Baird W. F.
Published: January 2010

An improved instrumentation scheme has been designed and tested for measuring the generalized forces occurring within armour units in a physical model of a breakwater subjected to wave action. The fundamental change is centered around the concept of a load cell. Compared with previous devices developed by the authors, this new unit has improved sensitivity, full protection from all environmental influences, and a wider range of applicability. These improvements were substantiated by a number of static and hydraulic tests. Key words: breakwaters, armour, model, analysis, instrumentation.
Analysis of continuous curved girder-slab bridges
Authors: Azad Abul K. , Baluch Mohammed H. , Ali Aejaz
Published: January 2010

A static analysis of horizontally curved, continuous multigirder slab type bridge decks has been proposed using finite difference method in conjunction with the method of consistent deformation. The deck is idealized as a curved thin plate supported by flexible supports having both vertical and rotational flexibility. The proposed Levy-type series solution requires generation of linear equilibrium difference equations only along the central radial line of the deck, thus obviating the need of a large computational molecule. The simple repetitive algorithm for this method of analysis is an advantage in computer programming. Key words: bridges (curved), beams (curved), structural analysis, computation, concrete, steels, moments.
Design recommendations for wind loading on buildings of intermediate height
Authors: Stathopoulos T. , Dumitrescu-Brulotte M.
Published: January 2010

The National Building Code of Canada (NBCC) specifies wind loads for the design of tall (height, H > width, W) and low (H < 10 m, or H < W and H < 20 m) buildings. Since there are no specifications for the design of buildings of intermediate height, the present project has been undertaken to help define wind loads appropriate for the design of such buildings. The experimental study was carried out at the boundary layer wind tunnel of the Centre for Building Studies at Concordia University. The methodology used for this project consisted of testing five square building models (12, 25, 55, 100, and 145 m high) under conditions simulating strong turbulent wind blowing over an open country terrain exposure. Both the lowest and the tallest buildings were tested for validation purposes. Statistics of wind induced pressures were measured at several points and areas on the walls and the roof of all buildings for both normal and oblique wind directions. Experimental data show good agreement with previous studies of buildings of similar height tested under different environmental and proximity conditions. Results for the intermediate height buildings are presented in the paper. Wind pressures are compared with the NBCC specifications for low and tall buildings. Key words: building, code, design, loads, pressure, roof, wall, wind.
Field measurements of the hydraulic resistance of sanitary sewers
Authors: Gerard R. , Bouthillier P. , Besmehn J.
Published: January 2010

Measurements of the in-service hydraulic roughness of some 33 lengths of small suburban sanitary sewers are reported. The test results indicate that the hydraulic roughness used in design should vary with pipe slope, material, and the proportion of the design flow that is dry-weather flow. In particular, the typical design roughness currently recommended seems low for low slope sewers, but high for those with slopes greater than about 1%. The tests revealed that sewers installed below the usual recommended minimum slope were operating as successfully as those of steeper slope, which implies that the current minimum-slope recommendations may be too conservative. An alternate approach to minimum-slope specification is suggested. Several augmented-flow tests were also carried out. These confirmed that the variation in effective roughness with depth is much stronger than is usually assumed. They also showed that there is a significant hysteresis in the roughness variation on the rising and falling limbs of a hydrograph. Key words: sewers, pipeflow, coefficients, roughness, resistance, hydraulics, wastewater, sanitary.
Détérioration de fondations de pylones d'ancrage de lignes de transport d'électricité par des réactions alcalis–granulats, performance mécanique et réparation du béton
Authors: Bérubé Marc-André , Fournier Benoit , Frenette Jean
Published: January 2010

A number of concrete tower foundations that support power lines over the St. Lawrence River in the Quebec City area were showing deterioration related to alkali–aggregate reactions. The aggregates involved are siliceous limestones commonly exploited in the area. Many foundations have been cored down to the rock basement and samples were taken all along the cores for petrographic examination and mechanical testing. These studies show that the concrete presents some mechanical weaknesses but only in the first decimeters close to the surface, even if the entire mass of the concrete foundations is affected by alkali–aggregate reactions. The results also suggest that the deterioration is isotropic in the concrete and that the compressive strength is affected as much as the tensile (Brasilian) strength. Various types of corrective measures were applied to the deteriorated components: sealing of cracks, removing of the deteriorated concrete and replacement with a new concrete containing silica fumes in addition to a low alkali cement, insertion and posttensioning of steel rods in some components, application of water-tight elastomer liners on the exposed concrete surface, etc. Key words: concrete, aggregate, cement, alkali–aggregate reaction, expansion, mechanical strength, repair, protection.
Line haul transport cost and pavement damage characteristics of some Ontario trucks
Authors: Hutchinson B. G. , Mallett J. J. L.
Published: January 2010

The factors contributing to the line haul transportation costs of very large trucks operating on the Ontario highway system are calculated from fundamental tractive resistance equations and tractive effort characteristics for two "weigh-out" commodity types and representative haul routes. These calculated costs are compared with some observed costs and earlier analyses to check the validity of the models. The theoretical models are then used to assess the impact on operating costs of a variety of truck parameters which include truck type and tire pressures. The pavement damage created by the different truck types are estimated and the damage costs compared with the savings in line haul transportation costs. It is concluded that the pavement damage impacts of different truck types should be carefully compared with potential line haul transportation cost savings to ensure that allowable truck configurations are economically efficient with respect to both public and private costs. Key words: highway engineering, pavement damage, pavement cost, truck operating cost, vehicle weights.
Modelling water temperature beneath river ice covers
Authors: Marsh Philip
Published: January 2010

The water temperature beneath river ice covers has an important influence on the heat flux to the overlying ice cover and on ice melt. Measurements of water temperature beneath the Liard River ice cover showed that prior to spring breakup, the water temperature was always between 0.0 and 0.025 °C, with important cross-channel and diurnal variations. The lowest temperatures were controlled by the bed heat flux and frictional heating, while variations above these minimum values were explained by changes in solar radiation. Using measurements of these heat fluxes, in conjunction with measurements of ice and bed roughness, water depth and velocity, and slope, a simple method which assumes the similarity between heat and momentum transfer was able to accurately predict water temperatures beneath the ice cover. During breakup when the river had both ice-free and ice-covered sections, water temperatures rose to a few degrees above 0 °C. When this water entered an ice-covered reach, the water temperature declined rapidly to near 0 °C within 10 km. This temperature decay was predicted from measurements of the initial temperature, ice and bed roughness, and water depth. Key words: water temperature, ice, thermal regime, ice melt.
Truck weights as a function of regulatory limits
Authors: Clayton A. , Plett R.
Published: January 2010

Models are developed for the gross vehicle weight and axle weight distributions of laden trucks as a function of governing weight limits. The models are based on truck weight surveys conducted in Manitoba between 1972 and 1986, a period of changing weight limits. They are developed for 2-axle trucks, 3-axle trucks, 5-axle (3-S2) tractor-semitrailers, 7-axle (3-S2-2) A-trains, and 7-axle (3-S2-S2) B-trains. The models can provide important input to the analysis of pavement loadings (and costs), given particular weight limits or changes in weight limits. They can also provide useful input to estimates of the relative benefits of alternative weight limit regimes. Key words: truck weights, weight limits.
Improved finite strip method for nonlinear analysis of long-span cable-stayed bridges
Authors: Cheung M. S. , Li Wenchang , Jaeger L. G.
Published: January 2010

As the spans of cable-stayed bridges increase, the degree of nonlinearity of structural response increases markedly. For future spans greater than (say) 800 m, existing three-dimensional software then becomes very time consuming and costly, and a finite strip approach becomes more attractive and preferable. An improved finite strip method using two types of longitudinal shape functions is developed in this paper for the analysis of girders of such bridges. The nonlinearities due to sag and angle change of the cables are taken into account by means of catenary theory. The substructuring technique and the modified Newton–Raphson iteration method are used for nonlinear solutions. A number of numerical examples are given to show the accuracy and efficiency of this method. Key words: finite strip, continuous structure, cable-stayed bridge, substructuring, catenary, nonlinearity, iteration.
Durability of concrete containing chloride-based accelerating admixtures
Authors: Rezansoff T. , Stott D.
Published: January 2010

The influence of CaCl2 or a chloride-based accelerating admixture on the freeze–thaw resistance of concrete was evaluated. Three air entrained mix designs were investigated using ASTM C666-84, Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing. All mix designs were similar, using cement contents of 340–357 kg/m3 of concrete, except for the addition of either 2% calcium chloride or 2% High Early Pozzolith, while no accelerating admixture was added to the control mix. The entire test program was repeated four times with water-to-cement ratio of 0.46 and three times with the ratio of 0.43. For the Pozzolith-accelerated concrete, half the samples were coated with boiled linseed oil in all seven series. For the control (unaccelerated) concrete, half the samples were coated with boiled linseed oil in one series for each water-to-cement ratio. Performance was monitored using the dynamic modulus of elasticity as obtained from transverse resonant frequency measurements. Weight loss of the specimens was also measured. Only the control samples (no accelerators) showed sufficient durability to satisfy the standard of maintaining at least 60% of the original dynamic modulus after 300 cycles of alternate freezing and thawing. Sealing with linseed oil showed inconsistent improvement in the durability in the various test series when defined in terms of the dynamic modulus; however, weight losses were the lowest of all categories and surface scaling was minimal. Key words: concrete, durability, freeze–thaw testing, calcium chloride, admixtures, sealants, air void system.
Construction of the Iona Outfall submarine section
Authors: Lively T. W. , Gowe C. D. , Woodhead H. R.
Published: January 2010

In February 1987, the Greater Vancouver Sewerage and Drainage District awarded an $8.5 million contract for the construction of the Iona Outfall submarine section. The contract awarded to the Dillingham–Manson joint venture involved the installation of approximately 3200 m of twin 2.3 m diameter steel outfall, of which 500 m was twin 2.1, 1.8, and 1.4 m diameter steel diffuser sections. The outfall extended from the end of the Iona Jetty into the Strait of Georgia near the mouth of the Fraser River and was 107 m deep at the end of the diffuser. The tender documents suggested a method of installation such that the entire twin outfall pipe was fabricated on an existing jetty complete with flotation pipe and pulled into the water. The contractor submitted an alternative method with the tender and was the successful low bidder. The proposed installation method was to assemble the pipe into nominal 300 m lengths in Dillingham's North Vancouver yard, launch them, tow them to the site, and sink and bolt them together underwater. This paper discusses the more interesting aspects of the project. Key words: construction, pipelines, robotics, sewage treatment, bolted joints.
Buckling of continuous steel girders with flange restraint
Authors: Albert C. , Dawe J. L.
Published: January 2010

A theoretical investigation of the buckling strength of continuous steel girders with top flange restraint is presented. Girders consisting of two equal spans are analyzed using a finite element technique to determine the effects of partial and full restraint conditions commonly found in bridge design. The effects of loading conditions, span length, and web stiffeners are also considered. A refinement is introduced for the purpose of modelling inelastic behavior due to combined bending and residual stresses. The theoretical method shows excellent agreement with experimental results obtained by others. A parametric study is conducted using the verified analytical technique. Key words: stability, buckling, plate girders, flange restraint, inelastic behavior.
Scale effect on dispersion in chlorine contact chambers
Authors: Mitha Sohail A. , Mohsen M. F. N.
Published: January 2010

An experimental research involving tracer studies, carried out in four geometrically similar models of contact chambers and operated under an equal detention time criterion, is presented. The scale effect on dispersion characteristics is investigated to determine how closely the performance of a prototype can be predicted from a laboratory study on scaled-down models. A number of parameters and indices, including dispersion number, are considered in the investigation. It is observed from the output-generated curves that the coefficient of dispersion is influenced by scale. However, the normal variance and the dispersion number are, to a large extent, independent of scale, at least for longitudinal basins larger than 5.6 cm (2.2 in.) width and for all practical detention times. Key words: longitudinal dispersion, dispersion number, model study, scale.
Stability of province/state wide transport planning model
Authors: Wilson F. R. , Abl El Megeed Ahmed E. T.
Published: January 2010

This paper assesses the temporal stability of trip generation, distribution, and assignment process at a state or provincial level. The assignment used data from a test study area that included the southwest part of the Province of New Brunswick with a total area of 30 000 km2. For the test year of 1979, trip generation data were developed using three models. The models were based on stepwise regression, principal components, and ridge regression. Following the trip generation phase, a gravity model was used to distribute the output of each model. Given the limited number of alternative routes, an all-or-nothing assignment was used. The stability of the models was assessed using data for 1971. Of the three models evaluated only the one based on ridge regression proved to be reasonably stable over the term period. A stepwise regression model without intercept was also developed and reasonable results were obtained for the stability of this model. Key words: planning, model, stability, trip generation, distribution, assignment, provincial.
Parametric effect of vertical ground acceleration on the earthquake response of elastic structures
Authors: Ariaratnam S. T. , Leung K. C. K.
Published: January 2010

An analytical procedure is presented for the calculation of the statistical properties of the response of a linear elastic tall building under earthquake excitation. Emphasis is placed on the effect of the vertical ground motion. The restoring force in each story of the structural model is assumed to arise from the bending deformation of the columns whose rigidities are subjected to a general reduction due to the combined action of gravitational forces and the random variations due to vertical ground acceleration. Since earthquakes are random phenomena, stochastic modelling of ground motion seems appropriate. Both the vertical and the horizontal accelerations are treated as amplitude-modulated Gaussian random processes. With these models, the techniques developed herein, using the concept of Markov processes and Itô's stochastic differential equations, may be applied. To illustrate the application of the method, numerical results are presented for a six-story building. For computational purposes, the structural properties are evaluated using the finite element method. Within the limit of linear elastic deformation, the vertical ground acceleration is shown to be capable of causing only a slight increase of 0.08% in the lateral displacement for this moderately tall building. The percentage is expected to be larger for a taller building and much larger when the deformations exceed the elastic limit. Key words: earthquake excitation, elastic frames, random vibration, Markov process, dynamic response.
A review of pilot-scale studies of bottom and surface velocities within air-agitated circular and rectangular vessels
Authors: Machina David W. , Bewtra Jatinder K.
Published: January 2010

The use of bottom or surface fluid velocity within air-agitated circular and rectangular vessels has been studied as a possible design parameter to achieve a specified scale of agitation. Experimental data are presented in terms of five dimensionless numbers involving the fluid velocity, the depth of fluid in the vessel, the elevation of the diffuser above the vessel floor, the air flow rate, and the compressor power required. Design equations are obtained for a total of 506 physical observations with a ring diffuser around the perimeter of a circular vessel, a pipe diffuser at the centre of a circular vessel, and a line diffuser at the centre line or end wall of a rectangular vessel. The applicable range of variables for each equation is provided. It is shown that both bottom and surface velocities increase with an increase in air flow rate or compressor power requirement for a specified fluid depth. For a constant air flow rate and fluid depth, the surface velocity always exceeded the bottom velocity. The surface and bottom velocities are related to operating conditions in different water and wastewater treatment units in which a specified degree of uniformity of the vessel contents has to be maintained in order to keep a specified particle in suspension. The sensitivity analysis of the model revealed that the fluid depth was the most important design parameter in controlling the velocities within air-agitated vessels. Key words: bottom velocity, surface velocity, velocity gradient, degree of uniformity, air-agitated rectangular vessels, air-agitated circular vessels.
Numerical solutions to wave interaction with rubblemound breakwaters
Authors: Hall Kevin R.
Published: January 2010

The interaction of a wave with a rubblemound breakwater results in a complex flow field which is both nonlinear and turbulent, particularly within a region close to the surface of the structure. Numerical models describing internal flow in a rubblemound breakwater are becoming increasingly important, particularly as the influence of scale effects on internal flow in physical hydraulic models are becoming understood as important. A number of numerical models to predict the internal breakwater flow kinematics have been produced in the past two decades. This paper provides a review of the state-of-the-art of numerical modelling of wave interaction with rubblemound breakwaters. Details of the theoretical development and the resulting numerical solution techniques are presented. Methods for incorporating secondary effects such as two-phase (air–water) flow, inertia, and unbalanced boundary conditions are discussed. Limitations of the models resulting from the validity of the assumptions made in order to effect a numerical solution are discussed. Key words: breakwaters, internal flow, porous media flow, numerical modelling, rubblemound breakwaters.
Preliminary design of standard prestressed bridges using box girders or hollow slabs
Authors: Fereig Sami M. , Smith Kenneth N.
Published: January 2010

This study uses a linear programming mathematical model to establish preliminary design charts for prestressed bridges using box girders or hollow slabs, giving the required prestressing force after losses for an interior girder for various spans and spacings. The structure is designed to carry the MS200-77 loading, and the design conforms with the Canadian Standards Association Standard CAN3-S6-M78 for design of highway bridges. The bridge considered is single-span, with a cast in situ concrete deck acting compositely with the prestressed girders under live load. The linear programming model is also used to determine the design criteria that will control the designs for the cases investigated, and to perform the parametric study to evaluate the effect of variations in deck thickness, girder concrete strength, and prestressing losses on the value of the required prestressing force. Key words: box girder, bridge, design, hollow slab, linear programming, prestressing.
Effect of concrete specifications and inspection practices on freeze–thaw resistance: a field study
Authors: Ward M. A. , Langan B. W.
Published: January 2010

In the late sixties significant durability problems were encountered in a major metropolitan center in Canada. A review of prevailing construction practices was undertaken, together with a rigorous statistical analysis of the air content and compressive strength results. The main outcome of that study was a conclusion that a significant amount of the concrete placed on the job site had an unacceptably low air content. It is understood that these results, coupled with a review of specifications used in other metropolitan centers, provided the basis for revising the concrete materials specification in 1970. A similar review of strength and air content results was carried out at the end of that year. It was evident that an increase of approximately 1% had occurred in the average measured air content together with a small increase in compressive strength as the result of the specification changes. To assess the effect of this specification and further changes that have occurred since 1970, a third review was carried out in 1987. It was noted that during the intervening period a further increase in air content had taken place. Reasons for these changes are reviewed with respect to current construction practices. Also included is a review of the current specifications for this class of concrete in use in Canada. Key words: air content, compressive strength, specifications, inspection, statistics, durability.
Computer simulation of ice control with thermal-bubble plumes — line source configuration
Authors: Baddour R. E.
Published: January 2010

Thermal-bubble plumes in a freshwater environment are studied to determine their ice control capabilities. A computer model is developed to optimize the operation of thermal-bubble installations when designed to control ice. Steady-state and transient simulations of ice control are presented. It is conceivable to fully computerize the operation of thermal-bubble installations by combining data acquisition, data analysis, computer simulation, and control automation. Key words: ice control, ice management, thermal-bubble plume, computer simulation.
Wind pressures on buildings with stepped roofs
Authors: Stathopoulos T. , Luchian H. D.
Published: January 2010

The paper describes an experimental study for the evaluation of wind pressures on buildings with roofs of two different heights, such as one building with roofs at two levels or, more commonly, two flat-roofed buildings in a row. The study is experimental and consists of an extensive series of tests in a boundary layer wind tunnel simulating the flow over an open country terrain exposure. The basic model of the study has been designed and constructed in sections so that it can represent flat roofs in steps of different relative heights and widths. The maximum height of the model is variable and can represent a building up to 60 m high. The results of the study for buildings with a two-level flat roof are discussed in the paper. Data are presented in pressure coefficient form (both mean and peak values) measured locally on a number of pressure taps placed at strategic locations on the roof and wall sections of the model. The results of the study are compared with the flat-roof specifications described in the American National Standards Institute wind standard and the National Building Code of Canada. It has been found that some modifications of these standards are required to accommodate the wind loading of these building configurations. In particular, the inclusion of positive pressure coefficients must be considered for stepped roofs. Key words: building, code, design, loads, pressure, roof, wall, wind.
River intake works for a hydroelectric plant in Papua New Guinea
Authors: McCreath P. S. , Neill C. R. , Sawatsky L. F. , Mannerstrom M. C.
Published: January 2010

The Ok Tedi mining development in Papua New Guinea is served by a 50 MW hydroelectric plant completed in 1988. The plant draws water from a run-of-river intake on the Ok Menga, a torrential mountain stream in tropical rain forest subject to frequent flash floods and carrying substantial sediment loads. Design and construction of a diversion weir and intake posed a number of severe problems, such as difficult access, the torrential and flashy nature of the river flows, severe constraints on location due to unstable banks and substrata, and uncertain loads of sediment and debris. Site investigations of a hydro technical nature included monitoring of precipitation, streamflow and flood levels, sampling of suspended sediment, and special measurements of bed material and bed load. On the basis of these investigations, preliminary concepts were developed for a diversion weir and intake chamber. A hydraulic model was then constructed to examine alternative forms of weir construction and to study the hydraulic behaviour of various intake chamber designs with special attention to exclusion and ejection of coarse sediment. The final design was based largely on the indications of the model study. Initial operating experience generally confirmed the validity of the design, although one or two problems arose that were not sufficiently appreciated at the design stage. These were mainly associated with organic debris and with excessive inflow of coarse sediment due to inexperienced operation. Relatively minor changes were made in operational procedures and equipment in order to remedy these problems. Key words: river, intake, sediment, diversion, weir, bedload, debris, torrent.
A knowledge-based expert system for flood frequency analysis
Authors: Chow K. C. Ander , Watt W. E.
Published: January 2010

Single-station flood frequency analysis is an important element in hydrotechnical planning and design. In Canada, no single statistical distribution has been specified for floods; hence, the conventional approach is to select a distribution based on its fit to the observed sample. This selection is not straightforward owing to typically short record lengths and attendant sampling error, magnified influence of apparent outliers, and limited evidence of two populations. Nevertheless, experienced analysts confidently select a distribution for a station based only on a few heuristics. A knowledge-based expert system has been developed to emulate these expert heuristics. It can perform data analyses, suggest an appropriate distribution, detect outliers, and provide means to justify a design flood on physical grounds. If the sample is too small to give reliable quantile estimates, the system performs a Bayesian analysis to combine regional information with station-specific data. The system was calibrated and tested for 52 stations across Canada. Its performance was evaluated by comparing the distributions selected by experts with those given by the developed system. The results indicated that the system can perform at an expert level in the task of selecting distributions. Key words: flood frequency, expert system, single-station, fuzzy logic, inductive reasoning, production system.