bluuebunny/crossref_metadata_2025 huggingface dataset:
A prototype knowledge-based expert system for the design and detailing of reinforced concrete beams
Authors: Akhras George , Fedoruk John A.
Published: January 2010

Most computer programs developed for reinforced concrete beam design either analyze a given cross section for load capacity or offer a limited solution from which the engineer must continue toward the final design. These programs are very useful in performing many tedious calculations. However, they generally do not offer assistance in areas of design that require intuitive reasoning, experiential knowledge, rules of thumb, and sound engineering judgement. This type of heuristic knowledge has been incorporated into a prototype knowledge-based expert system for reinforced concrete beam design and detailing called BeamEx. BeamEx interacts with the user to advise and establish suitable parameters required for the comprehensive design of rectangular simply supported and continuous beams. It incorporates heuristic rules drawn from the governing Canadian codes and textbooks to design alternative suitable beams which are presented in graphical form. It is shown that a knowledge-based system approach can be used effectively in engineering design by encapsulating domain expertise in a program to complement and check the experience of the users in design. Key words: knowledge-based expert system, reinforced concrete, beams, design, detailing.
Use of tilt sensing equipment for monitoring long-term bridge movement
Authors: Wipf Terry J.
Published: January 2010

Accurate monitoring of long-term movements in bridges can be difficult primarily because of the relatively long time period over which the movements occur and inadequate instrumentation and technique. A stable reference point for measurements is difficult to obtain over these long time periods. Two bridges were monitored for long-term structural movement; the results are presented here. Instrumentation including temperature transducers and tilt sensors placed on and near piers determined the pier movement. The results of the study indicate that a superstructure expansion pier on one of the bridges monitored actually behaved as a fixed pier. The equipment used in the study, including data acquisition components and tilt sensors, proved reliable and accurate. Key words: bridges, girder, field tests, foundations, measurement instruments, piers, structural engineering.
Performance-based specifications for pavements
Authors: Kuzyk P. , Haas R. C. G. , Cockfield R. W.
Published: January 2010

Pavements represent a very substantial portion of the public's investment in infrastructure. It is essential that this investment be preserved through cost-effective planning, design, and maintenance. One way of achieving this is through the use of long-term performance-based specifications. This paper first describes the current practice for pavement specification. For the most part, these specifications are "recipe" orientated. Very specific requirements are set for procedures, such as compaction, or as constructed properties such as density. With the proposed system, the contractor would be required to warranty the actual performance of the pavement over an extended term. The paper describes the overall scope of the system, its key elements and advantages, and the major risk factors. As well, the measures that can be used to characterize performance and a model for estimating performance are identified. A stochastic formulation of the model is used to present a method of determining the risk to the contractor based on a design example. Finally, the paper explores some of the concerns associated with the implementation of the system and how these concerns might be addressed. Key words: long-term warranties, pavement contracting, pavement performance.
Freeze–thaw sludge conditioning and double layer compression
Authors: Vesilind P. Aarne , Wallinmaa Seppo , Martel C. James
Published: January 2010

Freeze–thaw conditioning of water and wastewater sludges is known to be an effective and economical means of promoting dewatering when natural freezing is employed. When sludge freezes, both the suspended and dissolved solids are rejected by the growing ice front. Particles trapped in ice are known to have a very thin layer of water surrounding them and this water does not freeze at normal temperatures. Dissolved solids are thought to accumulate in this layer, causing an increase in the ionic strength of the water. This may cause compression of the double layer, leading to neutralization of repulsive forces, thus promoting aggregation. In order to test this hypothesis, ionic strength was increased by adding sodium chloride (NaCl) to water and wastewater sludges and measuring dewaterability (filtration) with the capillary suction time (CST) apparatus. Four different kinds of sludge were used: alum sludge (water treatment), waste-activated sludge, simultaneous precipitation, and anaerobically digested mixed sludge. Salinities of 0–20 000 mg/L as NaCl were tested with every sludge. No enhancement in dewaterability with freeze–thawed sludges of raised ionic strength compared to zero salinity was recorded, therefore the hypothesis of double layer compression being a major factor in freeze–thaw conditioning does not seem to be correct. Key words: sludge, freezing, coagulation, dewatering.
Déformations générées dans les bétons sous l'influence des conditions climatiques
Authors: Ballivy Gérard , Benmokrane Brahim , Chaallal Omar
Published: January 2010

This paper presents the results of an experimental study of strains generated in concrete by variations in climatic conditions. Three 0.16 m3 concrete blocks, instrumented with vibrating wires strain gauges, were exposed to various environmental conditions (drying–wetting) during approximately 3 years and strains were measured. The study shows that concrete strains induced by environmental agents acting alone can reach levels that may jeopardize the structural integrity of concrete structures exposed to similar conditions, when the boundary conditions cannot accommodate the resulting extensive volume changes. Key words: environmental conditions, relative humidity, temperature, drying, wetting, vibrating wires strain gauge, concrete strains.
Flexural tests of two full-scale composite trusses
Authors: Brattland Anita , Kennedy D. J. Laurie
Published: January 2010

Steel trusses acting compositely with concrete slabs on wide rib profile steel deck have proven to be an economical system for long span floors. The flexural behaviour of two composite trusses with a span of 11.5 m was studied. The truss configuration consisted of hollow structural section chords with double angle web members welded on either side. The flexural tests showed that ductile behaviour up to failure can be obtained without failure of the web members, provided that the design is based on the ultimate tensile strength of the bottom chord, and the web members and shear connection are designed for the concomitant forces. The maximum moments attained were about 1.2 times the unfactored ultimate moment predicted by CSA Standard S16.1. The maximum strain in the bottom chord of both trusses was significantly higher than the yield strain, but did not reach the ultimate strain due to premature shear connection failure. The failure mode of the first composite truss demonstrated the need for additional rules for establishing the length of stud shear connectors for use in slabs on ribbed deck, as has been incorporated in S16.1-M89. A design procedure for double angle web members was developed, based on the test results. Key words: behaviour, composite steel–concrete trusses, flexure, long span, ultimate moment resistance.
Shrinkage tests of two full-scale composite trusses
Authors: Kennedy D. J. Laurie , Brattland Anita
Published: January 2010

The shrinkage behaviour of two composite trusses with a span of 11.5 m was studied. Shrinkage measurements to determine the effects of slab shrinkage on truss deflections and member strains were recorded over periods of 65 and 85 days. A method is developed to compute shrinkage deflections, based on equilibrium of the shrinkage-induced forces at midspan, which gives excellent agreement with the test results. This method assumes a linear strain distribution through the depth and is based on the free shrinkage strain of the concrete and the average stress–strain characteristics of the concrete in tension under restrained shrinkage conditions as it drys, creeps, and eventually may crack as it is gradually loaded from the green state. The method is extended to composite steel-beam concrete-slab members. It is equivalent to Branson's "composite section method" provided that the correct values for the shrinkage strain and the effective modulus of elasticity of the concrete in tension are used in the latter. Key words: behaviour, composite steel–concrete beams, trusses, shrinkage deflections.
Behaviour of transversely loaded continuous steel-concrete composite plates: analyses and design applications
Authors: Kennedy Stephen J. , Cheng J. J. Roger
Published: January 2010

A flexural and membrane model and a failure criterion have been developed to describe the load–deflection response of two-dimensional continuous flexible steel–concrete composite plates. These nonlinear analytical models have a wide range of applicability and are not limited by plate thicknesses, section depth, material properties, or boundary stiffness. Although the analytical models were developed for a particular load configuration, they can be modified to apply equally well to other load configurations.The overall behaviour of the composite plates ranged from flexural to membrane behaviour; and within the ranges of applicability of the models developed for flexural and membrane behaviour, there is good agreement with the test data. The limiting strength of the composite plates is a function of the internal stresses in the steel plates, and is given by the failure criterion which is based on a combined stress state of shear and tension and an extension of the von Mises–Huber–Hencky yield criterion to ultimate. The mean test-to-predicted ratio for the ultimate load was 1.128, with a coefficient of variation of 0.037.The models, together with the failure criterion, allow the design engineer to easily apply a two-load-level design philosophy, consistent with limit states design format, for the design of flexible steel–concrete composite plates. Key words: analysis, composite, concrete, design applications, ductility, energy absorption, flexible, flexural behaviour, membrane behaviour, plates, steel.
Analyse hydro-météorologique des débâcles de glaces de la rivière Nashwaak (Nouveau-Brunswick)
Authors: Hebabi S. , El-Jabi N. , Sarraf S.
Published: January 2010

The problems associated with ice cover formation, development, and breakup are numerous. In fact, every year ice breakup and ice jams cause damage throughout Canada. In New Brunswick, ice breakup is responsible for 35% of floods and 70% of damage to bridges. This paper describes a hydro-meteorological analysis of ice breakup along the Nashwaak River in New Brunswick. Thirteen events that occur between 1969 and 1982 were studied. First, river records were used to determine a breakup initiation index. A dimensional analysis was then performed integrating the index with meteorological variables and river flows. Although there was no resemblance between variations of meteorological factors from one event to the next, the results suggest that the index formulated has potential as a tool for development of predictive models for ice breakup. Key words: ice breakup, ice jam, floods, meteorology, flow, predictive model, damages, bridges, Nashwaak River.
Comparison of bottom and surface cooling water withdrawals on the thermal regime of Hamilton Harbour
Authors: Lee Daesoo , Hamblin P. F. , Smith A. A. , Snodgrass W. J.
Published: January 2010

An analysis of the sensitivity of the annual thermal regime of Hamilton Harbour to the depth of intake of industrial cooling water was conducted using a one-dimensional thermodynamic model. The intake of approximately 20 m3/s of cooling water from the bottom of the harbour, as opposed to the current practice of surface withdrawal, was calculated; the result indicates marginally reduced thermal stratification and hypolimnetic volumes in summer. It was shown by a further sensitivity analysis that the reason for this relatively weak response to the withdrawal level was due to the overwhelming input of colder Lake Ontario water to the Harbour. Key words: harbour water quality, thermodynamic modelling.
Development of speed curves and traffic flow measures for the Highway User Benefit Assessment model
Authors: Robichaud Karen , Wilson Frank , Christie James
Published: January 2010

Transport Canada has developed a model, called the Highway User Benefit Assessment Model (HUBAM), as part of their assessment procedure for selecting projects for federal funding. A key step in this model is the estimation of average speed. These speed equations are the focus of the research on which this paper is based.The University of New Brunswick (UNB) recently completed a research project funded by Transport Canada and the New Brunswick Department of Transportation on the factors that influence highway speed. The purpose of the study was to develop speed equations for the Province of New Brunswick which could be incorporated into HUBAM. As part of the research, this paper evaluated the accuracy of the default equations in HUBAM relating speed and flow rate.An analysis of the speed and traffic flow data indicated that HUBAM underestimates speed for New Brunswick conditions. The low estimates appear to result from the curves of speed versus volume to capacity. It was concluded that regression equations developed by UNB should provide more realistic results, since the UNB equations provide a superior estimate of the observed field data. Key words: speed, traffic flow, highway access, highway user costs.
Overview of seismic provision changes in National Building Code of Canada 1990
Authors: Tso W. K.
Published: January 2010

This paper highlights the changes of the seismic provisions in the 1990 edition of the National Building Code of Canada (NBCC) and provides the reasons and interpretations for these changes. The major changes include load factor for earthquake load, base shear formula, force modification factor in place of structural coefficient, story drift estimation, design and anchorage force for parts of portions of building, importance factor, foundation factor, and top concentrated force on structure. A comparison of the base shear calculated according to NBCC-1985 and NBCC-1990 is given to show that the base shears for most structural systems are similar. The major exceptions are the ductile flex-ural wall systems and the unreinforced masonry system. The base shear is reduced for the former system and increased for the latter system in NBCC-1990. Key words: earthquake, seismic design, code, lateral loading, overstrength.
New designs for vertical slot fishways
Authors: Rajaratnam N. , Katopodis C. , Solanki S.
Published: January 2010

This paper presents the results of an experimental study on 18 designs of vertical slot fishways. Based on these results, it appears that a width of 8b0 and a length of 10b0 for the pools, where b0 is the slot width, are satisfactory, and minor variations can be made to these dimensions without affecting their satisfactory performance. In the two general groups of designs, design 6 in the first group and designs 16 and 18 in the second group are recommended for practical use. Key words: fishways, hydraulics, turbulent flow, open-channel flow, hydraulic design.
Monotonie and cyclic tests of timber shear walls
Authors: Dolan J. D. , Madsen B.
Published: January 2010

The results for monotonic (ramp load) and slow cyclic racking tests of timber shear walls are presented. The tests are part of an extensive experimental and analytical study to investigate the behaviour of timber shear walls subjected to earthquakes. The results of full-size shear wall tests show the important influence of the nail connection between the sheathing and the framing on the load-displacement characteristics of shear walls. The premise that the hysteresis for the shear wall is contained within an envelope defined by the monotonic load-displacement curve for the wall is confirmed. Also, the hysteresis is studied to determine the physical behaviour that causes the shape of the hysteresis to be dependent on the maximum displacement of the wall. Both the monotonic and cyclic racking behaviours of timber shear walls are established; and the performances of plywood and waferboard sheathed shear walls are compared. Key words: full-scale monotonic and cyclic tests, plywood, waferboard, timber shear walls.
Confinement limits for tension lap slices under static loading
Authors: Rezansoff T. , Konkankar U. S. , Fu Y. C.
Published: January 2010

In tension lap splices, the benefit provided to the lap by stirrups placed to intercept longitudinal cracking due to bond splitting action is recognized by the American Concrete Institute code (ACI 318-89) and the design recommendations of ACI Committee 408, on which the American code provisions are partially based. However, a limit exists on the benefit that can be derived from this confinement. In Canada, Canadian Standards Association Standard CAN3 A23.3 M-84 does not directly recognize the confinement benefit provided by stirrups placed along a lap splice. The current study shows that the ACI limit of 1 bar diameter of equivalent concrete cover provided by the transverse reinforcement confinement is too restrictive under static loading. When the concrete cover is small, much larger transverse reinforcement confinement, up to 2-2.5 bar diameters of equivalent concrete cover, can be utilized, in lieu of requiring very long lap lengths. The tests also show that total confinement (actual concrete confinement plus equivalent concrete confinement provided by stirrups) is effective beyond the current limit of 3 main bar diameters, when stirrups are provided. Good performance was found with confinements of 4-4.5 bar diameters, and correspondingly shorter lap splice lengths. Key words: concrete, reinforcement, lap splices, beams, confinement, stirrups, tension, static loading.
Stability of conduit walls of soil-steel bridges
Authors: Abdel-Sayed George , Girges Youssef
Published: January 2010

The problem of stability of the conduit walls of soil-steel structures has been examined by many investigators using either the continuum theory or the Winkler approach in which the soil media is replaced by spring supports. Because of the form of application and assumptions, the continuum analysis overestimates the buckling load while the Winkler analysis underestimates the buckling load. The present paper examines the causes of the discrepancy between the published results obtained from the continuum and the Winkler analysis and arrives at a rationally realistic buckling formula. Furthermore, the effect of spacing between multispan conduits is examined and is taken into consideration in the modified buckling equations, which are adopted by the forthcoming Ontario Highway Bridge Design Code. Key words: conduit, corrugated steel, elastic-plastic, stability, soil-steel bridges.
Potential applications of neural networks in construction
Authors: Moselhi Osama , Hegazy Tarek , Fazio Paul
Published: January 2010

During the past decade, several engineering disciplines, including construction, have embarked on developing “intelligent” decision support systems based on artificial intelligence (AI) techniques, including expert systems, symbolic knowledge representation, and logic programming. These systems attempt to capture the domain experts' intelligent behaviour and reasoning process utilized in decision-making, without regard to the underlying mechanisms producing that behaviour. This approach involves describing behaviours, usually with rules and symbols. In contrast, neural networks (NN), another AI-based technique that has been pursued on a large scale during the past few years, does not describe behaviours but rather imitate them. Neural networks are particularly superior to traditional expert systems in providing timely solutions based primarily on analogy with previous experience, rather than reasoning or computation. As such, neural networks have a great potential to work either as a supplement or as a complement to algorithmic and (or) other AI-based systems, providing more suitable tools for solving the industry ill-structured problems.This paper describes several characteristics of neural networks and outlines the advantages and limitations of commonly used NN paradigms. Potential applications of each paradigm in construction are identified. Two example applications are provided to demonstrate the problem-solving capabilities of neural networks: (i) estimation of hourly production rate of an excavation equipment; and (ii) estimation of productivity level for a construction trade. Future possibilities of integrating neural networks with other problem-solving techniques are described. Key words: construction, management techniques, neural networks, expert systems, pattern recognition, computer applications.
Soil–steel structure design by the third edition of OHBDC
Authors: Abdel-Sayed George , Bakht Baidar , Selig Ernest T.
Published: January 2010

The Ontario Highway Bridge Design Code (OHBDC) introduced in 1979 a new set of provisions for the design of soil–steel bridges. Some of these provisions have been revised in the third edition of OHBDC (1991) to reflect the outcome of research that has been conducted since. This paper presents details of these revisions and provides the reasons for their inclusion. In particular, a new method of calculating dead load thrust and improvement to the buckling analysis of the conduit wall are discussed. Key words: buckling, pipe-arch, soil–steel structure, thrust.
Nonlinear earthquake response of structurally interconnected buildings
Authors: Filiatrault André , Folz Bryan
Published: January 2010

This paper evaluates the performance of closely spaced plane steel framed buildings interconnected by horizontal structural links to prevent pounding during earthquake excitations. Friction damping capability is incorporated into the modelling of these structural links in order to also determine their potential for dissipating energy during a seismic event. Six pairs of building models, having widely different dynamic characteristics, are considered in this investigation. A parametric study, utilizing nonlinear time-history dynamic analysis, is performed to determine the optimum properties for the structural links when each building pair is excited by three different historical earthquake ground motions. This is followed by a detailed reponse analysis comparison of each of these optimized friction damped coupled structures against their uncoupled and elastically coupled counterparts. Key words: earthquake, steel, frames, inelastic, pounding, friction, damping.
A sensitivity method for ice floe trajectory calculations
Authors: Thomson N. R. , Sykes J. F.
Published: January 2010

The simulation of an ice floe trajectory normally involves the solving of a physically based governing equation in order to determine the temporal variation of ice floe velocities. As part of this calculation process, a sensitivity analysis is usually undertaken to determine the response of the solution to variations in the system or input parameters; thus providing a quantitative procedure to help interpret the results of the simulation. In this paper, a versatile sensitivity method is described, which can be employed in this sensitivity analysis. This sensitivity method is based on the adjoint operator technique which involves the calculation of an adjoint state variable. The required sensitivities are determined from the temporal variation of this adjoint state variable and the ice floe velocity. The results from a comparison between a numerical and an analytical solution for a one-dimensional free drift ice floe example are presented. In addition, an example dealing with the sensitivity of the distance between a drilling location and an ice floe trajectory to changes in the input parameters is discussed. Key words: free drift, sensitivity, adjoint, ice floe, transient, iceberg.
Use of Akaike information criterion for selection of flood frequency distribution
Authors: Chow K. C. Ander , Watt W. Edgar
Published: January 2010

When conducting a conventional single-station flood frequency analysis, an appropriate distribution must be selected. Typically, sample statistics, probability plots, goodness-of-fit tests, etc. are used to facilitate the decision process. For the predominate case of a relatively short record length of flood series, this standard approach leads to undue emphasis on goodness of fit and virtually no consideration of the uncertainty due to additional parameters. The information criterion suggested by Akaike (AIC) is a measure to evaluate the "benefit" of goodness of fit and the "cost" of parameter uncertainty. The criterion is tested for 42 long-term hydrometric stations across Canada and its applicability and limitations are demonstrated in eight samples. The AIC is recommended as an aid in selecting a flood frequency distribution. Key words: flood frequency, goodness of fit, single station, information criterion.
Assessing effluent fluoride concentrations following physicochemical wastewater treatment
Authors: Gehr R. , Leduc R.
Published: January 2010

The anticipated fluoride concentrations in untreated wastewater, as well as their removal during physicochemical treatment, were determined in order to assess potential risks to the aquatic ecosystem of the St. Lawrence River due to proposed fluoridation of Montreal's drinking water. Monitoring of the raw wastewater yielded average daily fluoride concentrations of 0.22–0.58 mg/L, but discrete sample concentrations ranged from 0.20 to 1.11 mg/L. This indicates that significant massive point discharges occur in the Montreal Urban Community (MUC) sewer system. Jar tests suggest that no precipitation of fluoride would occur following ferric chloride and polyelectrolyte addition at doses similar to those used on the full-scale wastewater treatment plant. This is confirmed by thermodynamic analysis of the solubility of various fluoride species. Full-scale tests, conducted by applying a continuous fluoride dose to the plant influent, confirmed that no removal would result from the treatment process. However, the plant did dampen the shock loads of fluoride from industrial sources. The predicted average raw wastewater fluoride concentration, including ground water and unidentified industrial discharges, was calculated to be 0.83 mg/L. Unidentified sources contribute 132 kg/d (~ 40% of the total). The average fluoride flux in the St. Lawrence River, as a result of fluoridation of the drinking water, would increase by 1.2%. Key words: fluoridation, physicochemical wastewater treatment, St. Lawrence River, mass balance analysis.
Highway cost allocation methodologies
Authors: Ambo Alemayehu , Wilson F. R. , Sevens A. M.
Published: January 2010

Four methodologies of life-cycle highway cost allocation were examined using the province of New Brunswick, Canada, as a case study. The first two methodologies were reported by Wong and Markov. The third methodology was suggested by Rilett et al. The fourth methodology was introduced as part of the research project. It was in line with the procedures practised in public accounts for the construction and maintenance of roads on a continuing basis. The four methodologies were tested using the same data base pertaining to vehicle types; traffic measures (independent vehicle, passenger car equivalents, and equivalent standard axle loads); and costs of construction, maintenance, and rehabilitation. These data were applicable to a major two-lane highway in the study area. Six sites were selected for the case study. An analysis period of 60 years, three traffic growth scenarios, and three pavement design periods were considered. Eleven types of vehicles, comprising passenger cars, light trucks and vans, trucks, buses, and recreational vehicles, were used in the analysis. The assessment of the methodologies resulted in the recommendation of, and the suggestions for, the costing of highways. Key words: equivalent standard axle loads, passenger car equivalents, vehicle count, life-cycle costing, unit costs, accumulated costs, annual costs, discounted costs.
Extreme values of thermal loading parameters in concrete bridges
Authors: Maes Marc A. , Dilger Walter H. , Ballyk Peter D.
Published: January 2010

The present paper addresses the question of developing design criteria for thermal effects in concrete bridges. The objective is to determine extreme temperature effects having specified return periods. The parameters of the local meteorological regime which critically affect the extreme thermal effects are identified. Their variation in time is analyzed and related to the thermal loading parameters in a concrete bridge. These include average temperature, temperature difference between sections, linear temperature differential, and residual temperature fields. The analysis of the extreme values of these parameters is described in detail.The reduction of data, the model development, and the statistical analysis are clarified by the application to the Bow River light rail transit bridge in Calgary, Alberta. Temperature profiles in several sections of this structure are being measured on an hourly basis. The findings of this study show certain shortcomings of the temperature effects design criteria currently included in the Canadian bridge design codes. Key words: extreme values, design temperature, thermal loading, thermal gradients, temperature measurements, concrete box girder bridges.
Development of disaggregate mode choice models of intercity travel in Canada
Authors: Abdelwahab Walid M. , Innes J. David , Stevens Albert M.
Published: January 2010

This paper reports and discusses the results of an effort to develop disaggregate behavioral mode choice models of intercity travel in Canada. Currently available data bases of intercity travel in Canada are reviewed. The feasibility of using data from national travel surveys to develop statistically reliable intercity mode choice models is examined, and directions for future disaggregate data collection efforts are offered. The models developed are of the multinomial logit (MNL) type which included all intercity passenger travel modes: auto, air, bus, and rail. For purposes of estimation, the travel market was segmented by trip length (short, long); trip purpose (business, recreational); and geographical location of the trip (east, west). Then, a separate model was estimated in each sector. The models were estimated using the data collected by Statistics Canada as a part of the Labor Force Survey (The Canadian Travel Survey, CTS). The quality of the calibrated models varied from one region to another and from one travel sector to another. Overall, the models were reasonably accurate in predicting modal shares of the most frequently used modes (auto and air). The underrepresentation of the bus and rail modes in the data sets led to a deterioration in the performance of the models in predicting market shares of these two modes. More specifically, the predictive ability of the models measured by the likelihood ratio index varied from a low of 0.58 in the short travel sector to a high of 0.94 in the long travel sector. The transferability of the models described in this study was recently examined by Abdelwahab (1991). Key words: mode choice, disaggregate, travel behavior, multinomial logit, intercity, data base.
La durabilité au gel des bétons à haute performance
Authors: Pigeon Michel , Gagné Richard , Aitcin Pierre-Claude , Langlois Marcel
Published: January 2010

Frost resistance of high-strength concrete (80–100 MPa) was studied by subjecting 44 concrete mixes to freeze–thaw cycles in water (ASTM C666, standard procedure A) and to scaling tests in the presence of deicer salts (ASTM C672, standard). The test programme was designed to analyze the effects of the water/cement ratio, the type of cement, the type of coarse aggregate, the duration of curing, and the air-void spacing factor. Results demonstrate that the water/cement ratio limiting value, below which entrained air is no longer necessary to protect concrete against freeze–thaw cycles, is sometimes higher than 0.30 but is more often below 0.25. This limiting value is affected most by cement characteristics: type 30 cement yielded much more durable concretes. Laboratory scaling tests demonstrated that when water/cement ratios are less than 0.30, the resistance deicer salt is generally very good, no matter what are the type of cement, the silica fume content, or the air-void spacing factor of the concrete. Key words: durability, freeze–thaw cycle, silica fume, scaling, curing, spacing factor, water/cement ratio, compressive strength, cement type, entrained air, aggregate. [Journal translation]
Canadian highway bridge evaluation: a general overview of Clause 12 of CSA Standard CAN/CSA-S6-88
Authors: Buckland Peter G. , Bartlett F. Michael
Published: January 2010

Because upgrading a bridge is usually far more costly than incorporating extra capacity at the design stage, a different approach is appropriate. Clause 12 of CAN/CSA-S6-88, published in 1990, was developed specifically for evaluation. The development of Clause 12 is reviewed, as is the philosophy of varying the load factors based on how well the loads are known, the consequences of failure, and other variables. An overview of Clause 12 is presented and reference is given to three companion papers describing the derivation of numerical values used in Clause 12 and their adaptation for the Standard. Key words: bridges, evaluation, assessment.
Canadian highway bridge evaluation: reliability index
Authors: Allen D. E.
Published: January 2010

So that the limited funds available for bridge upgrading can be spent in the most effective manner, the reliability index assumed for evaluation of existing bridges requires a closer definition than that assumed for the design of new bridges. A reliability index which varies between 2.0 and 3.75 is determined for bridge evaluation in Clause 12 of CAN/CSA-S6-88 on the basis for life-safety considerations and calibration to experience. The reliability index is chosen by the evaluator as a function of structural behaviour, level of inspection and evaluation, and traffic situation for which the evaluation is made, all of which affect life safety. Economic considerations are also taken into account; the highway authority may, however, wish to increase the values of the reliability index for critical bridges whose failure seriously affects the traffic network. Key words: bridge evaluation, reliability index, life safety, economics.
Canadian highway bridge evaluation: load and resistance factors
Authors: Kennedy D. J. Laurie , Gagnon Darrel P. , Allen David E. , MacGregor James G.
Published: January 2010

Consistent load and resistance factors are developed for a range of target values of the reliability index, β, following first-order second-moment analysis techniques for use in the evaluation of highway bridges. Dead load factors are established for steel girders, concrete girders, concrete bridge decks, and wearing surfaces, taking into account the statistical variations of weights and the range of load fractions as determined from field measurements. Live load factors are established for four categories of live loads: NP — non-permit traffic that are permitted by legislation; PM — permit, multiple trip, bulk haul, divisible loads; PS — permit, single trip, unsupervised, mixed with non-permit traffic; and PC — permit, controlled, supervised extremely heavy loads with escort. These live load factors are based on field surveys of truck weights, in Alberta and elsewhere. The event curves for NP, PS, and PM traffic have been used to determine the maximum annual truck, as the period of evaluation was chosen as 1 year based on a life-safety criterion-related to the consequences of failure. Because PC traffic is so rare, it was dealt with on an event basis. Impact data of others were analyzed to determine the appropriate bias coefficients and coefficients of variation. Uncertainties in the transverse distribution of both dead and live loads were also considered.Resistance factors are based on statistical data reported in the literature and take into account the variation in material properties, member size, and the resistance formulations. Key words: dead and live load factors, resistance factors, impact, maximum annual, traffic categories, transverse distribution, weight fractions.
Performance of alternative methods of bank protection
Authors: Doyle P. F.
Published: January 2010

The durability of several common bank protection methods used as less expensive or environmentally acceptable alternatives to toe-trenched angular rock riprap has been documented during the 1980s at seven typical bank erosion sites in British Columbia. Since the sites were uncontrolled examples of actual river training works in operation, natural events hindered a precise comparison of each scheme with toe-trenched angular rock riprap protection. However, of the four alternatives investigated – gravel dykes, tree revetments, riprap with toe apron, and semi-round riprap – all but semi-round riprap performed less than satisfactorily over the years of observation. Documentation of performance is sufficient to conclude that on steep gravel-bed rivers, gravel dykes do not endure; tree revetments require constant maintenance and will not endure large floods, unless extremely well-constructed; toe aprons are not as reliable as toe trenches for the same volume of rock; and well-placed, large semi-round rock performs well under moderately severe attack. Key words: erosion, bank protection, channel stability, river training structures, gravel-bed.
Urban snow dump quality and pollutant reduction in snowmelt by sedimentation
Authors: Droste R. L. , Johnston J. C.
Published: January 2010

Four snow dump sites in the Ottawa-Carleton region were analyzed for BOD, total and fecal coliforms, chlorides, sulfates, specific conductance, suspended solids, metals, and other parameters. Sites were sampled at various depths during the months of February through May. There was no trend in variation of quality in the dump piles with time. The black crust that formed on the top of the pile was heavily laden with solids and metals.Snowmelt samples were also taken over the same time period and analyzed for the above parameters. The process of snowmelt reduced the concentrations of most metals and suspended solids from the dump by 50–70%. Dissolved constituents in snowmelt are discharged at very high levels during the initial stages of snowmelt and rapidly decrease to low concentrations. Suspended solids and associated metals in snowmelt exhibited variability with snowmelt conditions and the state of the dump pile. The concentrations of a number of metals in settled snowmelt exceeded provincial objectives for surface waters.An analysis of settled snow dump and snowmelt samples for suspended solids and metals was conducted for settling periods of 1, 6, 12, and 24 h. A settling time from 2 to 6 h would achieve most of the removal that could be expected from sedimentation. The overall removal of suspended solids and the metals in settled snowmelt would generally be better than 90%. There were no significant trends in removal behavior as the snowmelt season progressed. The removal of metals lagged slightly behind the removal of suspended solids after settling because of the stronger association of metals with smaller sediment particles. The residue at the dump site is highly contaminated. Key words: snowmelt, runoff, stormwater, sedimentation, road deicing, snow dump, pollution.
Behaviour of volatile and nonvolatile suspended solids in the pilot-scale aerobic digestion of waste-activated sludges
Authors: Anderson B. C. , Mavinic D. S.
Published: January 2010

Pilot-scale research into the characterization and enhancement of the aerobic digestion of waste-activated sludges was performed. Waste sludge from two sources was aerobically digested at varying operating temperatures; to offset the naturally occurring mixed liquor pH (MLpH) decrease due to nitrification, small amounts of Ca(OH)2 or NaHCO3 were added to maintain target MLpH levels of pH 6, 7, and 8. Results indicated that volatile mass reduction was severely curtailed at low MLpH, but could be significantly improved through MLpH control, with increases of > 100% in performance over the low MLpH reactor noted. However, the process was found to be very "sludge-specific", in that the two test sludges behaved quite differently under similar operating conditions. A separate mass balance on the nonvolatile sludge fraction illustrated the action of the controlling chemicals in terms of reduction in cell lysis; it was also observed that some precipitation of inorganic materials was occurring, depending on chemical type and dose. While it was not possible to suggest an optimized chemical and dose, it was concluded that this process had very real potential for full-scale implementation, as an effective and simple method for rehabilitation of poorly functioning digesters. Key words: aerobic sludge digestion, Ca(OH)2, enhancement, inhibition, mixed liquor pH control, NaHCO3, volatile and nonvolatile suspended solids.
Unidirectional spreading of oil under solid ice
Authors: Weerasuriya Sujeeva A. , Yapa Poojitha D.
Published: January 2010

A theoretical and experimental study on unidirectional spreading of oil under solid ice in calm waters is presented. The emphasis of the study is on the dominant spreading mechanism for oil under ice, which is the buoyancy-viscous phase. The equations derived cover both the constant discharge and the constant volume modes. Laboratory experiments were conducted for ice cover roughnesses varying from smooth to rough, using different discharge rates, and oils of different viscosities. The experimental results agree closely with the theory. Key words: oil spreading, oil slicks, oil under ice, buoyancy-viscous phase, constant discharge, constant volume.
Biolixiviation des métaux lourds et stabilisation des boues d'épuration : essai en bioréacteur opéré en mode cuvée
Authors: Tyagi R. D. , Blais J. F. , Meunier N. , Kluepfel D.
Published: January 2010

A biological process of heavy metals solubilization and sewage sludge stabilization was studied in a batch reactor of 30-L capacity. The acclimatized leaching microflora was composed of two major groups of thiobacilli: less acidophilic and acidophilic. A batch time of 10 days allows a substantial metal solubilization: cadmium (100%), copper (80%), manganese (80%), nickel (46%), and zinc (100%). The bioleaching process also causes a significative decrease in sludge total suspended solids (25%) and volatile suspended solids (32%), and a considerable reduction (under the detection limit of 10 cfu∙mL−1) of indicator bacteria (total coliforms, fecal coliforms, fecal streptococci). After filtration or centrifugation of the leached sludge, the solubilized metals were precipitated by lime neutralization. The phosphorus and potassium sludge contents were not affected by bioleaching process. These results indicate that the process of sludge digestion and metal leaching can be conducted in parallel in the same reactor. Key words: sewage sludge, heavy metals, bioleaching, stabilization, thiobacilli, elemental sulfur.
Evaluation of foundation tie requirements in seismic design
Authors: Heidebrecht A. C. , Rutenberg A.
Published: January 2010

A simple structural model is proposed to evaluate the axial force acting on tie beams interconnecting spread footings or pile caps due to differential ground motion estimated on the basis of the travelling wave assumption. The approach is intended to supplement the "ten percent rule" or similar multipliers specified by seismic codes as design axial forces on tie beams. It is shown that the axial force demand is rather modest. However, shear forces between footing and soil may be quite large depending on maximum column displacements and superstructure rigidity. Key words: foundations, tie beams, earthquake, travelling waves, seismic codes.
A regression method for estimating suspended sediment yields for ungauged watersheds in Atlantic Canada
Authors: Bray Dale I. , Xie Huixi
Published: January 2010

The problem of estimating suspended sediment yields from ungauged watersheds is described. Results from regression analyses using hydroclimatic and geomorphic variables are presented for 14 watersheds in Atlantic Canada. Estimates are given for long-term mean suspended sediment yields and for annual suspended sediment yields for a particular year. The effects of incorporating an added constant term in the regression equation are considered. Limited tests are presented for two small watersheds not used in the development of the adopted regression equations. Key words: suspended sediment yields, ungauged watersheds, regression analysis, Atlantic Canada.
Numerical computation of river ice jams
Authors: Beltaos S.
Published: January 2010

A numerical model called RIVJAM has been developed to compute the configuration of and water levels caused by ice jams of the "wide" kind, under natural stream conditions and regardless of whether the jam has attained its full potential, known as equilibrium. Account of seepage flow through the voids of the jam enables predictions of grounding conditions to be made, in accord with observations. The model is applied to three case studies of ice jam events and found to perform satisfactorily. The various model coefficients fall within the expected ranges, with the exception of a parameter characterizing the intensity of seepage flow. More field data are needed to elucidate this matter. Key words: grounding, ice, jam, model, numerical, river, seepage, thickness, toe, wide.
Laboratory and field performance of high alumina cement-based grout for piling in permafrost
Authors: Biggar K. W. , Sego D. C. , Noël M. M.
Published: January 2010

A grout for use in pile installation in permafrost is described. The high alumina cement (Ciment Fondu) based grout cures by rapidly evolving heat which maintains it above 0 °C until it hydrates and hardens. The laboratory development program of the mix design along with the cement admixtures which allows the grout to cure at temperatures as low as −10 °C and to remain workable during field use is reviewed. The development of installation procedures for the grout during construction of short range radar foundations is described along with field measurements of the compressive strength and the temperature profiles of the grout after placement in permafrost as cold as −14 °C. The Ciment Fondu grout performed according to the design requirement of hardening without freezing in permafrost colder than −10 °C during the installation of about 2000 piles for part of the short range radar project. Key words: permafrost, grout, laboratory, field, installation procedure, mix design.
Study of a curved continuous composite box girder bridge
Authors: Ng S. F. , Cheung M. S. , Hachem H. M.
Published: January 2010

To better understand the behaviour of curved box girder bridges in resisting eccentric design truck loads, and the influence of plan curvature on the structural response, a model study was conducted at the University of Ottawa. In this study, the elastic response of a curved composite box girder bridge model was evaluated experimentally and confirmed analytically using the finite element method. Analytical predictions of both vertical displacements and normal stresses at critical sections compared fairly well with those evaluated experimentally. The isoparametric thin shell element employed in the analysis proved to be versatile and provided an accurate representation of the various structural components of a curved box girder bridge. Despite the eccentric nature of the applied OHBDC design truck loads and the bridge plan curvature, it was evident that in resisting the applied live loads, the girders at critical sections share equal proportions of the applied bending moments. Key words: bridge, curved, cellular, composite, eccentric loads, static, linear, experimental, finite element.