bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial distribution of the transient bed boundary condition for small lakes with weeds
Authors: James William , Eid Basem
Published: January 2010

Although there are a large number of studies on large lakes such as the Great Lakes, little work is being done on small lakes such as those that are used for recreational purposes and that abound in North America. Such water bodies often suffer from nutrient loadings and prolific weed growth; there appears to be a definite need for model development in this area. In this study, wind-driven currents in a shallow homogeneous lake with extensive weed growth have been modeled using the common hydrodynamic equations that describe lake circulation. The method has also been applied to a large stratified harbour. An approximate analytical procedure is presented for modeling the bottom roughness due to weed growth. As in meteorology, the Karman–Prandtl equation for the velocity distribution near the boundary of an open channel has been modified and applied in conjunction with empirical factors obtained from observed velocity profiles inside and above aquatic vegetation. Field experiments were carried out at Valens reservoir (a small recreational lake) and in Hamilton harbour. Surface currents, wind speeds and directions, and weed distributions were measured. Good agreement was found between the model results and observations. The model has especial application where spread of surface contaminants is a problem in lakes with heavy weed growth.
Steel beams with web openings reinforced on one side
Authors: Lupien Roger , Redwood Richard G.
Published: January 2010

Tests are described on six beams containing mid-depth rectangular holes which were reinforced by welding horizontal bars to one side of the web. The objective was to evaluate the effect of one-sided reinforcement on the ultimate strength. Particular reference was made to beams with slender webs and to the effect of moment-to-shear ratio. The efficiency of the one-sided reinforcement was judged on the basis of the predicted capacity of a symmetrically reinforced beam with the same reinforcement area. It was found that, due to strain hardening, the ultimate strength achieved was in some cases equal to this predicted strength and, on the basis of such results, suggestions relating to design are made.
A finite element investigation of the post-buckling strength of thin-walled structural members under compression
Authors: Lee H. P. , Harris P. J.
Published: January 2010

By employing the finite element displacement method using the tangent stiffness approach, the paper presents results of post-buckling analysis of plates and three-dimensional thin-walled members subjected to uniaxial compressive loads. A simple rectangular element with six degrees of freedom at each node, suitable for the analysis of nonplanar prismatic members with slope discontinuities (folded plates), is employed. Both geometric and material nonlinearities have been considered based on a Lagrangian coordinate system and. the flow theory of plasticity. The nonlinear equations are solved using the Newton–Raphson method in the elastic range and the step-by-step method with equilibrium corrections in the plastic range. A modified Cholesky decomposition technique is employed to solve the basic stiffness equations.
A computational procedure for assessing the effect of water pollution on a salmon run
Authors: Brox G. H. , Russell S. O.
Published: January 2010

The difficulties in assessing the effects of water pollution on a salmon fishery are illustrated with the example of pollution in the lower Fraser River and the Chilko run of sockeye salmon. Changes in water quality in the lower Fraser affect the salmon as they migrate to sea as smolts and as they return to spawn. A procedure is presented for making a preliminary assessment of the effect of additional mortality induced by water quality changes on the average size of the run; ways of extending the analysis to estimate probable trends in water quality and the effects this would have on the salmon fishery are outlined.
Seismic design of multistorey steel-frame buildings using dynamic analysis
Authors: Humar J. L.
Published: January 2010

A study is made of the feasibility and usefulness of a seismic design method for multistorey steel-frame buildings. The method employs a time-series elastic response analysis of the structure for a ground motion compatible with a design response spectrum. The correlation between the elastic and elasto-plastic response is investigated and it is suggested that the design forces in the members of an elasto-plastic structure can be obtained by applying appropriate reduction factors to the forces obtained in an elastic analysis.A design example is presented in which a multistorey steel-frame building with a rather large setback is designed for seismic forces by using the results of an elastic dynamic analysis for a selected ground motion and reducing the forces so obtained by applying one uniform force reduction factor to all girder moments and another, a smaller one, to all column moments and axial loads.
Predictions of ice-cover development in streams and its effect on dissolved oxygen modelling
Authors: McBean E. , Farquhar G. , Kouwen N. , Dubek O.
Published: January 2010

A two-stage mathematical model is developed for predicting dissolved oxygen levels in ice-covered rivers. The first stage of the model is a prediction model for ice-edge progression as a function of time, and the second stage consists of an extrapolation of a widely used 'summer condition' water-quality model. The results of a series of experiments, both field and laboratory-based, which served as data input generators and calibration testing of the model, are provided.Briefcase-study applications of elements of the model to the Speed River and to the Saint John River are included.
Manual analysis of cantilever slabs of semi-infinite width
Authors: Bakht Baidar , Aziz Tarek S. , Bartusevicius Kestutis F.
Published: January 2010

Some structural components of bridges can be idealized as cantilever slabs in isolation, for the purpose of analysis. Usually a realistic analysis of such components, when subjected to concentrated loads, is done by methods that are either computer-based or too complex for everyday design application. A semi-graphical manual method for the analysis of semi-infinite cantilever slabs is presented as an alternative to rigorous solutions.The method presented supplements an earlier published manual method for the analysis of infinitely wide cantilever slabs.
Empirical studies of the journey to work in urban Canada
Authors: Hutchinson B. G. , Smith D. P.
Published: January 2010

The 1971 census journey-to-work data supplemented by road-network data for 30 Canadian census areas are analyzed. The data are used to examine the degree to which the commonly used trip-generation and trip-distribution techniques might be used to synthesize journey-to-work patterns and the extent to which the parameters may be generalized across these urban areas.The extent to which intercensus-tract variations in labour force are explained by several separate measures of census-tract residential activity are analyzed by regression analysis. Dwelling-unit composition is isolated as the most effective predictor of census-tract labour force. These multiple regression equations explain from 96–99% of the intercensus-tract variations in labour force and the partial regression coefficients are consistent between census areas.Production-constrained and production-attraction-constrained forms of the gravity model are calibrated. Although conventional goodness-of-fit statistics suggest that these gravity models have a high degree of explanatory power, a detailed examination of the trip-interchange residuals shows that model performances are less than adequate. It is concluded that significant modifications to the traditional gravity trip-distribution models are required if interzonal travel demands are to be estimated with confidence.
Effective width of stiffened cold-formed steel plates
Authors: Roorda J. , Venkataramaiah K. R.
Published: January 2010

This paper reviews the experimental data available in the literature concerning the effective width concept. The formulae for effective width that are contained in the AISI-68 and the CSA S136-74 specifications are critically discussed in relationship to the experimental data. The effective width is shown to be clearly a function of the actual width, in contrast to the constant value implied by the CSA S136-74 specification. A formula of the type used in the AISI-68 specification is found to be very suitable. It provides for reduced strength due to interactive effects in plates of moderate width to thickness ratios and places a limiting value on the effective width of very thin plates.A new design rule, of the simple form Be = 2 − 1/B, is proposed as an appropriate guide for the design of stiffened cold-formed steel plates.
Effect of plate and hole size on Griplam-nail load capacity
Authors: Fox Selwyn P. , Lincoln Roy G.
Published: January 2010

Compression-type single-shear plate–wood–plate specimens were used to measure the effect on the yielding mode capacity of single Griplam nails by increasing plate hole diameters from 1/4 in. (6.4 mm) to 9/32 in. (7.1 mm) and by decreasing steel-plate thicknesses from 1/4 in. to 3/16 in. (4.8 mm). Both changes reduced the load capacity; the effect of increasing hole diameter was greater. Table 49 of CSA Standard 086-1976 was confirmed as realistic, but slightly conservative. The reduction of capacity by use of 7 mm diameter holes in 3/16 in. plate was about 10%.
Internal vibration and the lateral pressure exerted by fresh concrete
Authors: Gardner N. J. , Quereshi A. R.
Published: January 2010

The design of formwork for vertical surfaces is dependent upon the magnitude of the lateral pressure assumed to act on the form face. This paper describes an experimental investigation to determine the variation of the lateral pressure exerted by fresh concrete with depth of immersion of the vibrator, duration of vibration, and power of the vibrator while keeping the rate of pour, form dimensions, and slump nominally constant and measuring the temperature.It was concluded that the lateral pressure is dependent upon the vibration parameters of depth of immersion of the vibrator, duration of vibration, and power of the vibrator and varies inversely with the temperature of the concrete mix.The experimental results were compared with the CIRIA (Civil Industries Research and Information Association, United Kingdom) and ACI (American Concrete Institute) design recommendations. It was concluded that the CIRIA arching criterion should be used with caution as it was not conservative for low friction formwork surfaces, and that both the CIRIA stiffening criterion and the ACI recommendations are conservative.
Design guidelines for incompletely mixed or aerobic–anaerobic aerated lagoons
Authors: Thirumurthi D.
Published: January 2010

Investigations with three laboratory-model aerated lagoons proved that incompletely mixed (or aerobic–anaerobic) aerated lagoons can be rationally designed by using the Wehner–Wilhelm equation or Thirumurthi chart, which graphically depicts that equation for applications in biological wastewater treatment. Whereas the biological factors (such as temperature and wastewater quality) are delineated by a first-order biochemical oxygen demand (BOD) removal coefficient (K), the physical–hydraulic regimes (such as mixing pattern and depth–width ratio of lagoon) are represented by a dispersion index. The key to the design is the standard BOD removal coefficient (Ks), which is evaluated to be 0.29/day for municipal wastewater at a standard temperature (T) of 20 °C and organic load (L) of 20 g∙m−3∙day−1. When the actual T and L of a lagoon, however, are other than the standard values, appropriate corrections should be assigned to Ks to obtain K. Two equations for such corrections are provided.Two companion papers of previous studies demonstrated the successful application of the same method for designing waste stabilization ponds and completely mixed (aerobic) aerated lagoons; the present study accomplishes the same for incompletely mixed lagoons. An example design is included; the technique, however, needs to be verified by investigating the actual, field lagoons.
Graphed equilibrium parameters of channels formed in sediment
Authors: Peterson A.W. , Blench T.
Published: January 2010

This paper, for river engineers and their environmental counterparts, presents and explains the origin and potential of four-dimensional charts that smooth most of the world's numerical data obtained from the equilibrium dimensions of sand rivers, gravel rivers, and laboratory flumes. These charts aim to provide a practical service comparable with that provided by factual plots on the comprehensive classic three-dimensional Stanton friction-factor diagram for circular pipes and clean Newtonian fluid. In the river problems, especially, the existence of different phases (whose transitions are not susceptible to formulation), the inadequacies of textbook theories even for simple phases, and the unavoidable imperfections of both field and laboratory measurements combine to prevent responsible design. The remedy is a graphing of total information backed by references from which its reliability and practicability can be assessed.The references have been chosen to contain principal information in the forms of: (i) usable photos, graphs, and tables; (ii) explanations free from specialized mathematics and speculative arguments; and (iii) papers with discussions, authors' replies, and further useful references (since a major reference list would be too long for this paper). Because condensation has had to be extreme the authors will be glad to attempt answers to discussions and questions on the subject matter, its practical applications, and its implications in teaching and research.
Ultimate web shear capacity in large rectangular ducts
Authors: Sherbourne A. N. , Haydl H. M.
Published: January 2010

Existing methods of calculating the web shear capacity in plate girders are examined and their applicability to large rectangular duct analysis is investigated. It is suggested that a modified Wagner theory, combined with the method developed by the NACA, offers a rational approach to the evaluation of web shear capacity in rectangular ducts.
Elastoplastic material model for nonlinear analysis of planar RC structures under cyclic loadings
Authors: Agrawal Awadh B. , Jaeger Leslie G. , Mufti Aftab A.
Published: January 2010

This paper presents what is believed to be the first successful attempt to apply an elastoplastic material model to planar reinforced concrete under cyclic loads. The model treats an element of reinforced concrete in biaxial stress states, and provides for the cracking and crushing of concrete, opening and closing of previously formed cracks, and yielding of steel reinforcement. The model offers both computational efficiency and an adequate level of accuracy.A rectangular plane stress finite element with three degrees-of-freedom per node, two translations, and an in-plane rotation is employed to discretize the continuum. The presence of rotational degrees-of-freedom at nodes allows an application of the proposed model to the analysis of coupled shear walls and shear wall – frame systems.When the nonlinear finite element analysis results are compared with the experimental response of a shear panel and a shear wall subject to reversed cyclic loads, a good comparison is achieved. The analytical results for the shear panel are also compared with those obtained by other investigators using a degrading nonlinear material model, and a close correspondence is obtained.
Etude des propriétés fondamentales de bétons courants soumis à de longs cycles de gel–dégel
Authors: Pigeon Michel , Lemaire François
Published: January 2010

This article describes the change in the basic properties of standard concrete subjected to 12 h freeze–thaw cycles. Basic properties considered are resistance to compression and other parameters describing concrete behavior in axial compression with axial and transverse expansion. Although 300 freeze–thaw cycles have relatively little effect on standard concrete (without air entrainment), results show that the basic property most affected by slow freeze–thaw cycles is compressive strength and not modulus of elasticity. Furthermore, nondestructive testing indicates that only the residual axial elongation allows detection of minor concrete deterioration. Finally, the authors put forward a theory that the presence of air that has been entrained in the concrete, even though specific air entrainment agents have not been used, explains the observed minor deterioration of standard concrete subjected to slow freeze–thaw cycles. [Journal translation]
Dynamic tests and analysis of a massive pier subjected to ice forces
Authors: Montgomery C. James , Lipsett A. William
Published: January 2010

This paper describes the field tests and analysis of a massive bridge pier that is subjected to the action of dynamic ice forces. The field results indicate that the pier has a natural frequency of 8.9 Hz and a damping ratio of 0.19 in the fundamental mode of vibration. By using these dynamic characteristics, the response of the pier to dynamic ice forces was analyzed. This analysis confirms that the pier is capable of responding in full to short duration peak ice forces.
Stud welding at low temperatures
Authors: Kennedy D. J. Laurie
Published: January 2010

The results are reported of static tension tests and impact bend tests on studs and push-out tests on stud shear connectors with the stud welds made on bare steel and through 20 and 18 gage (0.953 and 1.27 mm) wipe coated galvanized decking at temperatures ranging from 20 to −40 °C. Welding procedures, qualified on the basis of static tension tests, are developed for welding studs over this temperature range. Increased heat input is required to obtain satisfactory welds, both for decreased temperature and increased thickness of galvanized decking. Impact bend tests do not provide a satisfactory criterion for the rejection of stud welds in the field at temperatures below −5 °C. The angle of bend is a function of the test temperature and not the temperature at which the qualified weld was made. Static tension tests at room temperatures form an adequate basis for qualifying stud welding procedures.
Effect of guy cable constraint on structural damping of open lattice antenna towers
Authors: Kennedy J. S. , Wilson D. J. , Adams P. F. , Perlynn M.
Published: January 2010

This paper presents the results of full-scale field tests on two steel guyed latticed towers. The towers were approximately 83 m in height, were guyed at three levels, and were of bolted angle construction. The observed results consist of the natural frequencies of the first two modes of vibration as well as the damping ratio for the first mode. The observed results are compared with analytical predictions and observations made concerning the contributions of structural and cable action to the damping ratio.
Design recommendations for steel beams with web holes
Authors: Redwood R. G. , Shrivastava S. C.
Published: January 2010

Concise design recommendations are given relating to the design of W-shaped beams for building structures when it is necessary to provide large web openings. These recommendations are followed by a commentary describing the background to each of the recommendations, and references are given that will be useful for designers who wish to treat situations beyond the scope of the recommendations presented.
Probability of failure of a box beam using simulation techniques
Authors: Monnier P. Y. , Schmalz P.
Published: January 2010

Though structures designed according to codes do not generally fail, it is interesting to know their true probability of failure in view of the economic consequences.A simply supported uniformly loaded box beam is considered. Based on real statistical data derived from tests or adequate and realistic assumptions, the factored moment Mf and the resisting moment Mr are calculated using Monte Carlo simulation. In order to take into account some important phenomena for prefabricated beams, such as residual stresses, initial crookedness, and end conditions, the random variable α, which multiplies Mr, and its variation coefficient Vα are introduced. The α coefficient is defined as the tested capacity divided by the code predicted capacity. After interpolation, the variable Z = Mr − Mf is assigned a normal (Gaussian) frequency distribution. Then, the probability of failure is evaluated using a well tested mathematical technique.
Limit states design: What do we really want?
Authors: Allen D. E.
Published: January 2010

The purpose of the paper is to open discussion on the development of Canadian structural codes and standards. It argues for a common simple limit states format for all civil engineering structures, with the loading function contained in structural use codes the same for all construction materials, and the resistance function contained in materials design standards the same for all structural uses. The format for loading and resistance functions and the degree of code complexity are discussed.
Developments in the seismic design of reinforced concrete frames in New Zealand
Authors: Paulay T.
Published: January 2010

A review of recent developments in the formulation of a design approach for ductile earthquake resisting reinforced concrete frames is presented. In particular the concepts of a deterministic design procedure, termed "capacity design," the advantages of moment redistribution, and the effects of gravity load dominance are discussed. In capacity design (a detailed definition of the term is given in Sect. 2.1) the designer attempts to enforce the development of a unique and desirable pattern of plastic hinges when these are required to dissipate significant amounts of energy to ensure the necessary hysteretic damping. The application of a capacity design procedure in determining the design actions for columns of multistorey frames is examined. Some issues relevant to instability during the inelastic dynamic response of frames are also discussed. Using recent experimental evidence, the inelastic behaviour of reinforced concrete columns, shear effects on potential plastic hinges, and special features of the behaviour of beam–column joints, when these are subjected to severe earthquake simulating reversed cyclic loading, are briefly described. Conclusions drawn from these recent experimental studies, which are being considered for incorporation into the new New Zealand concrete design code of practice, are also reported.
The Lions' Gate Bridge — investigation
Authors: Buckland Peter G.
Published: January 2010

A careful investigation of the Lions' Gate suspension bridge yielded new information and techniques relevant to suspension bridges. These included traffic loading, wind loading, natural frequencies, structural damping, the effect on aerodynamics of the centre of rotation and turbulence, criteria for aerodynamic stability, concrete strength, crevice corrosion, long term cable stretch, relationships of structure temperature to ambient temperature, limit states design for towers, and the influence of various effects on stiffening truss stresses.
Design of reinforced masonry walls and columns for gravity loads
Authors: Ojinaga Jose , Turkstra Carl J.
Published: January 2010

The ultimate strength of reinforced masonry compression members subjected to axial or eccentric vertical loads is the main concern of the paper. As an initial step, the literature is reviewed so as to arrive at reasonable assumptions relating to the stress–strain properties of the material; these are necessary to define the load–moment interaction curve for a short column or wall. A method that can account for the weakening effect of slenderness is also discussed. These two fundamental components of the procedure are then judged relative to experimental test data. Axially loaded walls are modelled quite well but the theory is conservative for walls tested eccentrically. Although the inclusion of a strain gradient factor and consideration of nonlinear behaviour would improve analytical predictions for the latter case, these extra factors are not applied to the results due to a lack of definitive knowledge relating to the latter.
Modelling side-weir diversion structures for stormwater management
Authors: James William , Mitri Hani
Published: January 2010

Combined sewer diversions are designed to divert significant flows directly to the receiving water during rainstorms. To estimate pollutant loadings to the recipient water it is necessary to compute continuous hydrographs and pollutographs for the full period of potential overflow. Since a diversion is active only during part of a storm, diverting only part of the flow, a rating curve for the diversion structure must be obtained. Few structures have been adequately calibrated and their rating curves are not usually available.Overflow and diversion structures may be classified according to the shape of the sill or overflow control: end weirs, oblique weirs, and side spillways. Many structures experience hydraulic jumps of complex shape over much of the operating range. This paper reviews the hydraulics of side spillways and the SWMM-EXTRAN computer program. A new program called OVRFLO3 has been developed to dovetail with the SWMM package. Internal SWMM coding has not been changed. As a stand-alone program, OVRFLO3 will produce rating curves for side-weir diversion structures. The program has been applied to urban catchments in Hamilton, Canada.Validation of OVRFLO3 is discussed in the paper. Comparisons were also made between OVRFLO3, SWMM-EXTRAN, and a series of previous laboratory experiments conducted by others.
Seismic risk to pipelines with application to Northern Canada
Authors: Atkinson G. M. , Davenport A. G. , Novak M.
Published: January 2010

Proposed northern pipeline projects necessitate the estimation of seismic risk in the Arctic. Such estimates are difficult to obtain due to the lack of a good instrumental or historical data base, and the sparsity of tectonic information.Seismic risk estimates are commonly based on the procedures proposed by Milne and Davenport or those described by Cornell. The methods are inherently similar and the choice between the two is largely a matter of convenience. A modified Milne and Davenport approach (based on the amplitude recurrence distribution) appears to offer advantages in Northern Canada since it avoids the seismological problems of defining tectonic zones and maximum magnitudes.Uncertainties in the model assumptions are described by a factor having a log-normal distribution that modifies the predicted acceleration. The variability of the distribution can be adjusted regionally to reflect the quality and extent of seismic information.Seismically induced hazards to pipelines include overstressing due to travelling waves, liquefaction of silt-laden soils (possibly resulting in landslides), and abrupt displacement due to fault crossings. The potential for seismically induced liquefaction and for overstressing can also be evaluated probabilistically using modified forms of the amplitude recurrence distribution.
Strength and rotational behaviour of composite beam–column connections
Authors: Dalen Karl Van , Godoy Hernan
Published: January 2010

The results of an experimental study of the strength and rotational characteristics of composite steel–concrete beam–column connections are reported. Three types of connection, flexible, semi-rigid, and rigid, were studied. Specimens in which the steel elements were connected in identical fashion were tested with no concrete slab and with a heavily and a lightly reinforced composite slab that was continuous around the column.It was found that provision of as little as 0.46% of the concrete slab area, as slab reinforcement continuing around the column, enabled a beam–column connection to develop a moment of resistance at least equal to the ultimate moment capacity of the associated composite beam, even when the connection between the steel elements themselves had no significant moment carrying capacity. The rotational capacity of the composite beam–column connections was at least equal to that of a conventional noneomposite rigid steel connection.
A design method for bearing stresses in wood
Authors: Madsen Borg , Hooley R. F. , Hall C. P.
Published: January 2010

The paper points out that the present method used to design bearing plates for wood subjected to stresses perpendicular to the grain is inadequate because it neglects the effect of the specific geometry. A design method that more correctly reflects the actual conditions is presented together with test data that represent the material properties in a more realistic way.The design method is discussed and compared with limit states design and design examples are presented. The method includes a conservative estimate of the deflections.
In-plane tensile strength of concrete masonry
Authors: Drysdale Robert G. , Hamid Ahmad A.
Published: January 2010

Splitting tension tests of concrete block masonry specimens were used to investigate the in-plane tensile strength of concrete block masonry. The strength and geometric properties of the blocks and of various strength grouts were included as test parameters. Explanations for the observed behaviour were suggested. In addition to providing test data for evaluating current design provisions for tension produced by combinations of in-plane loads, documentation of the relative influence of grouting is an important objective of this paper. The results indicate inconsistencies with the current design assumption that grouted blockwork is equivalent to construction with solid units. Some general conclusions related to design provisions are provided.
Road vehicles on bridges
Authors: Navin F. P. D.
Published: January 2010

Analytical techniques and the ability to simulate complex traffic situations have advanced to a state that now makes it possible to more accurately estimate the vehicle design load for bridges. A detailed road traffic simulation was developed to estimate the maximum vehicle loading over varying lengths of the Lions’ Gate Bridge. The simulation was generalized and used to develop vehicle loads used in the ASCE procedure.A sensitivity analysis indicated that the maximum truck weight and the percentage of trucks in the traffic stream were the two most important variables of the eleven used. The simulation method may be used for detailed load estimates on existing bridges as well as in the design of future bridges. Keywords: bridge live loads, traffic, trucks, computer simulation, traffic simulation, extreme value estimation
Duration of load effects in lumber. Part II: Experimental data
Authors: Madsen Borg , Johns Kenneth
Published: January 2010

The viscoelastic fracture mechanics model developed in Part I is calibrated using a 70-day duration of load test on commerical lumber. The model is then verified using another similar test on a different population of boards, and on a unique 6-year test just terminated. All three test programs are described. The model is used to tentatively project results beyond the period of testing. The strength predictions of the model compare well with those obtained experimentally during the tests, the coefficient of correlation being 0.95. Implications for design practice are outlined in Part III of this paper.
Temperature effect on the anaerobic treatment of potato-processing wastewater
Authors: Lin K. C. , Landine R. C. , Bliss S.
Published: January 2010

The performance of a laboratory-scale anaerobic lagoon–filter system treating unsettled potato-processing wastewater has been studied under controlled temperature conditions below 20 °C. The wastewater contained approximately 2700 mg/L of chemical oxygen demand (COD) and 1380 mg/L of suspended solids (SS). The system, buffered with lime, was fed continuously; detention times were 7.0 and 1.5 days for the lagoon and filter, respectively. The loading rate was 0.35 kg COD/(m3∙day) based on lagoon volume. There was 100% recycling but no sludge wastage.Between 20 and 10 °C, the system removed approximately 94% of the COD and 95% of SS. Down to 4 °C removals of 85% of COD and 93% of SS were obtained. At 2 °C system failure was imminent. Sludge accumulation rate was highest at 6 °C (0.41 g of SS accumulated per gram SS fed), four times the rate at 20 °C. Total methane production varied from 0.35 m3/kg COD removed at 20 °C down to 0.24 m3/kg COD removed at 4 °C, with a 62% decrease in volumetric rate. Methane content in the gas was 75–84%. The filter had a higher methane production-to-COD removal ratio and a higher methane content than the lagoon. Keywords: anaerobic lagoon, anaerobic filter, temperature effect, potato waste.
Modèle mathématique de gestion de la qualité de l'eau en rivière : application à l a rivière Yamaska
Authors: Pineau M. , Villeneuve J. P. , Campbell P. G. C.
Published: January 2010

In the more populous watersheds of southern Quebec eutrophication of surface waters is a current problem, linked to excessive nutrient loadings from various municipal, industrial, and agricultural sources. A simple mathematical model has been developed to identify the optimal strategies for controlling nutrient loadings at various points in a river basin; for this optimization the key water quality parameter is phosphorus and the objective is to meet a fixed water quality criterion (0.06 mg total phosphorus per litre) at minimum cost.The potential utility of the model in a water management context has been demonstrated in a case study of the Yamaska River, Quebec, which drains regions of intense agricultural activity and is also subject to phosphorus pollution from numerous point sources of municipal and industrial origin.
Behaviour of round-chord, cropped-web truss joints
Authors: Ciwko J. B. , Morris G. A.
Published: January 2010

An experimental investigation of the static behaviour of cropped-web joints is presented. The joints involve round hollow structural section chords and round hollow section webs with ends cropped in the plane of the joint. Such joints have the advantage of low fabrication cost compared with that of joints with profiled webs. Tests of 61 isolated joints with Pratt-type configurations are reported. The measured deformations at the joints are described. Equations obtained using multiple regression analysis to relate the strengths and flexibilities of the joints to various parameters are presented. The strengths of the joints were found to be acceptable. The flexibilities of the joints were found to be only one third to one half as large as those for comparable square-chord joints.
Decision analysis applied to structural code formulation
Authors: Maddock W. P. , Jordaan I. J.
Published: January 2010

Recent work has focussed attention on the increasing complexity of structural codes of practice. The question arises: how should a proposed code provision, which might embody a simplification, be assessed? It is suggested that decision theory can be used in making such an assessment. This is explored by means of an example, namely a reinforced concrete portal frame. The analysis focussed on the limit state of cracking and various strategies for the analysis of the frame were considered. For instance, one strategy considered the frame as uncracked; others included assumptions regarding cracking. The frame was analysed using a computer program, in which the frame was discretised and realistic models of material behaviour were incorporated. A Monte Carlo procedure was followed, taking into account uncertainties regarding loading, material properties, and the position of steel reinforcement. Utility functions were developed; these were a function of the action taken and the (random) crack width. The most simple action, i.e., treating the frame as uncracked, gave the maximum expected utility. The basic approach should prove useful for other problems related to code formulation.
Flow conveyance with ice cover for the Nashwaak River, N.B.
Authors: Burrell B. , Davar K. S.
Published: January 2010

Measurements were undertaken along a 460-m long portion of the Nashwaak River, N.B., in order to study the flow conveyance characteristics of a regional watercourse during ice-cover and open-water conditions. Elevations of the water surface under both conditions were obtained at five cross sections for varying water levels and discharges. Various difficulties experienced in defining the cross-sectional area of the flow section, determining the influence of slush and anchor ice on the slope, and the roughness characteristics of the undersurface of the ice cover are described in order to provide a perspective on some commonly encountered problems.
Evaluation of effective length factors in braced frames
Authors: Fraser Donald J.
Published: January 2010

A designer-oriented iterative method for the evaluation of effective length factors in braced frames is described. The formulae used in the method have been expressed in terms of effective length factors because designers use this parameter, rather than the values of critical buckling loads, in the analysis and design of columns. The method takes into account the reduced stiffness of restraining members due to the presence of significant axial forces and also allows for the stabilizing effect of tension members. Application of the method is demonstrated by numerical examples. Keywords: braced structures, buckling of continuous columns, frame buckling, truss buckling, effective length factors, accurate stability functions, linear approximations of stability functions, structural stability.
Ultimate strength of concentrically loaded cold-formed angles
Authors: Madugula Murty K. S. , Prabhu T. S. , Temple Murray C.
Published: January 2010

Results of the tests carried out on eight 45 × 45 × 3 mm and eight 65 × 65 × 4 mm concentrically loaded cold-formed single angles with hinged end conditions are presented. The nominal slenderness ratios of the test specimens varied from 90 to 250. Experimental failure loads are compared with loads calculated in accordance with North American and European specifications. A finite element computer program, which takes into account the effect of the initial out-of-straightness, was developed to predict the flexural failure loads of cold-formed angle sections. The out-of-straightness of the test specimens was measured. Load–deflection curves were obtained experimentally and theoretically. The magnitude and distribution of residual strains were also determined.
Ice breakup and jamming observations along the Mackenzie River
Authors: Kamphuis J. W. , Moir J. R.
Published: January 2010

The breakup of ice along the Mackenzie River between Fort Simpson and Fort Good Hope was studied in 1979, 1980, 1981, and 1982. This paper describes the 1980 and 1981 observations. An aircraft dedicated to this task was used to make over 40 observation flights during those two breakup seasons in which more than 20 major ice jams were observed during their formation, stationary position, and breakup. Although the paper is based on experience gained during only 4 years, it was found that all observed jams displayed the same major characteristics; hence it appears that general descriptions of ice melting, breakup, and jamming for the section of the Mackenzie River under investigation are possible. Although there could be additional variations, these are expected to be minor.The paper describes the ice melting process prior to any ice movement. The ice jamming process as it takes place along the Mackenzie River is discussed as well as the various parameters that affect this process. Several secondary factors that influence the detailed character of the jams are also addressed.
Current design procedures for steel-lined pressure tunnels
Authors: Nicolopoulos A.
Published: January 2010

A systematic procedure for the design of steel liners for penstock tunnels is presented in this article. Useful hints and other relevant information are also provided to help in decision-making. Special attention has been paid to factors of safety and allowable stress, areas where a certain amount of controversy exists.The application of the procedure is facilitated by the development of computerized design graphs. These graphs are presented using a common notation and an appropriate scale, which makes it possible to evaluate the different theories by direct comparison. Finally, a detailed design example is given for a better understanding of the proposed procedure. Keywords: hydroelectric structures, structural steel, linings, tunnels, state-of-the-art review.
Deflections of a composite floor system
Authors: Montgomery C. J. , Kulak G. L. , Shwartsburd G.
Published: January 2010

A case history of a steel beam – concrete slab composite floor system which had deflection serviceability problems is presented. Load tests carried out to assess the structural adequacy of the floor system are described. Practical methods for predicting elastic, creep, and shrinkage deflections of composite floors are summarized and recommendations for design are made.
Improving the bearing strength of supports of light wood trusses
Authors: Bulmanis N. S. , Latos H. A. , Keenan F. J.
Published: January 2010

It is often necessary to reinforce the supports of light wood trusses to avoid overstresses in compression perpendicular to grain at the interface between the bottom chord of the truss and the top plate of the supporting wall. Two methods of reinforcement were studied: placing a bearing bracket on the top plate and locating the heel plate of the truss so that its lower edge is at the lower edge of the bottom chord. A combination of the two methods was also examined. It was found that very little, if any, increase in allowable compression stress perpendicular to the grain is warranted for the bearing bracket alone, a 15% increase is recommended for the heel plate method, and a 30% increase is justified for the apparently symbiotic combination of the two methods.
Composite design method for masonry walls on concrete beams
Authors: Smith B. Stafford , Pradolin L.
Published: January 2010

This paper describes a design method for structures consisting of a vertically loaded masonry wall supported by a reinforced concrete beam, taking account of the composite tied-arch action of the wall and beam. Experimental results have shown that the behaviour of walls on reinforced concrete beams is similar enough to that of walls on steel beams to allow the development of a design procedure for the former using similar principles to that for walls on steel beams. Therefore, the design approach is based on the assumption of triangular distributions of vertical stress at the wall–beam interface, where the length of the distributions are a function of the beam-to-wall relative stiffness. In the design method the beam flexural stiffness is designed to give an adequate distribution of the interface stress so that the maximum stress in the wall does not exceed allowable limits. The beam is also designed with flexural and shear reinforcement sufficient to resist the bending moment, tie force, and shear forces applied by the normal and shear interface loading. Experimental evidence as well as analytical results are cited to support the assumptions and the resulting design method.
Hétérogénéité des aciers de construction et calcul aux états-limites
Authors: Dumonteil P.
Published: January 2010

Proceeding from yield stress tests on ductile structural steels, the article studies the various factors influencing the ultimate strength of beams in plastic bending. The influence of the testing speed is briefly reviewed. The heterogeneity with the cross section of rolled shapes is then examined to bring out the fundamental importance of the ratio of flange yield stress to web yield stress. The mean value of this ratio is of the order of 0.87 and its coefficient of variation approximately 0.06.The influence of thickness is studied to show the desirability of systematic testing.The data supplied by AISI surveys permit the investigation of longitudinal heterogeneity and its impact on bending strength test results. It is then shown why tests on redundant beams and frames are more useful than those on determinate beams.Combining the two types of heterogeneities, longitudinal and transversal, the approximate values of the performance factors may be calculated and compared with the values published until now.Finally, the aspect of quality control is examined and some remarks made on stub column tests. The conclusion is offered that, in accordance with logic, test coupons should no longer be taken in the web, but rather in the flanges of rolled shapes.
Bridge aesthetics
Authors: Bakht Baidar , Jaeger Leslie G.
Published: January 2010

This paper attempts to raise among bridge designers the level of awareness regarding the appearance of bridges. Bridge aesthetics should be evaluated with respect to five specified vantage points, and bridges should be made to look beautiful from the most frequently used vantage points. Involvement in the design team of professionals who have background training in aesthetics, such as landscape architects, is advisable.
Adaptation des procédés stéréologiques à la mesure des bulles d'air et des fissures dans le béton
Authors: Houde Jules , Meilleur Serge
Published: January 2010

Mathematical morphometry is the science of classifying forms through parameters such as length, area, perimeter, and projected length. Image analysers have been built to measure these parameters rapidly. Stereological equations are used to define three-dimensional characteristics from elementary count operations made in a plane.These techniques were used to characterize the air bubble system of six different concretes. All measurements were made on polished sections with a linear traverse apparatus as well as with an image analyser. The precision of the data obtained is about equal with both measuring techniques. The image analyser was able to measure the air content and the spacing factor in one-eighth of the time necessary for a linear traverse; moreover, histograms of the bubble sizes were readily available.Measurements of cracks caused by early freezing of plastic concrete made on the linear traverse apparatus, coupled with total porosity measurements by the image analyser, were used to relate the decrease of compressive strength to the increased crack density.
Dynamic analysis of a suspended pump in a vertical well connected to the ocean
Authors: Eid Bassem M. , Zemell Sheldon H.
Published: January 2010

In the design of a salt-water intake system which is connected to the ocean, a numerical model is developed to simulate the hydraulic and structural dynamic responses to the ocean's wave action. On the basis of available data, the design wave height is determined from the condition for breaking. For such a complex system, wherein several natural periods are contributing to the total response, a range of wave periods is considered. The standing wave system resulting from the reflection of a progressive wave train from a vertical wall (clapotis) is modelled and the hydrodynamic response of the system is computed. To limit water level fluctuations in the well, a strong damping of the water column is provided by constricting the flow through an orifice plate installed at the bottom of the pump well. The hydrodynamic force on the suspended pumps due to nearby submerged turbulent jet flow is described. A damped single-degree-of-freedom oscillator is employed to represent the structural dynamics of the pumps. Extensive experiments are required to supplement this work in order to describe the complex system fully. Keywords: dynamic analysis, salt-water intake, waves, hydrodynamic force, suspended pump, submerged jet, oscillator.