bluuebunny/crossref_metadata_2025 huggingface dataset:
A study of some factors affecting the fiber–matrix bond in steel fiber reinforced concrete
Authors: Banthia Nemkumar
Published: January 2010

With the objective of understanding the reinforcing mechanisms of fibers in steel fiber reinforced concrete, the bond between the fibers and the surrounding matrix is studied by conducting single fiber pull-out tests on fibers bonded in cementitious matrices. Various matrix compositions and fiber geometries have been investigated and the effects of various other factors on the pull-out behavior of the fibers have been quantified through pull-out load–extension plots. Finally, the various modes of fiber–matrix load transfer have been discussed and the favorable and unfavorable conditions for such a transfer have been recognized. Key words: steel fiber reinforced concrete, toughness, fiber–matrix bond, deformed fiber, pull-out tests, load–extension plots.
Moment and shear transfer between columns and concrete slabs
Authors: Ghali Amin , Elgabry Adel A.
Published: January 2010

Gravity and horizontal forces cause the transfer of vertical shear and moments between concrete flat slabs and their supporting columns. These forces can cause punching failure. Design equations for safety against punching given in the Canadian Standards Association and the American Concrete Institute codes are critically reviewed. It is shown that the equations give in some cases incorrect stresses which do not satisfy equilibrium. A modification is suggested which makes the equations applicable to all cases. The paper also discusses the codes' approach of sharing the resistance to transferred moment between resistances by flexure and by eccentricity of shear, using the coefficient γv. Comparisons are made with the result of finite element analyses. It is concluded that the code equations, with the suggested modification, are adequate, provided that appropriate values are used for the coefficient γv. Key words: columns, connections, flat concrete plates, moments, punching shear, reinforced concrete, shear strength, slabs, structural design.
A case study in integrated building design
Authors: Fazio Paul
Published: January 2010

The review of the design and construction details of the external wall assembly of a 122 m (400 ft) tall building in a Canadian city is presented. Inadequate tolerance consideration for the steel frame structure and elements of the building envelope and changes in the fireproofing method led to a series of changes and conflicts, delay in the project, and added costs. This case study is presented to show the need to adopt integrated building design principles from the conceptual stage to achieve compatibility between building subsystems while they are being assembled and during the life of the building and to accelerate the construction process. Key words: building envelope, tolerances, integrated building design, metal air pan, tall buildings, building engineering, case study, fireproofing.
Static and dynamic analysis of timber shear walls
Authors: Filiatrault A.
Published: January 2010

Light-frame wood structures have evolved in recent years to the point where their earthquake resistance is now questionable. Shear walls are commonly used to provide lateral stiffness and strength in wood buildings. Therefore, accurate predictions of the seismic behaviour of timber shear walls are necessary in order to evaluate the safety of existing timber buildings and improve design practice. This paper develops and validates a simple structural analysis model to predict the behaviour of timber shear walls under lateral static loads and earthquake excitations. The model is restricted to two-dimensional shear walls with arbitrary geometry. The nonlinear load –slip characteristics of the fasteners are used in a displacement-based energy formulation to yield the static and dynamic equilibrium equations. The model is embedded in a shear wall analysis program (SWAP) developed for microcomputer applications. The predictions of the model are compared with full-scale racking and shake table tests. The ability of the model to accurately predict the lateral stiffness, the ultimate lateral load capacity, and the complete earthquake response of timber shear walls is clearly demonstrated. Key words: dynamics, earthquakes, seismic response, timber construction, walls, wood.
Ice jam mitigation
Authors: Belore Harold S. , Burrell Brian C. , Beltaos Spyros
Published: January 2010

In Canada, flooding due to the rise in water levels upstream of an ice jam, or the temporary exceedance of the flow and ice-carrying capacity of a channel upon release of an ice jam, has resulted in the loss of human life and extensive economic losses. Ice jam mitigation is a component of river ice management which includes all activities carried out to prevent or remove ice jams, or to reduce the damages that may result from an ice jam event. This paper presents a brief overview of measures to mitigate the damaging effects of ice jams and contains a discussion on their application to Canadian rivers. Key words: controlled ice breakup, flood control, ice jams, ice management, river ice.
Membrane action in reinforced concrete slabs
Authors: Vecchio F. J. , Tang K.
Published: January 2010

The formation and influence of compressive membrane action in reinforced concrete slabs is discussed. An experimental program is described, in which two large-scale slab specimens were tested under concentrated midspan loads. One slab was restrained against lateral expansion at the ends, while the other was free to elongate. The laterally restrained specimen developed high axial compressive forces, which resulted in a significant increase in flexural stiffness and load capacity. A nonlinear analysis procedure was used to model specimen behaviour. The analysis method was found to adequately represent important second-order effects, and thus gave reasonably accurate predictions of load–deformation response and ultimate load. Key words: analysis, concrete, deformation, load, membrane, reinforced, slabs, strength, tests.
On the nonlinear behaviour of reinforced concrete frames
Authors: Vecchio F. J. , Balopoulou S.
Published: January 2010

An experimental investigation is described in which a large-scale reinforced concrete plane frame is tested to study factors contributing to its nonlinear behaviour under short-term loading conditions. The test results indicate that frame behaviour can be significantly affected by second-order influences such as material nonlinearities, geometric nonlinearities, concrete shrinkage, tension stiffening effects, shear deformations, and membrane action. A nonlinear frame analysis procedure, previously developed taking these mechanisms into account, is shown to accurately predict most aspects of behaviour, including deflection response, ultimate load capacity, and failure mechansim. Aspects of the theoretical modelling which are in need of further improvement are also identified. Key words: analysis, behaviour, deformation, frame, large scale, nonlinear, reinforced concrete, strength, test.
The strength and testing of window glass
Authors: Dalgliesh W. Alan , Taylor Donald A.
Published: January 2010

This paper presents some of the background to the new Canadian General Standards Board (CGSB) standard on the structural design of glass for buildings. It also describes strength testing of window glass at the Institute for Research in Construction of the National Research Council of Canada using three quite different testing machines. (i) A dynamic glass testing rig, with a large 2.35 m diameter piston, applies dynamic air pressures to large panes of glass in the vertical position. Results of 107 tests to failure show the considerable effect of loading rate on strength. (ii) A loading table applies linearly increasing pressures to panes of glass in the horizontal position. Results from 47 fifteen-year-old windows confirm assumptions about the deterioration of strength with in-service use in the new CGSB standard on the structural design of glass for buildings. (iii) A ring-on-ring tester applies linearly increasing loads to small 180 × 180 mm samples; the equivalent of coupon tests for steel or cylinder tests for concrete. The resulting uniform tensile stress fields avoid failures starting at the edges of the samples. Some results are given. Testing provides the basis for the structural design of glass cladding as it does for other structural materials. A great deal more testing of window glass is required. Key words: glass strength, window strength, testing, strength deterioration, rate effect, dynamic loading.
Effect of butt joints on the flexural stiffness of laminated timber bridges
Authors: Jaeger Leslie G. , Bakht Baidar
Published: January 2010

Prestressed and nailed laminated timber bridge decks are made from laminates which, because of their being usually shorter in length than the deck span, are butt-jointed at regular intervals. In calculating deflections of such decks, it is usual to ignore the reduction in flexural rigidity of the deck caused by the presence of the butt joint. The effect of butt joints on the flexural rigidity of the laminated deck is studied analytically, and it is shown that the deflections of a deck having such joints may be significantly larger than those of a deck without them. A simple method is presented to account conservatively for the presence of butt joints in the calculation of the deflections of a prestressed laminated timber deck. Key words: timber bridge, laminated deck, butt joint, prestressed wood deck.
New Canadian provisions for the design of steel beam–columns
Authors: Kennedy D. J. L. , Picard A. , Beaulieu D.
Published: January 2010

The beam–column interaction equations of the Canadian Standards Association Standard CAN3-S16.1-M84 "Steel structures for buildings — limit states design" are reviewed and areas of concern in the formulations are addressed. The interaction equations developed for the 1989 edition of the standard, CAN3-S16.1-M89 "Limit states design of steel structures," and the methods of dealing with the areas of concern in the previous standard are presented. The new standard requires that at least an approximate second-order geometric analysis be carried out. For frames dependent on the frame stiffness for lateral stability, no longer is the traditional method, using effective length factors greater than one, allowed. Unlike the current American Institute of Steel Construction "Load and resistance factor design'' (AISC LRFD) specification, two sets of interaction equations, one for in-plane member strength and the other for out-of-plane stability, are used. This results in considerably less unnecessary conservatism. In both sets of interaction equations, the component of the moment due to translation is increased by the second-order effects. The "double ω" problem has been resolved and the minimum sway effects for the gravity loading case have been increased substantially to guard against sidesway buckling. A design example using the new standard is given. By means of a series of analytical examples, the requirements of S16.1-M89 are compared with the traditional method of S16.1-M84. For frames with direct-acting bracing, S16.1-M89 gives interaction values about 1.15 times those of the previous standard with a coefficient of variation of 0.08, while for unbraced frames the corresponding values are 0.98 and 0.07. The S16.1-M89 values reflecting greater rigor in a number of areas are considered the more valid. The S16.1-M89 standard would give comparable results to the AISC LRFD specification for class 1 sections when out-of-plane behaviour governs. The latter specification does not specifically cover cross-sectional strength and in-plane behaviour as does S16.1-M89. Key words: beam–column, stability, strength, bending, compression, standards.
Laboratory and field tests with a new nondestructive apparatus
Authors: Al-Manaseer A. A. , Nasser K. W.
Published: January 2010

A new nondestructive test for estimating the compressive strength of concrete and mortar at early ages is described in this paper. The pin penetration test was used to relate the early age strength of hardened concrete and mortar in the laboratory. It was found that the pin penetration tester can be used successfully, under laboratory conditions, to determine the compressive strength of concrete cylinders and mortar slabs at early age from 10 hours up to 28 days. For concrete and mortar cylinders, slabs, and cubes with a compressive strength of up to 27.6 MPa (4000 psi), the pin penetration readings were found to be linearly related to the compressive strength. The tester was also used successfully in the field to determine the compressive strength of a concrete floor slab in a new building in order to post-tension the strands and remove the forms. The building was constructed in winter under severe climatic conditions. Key words: early age, strength evaluation, concrete slabs, form removal, nondestructive tests, mortar testing, pin penetration test.
Length effect on the performance of lumber in tension
Authors: Lam Frank , Varoglu Erol
Published: January 2010

A study was conducted to evaluate the effect of gauge length on the short-term performance of visually graded Select Structural and No. 2 kiln-dried nominal 38 × 89 mm spruce-pine-fir lumber in tension parallel-to-grain. The short-term tensile strength properties of three groups of lumber, matched for modulus of elasticity and having gauge lengths of 2642, 3683, 4877 mm, were obtained from test results where the effect of gauge length was isolated from the effect of grade. The performance of the lumber was evaluated by first-order second-moment reliability analyses. In the analyses, the lumber was treated as single tension members under uniform tensile stress along the member length, undergoing snow load conditions at various locations in Canada. The results indicate that the performance factor for Select Structural spruce-pine-fir lumber in tension parallel-to-grain should be multiplied by a factor of 0.92 to adjust for doubling the length from 2500 to 5000 mm to achieve a common reliability index of 3.0. The effect of doubling the length from 2500 to 5000 mm on the performance of No. 2 spruce-pine-fir lumber appears to be negligible. Key words: length effect, tensile strength, lumber, performance factor, reliability index.
Une nouvelle technique d'inclusion pour la mesure à long terme des déformations dans des barrages en béton
Authors: Ballivy Gérard , Benmokrane Brahim , Poulin Roch , Saleh Kaveh
Published: January 2010

This paper presents the results of an experimental study on the development of a simple yet efficient technique allowing for the long-term measurements of strains and stresses in working concrete dams. The proposed technique consists of installing a cylindrical concrete inclusion instrumented with vibrating wire gauges embedded into the concrete. The 140-mm cylinder is slipped into a 152 mm diameter hole, which is drilled into the dam and then filled with cement grout. This technique, which was tested in the laboratory on instrumented concrete blocks, has shown that it is now possible to measure the deformation variations in a working dam. The inclusion can be instrumented for both bidimensional and tridimensional cases. The volume of the cylinder makes room for a sufficient number (4–8) of vibrating wire gauges. Moreover, during the drilling process, the technique of overcoring makes it possible to determine the initial total stresses. This technique can also be used to instrument heavily loaded rock structures such as mine pillars or underground gallery walls. Current observations show that this technique, contrary to plastic inclusions, can be considered appropriate for permanent structures. Key words: vibrating wire gauges, strain gauges, instrumentation, strain measurements, long term, concrete dams, rock slopes, rock pillars, mines, underground excavations.
Spreadsheet solutions of elastic plate–beam problems
Authors: Small Gregory E. , Simmonds Sidney H.
Published: January 2010

Spreadsheets are among the most common microcomputer programs used by engineers because they provide an easy means of formulating equations in algebraic format. By introducing appropriate stiffness equations with numerical values representative of material properties, boundary conditions, and loading, spreadsheet templates can be developed to model specific structural systems. These equations are mutually dependent and may be solved using the iteration techniques that are part of the spreadsheet program. A common structural problem that is difficult to solve without a special computer program is the analysis of a slab arbitrarily supported on elastic beams and columns. The use of readily available spreadsheet programs to solve this problem is demonstrated. Equations for slab bending and for beams with finite flexural and torsional stiffnesses are derived using finite difference operators. These equations are then recast into a form more convenient for an iterative solution. The use of these equations is demonstrated with numerical examples. Key words: analysis, convergence criteria, deflections, finite difference, plates, spreadsheets.
Response of timber bridges under train loading
Authors: Uppal A. S. , Rizkalla S. H. , Pinkney R. B.
Published: January 2010

Timber bridges are still commonly used by several North American railroads. For short spans, they offer an attractive alternative to other types of bridges, as they are economical, faster to construct, and easy to maintain. Current design practices do not allow an independent consideration of the effects of the dynamic loads in sizing the bridge components, because very little information is available on the subject. Dynamic tests were carried out at two timber railroad bridge sites under the passage of trains at speeds varying from crawl, i.e., 1.6 km/h (1 mph), to 80.5 km/h (50 mph). The loads at wheel–rail interfaces, the vertical displacements, and the accelerations were measured at several locations on the bridge spans, the bridge approaches, and the normal track sections. The maximum values of the dynamic load factors obtained were 1.50, 1.65, and 1.85 for bridge, bridge approach, and normal track, respectively; and the corresponding maximum values of the dynamic displacement factors obtained were 1.30, 1.00, and 1.20. The main objective of this paper is to describe the experimental work and the influence on the measured values of the train speed and other factors. Key words: railroad, timber, bridge, wheel–rail interfaces, load, deflection, frequency, load factor, dynamic displacement, track modulus.
An analytical approach for dynamic response of timber railroad bridges
Authors: Uppal A. S. , Pinkney R. B. , Rizkalla S. H.
Published: January 2010

In the 1970s, it was reported that there were approximately 3700 track kilometers of timber railroad bridges in the United States and Canada. For short spans, they offer an attractive alternative to other types of bridges, as they are economical, faster to construct, and easy to maintain. Current design practices do not allow an independent consideration of the effects of the dynamic loads in sizing the bridge components, because very little information is available on the subject. Dynamic tests were carried out in 1986 on timber bridge spans at two test sites using test trains consisting of a locomotive unit, two loaded hopper cars, and a caboose. This paper gives a brief description of the analytical approach employed for determining the dynamic response of timber bridge spans under railway vehicles travelling at a constant speed. The model comprises a multi-degree-of-freedom system with each vehicle having bounce, pitch, and roll movements. Two parallel chords, each having its distributed mass lumped at discrete points, were used to idealize the bridge spans. A computer program developed on this basis was used to predict the loads at the wheel–rail interfaces and the vertical displacements at the discrete points on the spans. The predicted loads at wheel–rail interfaces and the maximum vertical displacements were found to be in agreement within about 20% and 16% respectively of the measured values. The program was utilized to study the effect of speed and other factors on the dynamic response of open-deck and ballast-deck bridges. Key words: analytical approach, timber railway bridge, railway locomotive and cars, constant speed, wheel–rail interface, loads, displacements, accelerations, dynamic response.
A geographic information system for prediction of design flood hydrographs
Authors: Muzik I. , Pomeroy S. J.
Published: January 2010

A geographic information system (GIS) supporting a flood hydrograph prediction software package is described. The hydrograph prediction method is based on the convolution of excess rainfall with a synthetic unit hydrograph, derived by the Soil Conservation Service runoff curve number and a regional dimensionless unit hydrograph method, respectively. The GIS uses a raster method to store the following data: land use and land cover, soil type, rainfall intensity–frequency–duration statistics, runoff curve numbers (CN), regional dimensionless unit hydrograph, and regional lag-time relationship. The GIS has also the capability of computing a number of watershed and hydrologic parameters required for predictions, such as a watershed average rainfall and CN value, area, centroid, stream length, etc. Most of the data for such computations are input from a digitizer. Substantial time and cost savings are possible once the data base has been created. Application of the system is illustrated by an example of predicting flood frequency curves for selected watersheds in Alberta's Rocky Mountain foothills. Key words: geographic information system, flood hydrograph, curve number, hydrologic simulation, flood frequency.
Predicted wave field in a laboratory wave basin
Authors: Isaacson Michael , Qu Shiqin
Published: January 2010

The present paper describes a numerical method for predicting the wave field produced by a segmented wave generator undergoing specified motions in a wave basin which may contain partially reflecting sides. The approach used is based on linear diffraction theory and utilizes a point source representation of the generator segments and any reflecting walls that are present. The method involves the application of a partial reflection boundary condition, which is discussed. Numerical results are presented for the propagating wave field due to specified wave generator motions in a rectangular basin. Cases that are considered include both perfectly absorbing and partially reflecting beaches along the basin sides, as well as the presence of perfectly reflecting short sidewalls near the generator. The method appears able to account adequately for the effects of wave diffraction and partial reflections, and to predict the generated wave field realistically. Key words: coastal engineering, hydrodynamics, laboratory facilities, ocean engineering, wave diffraction, wave generation, wave reflection.
Cable rime accretion measurements on a Laurentian mountain
Authors: McComber Pierre , Druez Jacques , Félin Béatrice
Published: January 2010

Rime is an important cause of damage to structures in northern Quebec, Canada, and a major concern about the reliability of power transmission lines. An atmospheric icing test line was set up at Mt. Valin (altitude 902 m), near Chicoutimi, to measure icing rates on stranded cables. Two cables, the first one 96.5 m (316.5 ft) in span and the second one 32.6 m (106.9 ft), were used to investigate transmission line icing by comparing icing, for a complete winter, on two stranded cables, 35 mm (1.38 in.) in diameter for the first cable and 8 mm (0.315 in.) for the second. Measurements taken during the 1986–1987 winter season are analyzed. Ice accretion and shedding are correlated with ice detector alarms and wind velocity respectively. The icing intensity, considered to be proportional to the number of icing alarms per unit time, is strongly correlated with the cable icing rate. A significant correlation is also verified between the wind velocity and the ice shedding. Results of this investigation indicate that wind velocity and icing detector alarm rate are important variables to predict total ice mass on cables exposed to winter in-cloud icing. With more similar data, the implementation of an empirical icing model to estimate cable icing in mountain ranges will become possible. Key words: transmission line icing, rime accretion, ice shedding.
Live coal storage structure, Genesee Generating Station
Authors: Chan C. E. , Martin R. L. , Weinreb D. , Trowsdale D. R.
Published: January 2010

The development, by Edmonton Power, of the Genesee Generating Station has necessitated construction of a 40 000-t live coal storage structure. The live storage is a 170 m long coal slot based 17 m below grade. It comprises a concrete U box and inclined reinforced earth sidewalls. The site is underlain by soft clays, which posed special problems for design and construction. Analytical and construction methods were developed to suit the geotechnical and site constraints. A monitoring program was instituted during construction to verify the design assumptions and to confirm the overall stability. This paper reviews the decisions involved in the basic design of the structure, and methods of dealing with design and construction problems. Key words: excavation, struts, earth pressure, reinforced earth, field measurements.
Transferability of intercity disaggregate mode choice models in Canada
Authors: Abdelwahab Walid M.
Published: January 2010

In many transportation studies, the time span of data collection, model development, and analysis is often too long to be responsive to the needs of policy analysts and decision makers. This problem is often exacerbated in situations with severely constrained analysis resources. Therefore, it is often useful to transfer a model from one area to another. Model transfer is defined as the application of a model developed in one area to describe the corresponding behavior in another area. This paper examines the transferability of a class of models used in intercity travel demand analysis. Specifically, disaggregate mode choice models of the multinomial logit type are developed for two regions in Canada, and some established measures of transferability are applied to assess the potential of calibrating these models in one region and applying them in the other. Comparison of mode choice models estimated on data sets from the two regions yielded inconclusive results regarding model transferability. In general, transferred models were found to be 18–23% less accurate than local models in predicting modal shares. Adjusting models' parameters to reflect observed modal shares in the application context improved the predictive ability of the models by about 10%. Key words: transferability, mode choice, disaggregate, travel behavior, multinomial logit, intercity.
Hydroelectric turbine setting – a rational approach
Authors: Gordon J. L.
Published: January 2010

There are no standards for the setting of a hydraulic turbine with respect to the tailwater level. Manufacturers rely on hydraulic model data to determine the required protection against cavitation, and never publish these data. Utilities and consultants must then rely on the interpretation of published statistical data relating submergence to various turbine parameters. In this paper, an alternative approach is proposed wherein a general equation is developed relating the submergence of a stainless steel or cast steel runner to the number of runner blades, the plant capacity factor, the turbine throat velocity, the tailwater level above sea level, the water temperature, and the acceptable amount of cavitation. The equations have been tested on 39 different power plants having either horizontal or vertical axis Kaplan, propeller, or Francis turbines, both large and small. The equations are particularly useful for establishing the turbine diameter and setting during feasibility assessment, and for comparing manufacturer's suggested turbine parameters in the final design stage. The equations can also be used to determine the capacity of a new runner in an existing casing. Key words: hydroelectric, turbines, cavitation, design.
Computation of uniform flow in open channels with flood plains
Authors: Satish Mysore G. , Guo Yiping , Rahman Matiur
Published: January 2010

For the computation of flow characteristics in open channels with flood plains, two-dimensional depth-averaged mathematical models have been used in the past. In the present study, the depth-averaged version of k–ε model including the term that accounts for the effect of the submerged vertical or steep boundaries on the flow characteristics in the momentum equation is presented. It is observed that inclusion of this term plays an important role in the distribution of the computed eddy viscosity in the interaction region between the flood plain and the main channel. The model is validated using the experimental data from earlier investigators. Key words: open channels, flood plains, two-dimensional depth-averaged model, uniform flow, k–ε turbulence model.
Prestressing force increment of two-span steel girder
Authors: Troitsky M. S. , Zielinski Z. A. , Rabbani N. F.
Published: January 2010

The economic advantages and the advanced technology of prestressed steel bridges has opened new opportunities in bridge engineering. The girder bridges prestressed by cables have been recognized as a technique for the design of new bridges as well as the rehabilitation and increasing the load-bearing capacity of the existing bridges. However, the prestressing of steel girders introduces new problems which require special attention and studies. The objective of this paper is to analyze the influence of the prestressing force increment and the induced negative bending moment in two-span steel girder bridges prestressed by external tendons (cables of high strength steel). The proposed analysis is based on the flexibility method. The deformations are calculated by the virtual work method. The analysis is limited to elastic stage only. The equations for calculating the prestressing force increment and the bending moment at the middle support are derived. Numerical examples are solved and the results are compared with those of similar non-prestressed girders. The influence lines are prepared and evaluated for a continuous girder of two equal spans of 60 m in length each. Key words: bridges, post-tensioned steel, force increment, analysis, influence line.
Évaluation des règles d'exploitation de systèmes de réservoirs
Authors: Acosta Alejandro Guerrero , Leclerc Guy , Tremblay Michel
Published: January 2010

During the operating phase, the evaluation of the risks of failure generates additionnal information that is essential for water reservoir system management. This information throws light on the selection of a release policy for the mid-range operating horizon and helps to determine, at the beginning of each period of the short-range horizon, if the risks of failure resulting from the application of the current release policy remain acceptable. A method of evaluation of the risks of failure of a reservoir system, variables that are not explicitly accounted for in the determination of the release policy for the mid-range horizon, is described. The evaluation method uses a stochastic simulation model to reproduce the evolution of the system operated according to the current release policy. It estimates the risk of the various types of failure for a known state of the system at the beginning of a decision period and those that the system may reach at the beginning of the other periods of the evaluation horizon. It also computes the statistics of the various types of failure encountered and of the net benefits. The evaluation method is applied to a system of one reservoir and one powerhouse. Key words: reservoirs, failure, stochastic simulation, risk evaluation, release policy.
Fate of indicator organisms in sludge during bacterial leaching of metals
Authors: Henry J. G. , Prasad D. , Lohaza W. B.
Published: January 2010

Biological extraction (bacterial leaching) of heavy metals from digested sewage sludge has been shown to be a practical means for decontaminating sludge for use on agricultural land. However, it was not known whether pathogenic organisms would survive or be destroyed in the acidic environment necessary for the bacterial leaching process. The purpose of the research reported herein was to assess the effect of bacterial leaching on various bacteria commonly used to indicate the possible presence of pathogenic organisms. Although pathogenic viruses, bacteria, protozoa, and helminths may be present in sludge, this study is concerned only with bacterial pathogens. The concentrations of the four indicator bacteria selected to represent the bacterial pathogens were determined in a series of laboratory bacterial leaching units. Results showed that, although about 80–90% metal removal efficiencies were achieved (at a pH of 4.0, an aeration rate of 100 mL of air per minute per litre of sludge) at a temperature of 20–25 °C, the indicator bacteria were not reduced during bacterial leaching at high suspended solids concentrations. The survival of indicator bacteria was found to be a function of the suspended solids concentration in the leaching units, regardless of the source or type of indicator bacteria. At suspended solids concentrations greater than 10 g/L, the indicator bacteria were able to survive, apparently unaffected by the unfavourable environmental conditions (10 days retention at pH 4.0). Below this suspended solids concentration of 10 g/L, significant reductions of total coliforms, faecal coliforms, and faecal streptococci were achieved. Total heterotrophs did not follow the same trends as the other indicator bacteria. Key words: bacterial leaching, Thiobacillus ferrooxidans, indicator bacteria, enteric pathogens removal, sewage sludge, sludge disposal.
Contaminant impact assessment and the contaminating lifespan of landfills
Authors: Rowe R. Kerry
Published: January 2010

Some of the factors to be considered in performing impact assessments for proposed municipal and non-hazardous waste landfill sites are discussed. These factors include the effect of the mass of contaminant, infiltration, and attenuation in the hydrogeologic system on the contaminating lifespan of a landfill. The potential impact of fracturing of the soil separating the landfill from an underlying aquifer is examined. The influences of a compacted clay liner and (or) a natural, intact clayey layer below the fractured soil are examined. The concept of developing "triggers" to initiate leachate control measures, and the associated potential impact on groundwater, is discussed in the context of the potential design life of the underdrain system in a landfill. Key words: environmental impact, contaminant migration, landfill, design, fractures, liners, groundwater, leachate collection.
Effet des murs de remplissage en maçonnerie sur la période de vibration des portiques
Authors: Elouali Taoufik , Houde Jules , Tinawi René
Published: January 2010

This paper examines the influence of masonry infill panels on the natural period of vibration of multi-storey frames in relation to seismic load resistance. Simple analytical expressions are presented to evaluate the natural period of these types of structures with varying number of bays and stories. Results obtained with the proposed formulae were found to correlate well with numerical values obtained from a dynamic analysis program. Key words: masonry infills, seismic behaviour, natural periods, frame structures.
Proof load test levels by exact integration
Authors: Hong Han Ping , Lind Niels C.
Published: January 2010

Structural design standards usually contain rules for load testing to verify the load-carrying capacity. This paper determines the proof load test level as a function of the target safety index, the safety index before the test, and the ratio between the standard deviations of strength and load. The distributions of the load and the load-carrying capacity are assumed to be independent and lognormal. Using exact probability integration, comparison is made with earlier approximate values, and the results are verified independently by simulation. Several examples of application are presented. It is concluded that the values of the normalized proof load test level, obtained by a second-order approximation, are sometimes not sufficiently accurate for practical applications. The values given in this paper are recommended. Key words: structure, proof load testing, probability, safety index, numerical integration, simulation.
Engineering software – a structural consultant's perspective
Authors: Duchesne D. P. J. , Humar J. L.
Published: January 2010

The advantages that automatic computing offers in structural analysis, design, and drafting are now well known. Computers offer great speed and accuracy in the process of analysis and design, relieving the engineer of the drudgery of number crunching, permitting more time for innovation and creativity, and affording the opportunity of trying out several design alternatives. However, to realize the productivity gains and the improvements in design quality that computers offer, the engineer must be aware of the many pitfalls and problems associated with computerization: the financial commitment, the need for training, the difficulty in obtaining quality software, and the risk associated with using unreliable software compounded by the inadvertent complacency that computer usage may encourage. This paper attempts to provide an overview of the issues involved in computerizing a structural engineer's office. The advantages and disadvantages of computerization are discussed. The additional management responsibilities that computerization brings are highlighted. The types of software usually needed in a structural office are outlined. The constituents of good software are discussed with reference to user interface, analysis and design procedures, output, documentation, and program architecture. Finally, the concept of computer integration in structural design is explained and an example if provided to illustrate the technique. Key words: structural, computer, software, consultants, buildings, integration.
Multi-day flow forecasting using the Kalman filter
Authors: Fitch Murray A. , McBean Edward A.
Published: January 2010

A model is developed for the prediction of river flows resulting from combined snowmelt and precipitation. The model employs a Kalman filter to reflect uncertainty both in the measured data and in the system model parameters. The forecasting algorithm is used to develop multi-day forecasts for the Sturgeon River, Ontario. The algorithm is shown to develop good 1-day and 2-day ahead forecasts, but the linear prediction model is found inadequate for longer-term forecasts. Good initial parameter estimates are shown to be essential for optimal forecasting performance. Key words: Kalman filter, streamflow forecast, multi-day, streamflow, Sturgeon River, MISP algorithm.
A stochastic study of floods in Canada: truncation level by region
Authors: Caissie Daniel , El-Jabi Nassir
Published: January 2010

The main problem in applying a partial duration series model in flood frequency analysis lies in the selection of the truncation level. From a practical point of view, it is important to have a simple and effective way of selecting this level. A truncation level study was conducted on hydrometric stations across Canada and regional equations were developed for estimating the truncation level using regression analysis. The homogeneous region was selected based on previous countrywide hydrological studies. From the hydrologic and physiographic parameters used in the regression analysis, the mean annual flood best explained the truncation level for all of the regions. Key words: flood, partial duration series, truncation level.
Assessment of some Canadian seismic code requirements for concrete frame structures
Authors: Paultre Patrick , Mitchell Denis
Published: January 2010

Three buildings in Montreal were designed for different levels of "ductility" according to the 1990 National Building Code of Canada and the 1984 Canadian Standards Association standard for the design of concrete structures for buildings. Analytical procedures were developed in order to predict the responses of main structural components to the combined loading effects of axial load, moment, and shear. In addition, a hysteretic behavioural model was developed in order to account for strength and stiffness degradation as well as pinching of the hysteretic response. Nonlinear dynamic analyses were carried out on each building for a series of artificially generated accelerograms together with real earthquake records. The results of the nonlinear dynamic analyses enabled an assessment of the performance of different building designs and an assessment of current code requirements. Key words: seismic design, reinforced concrete, detailing, structures, codes.
Material selection and mix design considerations for constructing asphaltic roads and runways in Canada's north
Authors: Stewart J. A. , Aerde M. Van
Published: January 2010

The design of practical asphaltic roads and runways in Canada's north is very difficult due to the harsh environmental conditions under which the material needs to be placed in the field, the severe temperature loads to which the pavement is exposed, and the difficulty and (or) cost of obtaining appropriate materials. This paper summarizes the current state-of-the-art in terms of the selection of materials and the design of mixes for the construction of asphaltic pavements in Arctic and sub-Arctic climates. It is shown that the temperature susceptibility of the asphalt cement, the curing rate of cutback liquid asphalts, and the transport of asphalt emulsions at low temperatures are the main problems associated with selecting a binder material. Emulsions appear to be the best suited for use in cold climates, but there is little experience with their use in the far north. In addition, it is indicated neither standard nor the modified Marshall nor the Hveem tests provide ideal tests for selecting the optimum binder content, the degree of curing, the required aerating, or the amount of mixing water for designing asphalt mixes. Key words: asphalt pavements, northern roads, mix design, material selection.
Behaviour of recycled asphalt pavements at low temperatures
Authors: Sargious M. , Mushule N.
Published: January 2010

This paper summarizes the results of a study conducted to evaluate the behaviour of recycled asphalt pavements with respect to low-temperature cracking. For this purpose, a recycled mix consisting of 45.2% reclaimed materials and 54.8% virgin materials as well as a virgin control mix were used in the research program. In the design of both mixes, their initial properties were kept as close as possible to each other to allow for a proper comparison between recycled and virgin asphalt pavements. Using mix properties that were determined experimentally in the laboratory, thermal stresses resulted from drop in temperature and the expected cracking temperatures were determined for both mixes. An experimental analysis based on laboratory tests that consider the pavement properties only as well as a more complete theoretical analysis based on a finite element computer program known as FETAB were included in this study. The program incorporates subgrade parameters, as well as pavement properties and thickness. Using these variables as inputs to the program, the expected performance of recycled and virgin asphalt pavements of various thicknesses and resting on different types of subgrade, with respect to low-temperature cracking, was studied. The results of the study indicated that recycled asphalt pavements would perform better than virgin asphalt pavements of similar initial properties. Key words: asphalt, finite element, low-temperature cracking, reclaimed, recycled, thermal stresses.
Rationale for load specifications and load factors in the new CSA code for fixed offshore structures
Authors: Jordaan Ian J. , Maes Marc A.
Published: January 2010

The Canadian Standards Association (CSA) initiated effort in 1984 aimed at the development of an offshore code for production structures in the oil and gas industry. The present paper summarizes the rationale behind the development of design load specifications in the preliminary standard S.471 "General requirements, design criteria, the environment, and loads." As part of this development, background calibration studies were conducted in tandem with the work of various committees. Selected results from these studies are also discussed in this paper. The basic objectives and tools for developing load criteria for the design of offshore installations are discussed. The use of economic analyses of cost versus safety of structures does not provide clear guidance, and the perspective taken is that of acceptable risks to an individual. This is used in the context of limit states design, which, in S.471, incorporates two safety classes. In order to provide consistent safety levels, the environmental loads are divided into categories based on frequent and rare occurrence, examples being waves and earthquakes, respectively. The role of the annual probability of failure in setting target levels of reliability as well as in the calibration process is emphasized. Various aspects of calibration are summarized, including the background to the rare-frequent separation of loads, the objective function used to optimize the results, as well as the method of handling model uncertainty. Key words: environment, limit states, loads, offshore, reliability, resistance, safety, structures.
Impact of change orders on construction productivity
Authors: Moselhi Osama , Leonard Charles , Fazio Paul
Published: January 2010

In construction projects it is virtually certain that there will be changes made during the course of the work, and that the owner (or design professional) and the contractor will seldom agree on the cost and schedule impact of the changes. This is particularly so on fast track construction, where design and construction are overlapped to accelerate the delivery of projects. Without a doubt, the most contentious area of impact of change orders is their effect on the productivity of the contractor's labour force. This paper presents the quantitative results of a comprehensive field investigation using 90 cases drawn from 57 different construction projects to identify the effects of change orders on productivity. The results indicate a significant direct correlation between the labour component of change orders and the loss of productivity, for both civil/architectural and electrical/mechanical works. These losses are exacerbated by the added presence of other major causes of productivity losses such as acceleration and inadequate scheduling and coordination. Regression models are developed for the direct estimation of productivity losses due to change orders, incurred both independently and in conjunction with other major causes of productivity loss. Key words: construction, productivity, change orders, contemplated changes, impact cost, quantitative models.