bluuebunny/crossref_metadata_2025 huggingface dataset:
Collocation in finite element analysis of constrained problems
Authors: Pantazopoulou S. J. , Ding Y.
Published: January 2010

The concept of three-field displacement finite element formulations of constrained problems is explored in this paper. The approach studied uses collocation within the element domain to enforce the constraints of the problem and resembles mixed formulations because in addition to the approximation of the displacement field, all other auxiliary deformation variables that enter the constraint conditions are interpolated independently. Plate-bending as described by the Reissner–Mindlin theory is used as a model problem for the development of the approach. Two triangular plate elements are formulated based on this methodology, and their performance is investigated using several patch tests. Numerical examples are also considered to study the element behavior under locking conditions (which occur with the classical displacement approach at the thin plate limit). The ability of the elements to overcome locking is established using mathematical arguments and practical examples. The influence of the position of collocation points on the computed results is evaluated through sensitivity studies, with the aim to identify the optimal set. Results are compared with those obtained from the exact solutions and the associated classical displacement model with selective reduced integration of the constrained energy terms. Key words: finite elements, collocation, discrete constraints, mixed methods, thick plates, bending of plates, shear deformations.
Experimental determination of wind pressure distribution for cylindrical and spherical flexible membrane structures
Authors: Srivastava N. K. , Turkkan N.
Published: January 2010

Wind interaction with flexible structures, such as air-supported structures, is different from that of the standard rigid structures. Very few experimental studies are available in the literature with regards to wind effects on such structures. This paper presents an experimental wind tunnel study on hemispherical and cylindrical models of varying ratios of height to base width. The results of the steady state pressure distribution on flexible air-supported models are compared with those of the rigid models, which are generally known. Other varying parameters are also considered, such as wind velocity and direction, internal support pressure, and the Reynolds number. Key words: structure, experimental, wind pressure distribution, flexible membrane, cylindrical, spherical.
Étude de la réouverture de la lagune du Havre aux Basques. II. Modélisation numérique du processus de mélange des eaux
Authors: Khelifa A. , Ouellet Y. , Robert J.-L.
Published: January 2010

This paper, the second of a series, presents the results of a numerical study of the advection–diffusion water mixing process between the Havre aux Basques lagoon and the Gulf of St. Lawrence, after the proposed reopening of the lagoon. In this study, the reopening scheme of the inlet, which has been closed in 1957, is analyzed by using a horizontal two-dimensional numerical model. The transport model is based on the Douglas–Wang finite element formulation for a space discretization. The approximation is quadratic, using six-node triangular elements. The semi-implicit Crank–Nicholson scheme is used for a time discretization. The results show that after reopening the lagoon, mixing may take between 5 and 22 days for a diffusion coefficient considered constant throughout the region and varying from 5 to 500 m2/s. Key words: lagoon, Havre aux Basques, advection–diffusion, mixing, numerical model, finite element, Douglas–Wang.
Point-of-entry adsorbers for the removal of fumigants
Authors: Narbaitz Roberto M. , Parsons Frances Z. , Tzeng Tsong-Yih
Published: January 2010

Point-of-entry systems with granular activated carbon filters have been used extensively to provide safe water to rural homes with wells contaminated with synthetic organic chemicals. Because of the low cost of these systems, their design is generally based on the equilibrium column model, the isotherm data from the literature, and a scale-up factor. This paper analyzes the necessary scale-up factors for point-of-entry adsorbers based on fumigant adsorption data gathered through an extensive literature review. The fumigants evaluated are 1,2-dichloropropane, 1,2-dibromo-3-chloropropane, and ethylene dibromide. It was impossible to thoroughly assess the scale-up factors for 1,2-dichloropropane because of the limited data. Column data for the other two fumigants were sufficient to generate column loading lines, which can be used directly without resorting to scale-up factors. Column data showed that the scale-up factors are greatly affected by competitive adsorption with the naturally occurring background organic matter and by preloading of these organic matter. As these phenomena are not well understood, it is presently impossible to accurately predict the appropriate scale-up factors. A recommended design approach is outlined. Key words: adsorption, activated carbon, fumigants, point-of-entry.
Instrumentation de barrages par accélérographes
Authors: Darbre Georges R.
Published: January 2010

A better understanding of the dynamic behaviour of dams requires strong-motion instrumentations. In particular, it is necessary to observe the free-field motions at the dam sites and the effective motions along the abutments, and to determine the dynamic properties of dams and their response to severe earthquakes. Instrumentation schemes are developed for arch dams, gravity dams and embankment dams, considering specific observational needs and objectives. The technical specifications to be satisfied by the accelerographs and the arrays are developed. Four arrays, which have been installed in Swiss dams ranging in height from 120 to 285 m, for a total of 29 triaxial accelerographs, are also presented. Key words: earthquakes, strong motions, instrumentation, accelerographs, dams.
Separation between buildings to avoid pounding during earthquakes
Authors: Filiatrault André , Cervantes Mario
Published: January 2010

This paper presents an analytical investigation on the required separations between adjacent buildings to avoid pounding during earthquakes. Five wall buildings, having 3, 6, 10, 15, and 25 storeys, were designed for three different seismic zones in Canada: Montreal, Vancouver, and Prince Rupert. For each zone, an ensemble of code compatible ground motions was identified. Nonlinear time-step dynamic analyses were performed to determine the separations to avoid pounding between each building pair under each earthquake. The required separations, obtained by subtracting the time-histories of lateral displacements between adjacent floor levels, were compared with the requirements of the static method of the National Building Code of Canada. The results indicate that the static method of the code grossly overestimates the required separations. This is to be expected, since the static code procedure does not take full account of the intervening variables (periods, responses, and phases between building motions) which characterize the ground motion and building properties when determining the separation distances. A simplified spectral difference procedure is proposed for inclusion in future editions of the code. Key words: dynamics, earthquake, gap, pounding, seismic, separations.
Prediction of wind load distribution for air-supported structures using neural networks
Authors: Turkkan N. , Srivastava N. K.
Published: January 2010

It is shown in this article that neural networks can be used to predict wind pressure profile for a structure, provided that informative experimental data are initially available to train the network. Utilizing this technique, wind load profiles are obtained for various cylindrical and spherical air-supported membrane structures. The experimental results obtained by the authors have been used as the training set for the network to recognize the pattern. This method can be very effectively applied to other similar problems. Key words: neural network, wind pressure, structures, air-supported, cylindrical, spherical.
Floor vibration due to occupants and reliability-based design guidelines
Authors: Foschi Ricardo O. , Neumann Greg A. , Yao Felix , Folz Bryan
Published: January 2010

Lightweight floors for residential or commercial applications may exhibit annoying levels of vibration under occupancy loading. This paper presents an experimental and analytical study of the vibrational response of wood floors to impact produced by occupants. The results show that, for the analysis of this type of floors, it is necessary to consider the coupled dynamical system of floor and occupants. It is also shown that occupants may be modelled with simple oscillators, and that the dynamic analysis of the coupled system can produce close agreement with tests. Acceptability criteria are used to study design guidelines, combining the variability in floor stiffness with the variability in human tolerance to vibrations. Floors considered use 2 × 8 SPF joists and I-joists. Key words: vibrations, serviceability, occupancy loads, wood floors, reliability.
Rupture du barrage du lac Beloeil: causes et conséquences
Authors: Robert Bruno , Paré Jean-Jacques
Published: January 2010

The foundation failure of a small earth dam, 4.1 m in height, has created a large breach through the overburden foundation, down to the bedrock, and has produced the complete loss of the Beloeil Lake reservoir. The geological nature of the dam foundation was complex; its resistance to internal erosion has changed with time due to seepage forces. The design of the dam foundation treatment was marginal. In this paper, the conditions of the dam prior to failure are given, the probable causes of the accident are presented, and the environmental consequences are reported. Such a case history of a dam failure illustrates the necessity to have a thorough knowledge of the foundation conditions of existing dams even for a very small water retaining structure. That accident demonstrates also the need for a continuous and effective surveillance program. Damages consist mainly in overburden erosion and sediment transportation through a remote area without any loss of human life. Key words: earth dam, foundation, failure, environment, rehabilitation, dam safety, surveillance.
The effect of ammonia loading and operating temperature on nitrification and denitrification of a high ammonia landfill leachate
Authors: Azevedo B. D. , Mavinic D. S. , Robinson H. D.
Published: January 2010

The effect of ammonia loading and operating temperature on the treatment of high ammonia, methanogenic, landfill leachate was investigated. Two single-sludge, nitrification–predenitrification systems were operated in parallel: one with a 10-day aerobic solids retention time, and the other with a 20-day aerobic solids retention time. The study consisted of two phases: an ammonia loading phase and a cold temperature phase. From the first phase, it was found that, at an influent leachate ammonia level of up to 1500 mg N/L, both systems produced an effluent of < 1 mg NH4-N/L and approximately 170 mg NOx−-N/L. Aerobic nitrite and anoxic "free" ammonia were both observed to increase as the ammonia loading was increased. When the influent ammonia was raised from 1500 to 2000 mg N/L, nitrification in both systems failed. During the second phase, the temperature was decreased from 20 to 10 °C while maintaining the leachate ammonia level at 1500 mg N/L. Aerobic nitrite accumulation and rising aerobic BOD5 were observed to begin at 14 °C. When the temperature was dropped from 12 to 10 °C, nitrification failed in both systems. In both cases, nitrification was re-established at 10 °C, by ceasing to waste solids and by stopping methanol addition. Key words: ammonia, biological, denitrification, landfill, leachate, nitrification, temperature, treatment.
Les digues fusibles, un élément de sécurité additionnelle dans un aménagement hydro-électrique
Authors: Marche C. , Gagnon J. , Quach T. T.
Published: January 2010

A lot of existing hydroelectric developments do not meet current spillway capacity design standards. Statistics compiled indicate this is one of the main causes of dam failure. It is not, however, necessary to continually increase discharge capacity to maintain an acceptable risk level at a given development. In hydroelectric systems with large reservoirs, the very design of the many structures controlling the reservoirs and the introduction of the concept of fuse-plug spillways offer attractive alternative solutions. The digital tools required for a real impact and risk analysis were developed. This paper describes their use in a preliminary study of the La Grande 3 reservoir in Quebec. Key words: dams, safety, failure flow.[Journal translation]
Thermal protection of concrete dams subjected to freeze–thaw cycles
Authors: Léger P. , Côté M. , Tinawi R.
Published: January 2010

Concrete dams located in northern regions are subjected to severe cyclic seasonal temperature variations, which may contribute significantly to the deterioration of the exposed faces and the long-term degradation of strength and stiffness properties. This paper presents a comparative study of thermal protection methods that might be used to improve the durability of concrete dams subjected to freeze–thaw cycles. First, the thermal, structural, and physical processes that affect the dam's resistance to freeze–thaw cycles are discussed. The thermal durability of existing northern concrete dams is then reviewed. Three thermal protection schemes are presented: (i) insulation membranes applied directly to the concrete facings, (ii) insulation membranes with air spaces for drainage or visual inspection, and (iii) insulation made of granular material. Two-dimensional thermomechanical finite element analyses of a typical gravity dam located in Quebec are then carried out to assess the performance of thermal protection systems using different configurations of insulating materials and exposure conditions, and to develop appropriate design criteria. Key words: concrete dams, thermal analysis, insulation, finite element method.
Development of a decision support system for the planning of municipal solid waste composting and recycling programs
Authors: Barlishen K. D. , Baetz B. W.
Published: January 2010

The number and complexity of mathematical models to assist municipal solid waste management agencies in the planning of recycling programs are increasing. A survey of practising waste management professionals has indicated a general interest in mathematical modelling techniques to assist with decision-making, but there is a lack of practical applications of these techniques, particularly within the local and regional waste management agencies that are responsible for planning and implementing waste reduction and recycling measures. A prototype decision support system has been developed to assist with the preliminary planning of municipal solid waste composting and recycling programs and processing facilities. This prototype planning tool combines knowledge-based system components with spreadsheet models to assist with waste forecasting, technology evaluation, composting and recycling program design, and preliminary processing facility planning. The system was designed for use by local and regional solid waste management engineers and planners, and waste recycling coordinators. The prototype decision support system is considered to represent a reasonable, useful, and practical (with respect to data requirements and cost) planning tool. The knowledge bases, created for the prototype decision support system, represent the collection and organization of a significant amount of currently available expertise regarding composting and recycling program planning issues. Key words: municipal solid waste, waste management, recycling, composting, decision support systems.
Modelling of a circular-section floating breakwater
Authors: Isaacson Michael , Whiteside Neal , Gardiner Robert , Hay Duncan
Published: January 2010

The physical and numerical modelling of a circular cross-section floating breakwater subjected to normal and obliquely incident regular waves is described. The transmission coefficient, breakwater motions, and mooring line forces were measured in two- and three-dimensional laboratory tests for a range of wave conditions and breakwater parameters. The experimental results are compared with results of a numerical model based on linear two-dimensional wave diffraction theory. The performance of the breakwater is summarized and compared with that of a rectangular-section breakwater. Possible modifications to improve the breakwater's performance characteristics are considered. Key words: coastal structures, floating breakwaters, hydrodynamics, moorings, waves.
Correlation of the bond provisions of CSA A23.3-94 with tests on tension lap splices in beams
Authors: Rezansoff T. , Sparling B. F.
Published: January 2010

Data on beams with tension lap splices tested under static loading at the same institution over the past two decades are correlated with the bond provisions of the Canadian concrete standard CAN/CSA A23.3-94 (detailed design approach), as well as with the recommendations of ACI Committee 408, on which the Canadian standard appears to be largely based. The correlations show that transverse reinforcement is more effective than the new bond provisions allowed in cases where the bond failure is governed by splitting rather than bar pullout. Extending the effective limits for confinement provides a more accurate estimate of the bond resistance available at higher levels of confinement, resulting in a more uniform factor of safety over a wide range of confinements. Lap splices with no transverse confinement showed relatively poorer performance than lap splices with varying degrees of transverse confinement when correlated with resistances predicted on the basis of the new CAN/CSA A23.3-94 provisions. Weaker relative splice performance in the absence of transverse confinement raises a concern for the development lengths required by the CAN/CSA A23.3-94 provisions. With highly stressed lap splices, a class factor of 1.3 is applied to the basic development length to determine the lap length. Published information, on the other hand, has shown that lap splice lengths and development lengths should be the same for transferring or developing the same level of stress in tension reinforcement when the same level of confinement is provided along the anchorage. In contrast, the ACI Committee 408 recommendations use a larger factor of safety on development length and lap splice length, rather than applying class factors for splices only, making splice and development lengths the same for the same confinement and required strength transfer. For the data considered, required lap lengths are similar using both the CSA Standard CAN/CSA A23.3-94 (including the 1.3 class factor) and the ACI 408 recommendations, and only small differences in overall prediction accuracy were found. Differences in the definition of the concrete confinement term for close bar spacing by the two design models, different limits on the total confinement that can be considered effective, as well as a further modification factor for bar size in the CAN/CSA A23.3-94 provisions, result in only small differences in lap length requirements for most of the data considered. Key words: anchorage (structural), bond, confinement, lap splices, reinforced concrete, standards, static loading, tension.
Condition rating of rigid pavements by neural networks
Authors: Eldin Neil N. , Senouci Ahmed B.
Published: January 2010

This paper discusses the development and the implementation of a neural network for the condition rating of rigid concrete pavements. The condition rating scheme employed by Oregon State Department of Transportation was used as the basis for the development of the network presented. A training set of 298 cases was used to train the network. The network adequately learned the training examples with an average training error of 0.011. A testing set of 3902 cases was used to check the generalization ability of the system. The network was able to determine the correct condition ratings with an average testing error of 0.022. The network ability of dealing with noisy data was also tested. Up to 40% noise was added to the data and introduced to the network. The results showed that the network presented could accurately identify condition rating relationships at high level of noise. Finally, a statistical hypothesis test was conducted to demonstrate the system's fault-tolerance and generalization properties. Key words: neural networks, condition rating, condition index, rigid pavements, pavement distresses, pavement maintenance, fault-tolerance, generalization, noisy data.
Hydraulic jump in channel contraction
Authors: Yasuda Y. , Hager Willi H.
Published: January 2010

The hydraulic jump in a linearly contracting channel is studied in relation to choking flow. For a contraction intended to perform under supercritical flow, choking is an important design consideration because of the increase of flow depth and modified upstream conditions. Based on the momentum equation, a relation for the sequent depths ratio is determined and verified with extended experiments. Further, the mechanisms of both hydraulic jump and the choking flow are described. The wall surface profile is shown to be similar and equal to the profile of the classical hydraulic jump for a relatively small contraction rate. The lengths of roller and jump are determined, and substantial agreement with the classical jump is again found. The choking of a channel contraction is discussed as the limit condition of the hydraulic jump. A simplified model is shown to agree with observations. A design equation for choking is proposed. Key words: channel, choking, contraction, hydraulic jump, supercritical flow, water flow.
Accounting for connection behavior in steel frame design
Authors: Morris Glenn , Huang Jitian , Scerbo Mario
Published: January 2010

The behavior of a steel frame may be affected significantly by the moment versus rotational deformation (M–ϕ) behavior of its beam-to-column connections. Some of the effects of connection behavior are described and demonstrated. Because connection behavior is nonlinear and relatively difficult to model analytically, generally applicable analytical behavior models are not available. Nor, despite the availability of more than 300 experimentally measured connection M–ϕ data sets, are generally applicable empirically based behavior models available. Consequently, connection behavior continues to be accounted for only crudely in North American design specifications and in frame design. This paper describes a three-step strategy that would eventually permit the M–ϕ behavior of beam-to-column connections to be accounted for explicitly and routinely in steel design specifications and thus in frame design. The first step, to express connection M–ϕ behavior in a compact form suitable for incorporation into frame analysis software, has been demonstrated by curve fitting 274 experimental M–ϕ data sets to a specially developed function that requires only six parameters to describe connection behavior. The second step, to illustrate graphically the ranges of M–ϕ behavior exhibited by the common connection. types, and thereby to help designers to develop a "feel" for connection behavior, has been demonstrated by comparing the M–ϕ plots to the EUROCODE3 connection classification boundaries. The third step, to blend the standard connection geometries that have been developed in several countries into an international menu of standard connection geometries and, eventually, to generate and curve fit reliable experimental M–ϕ data for all of the standard connections, is summarized. Key words: beam-to-column connections, connection behavior, steel frames, structural analysis, steel design.
High ammonia landfill leachate treatment using anaerobic filter and rotating biological contactor
Authors: Henderson J. Paul , Atwater James W.
Published: January 2010

A pre-denitrifying anaerobic filter and a rotating biological contactor (RBC) were used to remove nitrogen from a high ammonia landfill leachate collected from a municipal and industrial solid waste landfill in Kaohsiung, Taiwan, Republic of China. The research indicated that greater than 95% ammonia removal from high ammonia-N (2140 mg/L) leachate can be achieved with RBC ammonia-N loading rates up to 1.5 g/(m2∙d). At RBC loading rates of 1.5–3.0 g/(m2∙d), ammonia removal ranged from 80% to 90%. Nitrogen removal averaged 66%, including an estimated 54% removal in the RBC. Nitrogen removal in the RBC was the result of either simultaneous nitrification and denitrification or air stripping of ammonia in combination with nitrification. Both alkalinity consumption and COD removal results support the explanation of simultaneous nitrification and denitrification (potentially aerobic denitrification); but since RBC off-gasses were not monitored, neither theory can be confirmed. The high nitrogen removal in the RBC suggests that for this leachate the anaerobic filter was not required for ammonia and nitrogen removal. BOD and COD removal averaged 92% and 49% respectively. Key words: landfill, leachate, treatment, ammonia, rotating biological contactor (RBC), nitrification, denitrification.
Influence of cable vibration on seismic response of cable-stayed bridges
Authors: Tuladhar Raju , Dilger Walter H. , Elbadry Mamdouh M.
Published: January 2010

In cable-stayed bridges, modelling the cables is of particular significance for the seismic behaviour of the structure. The common practice of modelling a cable by a single truss element is inadequate for seismic response calculations because it essentially precludes the lateral cable vibration modes. The present paper studies the influence of cable vibrations on the seismic response of cable-stayed bridges. Three bridge examples with different spans and properties were used. Cable vibrations are accounted for through the use of multiple links for each cable. Cable vibration effects are found to be significant for seismic response calculations, particularly when the cable fundamental frequencies are overlapping with the first few frequencies of the bridge. Parametric studies are conducted with regard to the number of links per cable, the effect of the modulus of elasticity of the cables, and different earthquakes on the bridge response. Modelling the cables by two links per cable such that at least the fundamental modes of the cable vibrations are represented can significantly account for the effect of cable vibrations. It is also observed that the equivalent modulus method cannot in any way account for the cable vibration effects. Key words: cable vibration, dynamic analysis, equivalent modulus, multiple links, seismic response, cable-stayed bridge.
Influence of soil conditions on the seismic behaviour of two cable-stayed bridges
Authors: Elassaly Mohamed , Ghali Amin , Elbadry Mamdouh M.
Published: January 2010

The results of a case study of the internal forces caused by earthquake in two examples of cable-stayed bridges are presented. A comparison is made between the behaviour of a model in which the structure is idealized without the foundation system and a model in which both the structure and the supporting foundation are idealized. The effects of varying the soil conditions on the seismic response are assessed. Also, the effects of out-of-phase support movements, caused by the lapse of time required for the seismic waves to travel from one support to the other, are considered. It is concluded that the effects of these parameters are significant and should not be ignored in the seismic analysis of cable-stayed bridges. Key words: bridges, cable-stayed, dynamic, earthquake, internal forces, seismic, soil–structure interaction.
A process-based approach to value-added construction — the CYCLONE/DISCO system
Authors: Halpin Daniel W. , Huang Rong-Yau
Published: January 2010

Recently, the study of processes and of non value-adding tasks at the process level has enjoyed a renaissance in the manufacturing sector because of the emphasis on total quality management and the work of W. Edwards Deming and others. Interest by the construction industry in the study of processes at this level has been negligible. In order to achieve better quality in construction, the industry must become more process oriented and involved in the study of resource interaction. The CYCLONE modeling system provides an environment for flow charting and studying the interaction of resources within a construction process. The DISCO program which is integrated with the CYCLONE modeling system provides a graphical modeling and simulation environment which facilitates the analysis of construction operations using simulation techniques. The CYCLONE modeling format and the DISCO program interface constitute a foundation upon which improved process design and efficiency can be established. Key words: construction management, simulation, flow modeling, computer methods, construction processes.
Shear distribution in simply supported skew composite bridges
Authors: Ebeido Tarek , Kennedy John B.
Published: January 2010

Composite steel–concrete bridges remain one of the most common types built. Proper design of new bridges and evaluation of existing bridges requires accurate prediction of their structural response to truck loads. The American Association of State Highway and Transportation Officials has traditionally applied a load distribution factor for both moment and shear. The Ontario Highway Bridge Design Code (OHBDC) considers several parameters in establishing load distribution factors for moment. However, the method is limited to bridges with skew parameters less than a certain value specified in the code. The presence of skew reduces the longitudinal moments in the girders. However, it also causes high concentration of shear in the girder closest to the obtuse corner and reduces shear concentration in the girder closest to the acute corner as well as in the interior girders. Therefore, shear should be considered in the design of such bridges. In this paper, the influence of skew on the shear distribution factor is investigated. The influences of other factors such as girder spacing, bridge aspect ratio, number of lanes, number of girders, end diaphragms, and intermediate cross-beams are presented. An experimental program was conducted on six simply supported skew composite steel–concrete bridge models. Results from a finite element analysis showed excellent agreement with the experimental results. An extensive parametric study was conducted on prototype composite bridges subjected to OHBDC truck loading. The parametric study included more than 400 cases. The data generated were used to develop empirical formulas for shear distribution factors for OHBDC truck loading and also for dead load. An illustrative example is presented. Key words: bridges, codes of practice, composite, distribution, reaction, reinforced concrete, shear, skew, structural engineering, tests.
Local effective length factor in the equivalent slenderness ratio
Authors: Temple Murray C. , Elmahdy Ghada
Published: January 2010

The Canadian Standard S16.1 specifies an equivalent slenderness ratio to be used when determining the compressive resistance of a built-up member when buckling occurs about an axis perpendicular to the interconnectors. This equivalent slenderness ratio is the square root of the sum of the squares of the slenderness ratio of the built-up member acting as a unit and the maximum slenderness ratio of a component part between fasteners. The Standard specifies for this second component that an effective length factor be used, the magnitude of which depends on the type of connection. An effective length factor of 0.65 is specified when welds are used. This is of concern to the authors. It is pointed out that the derivation of this equation by Bleich, and by Timoshenko and Gere, does not contain an effective length factor in the second term. The effective length factor of 0.65 comes from a paper by Duan and Chen. Results of tests on five built-up members, channels arranged in the toe-to-toe configuration, indicate that the use of an effective length factor of 0.65 gives unconservative results, especially when the member is slender. It is recommended that a factor of 1.0 be used in the second term of the equivalent slenderness ratio equation. Key words: battens, built-up members, equivalent slenderness ratio, interconnectors, standards.
Analysis of the braking performance of a tractor-trailer unit
Authors: Gangopadhyay S. , Wilson F. R.
Published: January 2010

An analysis of the braking performance of a tractor-trailer unit is presented in this paper. The analysis revealed that there existed a wide variation in the ratio of braking force to vertical load values on each axle of the tractor-trailer. Braking efficiency was higher for the loaded condition than for an empty tractor-trailer. At all initial speeds, the trailer axles attained the maximum ratio of braking force to vertical load and were the first to lock up. Key words: highway, safety, heavy vehicles, braking performance, tractor-trailers.
Equivalent capacity and efficiency of reinforced concrete beams strengthened with carbon fibre reinforced plastic sheets
Authors: Heffernan P. J. , Erki M. A.
Published: January 2010

Fibre reinforced plastic sheets have recently been used in Switzerland and Japan as an alternative to steel plates for the external strengthening of structural components. This paper presents the results of an experimental program that examines the behaviour of reinforced concrete beams strengthened using carbon fibre reinforced plastic (CFRP) sheets. The concept of equivalent strength is introduced for comparative purposes, and its applicability to design is discussed. The results and analysis of three 2 m reinforced concrete beams and two 5 m reinforced concrete beams of various tensile reinforcement configurations are presented. The CFRP sheets are shown to enhance the stiffness of the beams, the load at which the tensile steel yields, the stiffness of the beams after yielding of the tensile steel, and the maximum load of the beam. The behaviour of the rehabilitated beam is compared to the understrength beam and the equivalent all steel reinforced beam. An equivalent capacity based on the load at which the tensile steel yields is proposed to ensure adequate stiffness within the working stress range. The concept is equally applicable to strengthening as it is to rehabilitation. Key words: reinforced concrete, CFRP, rehabilitation, poststrengthening.
Shear strength of members without transverse reinforcement
Authors: Adebar Perry , Collins Michael P.
Published: January 2010

The variable angle truss model is extended to members without transverse reinforcement by introducing concrete tension ties perpendicular to concrete compression struts. The modified compression field theory approach of limiting the shear transfer across diagonal cracks is combined with the variable angle truss model to develop equations for the shear capacity of members without transverse reinforcement. These equations are the theoretical basis of tabulated values for members without stirrups in the general shear design method of the 1994 Canadian concrete code. This paper also presents the results from an experimental study in which 27 narrow (beam-like) wall elements, with significant longitudinal reinforcement and little or no transverse reinforcement, were subjected to combined axial tension, bending moment, and shear. The experimental results are compared with predictions from the 1994 Canadian concrete code, as well as the American Concrete Institute building code. Key words: building codes, reinforced concrete, shear strength, structural design, tension, tests, truss model.
Optimization of the city of Winnipeg water distribution system
Authors: Miles Terrence M. , Lence Barbara J.
Published: January 2010

A simplified representation of the city of Winnipeg water distribution system is developed and a linear programming model is formulated to represent this system. Six scenarios of the linear programming model are analyzed to determine the most efficient operating policy when the objective functions vary from minimizing reservoir drawdowns to minimizing pumping. This analysis reveals that low total pumping values and low maximum pumping values can be obtained if storage at the inner-city reservoirs is utilized. It is also shown that the system cannot satisfy demand during high demand periods without drawing down the Deacon Reservoir. Key words: reservoirs, water distribution, optimization.
The use of a one-dimensional depth-averaged moment of momentum equation for the nonhydrostatic pressure condition
Authors: Jin Yee-Chung , Li Baozhu
Published: January 2010

A depth-averaged model formulated in the Cartesian coordinate system for curved open-channel flows is extended to solve problems where the effects of nonhydrostatic pressure distribution and nonuniform velocity distribution are significant. The nonhydrostatic pressure condition is added to the z-direction momentum equation assuming that the pressure deviation from the hydrostatic condition at the channel bed decreases linearly to the water surface. The pressure-effect terms are modified in both the moment of momentum and momentum equations. The resulting system of nonlinear equations is solved by a finite-element method. The derived model is then applied to four sophisticated nonuniform flow experiments from the literature. A comparison of the actual experimental results with their numerical prediction results, as calculated with the model, is presented. Generally speaking, a fairly good agreement for the depth-averaged velocities as well as reasonable perturbation profiles were obtained from this comparison. Therefore, it can be said that the depth-averaged model for open-channel flow is reasonably accurate under the given conditions. Key words: open-channel flow, depth-averaged method, finite-element method, nonhydrostatic pressure, nonuniform flow.
Interpretation of field measurements for ice engineering applications
Authors: Gold Lorne W.
Published: January 2010

A description is given of the nature of problems caused by ice for the engineer. Factors controlling the deformation behaviour and strength of ice are discussed briefly. A distinction is made between the behaviour of the relatively small volumes of competent ice that are normally used for tests and the large, inhomogeneous bodies that must be considered by the engineer. Consideration is given to the implications of this for the conduct of in situ tests and the interpretation of their results. Key words: ice, mechanical properties, mechanical behaviour, in situ testing, pressuremeter.
Development of the original ice borehole jack
Authors: Masterson D. M. , Graham W.
Published: January 2010

A tool to obtain the engineering strength and stiffness properties of ice in situ is described; these properties are needed by engineers to estimate ice forces on structures and ice load bearing capacity. The strength and stiffness of the ice sheet will vary with depth and thus it is necessary to have a measure of strength that includes variation with depth to provide a means of determining average or global strength properties. To determine these properties it was necessary to have a tool that would measure strength and stiffness at 0.3–0.5 m intervals through the ice cover. A hydraulically activated borehole jack, operating at a pressure of 70 MPa and capable of fitting in a 150 mm diameter hole, was developed. This lightweight device has proven capable of measuring strength and stiffness properties and has been used by engineers and researchers in several parts of the arctic. It is now accepted as a standard tool for the verification of floating airstrips and other similar structures. Key words: ice, ice testing, ice testing in situ, ice strength, borehole testing, in situ borehole tests, engineering strength, ice compressive strength.
Assessing the fate of polynuclear aromatic hydrocarbons from oily waste land spreading by modelling
Authors: Drolet Clément , Banton Olivier , Lafrance Pierre , Villeneuve Jean-Pierre
Published: January 2010

The organic wastes produced by petroleum refineries are often treated by spreading them on land sites, allowing hydrocarbons to degrade naturally. In such conditions, mathematical models representing the transport of organics in the soil are useful for predicting the quantities of hydrocarbons, like polynuclear aromatic hydrocarbons (PAHs), that could reach the water table in the short and long term. The pesticide root zone model (PRZM) simulates the fate of pesticides in the soil. Because of the analogy between the agricultural use of pesticides and the land spreading of petroleum residues containing hydrocarbons, and the similar physicochemical characteristics of these two types of potential organic contaminants, this model was applied to a land-spreading site in southern Quebec. The simulation results indicate that the studied PAHs may not migrate to depths of more than 40 cm. The predicted concentrations may be several hundred times lower when the degradation rate doubles. Natural variations in the local hydrodynamic conditions caused by soil texture do not greatly affect the concentrations of a relatively mobile PAH in soil or in water. In contrast to the texture, the soil organic matter content greatly influences the distribution of PAHs between the liquid and solid phases and, consequently, their migration through the soil. Key words: PAH, phenanthrene, pyrene, refinery, land treatment, mobility, degradation, simulation, PRZM.
Iceberg – structure interaction probabilities for design
Authors: Fuglem Mark , Jordaan Ian , Crocker Greg
Published: January 2010

When designing systems to operate in regions through which icebergs travel, one of the first inputs of interest is the expected numbers of encounters with icebergs. In this paper, geometric solutions are presented for a cylindrical gravity-based structure, a floating production vessel, and a cargo vessel. The required inputs are the average areal density of icebergs, the average iceberg water line length, and the average iceberg drift velocity. Example calculations are presented for the Grand Banks region off Canada's east coast. Key words: iceberg, encounter, probability, risk, design, oil, production, Grand Banks, structure, tanker.
Reliability-based inspection of post-tensioned concrete slabs
Authors: Pandey M. D. , Nessim M. A.
Published: January 2010

In unbonded, post-tensioned prestressed concrete slabs and beams, corrosion of prestressed tendons due to moisture ingress and their subsequent breakage has been identified as a major problem raising serious concern over the safety of aged structures. The paper presents a practical Bayesian approach to reliability assessment of such structures based on the inspection of a randomly selected sample of prestressing tendons. To minimize inspection costs, clear guidelines are presented for selecting the minimum sample size necessary to demonstrate that the annual probability of failure of an existing structure is below the target value of 10−5, implied in the Canadian Standards Association concrete design code CAN3-A23.3-M84. A systematic and cost-effective incremental strategy is developed for inspection of existing prestressed concrete structures. Key words: reliability, Bayes theorem, prestressed concrete, unbonded post-tensioned system, inspection, corrosion, probability distribution, CSA Standard CAN3-A23.3-M84, slab.
Design of extended end-plate connections for hollow section columns
Authors: Mourad S. , Korol R. M. , Ghobarah A.
Published: January 2010

Extended end-plate connections have been widely used in moment-resisting steel frames with W-shape columns, due to their sufficient stiffness and moment capacity. In addition, such connections are easy to install and permit good quality control. Extended end-plate connections can also be employed in moment-resisting frames with hollow structural section columns by using high strength blind bolts. These bolts have been developed for installation from one side only where the rear side of the connection is inaccessible. In this study, a quantitative procedure for detailing and designing beam extended end-plate connections for rectangular hollow structural section columns using high strength blind bolts is proposed. The design procedure is consistent with the design philosophy given in limit-state codes. The proposed design is based on the results obtained from an experimental program and an analytical study. Key words: design, end plate, connection, hollow section, blind bolts, steel, frame.
Note on structural strength of asphalt rubber concrete developed through the stone mastic asphalt concept
Authors: Svec Otto , Veizer Robert
Published: January 2010

One serious environmental problem related to the transportation field is the stockpiling of old rubber tires. Several huge fires of old tires have already occurred in Canada and the United States and have caused considerable air and possibly soil pollution. Therefore it is of paramount importance to develop techniques to recycle this potentially valuable material, such as by incorporating it into asphalt concrete. The focus of current research at the Centre for Surface Transportation Technology has been to develop a high-performance rubber asphalt concrete based on the stone mastic asphalt (SMA) concept which will be flexible enough (yet strong enough) to resist differential frost heave along roadways better than standard hot-mixed asphalt. Results indicate that a special mix has been successfully developed based on the SMA aggregate concept in which all components, including 0%, 5%, 10%, 15%, and 20% of small rubber crumbs content (based on bitumen weight), are properly sized and designed. Key words: stone mastic asphalt, crumb rubber, laboratory testing, mix design.
1991 ice jamming along the Saint John River: a case study
Authors: Beltaos Spyros , Burrell Brian , Ismail Sayed
Published: January 2010

During April 1991, major and damaging ice jams formed on the Saint John River at Dickey, Maine, and at Sainte-Anne-de-Madawaska, New Brunswick. Field investigations included the measurement of five water surface profiles along the ice jam at Sainte-Anne-de-Madawaska and of shear wall heights at both Dickey and Sainte-Anne-de-Madawaska after the jams had released. These measurements were supplemented by considerable information from local observers and data collection agencies. Following a description of freeze-up and winter conditions, and a chronology of 1991 breakup events, the available data were analyzed according to current ice jam theory. Using a simplified equilibrium analysis and taking into account discharge and channel characteristics, the 1991 Dickey ice jam thickness and water level were calculated and were in general agreement with observed values. In the case of the Sainte-Anne-de-Madawaska jam, sufficient data were obtained for application and calibration of the numerical model RIVJAM which determines the configuration of a jam in nonequilibrium reaches. This resulted in successful reproduction of a measured water profile along the jam and approximate prediction of jam thickness. Implications of the calibrated model coefficients are discussed. Key words: ice jams, flooding, modelling, water level profiles.