bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of the infiltration and migration of brine in potash tailings
Authors: Wong Daniel K. H. , Barbour S. L.
Published: January 2010

A series of infiltration tests were conducted on the potash tailings pile at the Lanigan Division Potash Mine in Saskatchewan. These tests included single ring infiltrometer, shallow pit, open caisson and trench type infiltration tests. The fluid retention curves for the tailings were established in the field using tensiometers and neutron probes to monitor in situ negative fluid pressures and fluid contents respectively. These field-measured curves were then compared with the laboratory-evaluated fluid retention curves.The responses of the field instrumentation during the trench infiltration test were also compared with the results of a computer simulation of infiltration, which utilized the laboratory-evaluated fluid retention curve and the calculated permeability-suction curve as input data. The good agreement obtained between the measured and simulated field responses validates the application of saturated–unsaturated flow theory to the analysis of the flow of brine within the unsaturated tailings. It also verifies the accuracy of the fluid retention curve determined in the laboratory as well as the calculated permeability-suction curve. Key words: potash tailings, infiltration testing, single ring infiltrometer, tensiometer, neutron probe, saturated–unsaturated flow, fluid retention curve, permeability-suction curve, finite-element flow model.
Numerical study of some post-cracking material parameters affecting nonlinear solutions in RC deep beams
Authors: Al-Manaseer A. A. , Phillips D. V.
Published: January 2010

This paper describes a numerical study of some of the quasi-material parameters which are used to define the post-cracking response in smeared crack models for the nonlinear finite element analysis of reinforced concrete. The two major effects studied were interface shear transfer and tension stiffening. The investigation was carried out on a solid deep beam using a nonlinear plane stress formulation. Parabolic isoparametric elements were used with a standard nonlinear solution procedure.The effect of the quasi-material parameters was found to be significant in predicting the behaviour of the deep beam. A sudden drop in the stress at the cracking load was found to be important in the tension stiffening model. Different values can lead to different solutions for load–deflection curves, ultimate loads, and crack patterns. Also it was found that a large reduction in shear modulus to account for interface shear transfer can affect the nonlinear solution and cause numerical problems when used with a gradual release tension stiffening model with no discontinuity at the cracking load. Key words: deep beams, finite element, load deflection, post-cracking, shear transfer, tension stiffening, ultimate load.
Estimation of design hourly volume from seasonal traffic counts
Authors: Sharma Satish C. , Oh Jin Y. , Wyatt Jon J.
Published: January 2010

By considering the thirtieth highest hourly volume (30HV) as the design hour volume, this study reexamines a commonly used method of predicting the 30HV as a function of the annual average daily traffice (AADT) volume. Based on Alberta's highway system data, some common limitations of the traditional 30HV–AADT model are pointed out. Also included in the analysis presented is a proposed alternative model which utilizes July/August traffic data to estimate the design hour volume. The alternative model appears to provide more accurate prediction results and it also eliminates the need of subjectively classifying the roads into various groups as required by the 30HV–AADT method. Key words: annual average daily traffice, design hour volume, highway design, road classification, traffic volume counts, transportation.
A case study of Champlain toll station
Authors: Murthy A. S. Narasimha , Soliman A. H. , Sharma Satish C.
Published: January 2010

The objective of this paper is to study the impacts and quantify the various losses due to the presence of toll stations. For this purpose a survey was conducted on the Champlain toll bridge which connects Montreal Island and the suburban South Shore area. The presence of toll stations imposes restrictions on the free movement of traffic and leads to speed-change cycles, idling, queuing, and excess travel time with direct increase in user costs. The impact of the geometric design of the toll station is also studied with respect to the various losses.The quantification of the various losses is achieved by using queuing theory and simple mathematical relations. The losses are to be considered for two very important reasons; first the losses are incurred by the commuters and second the additional user cost sometimes exceeds the actual toll fee. The results of this study indicates that substantial energy savings could be achieved along with better environmental conditions by either eliminating existing tolls or improving (redesigning) them. In constructing new transportation structures where above losses are likely to occur, the additional user cost due to the losses should be taken into consideration during economic analysis. Key words: fuel consumption, fuel emission, geometric design, idling, queuing, toll station, toll fee, travel time, user cost.
Seismic response of tuned systems
Authors: Ghobarah A. , Aziz T. S.
Published: January 2010

A study is made of the seismic behaviour of tuned equipment–structure systems where one or both of the system components experience inelastic deformation. The response is determined using coupled and decoupled models of the system. The effect of various parameters such as mass ratio and yield level on the system response is evaluated.It was found that the mass ratio and yield level of the tuned inelastic system are the key parameters affecting the response of the coupled system. The response of the primary system is found to be insensitive to the variation of the yield level of the secondary system. In addition, the response obtained using uncoupled analysis of the equipment and structure system is generally higher than the response obtained using coupled analysis and may result in grossly overdesigned systems. Key words: dynamic, seismic, response, tuned, coupled, equipment, structure, earthquake, inelastic.
Concrete trussed arch bridges in China
Authors: Yu Tong-Hua
Published: January 2010

In this paper, the following points are presented: the valuable advantages of the concrete trussed arch bridge; the design consideration and simplified analysis of the bridge; the level of secondary stresses induced in the ends of truss members; the application of prestress to tensile members and bending sections of trusses; and different ways of construction of the bridge.A five-span prestressed concrete trussed arch bridge named the Zhushanlu Road Bridge at Jingdezhen City, Jiangxi Province, is described as an example of medium span bridges of the type popularly adopted in Chinese highway system and the municipal construction since the late sixties. Key words: prestressed concrete, hinged truss, thrust, secondary stress, anchorage, pretensioning, precast.
Wave attenuation by rubble-lined channel walls
Authors: Bishop Craig T.
Published: January 2010

An existing analytical model to predict wave attenuation in a straight vertically walled channel with one or both walls lined with rubble is tested and modified. Placing rubble at side slopes of 1.5 or 2 to 1 along vertical entrance channel walls is a technique used more and more to correct wave agitation problems in harbours. Tests were conducted in a laboratory flume with monochromatic waves and four different sizes of stone from 7.7 mm gravel to 90 mm gabion stone. The attenuation coefficient is found to vary with the ratio of water depth to period squared, d/gT2, with the relative channel width, w/d, and with the side slope of the rubble, m. Preliminary design curves are provided which allow a desk assessment of this technique to be made for a given harbour. The scale effects on wave attenuation due to stone size or shape appear to be negligible. Reynolds number scale effects are also shown to be unimportant over the range tested. Key words: coastal engineering, waves, marinas, wave agitation, wave attenuation.
La tranchée à boue lourde du barrage OA-11
Authors: Massiéra Michel , Paré Jean-Jacques
Published: January 2010

The OA-11 dam is the most important impounding structure of the Opinaca reservoir created by the water diversion of the Eastmain, Petit Opinaca and Opinaca rivers to the La Grande River to increase the hydroelectric potential of the LG-2 power plant. With a maximum height of 32.2 m and a crest length of 3214 m, this earthfill dam was built on relatively pervious fluvio-glacial deposits that made it necessary to use two impervious deep cutoffs (a slurry trench and a cast-in-place concrete panel wall). On the right shore, a slurry trench, 2180 m long, 1.5 m wide, and varying in depth from 3 to 22.7 m, was built.This paper describes the different construction phases of the slurry trench with emphasis on excavation and backfilling, and quality control. The slurry trench performance has been assessed in terms of the pore pressures developed in the foundation and at the toe during and after reservoir filling. Key words: dam, construction, cutoff, excavation, foundation, backfilling, soil–bentonite mixture, slurry trench, treatment.
Numerical analysis of the effects of aquatic weeds on the performance of irrigation conveyance systems
Authors: Manz David H. , Westhoff Dennis R.
Published: January 2010

Aquatic weeds growing in irrigation conveyance systems of the earth-lined, open-channel type retard the flow and reduce the efficiency of the systems. The aquatic weed infestations, consisting of both submerged and emergent vascular plants and algae, also reduce system capacity and may result in increased seepage and spill losses. The flow retardance effects and their impacts on the performance of the irrigation conveyance system are evaluated using a modified version of the irrigation conveyance system simulation (ICSS) model developed at the University of Calgary. Key words: aquatic plants, irrigation conveyance systems, efficiency, performance.
Application of computer-aided design in the Ontario Domed Stadium project
Authors: Allen C. Michael , Duchesne Donald , Humar Jagmohan
Published: January 2010

Application of computer-aided design (CAD) in civil engineering is most effective when the entire design process, from design and analysis to construction, is integrated. Owing to the complexity of civil engineering projects, complete integration of design has not been achieved as yet. However, even partial integration considerably improves the reliability and efficiency of the design process. This is illustrated in the paper through a case study on the application of CAD in the structural design of the Ontario Domed Stadium. The Ontario Domed Stadium, currently being constructed on a site near the Toronto harbour, will have a seating capacity of 55 000. A unique feature of the stadium is its fully retractable roof. The proposed roof has four separate steel space truss panels, three of which move along tracks and one of which is fixed. To handle the large volume of data involved in the design and analysis of the roof structure, generation of data files containing information on the geometry and topology of the roof structure was automated as much as possible. Special interfaces were developed to transfer this data to application programs for structural analysis, design, and production of working drawings. Computer graphics played a vital role in the design process, assisting in data generation, visual check of geometry and deflected shapes, and seating layout. Key words: computer-aided design, CAD, computer graphics, Ontario Domed Stadium, sight line studies, solids modelling.
The first incrementally launched bridges in Hong Kong
Authors: Tung Henry S. S. , Pang M. T. , Roblin E. J. , Tang Man-Chung , Shawwaf K. , Conway T. P. , Mak Y. M.
Published: January 2010

The Hong Kong Government invested HK$1760 million (US$225 million) to build a 24 km trunk road with a dual 3-lane carriageway from Sha Tin to Fanling in the eastern New Territories to serve the new towns and also to cater to the increase in cross-border traffic with China. The section Tai Po Bypass, which is 2.9 km long, required the construction of four viaducts ranging from 116 to 242 m long with columns up to 30 m high. The original design of these bridges adopted precast prestressed concrete beam construction. An alternative design using the incremental launching method to construct these bridges was proposed by the contractor with a saving of HK$10 million in contract costs. Specialist subcontractor and consultants from overseas were involved in the design and construction of these launched bridges, which were the first to be constructed in Hong Kong. With the effort of engineers from four continents, this project was completed ahead of schedule, and the road system was open to traffic in September 1985. Key words: prestressed concrete, alternative design, incremental launching.
Aerodynamics of urban transit vehicles
Authors: Surry David , Cooper Kevin R. , Davenport Alan G.
Published: January 2010

The paper discusses the problems of wind loading of urban transit vehicles in the context of the overturning problem. It is shown that vehicles will respond to gusts of the order of only a few seconds in duration. The available aerodynamic information for vehicle shapes is reviewed, as is the nature of the wind environment in urban areas. The implications of these data are placed in a simplified probabilistic perspective that suggests that the risk of overturning can become very significant if a number of factors are unfavourable. While the details of assessing the risks more precisely are described and have been developed in detail elsewhere, they cannot be applied to this problem until better information for particular cases is developed. Better data on both vehicle aerodynamics and the wind statistics for actual vehicle routes are needed. Key words: urban transit vehicles, overturning, wind loading, aerodynamics, wind engineering.
River flow forecasting for multiple time periods
Authors: Burn Donald H.
Published: January 2010

The performance of a river flow forecasting model employing a Kalman filtering algorithm was evaluated for increasing forecast lead times. The expected decrease in forecast accuracy was quantified and a decrease in forecast precision was noted for increased lead times. The merits of external estimates of meteorological inputs to the model were evaluated through an examination of different forecasting options. It was revealed that even noisy estimates of meteorological events improved the flow forecasts. Key words: forecasting, Kalman filter, real time, precipitation, snowmelt.
Dynamic loading and response of footbridges
Authors: Rainer J. H. , Pernica G. , Allen D. E.
Published: January 2010

Dynamic forces were measured during walking, running, and jumping, using an instrumented platform. The results are expressed as sinusoidal force amplitudes normalized by the subject's weight and are plotted versus frequency. The maximum dynamic loads for walking were found to be nearly twice as large as those recommended in the 1983 Ontario Highway Bridge Design Code or the British Standard BS5400, and those for running or jumping, more than six times as large.Responses of footbridges are calculated using a simple formula based on the dynamic loading due to one person, the response of a simple span at resonance, and limited duration of excitation. Good agreement was obtained with the measured response of two 17 m experimental spans subjected to human excitation, for both the first and second harmonics of the step rate. The resonant vibrations of the spans can be substantially reduced by resonant dampers. Key words: footbridges, dynamic loads, dynamic response, design criteria, resonant dampers.
The toxicity and chemical composition of urban stormwater runoff
Authors: Hall Ken J. , Anderson Bruce C.
Published: January 2010

The effects of land use on the chemical composition of urban stormwater runoff and its subsequent acute toxicity to the aquatic invertebrate Daphnia pulex have been investigated in the Brunette drainage basin of Burnaby, British Columbia. Both land use and interval between rainfall events influenced the chemical composition and toxicity of the stormwater. The industrial and commercial land use sites were the major source of those trace metals most often considered toxic to aquatic invertebrates, with runoff from the commercial sites proving most frequently toxic to the test organism. Toxicity followed the sequence commercial > industrial > residential > open space. A detailed study of a single storm event indicated that while the “first-flush” of the storm contributed to toxicity—through the physical scouring of insoluble pollutants—some soluble pollutants, which were washed out of the watershed later in the storm event, also proved to be toxic. This finding has implications for the collection and treatment of stormwater runoff. Laboratory bioassays with synthetic stormwater composed of the trace metals Cu, Fe, Pb, and Zn at concentrations observed in field samples demonstrated that pH and suspended solids helped to regulate the toxicity of trace metals, and implicated the importance of these factors in natural stormwater toxicity. Key words: stormwater, street surface sediments, land use, buildup time, trace metals, toxicity, Daphnia bioassays, pH, suspended solids effects.
Béton produit en bétonnière mobile et en usine conventionnelle : comparaison des caractéristiques du réseau de bulles d'air
Authors: Larose Gaston , Pigeon Michel
Published: January 2010

The durability of concrete to freeze-thaw cycles is dependent upon the existence of an adequate air-void system. There are very few studies on the air-void system of field concretes. Laboratory tests have proven that the air content measurement on the fresh concrete is not sufficient to judge the aptitude of the air-void system to protect the concrete from frost damage.This paper is a comparison of the air-void systems of field concretes produced in either a conventional plant or a mobile unit the use of which is becoming more and more frequent. The concretes produced in the conventional plant generally had sufficient air-void systems for air contents in the usual range (5–7%). The mobile unit showed that a slightly higher air content (8%) was needed to produce an adequate air-void system. Key words: concrete, mobile concrete-mixer, air-void systems, air-entraining agent, spacing factor, surface area, air content.
Indice de qualité de l'eau permettant le suivi environnemental et la mesure des impacts locaux
Authors: Cluis Daniel A. , Lefebvre Yves , Laberge Claude
Published: January 2010

Environmental indices are useful as a means of communication between governmental control agencies and the general public. While air quality indices are broadly used, water quality indices have found little practical application. The multiplicity of parameters necessary to describe water quality (coliforms, BOD, toxicants, nutrients) renders the public perception of pollution unclear.The present study proposes a new local index for the evaluation of effluent impacts on a receiving water body; this index makes use of linear weighting functions calculated on the differences between the upstream and downstream measurements of parameters which are affected by specific effluents. The procedure ranks each parameter value with regard to the maximum and minimum values observed before and after the outfall. For this reason, the resulting values are very sensitive to local perturbations. Linear characteristics of the index structure allow simple conversion from local databases to broader ones, thus allowing the measure of the cumulative impacts downstream. This index also allows the comparative rating of the water quality through time, if the effluent is subjected to some intervention. As such, it can also contribute to the environmental follow-up of a sanitation program.If a hydrological basin is equipped with a monitoring network, the proposed methodology permits the use of the resulting global database to quantify relative impacts of different effluents, and thus allows a hierarchical classification of the effluents to be treated according to priority.The proposed impact index has been tested with water quality data obtained during one year on a bi-weekly basis upstream and downstream from the untreated sewage outfall of Sainte-Anne de la Pérade (Portneuf, Province of Québec). The computed index as a whole is more sensitive to changes in water quality than individual parameters. External factors such as river flow and temperature do not significantly affect the values of the index. Key words: index, quality, river, impact, environment. [Journal translation]
Comportement dynamique d'une éolienne à axe vertical (développement théorique)
Authors: Veilleux Mario , Tinawi René
Published: January 2010

Complex frequencies and mode shapes are evaluated and presented for a guyed vertical axis wind turbine to detect any dynamic instability for a given speed of rotation. The equations of motion are developed in the rotating system of axes of the rotor to eliminate the time dependent terms. These equations take into account gyroscopic effects by evaluating the Coriolis and Circulatory (softening) matrices. The guys are replaced by nonlinear springs. The geometric stiffness matrix is also considered by performing a nonlinear static analysis that includes centrifugal effects and gravity loads, as well as compression from the vertical component of the guys. A reduction of the dynamic degrees of freedom is performed using the Rayleigh–Ritz technique. The complex frequencies and mode shapes are obtained using the QR algorithm. A program developed on a microcomputer was used to evaluate the dynamic instabilities of the ÉOLE Project. These results are described in the following paper. Key words: Vertical axis wind turbines, guys, complex frequencies, complex mode shapes, centrifugal forces, Coriolis forces, numerical software.
Comportement dynamique d'une éolienne à axe vertical (application pratique)
Authors: Veilleux Mario , Tinawi René
Published: January 2010

The dynamic behaviour of the vertical axis wind turbine of the ÉOLE Project is examined using a special purpose program developed for extracting the complex frequencies and mode shapes of the structure. The precise evaluation of the frequencies is an important step in the design process, to detect any dynamic instabilities of the rotor for a given speed. Gyroscopic effects and geometric nonlinearities due to centrifugal and gravity forces as well as the vertical compression due to the tension of the guys are also considered. Nonlinear behaviour of the guys is also accounted for. The influence of the variation in the stiffness of the guys on the dynamic behaviour is examined specifically for the ÉOLE Project. Results indicate that this effect is not important if the initial tension in the guy is high. Key words: Vertical axis wind turbines, guys, complex frequencies, complex mode shapes, centrifugal forces, Coriolis forces, Campbell diagrams, numerical software.
Tunnel and reservoir plan solution to Chicago's combined sewer overflow, basement flooding, and pollution
Authors: Bergman W. A. , Kapadia D. H.
Published: January 2010

In 1890, the Metropolitan Sanitary District of Greater Chicago was formed to permanently protect the region's drinking water supply from devastating contamination by sewage. The solution was to excavate a massive canal across the continental divide and to thus reverse the flow of the Chicago River, causing it to flow into the tributaries of the Mississippi River and away from Lake Michigan. Later, sewage treatment works were constructed to treat dry weather flows.Each time rainfall exceeds 8.4 mm, the combined sewers' capacities are exceeded, and they discharge directly to the canal system on the average of 100 times per year without benefit of treatment. When the sewers and canal system are overtaxed, raw sewage backs up the sewers in Chicago and 51 suburbs, flooding streets, businesses, and home basements.In order to solve these problems on a regional basis, the Sanitary District in 1972 adopted the tunnel and reservoir plan (TARP). TARP is a second river system which is being constructed by boring tunnels up to 11 m in diameter in rock as much as 100 m under the city. When the surface sewers' capacities are exceeded, the excess flows will drop into TARP. Huge reservoirs totalling 157 000 000 m3 capacity will store the sewage until it can be gradually pumped back to the treatment works. Key words: sewage, combined sewers, overflows, water pollution, water quality, stream pollution, flood control, tunneling.
Finite strip analysis of continuous structures
Authors: Cheung M. S. , Li Wenchang
Published: January 2010

The eigenfunctions of a continuous beam are found numerically. The folded plate type of finite strip with intermediate supports is formulated by combining such an eigenfunction in the longitudinal direction with an appropriate finite element shape function in the transverse direction. The numerical examples given in this paper, such as the continuous beam and plate, demonstrate the advantages of this method: simplicity, accuracy, and convenience. Key words: finite strip, continuous structure, eigenfunction, folded plate, plate bending.
Probability and stochastic modelling of water quality parameters in the Thames River
Authors: Logan L. , Graham V. , Unny T. E.
Published: January 2010

Baseline information on water quality parameters is essential to the development of policies to manage and control con taminants in streams. Investigations on the probability behaviour of monthly statistical estimates reveal that the governing probability distributions are not fixed but change on a monthly basis; and they are non-Gaussian. Probability density functions are developed using a five-parameter polynomial density function, which allows successful preservation of the key moments of the baseline water quality sequence. Stochastic models for transformed series of concentration of total phosphorus and suspended solids are determined using the ARIMA process. Since the ARIMA family of processes requires that the underlying distributions for monthly events be Gaussian and time-invariant, appropriate transformations are made for mapping the monthly water quality data from its parent distribution to a N(0,1) distribution. The model constructed for the transformed monthly phosphorus variable is an ARIMA [1, 1, 0], while the transformed suspended solids series of monthly time step is adequately described using a white noise ARIMA model. The methodology developed provides a framework for modelling baseline water quality data at various tributaries. The transformations guarantee that the probability distribution of the observed series is incorporated into the model structure. Therefore, synthetic water quality series generated using these models reproduce the non-Gaussian time-varying probability distributions and maintain the serial relationship between consecutive monthly events. Key words: ARIMA process, non-Gaussian probability distribution, water quality time series, suspended solids data, phosphorus concentration series.
An experimental investigation of the effects of imperfections on the strength of steel box girders
Authors: Korol R. M. , Thimmhardy E. G. , Cheung M.S.
Published: January 2010

As part of a major study, an experimental box girder having nominally identical cantilever sections was constructed to model the geometry of a pier girder of the Hunt Club–Rideau Bridge structure in Ottawa. The one-fourth scale model did not, however, replicate the varying depth of the prototype. The objective was to determine whether a deliberate reduction in the gross heat input for welds attaching longitudinal stiffeners to the flange plates for one end of the girder (and hence would incur reduced plate distortions and residual stresses) could augment the carrying capacity of a statically loaded box girder. In fact, the results from the two tests are such as to suggest that inward bent transverse stiffeners may account for a greater reduction in strength than do the imperfections of local plate panels of compression flanges. Key words: box girders, bridges, experiments, geometric imperfections, residual stresses, strength, structural steel.
Practical design of holes in steel webs
Authors: Buckland Peter G. , Bartlett F. Michael , Watts Ralph D.
Published: January 2010

Solutions are presented for the design of reinforcement for a wide range of holes in steel webs. Methods are derived for situations not covered in available published literature. Both elastic and plastic solutions are given for round holes, either unreinforced or reinforced with doubler or tripler plates. Welds and web stability are considered. A solution is given for small holes and a comparison is made with the recent research. For noncircular holes Vierendeel and finite element analyses are discussed, as well as a plastic analysis of rectangular doubler plates. Five methods of dealing with multiple holes in a web panel are presented, each appropriate for different circumstances: elastic analysis, Vierendeel action, plastic summation, the use of stiffeners for “trussing”, and the powerful “checkerboard” technique. It is found that reliance on the ductility of steel has considerable advantages. Fatigue is considered.The methods are appropriate for square or rectangular web panels with central or noncentral holes subjected to any applied in-plane stresses. Key words: webs, holes, girders, steel, design.
Ultimate load capacity of square shear plates with circular perforations
Authors: Martin A. , Stiemer S. F. , Osterrieder P.
Published: January 2010

Working platforms and support caissons of offshore steel structures are often designed with plate boxes or plate girders. The important shear walls or shear webs must often be perforated to allow utilities, etc., to pass through. The failure mode of these large perforated shear panels is typically shear buckling, usually in the plastic range. The paperpresents results of a finite element buckling analysis with inelastic material behaviour and gives general guidelines for the ultimate capacity design of perforated shear plates. The parameters affecting the ultimate capacity of square plates with circular perforations under uniform shear stress were investigated using the incremental structural analysis program NISA83. Nonlinearities in material properties and geometry were taken into account in the calculation of ultimate capacities of each perforated shear plate.The parameters investigated in the study were hole size for a concentric hole and hole location for a constant hole size. Only single unreinforced round holes were considered. Three capacities were calculated for each variation of these parameters: the ultimate in-plane capacity, the elastic buckling capacity, and the ultimate elastic-plastic buckling capacity.In order to check the input data and to provide concise display of the results, a graphic postprocessor was developed as part of the research. The program NISPLOT uses colour graphics to generate plots of the nodes, element mesh, the deflected shape, and stress patterns of the loaded plates. The plots were reduced to black and white for this paper. Key words: girders, holes, steel, ultimate capacity, buckling.
Fast-tracking of construction projects: a case study
Authors: Fazio P. , Moselhi O. , Théberge P. , Revay S.
Published: January 2010

The growing use of professional construction management has been synonymous with the development of new project delivery systems such as the phased construction approach and the fast-tracking technique. This paper establishes the distinction between these two types of approach which have become increasingly popular for reducing project duration. The paper further illustrates, through a case study, the possible consequences of compressing and overlapping design activities in a fast-track program to expedite project delivery. A delay analysis shows the impact of this accelerated technique on construction activities. The far-reaching effect of mistakes during the early design/engineering phase in a fast-track program is usually underrated. Accelerating a project through fast-tracking is a major decision, and construction professionals often are not aware of its implications. Based on the case study examined in this paper and other fast-track constructions previously analyzed, trouble areas requiring special attention have been depicted and recommendations with regard to the effective use of this technique are presented. It has also been shown that if intensified effort on problem areas is lacking, such a popular accelerated technique could result in unexpected delays. Key words: fast-tracking, phased construction, professional construction management, design management.
Pylons of cable-stayed bridges: a comparison
Authors: Aboul-Ella Fakhry
Published: January 2010

A new analytical model for the static analysis of cable-stayed bridges is presented taking into consideration the effect of soil–structure interaction. Bridges having pylons and piers of different degrees of restraint, such as fixed or hinged base pylons, fixed base piers, and pile-supported piers, are analyzed and compared to investigate the effect of these restraints on the response of the entire cable-stayed bridge system. The validity of the assumption of fixed support for pylons or piers is also examined. Key words: bridges, cables, foundation, towers, pylons, piers, piles, caissons, soil mechanics.
Fatigue analysis of groove weld with steel bar backing by fracture mechanics finite elements
Authors: Taheri Farid , Mufti Aftab A.
Published: January 2010

The purpose of this paper is to analyze the fatigue crack growth rate in groove weld with backing steel bar. The linear elastic fracture mechanics approach is used. This approach is coded in a special purpose fracture mechanics package FAST. By using FAST, the structure is modeled and analyzed by its finite element module FAST-I, and the cyclic life is estimated by its crack propagation module FAST-II.An example recently studied by Baker and Kulak is investigated by the FAST program. The S–N curve (stress range versus number of cycles to failure) obtained by FAST is compared with the curve presented by Baker and Kulak. Key words: Engineering, finite element, fracture mechanics, fatigue, steel, stress intensity factor, numerical, computer analysis, weld, stress ratio, enriched element.
Influence of different downstream users on single multipurpose reservoir operation by chance constraints
Authors: Simonovic S.
Published: January 2010

A chance-constrained model is applied to solve the problem of long-term planning of the operation of a single multipurpose reservoir. Apart from the direct multipurpose use of water from the reservoir downstream, releases are available for use. The influence of downstream users is taken into account by a special form of objective function. Releases are bounded by the capacity of the outlet works above and by the guaranteed minimum from below. These two bounds are constraints on the control space. The model uses a chance-constrained programming algorithm to yield the control trajectory (releases) closest to the optimum. The properties of the chance-constrained program reveal a strong influence of changes of the control space on releases. This enables a release strategy to be derived which will increase the utilization of water from the reservoir. The application and results presented in this paper refer to the Prohor Reservoir on the Pcinja River in the Vardar River basin, Yugoslavia. Key words: multipurpose reservoir, mathematical modeling, optimization, chance constraints, control space.
Damage resulting from a sudden river ice breakup
Authors: Doyle P. F.
Published: January 2010

On January 4, 1984, the Nicola River and its two main tributaries broke up suddenly due to a sharp increase in discharge from a rain-on-melting-snow event while the ice cover was still thick and strong. The resulting ice run and attendant jamming caused hundreds of thousands of dollars in damage to public and private property, including the destruction of a bridge and several riprapped banks. Four ice jams remained in place for up to a week after the ice drive. All the damage was due either to the severe ice run within the channel or to flow forced out over the floodplain by ice jams. Key words: flood damage, ice run, ice breakup, ice jams, riprap.
Effect of damping on the predicted seismic response of tertiary subsystems
Authors: Schriver A. B. , Heidebrecht A. C.
Published: January 2010

Many factors affect the seismic response of a structural system. A study was carried out to determine the effect of different combinations of damping on the predicted response of secondary and tertiary subsystems. To simplify the results and to allow for easier interpretation, two- and three-degree-of-freedom structural systems were investigated. The study involved determining the "best estimate" seismic responses for 12 historic earthquake time histories and comparing them to the predicted responses obtained by using two simplified methods of analysis which have been in common use. Curves have been developed which specify the expected average error for the simplified methods by mass ratio(s) and damping. These results provide an overview as to the ranges of parameters where upper level interaction and nonproportional damping effects are significant. Key words: nonproportional damping, complex modal analysis, dynamic, seismic, equipment, tertiary subsystems.
Secondary effects of intermediate diaphragms in beam-and-slab bridges
Authors: Jategaonkar Ravi , Jaeger Leslie G.
Published: January 2010

The effect of intermediate diaphragms on the distribution of longitudinal bending moments in beam-and-slab bridges has been studied previously. In the present paper, that work is extended so as to cover the effect of such diaphragms on transverse moments, shear forces, and support reactions.A method is developed which uses two non-dimensional parameters. The method enables the designer to obtain the necessary design information for bridges having any number of intermediate diaphragms of widely different stiffnesses, without having to do a separate analysis for each case. Key words: beam-and-slab bridge, diaphragm, cross-frame, grillage analogy, finite element method, orthotropic plate theory.
Configuration and properties of a breakup jam
Authors: Beltaos S.
Published: January 2010

Favourable weather conditions in January, 1986, resulted in a breakup jam on the Thames River that froze in place. This afforded safe access and performance of detailed thickness measurements that are normally not possible to obtain. The thickness of the jam is highly variable in the lateral direction but without consistent trends, which, in a crude sense, justifies the assumption of lateral uniformity made for analytical purposes. In the downstream direction, the thickness increased, except for a short reach downstream of the toe where it rapidly decreased to zero. Approximate assessment of the absolute roughness of the jam indicated fair agreement with earlier deductions based on hydraulic resistance data. Using existing theoretical concepts, it was deduced that the downstream portion of the jam was likely formed by "shoves" or internal collapse ("wide") whereas the upstream portion was likely formed by frontal progression ("narrow") and juxtaposition. For the former reach, the present data enabled approximate evaluation of coefficients utilized in pertinent theories. Agreement with previously published values was good, though in one instance there are no previous field determinations. To study the decline of jam thickness past the toe, the "wide" jam theory was adapted to describe a jam overlain by solid ice cover. This enabled approximate determination of the friction coefficient between the jam and the cover. Key words: breakup, coefficients, hydraulics, ice, internal collapse, jam, river, roughness, theory, thickness.
Influence of added mass on ice impacts
Authors: Isaacson Michael , Cheung Kwok Fai
Published: January 2010

The present paper applies potential theory to describe the variation of the added mass of an iceberg and its coupling effects on an offshore structure for various separation distances up to the point of contact. The strengths and weaknesses of the proposed model are discussed together with its practical application in ice mass impact problems. An impact model based on dynamic analysis is developed to calculate the impact force and response of a structure for head-on collisions. Both the contact-point added mass estimated in the present study and the traditionally assumed far-field added mass are used in the impact model separately. The results are compared and the crucial roles played by the ambient fluid during impact are discussed. Key words: added mass, hydrodynamics, ice impact, ocean engineering, offshore structures.
Initial attempt to optimize the operation of a hydrometric network using branch and bound algorithm
Authors: Pelletier Patrice M. , Simonovic Slobodan P.
Published: January 2010

The paper presents a new approach developed to formulate and solve the problem of field operation of a hydrometric network. In present practice, optimization techniques are not used for solving this problem. In the initial attempt, documented in the paper, the traveling salesman algorithm is used to find the optimal solution. Assumptions used and experience gained during the research are addressed in the paper. For the Dauphin hydrometric field area in Manitoba, an "optimal" solution has been obtained and presented. Based on the analysis of the results, conclusions were drawn about future research directions incorporating development of an effective heuristic algorithm for solving the traveling hydrometric technician problem. Key words: operation, hydrometric network, optimization, heuristic algorithm, traveling salesman algorithm.
Interconnection of widely spaced angles
Authors: Temple Murray C. , Tan Joo Chai
Published: January 2010

Research on the interconnection of widely spaced back-to-back angles has not been conducted. This research was carried out with the aim of developing rules for the design and spacing of interconnectors in such members. Four parameters—the number of interconnectors, the back-to-back spacing between angles, the weld pattern used to connect the interconnectors to the angles, and the thickness of the interconnectors—were studied. The experimental and the theoretical results for the slender double angles confirm that only one interconnector, of practical proportions, is required to make the widely spaced angles act as an integral unit. Both the separation between angles, within reason, and the weld pattern used to connect the interconnectors to the angles had an insignificant effect on the failure load and the failure mode. The thickness of the interconnector did affect the load-carrying capacity of the strut, but only when the thickness of the interconnector was impractically small. The forces and moments in the interconnectors are very small. Key words: angles, back-to-back, buckling, building (codes), columns (structural), design interconnection.
Head loss through porous dikes
Authors: Jain Subhash C. , , Jr. Forrest M. , Lee Tim H.
Published: January 2010

Porous dikes have been proposed for use in blocking access of fish to cooling water intakes in power plants using large cooling ponds for heat dissipation. Flow through such dikes is neither of the Darcy type nor quadratic, the friction factor depending on both the Reynolds number and material properties. Full-scale tests of the dike material proposed for the LaSalle County power plant confirmed the material-property and Reynolds-number dependencies reported in the literature and permitted calibration of the head-loss parameters for the prototype material under two placement configurations. Limited tests on dike clogging by surface debris permitted quantification of the additional head loss which clogging could cause. Key words: porous media, cooling ponds, dikes, scale model tests.
Performance of ilmenite concrete at sustained elevated temperatures
Authors: Wilson H. S.
Published: January 2010

Two similar mixes were made with cement contents of about 350 kg/m3 and a water–cement ratio of 0.50. The concrete specimens, moist cured for 7 days, were cured in air for 28 and 120 days, respectively, prior to heating. The exposure temperatures were 75, 150, 300, and 450 °C. The periods of exposure at each temperature were 2, 30, and 120 days.The compressive strengths, before heating, of the specimens cured for 35 and 120 days were 41.0 and 46.2 MPa, respectively, and the flexural strengths were 4.9 and 5.8 MPa. Compared with those strengths, the strengths of the specimens heated for 30 days or more increased at 75 °C but decreased at higher temperatures. The losses increased with increase in temperature, reaching about 30% at 450 °C.The flexural strength of the concrete cured in air for 28 days was more adversely affected than was the compressive strength. The flexural and compressive strengths of the concrete cured in air for 120 days were affected to about the same degree. The longer curing period had little effect on the relative losses in compressive strength, but the longer curing period reduced the loss in flexural strength. In most applications, the loss in strength could be compensated by proportioning the mix to overdesign for strength. Key words: high-density concrete, ilmenite, aggregates, high temperature, mechanical properties, nondestructive tests.
Head losses at manholes with a 90° bend
Authors: Marsalek J. , Greck B. J.
Published: January 2010

Head and pressure changes were studied at manholes with a 90° bend. For pressurized flow, such changes depend only on junction geometry. Among junction parameters, the benching was found particularly important. Full benchings reaching to the pipe crown produced the lowest head losses, particularly when combined with an enlarged pipe diameter at the junction. Head changes in open-channel flow were significantly smaller than those in pressurized flow. Key words: head loss, manholes, sewer junctions, sewer design, sewer hydraulics.
The significance of warping torsion in the design of straight concrete box-girder bridges
Authors: Waldron Peter
Published: January 2010

Out-of-plane warping, resulting from torsional loading, is an important feature of box-girder bridges of thin-walled cross section. This may be of some consequence in girders where warping is restrained, since it may alter the level of stress both around the cross section and along the entire length of the beam. It is well known that some girders with very thin walls are not susceptible to warping, whereas others, with thicker walls, warp significantly when twisted. It is shown that the degree of warping is not governed by wall thickness alone; cross-sectional geometry, girder configuration, and loading must also be considered. The significance of these various factors in estimating the effects of warping restraint is assessed. In many cases this will permit the selection of box-girder cross sections at the conceptual design stage for which torsional warping effects are negligible. A simply supported concrete box girder is used as an example to demonstrate the importance of cross-sectional geometry, girder configuration, and loading in the assessment procedure. This is extended to the more general case of multi-span girders subjected to realistic patterns of loading. Key words: torsion, warping, box-girders, bridges, concrete, design.