bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyse dynamique de l'interaction pont-véhicules pour les ponts routiers. II. Application au pont de Senneterre au Québec
Authors: Henchi Kamel , Talbot Martin , Fafard Mario
Published: April 2011

In this paper, an application of the algorithm for the dynamic analysis of bridge-vehicles interaction that the authors developed in the preceeding paper is presented. The numerical results are compared to the results obtained from experimental tests of frequencies and mode shapes and from forced vibrations carried out on the Senneterre bridge located in Quebec. The numerical model of the bridge is obtained by tridimensional finite element modeling, using shell and beam elements, and taking into account bridge-vehicles interaction and the road profile in a realistic way. The numerical vehicle model used in the province of Quebec is represented in a discrete form based on mechanical parameters calibrated and adjusted according to experimental results. A parametric study was then carried out. The results of this study allow us to present some recommendations with regard to bridge resistance to dynamic effects and the determination of a dynamic amplification factor based on the specific loading conditions of the bridge. Key words: shell, dynamic, finite elements, interaction, bridge, roughness, vehicle, amplification factor, experimental tests.[Journal translation]
Potential of dry drainage for controlling soil salinity
Authors: Khouri Nabil
Published: April 2011

The primary aim of this paper is to discuss the concept of "dry drainage," i.e., drainage by evaporation from fallow areas, as a possible technique for controlling soil salinization. The technique requires retirement to be imposed on a part of the irrigated land. The remainder of the land is used for crop production. While the retired area is unirrigated, normal irrigation practices are carried out on the remaining area. For the technique to be effective, it is essential that a shallow water table and high evaporation rates are present. These conditions are the characteristics of arid and semi-arid regions. A field-scale test of a dry drainage unit is illustrated numerically using a field-scale model and field-scale data from the San Joaquin Valley of California, U.S.A. It has been shown that it is possible to obtain an optimal land-use pattern for a dry drainage scheme that satisfies the design requirements. However, some limiting factors that influence the design have to be considered. These are related to the soil properties, the practiced crop, climatic conditions, and economic factors.Key words: salinity, drainage, leaching requirements, saturated and unsaturated zones, evaporation, mathematical modelling.
A stereometric knowledge-based system for maintenance of street networks
Authors: Obaidat Mohammed Taleb , Al-Suleiman Turki I , Ghuzlan Khalid A
Published: April 2011

The main objective of this work was to investigate the potential of integrating a stereometric vision system, i.e., using digital stereo images, and a knowledge-based system for flexible pavement distress classification. Classification process includes distress type, severity level, and options for repair. A hybrid stereo vision and knowledge-based system (called K-PAVER) was developed. The system extracts distress measurements using a PC-based stereo vision system. Geometric surface measurements such as point locations, distances, areas, volumes, and surface areas could also be computed. The knowledge-based system developed utilizes a set of if...then rules from the PAVER system (a pavement maintenance management system for roads and streets) and related literatures. New parameters, including shape parameters, orientation, and some geometrical measurements, were introduced to the system in order to facilitate the distress classification process. A criterion for maintenance priorities based on four parameters was developed. These parameters are pavement condition index, average daily traffic, location of distressed pavement, and street class. Surface measurements and automatic classification decision-making were validated and tested for all distress types. The developed system gives accurate results in both the measurement mode and the decision-making phase. This result opens the door for a fully automated distress classification process without any human intervention.Key words: knowledge-based systems, vision systems, stereo measurements, flexible pavement distresses, maintenance priorities, pavement maintenance management systems.
Application of polynomial transformation to normality in structural reliability analysis
Authors: Hong Han Ping
Published: April 2011

Polynomial transformations of a nonnormal variate to a normal variate are considered. Use of the polynomial transformations to normality representing some of the well-known distribution types is examined. Approximate solutions based on the polynomial transformation to normality models fitted to the simulated data points with fractile constraints are given to evaluate the probability of failure of a structural system. The approximate solutions do not require any stringent conditions on integrand or domain of integration. The approximation is easy to implement and can be used to reduce the required number of simulation cycles. Numerical examples indicate that using the approximate solutions accurate estimation of the failure probability can be obtained with fewer simulation cycles than the conventional simulation method.Key words: approximation, fractile, normality, reliability, polynomial, probability of failure, simulation, transformation.
Effective design width for perforated cold-formed steel compression members
Authors: Abdel-Rahman Nabil , Sivakumaran K S
Published: April 2011

Perforations are often provided in the web and (or) flange plates of beams and columns of cold-formed steel (CFS) structural members in order to facilitate duct work, piping, and bridging. This paper is concerned with the establishment of effective design width equations for the determination of the ultimate strength of such perforated members in compression. A proven finite element model has been used to study the effects of perforation parameters on the ultimate strength of perforated members. The finite element model consists of short columns of lipped channel CFS sections, discretized using nonlinear "assumed strain" shell finite elements, and utilising experimental-based material properties models. The parametric study covers web slenderness values between 31 and 194, perforation width to web width ratios up to 0.6, and perforation height to perforation width ratios up to 3.0. Effective design width equations for plates having square perforations and elongated perforations were developed. The efficiency and accuracy of these two equations in predicting the ultimate strength of perforated CFS compression members have been verified through a comparison with the ultimate load results of several experimental studies from the literature.Key words: cold-formed steel, compressive loads, local buckling, perforations, finite element analysis, experimental, post-buckling strength, ultimate strength, effective width, design.
Seismic performance of ductile and nominally ductile reinforced concrete moment resisting frames. I. Experimental study
Authors: Filiatrault André , Lachapelle Éric , Lamontagne Patrick
Published: April 2011

This paper is the first of two companion papers on the evaluation of the level of protection offered by ductile and nominally ductile reinforced concrete structures in Canada. In this paper, the seismic behaviour of two half-scale reinforced concrete moment resisting frames is investigated by shake table tests. In the second paper, the experimental results obtained from the shake table tests are compared with the results generated from inelastic time-history dynamic analyses. Each frame had two bays and two storeys with overall dimensions of 5 m in width and 3 m in height. The first structure was designed as a ductile frame according to current Canadian standards; and the second structure incorporated only nominally ductile details. Two levels of intensity were retained for the historical ground motion used in the tests. The first level was representative of the design earthquake considered; the amplitudes were doubled for the second intensity. The ductile structure performed well during both tests. The frame with nominal ductility performed well during the first test, but was on the verge of collapse after the second test. Based on these experimental results, recommendations are presented to harmonize the seismic protection of ductile and nominally ductile reinforced concrete frames in Canada.Key words: moment resisting frames, earthquakes, reinforced concrete, seismic, shake table.
Towards effective design coordination: a questionnaire survey 1
Authors: Hegazy Tarek , Khalifa Jameel , Zaneldin Essam
Published: April 2011

The design of medium- and large-sized projects is an iterative multi-disciplinary process often challenged by a tight budget and limited time. A quality design is highly dependent upon effective coordination among the diverse teams involved in the process. With the current fast pace of technological advances, design coordination becomes an essential element of success particularly within the prevailing market pressures on design firms to downsize, restructure operations, and work more productively and cost effectively. Despite its importance, however, coordination is neither simple nor error free, and has traditionally been applied through manual procedures that are slow and costly. As a step towards effective design coordination, this paper presents the results of a questionnaire survey conducted among 12 leading Canadian design firms. The survey elicited the manner by which expert designers prevent mistakes, detect mismatches, and effectively communicate design changes. Accordingly, solutions to some coordination-related problems have been presented and areas of potential improvement to the design process identified. A suggested coordination scheme has been presented and common interrelationships within the design development process have been explicated. Recommendations toward a more efficient design process have been presented.Key words: construction management, design coordination, quality design, value-engineering, constructability, computer applications, survey.
A simplified distortional buckling model for doubly symmetrical I-sections
Authors: Dekker N W , Kemp A R
Published: April 2011

Lateral torsional instability of I-beams considers the relative displacement of the unstable compression flange to the stable tension flange. It is commonly assumed that little or no distortion takes place between the two flanges. In this paper, an approach is proposed whereby the section properties that control lateral torsional buckling are adjusted to allow for the influence of cross-section distortion, by the use of simple spring models representing the relative stiffness of the flanges and the web. The model is developed for elastic, inelastic, and plastic cases and compared with the results obtained from finite element models developed by other researchers. A method of quantifying the lateral distortional buckling resistance of I-beams is of particular importance in the hogging moment region of continuous composite beams; the ability of the proposed model to deal with this complex problem has been previously demonstrated by the authors. In this paper, the proposed model is used to illustrate the influence of distortional buckling on doubly symmetrical I-sections.Key words: lateral, distortional, I-beams, elastic, inelastic.
Instantaneous water surface and bed scour profiles using video image analysis
Authors: Balachandar R , Kells J A
Published: April 2011

In steady open-channel flow, the use of a conventional point gauge to obtain the water surface profile yields reasonably accurate results. However, in unsteady and quasi-steady flows, the point gauge is not of much use. Furthermore, in flow fields where there is significant bed scour, it is often of interest to the hydraulic engineer to obtain the instantaneous bed scour profile during the scouring process. In most quasi-steady flows involving bed scour, the water surface profile continuously readjusts itself in response to the changes in the bed profile. To carry out a proper analysis of the entire flow field, it is necessary to obtain both the instantaneous water surface and the corresponding bed scour profiles. The development of a nonintrusive video image analysis procedure to simultaneously obtain the water surface and bed scour profiles in a two-dimensional flow field is presented in this paper. A computer program entitled PROSCAN has been developed to extract the water surface and bed scour profiles from digitized video images of the flow field. The use of PROSCAN is demonstrated by obtaining the instantaneous water surface and bed scour profiles for a two-dimensional flow field downstream of a sluice gate.Key words: image analysis, software development, water surface profile, bed scour profile, scour dynamics.
A neural network approach for predicting the structural behavior of concrete slabs
Authors: Hegazy Tarek , Tully Susan , Marzouk Hesham
Published: April 2011

In this paper the use of a nontraditional technique, neural networks, has been investigated as a means to develop efficient predictive models of the structural behavior of concrete slabs. The applicability of neural networks within the realm of structural analysis is first reviewed, along with their state-of-the-art applications and research efforts. Four neural networks have then been developed to model the load-deflection behavior of concrete slabs, the final crack-pattern formation, and both the reinforcing-steel and concrete strain distributions at failure. The four neural networks were trained and tested using the experimental results of 38 full-scale slabs. Details regarding data modeling, neural network training, and performance evaluation are described. Using the developed networks, a spreadsheet tool for the structural analysis of concrete slabs was developed with a simple interface, automated predictions, and what-if capabilities. The developed tool is useful for teaching purposes and for reasonable prediction of the behavior of concrete slabs without additional experimental testing.Key words: neural networks, structural analysis, reinforced concrete, load-deflection, crack pattern, artificial intelligence, concrete slabs.
Evaluation of remaining fatigue life for riveted truss bridges
Authors: DiBattista J D , Adamson DEJ , Kulak G L
Published: April 2011

The remaining fatigue life of riveted structures is a topic of considerable importance, particularly for owners of bridges. Improved methods for the estimation of the actual fatigue life of such structures are required in order to make their continued safe use possible while at the same time avoiding the expense of unnecessary repairs. To evaluate the fatigue life expectancy of a structural detail, it is necessary to obtain an accurate estimate of the stress history. Two analytical models are assessed through comparison with measured strains taken from a bridge in service. The results illustrate that a simple model with pinned connections is adequate for the determination of stresses in truss members and that more advanced analysis methods give only marginal increases in accuracy. Stresses in the floor system are most accurately predicted by a model that has full bending moment continuity between connected members. Standard and advanced methods of fatigue life evaluation are discussed and are then implemented in the evaluation of the remaining fatigue life for components of the bridge. Comparison with the actual fatigue life of the components, which were obtained from laboratory experiments, shows that both prediction methods give reasonable estimates of the fatigue life.Key words: bridge, fatigue, rivets, steel, model, analysis.
Identifying high accident risk trucking firms using Roadcheck vehicle inspections
Authors: Saccomanno F F , Kormendi S , El-Herraoui M , Lamble R W
Published: April 2011

In many jurisdictions, unsafe trucking firms account for a significant number of highway accidents. One way to reduce these accidents is to identify firms with a high potential for accidents and to target them for appropriate safety interventions. Vehicle roadside inspection programmes, such as Roadcheck, can provide an effective means of identifying high-risk trucking firms, based on vehicle-driver fitness rates. This paper makes use of the 1995 Ontario Roadcheck database to establish a link between vehicle roadside inspections aggregated at the carrier level and the carrier accident risk potential in the same year. In Roadcheck, trucks which are selected randomly from the traffic stream passing each inspection station are monitored for a range of mechanical defects, such as brake, suspension system, engine, and tire defects. The focus of this paper is to identify carriers with a high accident risk potential with respect to those accidents which are caused primarily by lack of truck fleet mechanical fitness. Preliminary results suggest that roadside inspections provide a simple, reliable way of establishing a trucking firm's accident risk potential (especially where truck fleet fitness is the central concern). The approach appears to be especially suited as a low-cost screening method for targeting high-risk trucking firms for appropriate safety interventions.Key words: truck, mechanical fitness, carrier, accident risk.
Strength of slotted tubular tension members
Authors: Cheng J J. Roger , Kulak G L , Khoo Heng-Aik
Published: April 2011

An experimental program and associated numerical analysis were undertaken to study the shear-lag effect in round hollow structural section (HSS) tension members that are welded to gusset plates at their ends. The connection is made by slotting the tube longitudinally, inserting the gusset plate, and then placing longitudinal fillet welds at the tube-gusset interface. A total of nine specimens with three different tube sizes (HSS 102 × 6.4, HSS 102 × 4.8, and HSS 219 × 8.0) and various weld lengths were tested in the program. Most of the specimens failed by fracture of the tube somewhere between the two gusset plates, and there was considerable ductility prior to fracture. Most importantly, there was no reduction in the effective net area for the tested specimens, even with a weld length as little as 80% of the distance between the welds. Numerical analyses of the connections were carried out using an elastoplastic model and measured material properties. The studies showed that the restraint provided by the gusset plate at the slotted end effectively increases the load-carrying capacity of the tube as compared with that of the unrestrained portion of the member. In the analysis, fracture is assumed to have occurred when the equivalent plastic strain reaches a critical value. The test results are discussed in light of the requirements in the Canadian standard for design of steel structures.Key words: connections, steel, shear lag, finite element analysis, gusset plates, hollow structural section, tension, welds.
Spline Kantorovich method and analysis of general slab bridge deck
Authors: Zhao J , Cheung M S , Ng S F
Published: April 2011

In this paper, the spline Kantorovich method is developed and applied to the analysis and design of bridge decks. First, the bridge deck is mapped into a unit square in the Xi - eta plane. The governing partial differential equation of the plate is reduced to the ordinary differential equation in the longitudinal direction of the bridge by the routine Kantorovich method. Spline point collocation method is then used to solve the derived ordinary differential equation to obtain the displacements and internal forces of the bridge deck. Mindlin plate theory is incorporated into the differential equation and, as a result, the effect of shear deformation of the plate is also considered. Possible shear locking is avoided by the reduced integration technique. Numerical examples show that the proposed new numerical model is versatile, efficient, and reliable.Key words: Kantorovich method, spline function, partial differential equations, ordinary differential equations, point collocation method, bridge deck.
An innovative digital image analysis approach to quantify the percentage of voids in mineral aggregates of bituminous mixtures
Authors: Obaidat Mohammed Taleb , Al-Masaeid Hashem R , Gharaybeh Fouad , Khedaywi Taisir S
Published: April 2011

The objective of this study was to examine the feasibility of using a semiautomated computer-vision system to quantify the percentage of voids in mineral aggregates (VMA%) of bituminous mixtures. The system used a hybrid procedure which utilized a digital image analysis scheme and a planimeter surveying instrument. Thirty-nine Marshall specimens were prepared using limestone and gravel aggregates. Values of VMA% were obtained using the ASTM conventional procedure and the computer-vision procedure. To compute VMA% using the computer-vision procedure, normal case photography with uniform scale images was used to map horizontal and vertical cross sections of Marshall specimens. Image domain measurements were corrected for distortion. Spatial filters and image processing operations were used to enhance the aggregate edges. Experimental results showed slight variations between VMA% computed using conventional and the computer-vision procedures. The average differences of VMA% between conventional and the computer-vision procedures were 0.81% and 0.006% for gravel and limestone specimens, respectively. Measurements of VMA% for limestone mixtures were more precise than those for gravel mixtures because of the angular edge shape of limestone particles. Variations in VMA% were due to the anisotropic properties of asphalt mixtures, aggregate distribution in the asphalt mixture, and different shapes of aggregates. Using the computer-vision-based technique, VMA% of horizontal and vertical cross sections were 50% consistent. The existence of fine aggregate in the asphalt mixture affected the accuracy potential of the developed system because a low-resolution camera was used. Increasing the camera resolution and automating the area computation of aggregate are expected to enhance the potential accuracy of the procedure. The proposed method for VMA quantification is anticipated to improve field quality control of hot-mix asphalt (HMA). The use of computer-vision technology with bituminous mixtures can open the doors to a wide variety of applications.Key words: bituminous mixtures, voids in mineral aggregate, computer vision, automation, image processing.
Régionalisation du régime des précipitations dans la région des Bois-francs et de l'Estrie par l'analyse en composantes principales
Authors: Siew-Yan-Yu T O , Rousselle J , Jacques G , Nguyen V.-T.-V.
Published: April 2011

A definition of homogeneous regions in terms of precipitation regime is achieved by the use of principal component analysis (PCA). The method has been shown to be a reliable regionalization tool even though it was applied to a territory showing rather complex physiography and high precipitation variation. Results based on the application of the PCA to the interstation correlation matrix of precipitation have indicated four distinct homogeneous regions. These regional patterns can be explained by the orographic effect and by the circulation of air masses within the study region.Key words: homogeneous regions, rainfall, principal component analysis, orographic effect.
Nonlinear thermal expansion and contraction of asphalt concrete
Authors: Zeng Menglan , Shields Donald H
Published: April 2011

Asphalt concrete for paving roads is a viscoelastic material. In the prediction of thermal stress in asphalt pavements, the thermal expansion-contraction property of the material is required. In current practice, thermal expansion-contraction is assumed to be a linear function of temperature, and a constant thermal coefficient is used. The fact that a viscoelastic material may have a glass transition temperature and the thermal property may have a discontinuity at the glass transition temperature has not been considered. This study investigates the thermal nonlinearity of asphalt concrete. In this research, the thermal expansion-contraction was continuously measured on a single type of asphalt concrete in the temperature range from +40°C to -40°C. It was found that the thermal expansion-contraction was a continuous nonlinear function of temperature, resulting in a variable thermal coefficient. Evaluations of the effect of the nonlinearity indicated that the assumption of thermal linearity can result in moderate errors in stress prediction in asphalt pavements.Key words: asphalt concrete, thermal expansion-contraction, thermal coefficient, nonlinear thermal behaviour, asphalt pavement, thermal stress.
Evaluation of the seismic level of protection afforded to steel moment resisting frame structures designed for different design philosophies
Authors: Biddah Aiman , Heidebrecht Arthur C
Published: April 2011

Steel moment resisting frames have been considered as excellent systems for resisting seismic loads. However, after recent earthquakes (e.g., Northridge, California, in 1994 and Kobe, Japan, in 1995) the confidence in this structural system was reduced as a result of various types of damage that moment resisting steel frames suffered. This paper presents the results of the evaluation of seismic level of protection afforded to steel moment resisting frame buildings designed in accordance with the National Building Code of Canada. Six- and 10-storey office buildings located in a region of intermediate seismic hazard are designed in accordance with the current Canadian code provisions. Three different design philosophies are considered, namely strong column - weak beam (SCWB), weak column - strong beam (WCSB), and strong column - weak panel zone (SCWP). The performance of these frames is evaluated dynamically by subjecting an inelastic model to an ensemble of 12 actual strong ground motion records. The model takes into account both connection flexibility and panel zone shear deformation. The results are presented in terms of response parameters determined from static pushover analyses, as well as statistical measures of the maximum response parameters determined from the inelastic dynamic analyses. The computed performance of the frames is evaluated in order to assess both the overall level of protection of the frames and the preferred design philosophy. It is concluded that a well-designed and well-detailed ductile moment resisting frame designed using either the SCWB or SCWP design philosophy can withstand ground motions of twice the design level with very little likelihood of collapse, whereas a frame designed using the WCSB approach is ill-conditioned and may develop a collapse mechanism at an excitation level well below twice the design level.Key words: seismic, ductile, steel, frame buildings, performance, design, ductility, damage, inelastic, dynamic.
Detention time selection for stormwater quality control ponds
Authors: Papa Fabian , Adams Barry J , Guo Yiping
Published: April 2011

Current stormwater quality control pond design in Ontario typically includes the specification of a uniform detention time for extended detention ponds to ensure water quality control. In reality, the pollution-control performance of such facilities is governed by two opposing forces: improved pollutant removal efficiency over longer detention times and the decreased volume of runoff captured and treated by the facility for longer detention times. The combination of these effects produces a maximum attainable level of long-term pollution-control performance at an optimal detention time. Derived probability distribution models for runoff control are used to investigate the quality-control behaviour of extended detention dry ponds for the case where a design storm is specified to establish pond storage requirements and for the more general case where storage requirements may be selected on the basis of the level of control desired. Graphical relationships are developed to facilitate the planning and design process. The methodology presented encourages efficient engineering design while promoting environmental protection by ensuring a maximum level of long-term pollution control.Key words: stormwater management, water quality, probabilistic models, optimization, stormwater ponds, detention time, pond design.
The use of enhanced positional weight method for constrained resources project scheduling
Authors: Tam Paul Wing Ming , Palaneeswaran Ekambaram
Published: April 2011

Scheduling of construction projects is normally performed with the critical path method (CPM). The popular CPM/PERT network techniques are based on the assumption that sufficient resources will be available when needed to complete all project activities on schedule. This unrealistic assumption can lead to ineffective resource usage and project delays. For scheduling of the project activities with resource constraints, other algorithms have to be used. This technical note first outlines the suitability of ranked positional weight method (RPWM), a heuristic resource scheduling method, to construction project scheduling. It then focuses on a new heuristic technique, the enhanced positional weight method (EPWM), which is an improved version of the RPWM. Some interesting comparisons between the results given by Primavera, Microsoft Project, RPWM, and EPWM are also presented.Key words: ranked positional weight method, enhanced positional weight method, and critical path method.
Behaviour of steel frames under fire conditions
Authors: Nwosu D I , Kodur VKR
Published: April 2011

A state-of-the-art review of the behaviour of steel frame structures in fire is presented. Results from different studies indicate that the behaviour of a complete structure is different from that of a single structural member under fire conditions from the point of view of fire resistance. Earlier studies also show that analysis and design of steel structures against fire based on their overall behaviour could lead to a reduction or the elimination of applied fire protection to certain structural members. The effects of continuity, restraint conditions, and load ratio on the fire resistance of frame structures are discussed. The beneficial aspects derived from considering overall structural rather than single-member behaviour in fire are illustrated through the analysis on two one-bay, one-storey, unprotected steel portal frames, a column, and a beam. Also comparison is made between the performance of a beam with different end restraints in fire. Results from the analyses indicate that the fire resistance of a member is increased when it is considered as part of a structure compared with when it is considered as a single member.Key words: steel, frames, fire resistance, buckling, loads, overall structural behaviour.
Une approche pour la sélection des distributions statistiques : application au bassin hydrographique du Saguenay - Lac St-Jean
Authors: Haché Mario , Perreault Luc , Rémillard Louise , Bobée Bernard
Published: April 2011

The knowledge of the probability of occurrence of hydrologic events such as flood volume, flood peak, maximum rainfall, and water equivalent of snow is essential to the optimum management of water ressources and planning of hydropower production. In this paper, we present a practical approach for the selection of an adequate statistical distribution to describe a hydrometeorological variable. The selection of the distribution is based on statistical (mean absolute value of deviation between empirical and theoretical quantiles, Akaïke criterion), qualitative considerations (parsimony, representation on normal probability plot), as well as hydrometeorological criteria (regional information, spatial coherence, temporal coherence). The approach is illustrated with the hydrometeorological data of the Saguenay - Lac St-Jean basins (Quebec, Canada). The proposed procedure reduces the subjectivity in the choice of an adequate statistical distribution but does not represent a completely objective methodology.Key words: frequency analysis, extreme event, statistical distribution, statistical criteria, hydrometeorological criteria, rainfall, inflow, water equivalent of snow, volume.
Laboratory tests of a time-domain reflectometry system for frazil ice detection
Authors: Yankielun Norbert E , Gagnon John J
Published: April 2011

A prototype, electromagnetic-based frazil ice detection system (patent pending) has been developed and tested under simulated frazil ice accretion conditions in an environmentally controlled flume. The system employs a time-domain reflectometer (TDR) and specially designed transmission line sensor to monitor the accretion of frazil ice by measuring the propagation time along the sensor when it is submerged. Changes in the round-trip travel time of the TDR pulse result from a decrease in the localized bulk dielectric constant as frazil ice accretes and displaces water around the sensor. Two frazil detection sensor configurations were tested, a parallel transmission line probe and a semicylindrical mesh coaxial probe. During 2 h long experiments, the TDR clearly indicated a decreasing probe propagation time as frazil ice continued to accrete. This is indicative of the decreasing bulk dielectric constant of the frazil ice and water mix. Continuous real-time data from the TDR were recorded. From these data, an estimate of volumetric ice fraction was calculated using a simple linear dielectric mixing equation. Volumetric ice fractions estimates for both probe configurations were calculated to increase from approximately 0.02 to 0.18 during the test. The system shows promise for detection and measurement of frazil ice growth and accretion in freshwater bodies.Key words: frazil ice, trash rack, water intake, icing detection, time-domain reflectometry, TDR.
Flow through the voids of breakup ice jams
Authors: Beltaos Spyros
Published: April 2011

Flow through the voids of breakup ice jams can be a major portion of the total river discharge, especially where the jam is so thick as to be grounded. Very little information is available on this question; it is derived from laboratory tests or from numerical modelling applications, and there is a discrepancy between respective seepage coefficients. A field program has been carried out to measure the flow through the voids in ice jams by taking advantage of favourable access conditions created by an ice-retention structure on the Credit River. The data obtained during two breakup events are described and an integral method of analysis is developed to identify areas of grounding and determine seepage coefficients. Values of the latter are in agreement with those deduced by numerical modelling.Key words: flow, ice jam, modelling, seepage, voids.
Le risque d'inondation et son évolution sur la rivière Châteauguay
Authors: Bouillon M -C , Brissette F P , Marche C
Published: April 2011

This article presents the first results of a three-year study that aimed at studying, understanding, and characterizing the evolution of flood risk in Quebec. In this study, flood risk is defined as the product of the return period of an event and the damages caused by this event. It is therefore important that both these components of the flood risk be assessed historically. The two components have been evaluated for a 32 km reach of the Châteauguay River located between the Canadian-American border and Ormstown, Quebec. A flood frequency analysis was undertaken on historical flow data for two gauging stations on the river and the data fitted with a log-Pearson type III distribution. The flood risk was then established using a three-step methodology. The first step was to establish flood levels over a range of discharges using a hydraulic model. Then the computed water levels were processed to define the flooded area and determine the property damage. The last step established the global flood risk, taking into account the complete flood distribution function. The results show that over the last 60 years, the global flood risk has increased for all of the study sites along the reach of interest. When the global flood risk is standardized based on population, the evolution of the risk differs greatly between study sites. For one site, the standardized global flood risk has increased by one order of magnitude over the period studied. The results also demonstrate that 75% of the global flood risk is due to floods having a return period of 4 years or less.Key words: flood, risk, damages, numerical modelling, flood forecasting.[Journal translation]
Caractéristiques de bétons légers à base de résidus d'exploitation de carrières et de bois
Authors: Benmalek M L , Bouguerra A , Ledhem A , Dheilly R M , Queneudec M
Published: April 2011

Five mineral fines, resulting from aggregate quarries, are used in lightweight concretes formulated with wood aggregates. This study is a first approach of the influence of the characteristics of mineral fines on the properties of elaborated concretes.Key words: mineral fines, lightweight concrete, thermal conductivity, mechanical characteristics, dimensional variations.
Prévision hydrologique par réseaux de neurones artificiels : état de l'art
Authors: Coulibaly Paulin , Anctil François , Bobée Bernard
Published: April 2011

Artificial neural networks (ANN) are a novel approximation method for complex systems especially useful when the well-known statistical methods are not efficient. The multilayer perceptrons have been mainly used for hydrological forecasting over the last years. However, the connectionist theory and language are not much known to the hydrologist communauty. This paper aims to make up this gap. The ANN architectures and learning rules are presented to allow the best choice of their application. Stochastic methods and the neural network approach are compared in terms of methodology steps in the context of hydrological forecasting. Recent applications in hydrology are documented and discussed in the conclusion.Key words: artificial neural networks, hydrological forecasting, stochastic models, multilayer perceptrons.
Évaluation des méthodes utilisées pour l'estimation de la crue maximale probable en régions nordiques
Authors: Debs I , Sparks D , Rousselle J , Birikundavyi S
Published: April 2011

Among all existing methods for estimating extreme floods, the probable maximum flood method is the safest, since it is a flood with a probability of excedance that is theoretically zero. In the early 1970s, this flood was calculated as the combination of the probable maximum precipitation (PMP) and the probable maximum snow accumulation (PMSA). In the 1990s, this combination has been considered to be highly improbable. Experts advise against combining two maximized events and, instead, recommend combining one maximized event with a relatively typical extreme event. This article presents a sensitivity analysis on the return period to be used for the typical extreme event to be combined with the maximized event to obtain a "more realistic" PMF. To achieve this, all the steps of a PMF study were reviewed and applied to the Sainte-Marguerite watershed, i.e., calibration and (or) validation of SSARR model, estimation of the PMP, the PMSA, and the temperature sequence. Different flood scenarios have been simulated including accumulated snowfall corresponding to return periods of 50, 100, and 500 years, followed by PMP and PMSA, followed by precipitation corresponding to return periods of 50, 100, and 500 years. It has been noticed that the use of a return period of 50, 100, or 500 years, to represent the unmaximized extreme event, has little effect on the hydrologic response of the basin. Based on the results of this work the use of a return period of 100 years is recommended.Key words: probable maximum flood, probable maximum precipitation, probable maximum snow accumulation, design flood, SSARR model.
Seismic evaluation of single-storey steel buildings
Authors: Medhekar M S , Kennedy DJL
Published: April 2011

The seismic performance of single-storey steel buildings, with concentrically braced frames and a roof diaphragm that acts structurally, is evaluated. The buildings are designed in accordance with the National Building Code of Canada 1995 and CSA Standard S16.1-94 for five seismic zones in western Canada with seismicities ranging from low to high. Only frames designed with a force modification factor of 1.5 are considered. Analytical models of the building are developed, which consider the nonlinear seismic behaviour of the concentrically braced frame, the strength and stiffness contributions of the cladding, and the flexibility, strength, and distributed mass of the roof diaphragm. The seismic response of the models is assessed by means of a linear static analysis, a response spectrum analysis, a nonlinear static or "pushover" analysis, and nonlinear dynamic time history analyses. The results indicate that current design procedures provide a reasonable estimate of the drift and brace ductility demand, but do not ensure that yielding is restricted to the braces. Moreover, in moderate and high seismic zones, the roof diaphragm responds inelastically and brace connections are overloaded. Recommendations are made to improve the seismic performance of such buildings.Key words: analyses, concentrically braced frame, dynamic, earthquake, flexible diaphragm, low-rise, nonlinear, seismic design, steel.
Velocity distribution and shear velocity behaviour of decelerating flows over a gravel bed
Authors: Afzalimehr Hossein , Anctil François
Published: April 2011

The behaviour of the bed shear stress in the presence of a decelerating flow over a gravel bed has been examined. The collected observations revealed that the velocity distribution in the outer region of the boundary layer may be described by a parabolic law. The results obtained by parabolic law are comparable to the bed shear stress estimated via the St-Venant method. At a specific cross section, shear velocities estimated by the parabolic and the St-Venant methods divert considerably from the estimation by zero pressure gradient method. For constant bottom slope and relative roughness, the estimated bed shear stresses based on the parabolic and the St-Venant methods are proportional to the flow discharge, whereas this tendency is not accounted for by the zero pressure gradient model.Key words: velocity distribution, shear velocity, decelerating flows, gravel bed, boundary layer.
Prédiction de la charge ultime de colonnes mixtes constituées de tubes remplis de béton à haute résistance : étude comparative des codes de calcul
Authors: Lahlou K , Lachemi M
Published: April 2011

Columns are the preferred structural application of high and very high strength concrete. The confinement of this type of concrete in steel tubes presents definite advantages from both a technical and an economical perspective. However, the present design code provisions do not allow this type of material to be considered. In certain codes, the validity limits have recently been widened, but these limits remain below the present performance of high-strength concrete. The results of a large experimental program aiming at studying the behavior of concrete columns confined in steel tubes were used in order to compare predictions by different design methods, and thus verify their applicability beyond their conventional validity limits. Based on these experimental results, a new equation is proposed to predict the ultimate load of concrete columns confined in a steel tube.Key words: high-strength concrete, ultimate load, design codes, mixed columns, confinement, slenderness.[Journal translation]
Evaluation of weigh-in-motion in Manitoba
Authors: Zhi Xun , Shalaby Ahmed , Middleton Dan , Clayton Alan
Published: April 2011

The primary objective of a weigh-in-motion (WIM) system is to provide highway designers and agencies with information on the loads and traffic volumes using a particular highway, thereby facilitating improved pavement design, management, and weight enforcement. In this paper, the historic performance of WIM systems in Manitoba is evaluated. The results indicate that large numbers of unreasonable data are produced from the WIM systems, calibration procedures are not standardized, and there is drift in calibration. The performance of the Brokenhead WIM system was evaluated through a detailed survey conducted at the Brokenhead WIM site and the Westhawk Permanent Truck Weigh Station in August 1997. The Brokenhead site is on the Trans-Canada highway east of Winnipeg. It is the only WIM system in the country that measures truck characteristics and movements between eastern and western Canada. The survey produced a large database permitting the comparison of truck dimension measurements, truck weights, and vehicle classification between those produced by the WIM system and those observed manually. The results indicate that WIM axle-spacing data sets were outside the tolerance for 95% conformity specified by the American Society for Testing and Materials (ASTM). The system classified 5 to 9 axle combination trucks more accurately than some 2- and 3-axle vehicles. The WIM system underestimated about 90% of truck weights in the survey period. The degree of underestimation exceeded 50% of the corresponding static weights. This finding highlights the importance of quality control and corrections on WIM data prior to their use in research or engineering practice.Key words: weigh-in-motion, vehicle classification, calibration, axle spacing, axle load.
Analysis of reinforced concrete beams strengthened in flexure with composite laminates
Authors: Nitereka C , Neale K W
Published: April 2011

The structural behaviour of reinforced concrete beams strengthened in flexure by means of externally bonded fibre reinforced composite laminates is simulated numerically using a nonlinear finite element layered model. The full-bond assumption between the composite laminate, steel reinforcement, and the concrete is assumed, and shear deformations are neglected. Interlayer compatibility is achieved by imposing the same displacements at the interfaces of adjacent layers. The concrete is assumed to be nonlinear in compression and to exhibit a post-cracking tension-stiffening behaviour in tension. The behaviour of the steel reinforcement is modelled as elastic-plastic, while that for the composite laminate is linear elastic using an equivalent elastic modulus obtained from the so-called "classical lamination theory" of composite structures. An incremental, iterative displacement-control numerical analysis is developed. The finite element code is validated using published test results for conventional reinforced concrete beams, as well as for beams strengthened with composite laminates. A comparison of the numerical and experimental curves shows very good agreement. The effects of various parameters on the behaviour of composite-strengthened concrete beams are examined.Key words: reinforced concrete beams, fibre reinforced composite strengthening, nonlinear finite element analysis.
A fuzzy optimal model for construction resource leveling scheduling
Authors: Leu Sou-Sen , Chen An-Ting , Yang Chung-Huei
Published: April 2011

Resource leveling is needed in the construction industry to ensure efficient use of resources. Traditional resource leveling models assume activity durations to be deterministic. Nevertheless, activity duration may be uncertain because of variations in the outside environment, such as weather, site congestion, and productivity level. A new optimal construction resource leveling model is proposed in this paper, in which the combinative effects of both uncertain activity duration and resource leveling are taken into consideration. Fuzzy theory is used to model the uncertainties of activity duration. A searching technique using genetic algorithms is adopted to search for the optimal resource leveling indices under different decision makers' risk levels (i.e., α-cut levels). The model can effectively provide the fuzzy optimal usage profiles of multiple construction resources subjected to the objective of resource leveling.Key words: resource leveling, genetic algorithms, fuzzy set, construction scheduling.