bluuebunny/crossref_metadata_2025 huggingface dataset:
Les bétons renforcés de fibres d'acier et la multifissuration
Authors: Bissonnette Benoît , Therrien Yves , Pleau Richard , Pigeon Michel , Saucier François
Published: April 2011

This paper presents the results of an investigation aimed at establishing if multiple cracking can be an intrinsic property of steel fibre reinforced concrete (SFRC) in the hardened state and identifying the conditions to obtain it systematically. For this purpose, uniaxial restrained shrinkage tests and tensile tests were performed on large-scale SFRC specimens. The parameters studied in the experimental program were the fibre content (0-100 kg/m3), the fibre geometry, and the water to cement ratio of the concrete matrix (w/c = 0.40-0.80). The test results tend to indicate that multiple cracking is not a property of SFRC as such, at least within the range of concrete matrices and fibre contents investigated and that were intended to be compatible with practical considerations. While it does not mean that fibre reinforcement is not effective in terms of crack control, it is important to be careful in the analysis of test results where the effect of the restraining and exposure conditions might have been significant.Key words: cracking, drying shrinkage, fibre-reinforced concrete, multiple cracking, repairs, restrained shrinkage, steel fibres, tension.
Biofiltration d'air pollué par du xylène sur un nouveau lit à base de cellulose
Authors: Bibeau L , Viel G , Heitz M
Published: April 2011

The problem related to air discharge contaminated with volatile organic solvents (VOS) is the scope of numerous researches. Throughout the last decades, the development of different types of bioreactors to treat atmospheric emissions contaminated with VOS has been observed, such as: the bioscrubber, the percolating filter and the biofilter. These bioreactors are processes that use microorganisms in order to degrade the VOS into carbon dioxide, water, and biomass. This paper presents the results of a study on degradation by biofiltration of xylene contained in air, with a new filtering bed composed of cellulose. We have studied the conversion, the capacity of elimination of xylene with respect to the inlet load and the production of carbon dioxide. An elimination capacity of 75 g·m-3·h-1 for an inlet con centration to the biofilter of 1.7 g·m-3 of xylene has been obtained, which is a value that is superior to values mentioned in the literature. Measurements of temperature, pressure drop, and moisture content have been taken regularly so as to evaluate the influence of these parameters in the degradation process of xylene by microorganisms. Counts of bacteria and yeast/mould present in the filtering bed have been performed in order to follow the evolution of these micro organisms. At last, modeling based on the Ottengraf's model (1986) has been developed with the experimental data.Key words: treatment, air, biofiltration, xylenes, cellulose, volatile organic solvents.
Short reinforced concrete column capacity under biaxial bending and axial load
Authors: Hong H P
Published: April 2011

The paper describes the development of a simple theoretical approach in estimating the capacity of short reinforced concrete (RC) columns under biaxial bending and axial load. The developed approach considers the nonlinear stress-strain relations of concrete and reinforcing steel and does not make the assumption about the limiting strain of extreme compression fiber of concrete. The solution is obtained using a nonlinearly constrained optimization algorithm. The approach was used to estimate the theoretical capacities of many tested RC columns found in the literature. A probabilistic analysis of the modeling errors was carried out using the ratios of the test-to-predicted results. The probabilistic analysis was extended to include two simplified theoretical methods: the reciprocal load method given by Bresler and the failure surface method given by Hsu.Key words: biaxial bending, modeling error, optimization, probability distribution.
Second-order analysis for semirigid steel frame design
Authors: Xu Lei
Published: April 2011

This paper presents an analysis method in which both the nonlinear rotational behaviour of beam-to-column connections and second-order (P-Δ and P-δ) effects of beam-column members are explicitly taken into account. By adopting the concept of an end-fixity factor, the proposed method is comprehensive regardless of the end rotational conditions of beam-column members and applies to frames with any combination of pinned, semirigid and rigid beam-to-column connections. In addition, the end-fixity factor simplifies the analysis procedure for semirigid frames. More importantly, the end-fixity factor may be valuable to the design of such structures because it provides a physical interpretation of the extent of rigidity available in a connection. Thus, it provides a convenient way for designers to compare the structural responses of a semirigid member to that of a rigid one. Examples are presented to demonstrate the validity and efficiency of the proposed approach. With only minor modifications, the proposed method is readily implemented in existing rigid frame analysis and design computer programs.Key words: steel frame, semirigid connection, second-order analysis, P-Δ effect.
Structural performance of scrap tire culverts
Authors: Yang Shiping , Kjartanson Bruce H , Lohnes Robert A
Published: April 2011

Culverts constructed of whole truck tires are a cost-effective alternative for draining water from small drainage basins with areas up to several hectares. Truck tire culvert design involves both hydraulic and structural performance considerations. This paper focuses on the structural considerations. Structural performance of truck tire culverts depends on the strength and stiffness of the truck tires and on their interaction with the surrounding backfill soil. The strength and stiffness properties of truck tires were determined by parallel plate testing. Field tests were conducted to evaluate the soil-structure interaction of buried truck tire culverts under a relatively shallow backfill. Responses with well-compacted and uncompacted (dumped) glacial till backfill soil were compared. Drawing on the results of the parallel plate tests and using the buried conduit test results for calibration, the Culvert Analysis and Design (CANDE) program was used to assess the load response of a truck tire culvert for a variety of backfill soils and to develop structural performance-based design guidelines.Key words: scrap tires, culvert, parallel plate test, field testing, CANDE.
A parametric study of masonry infilled steel frames
Authors: Dawe J L , Liu Y , Seah C K
Published: April 2011

A previously developed computer model was used to investigate the effects of a wide range of parameters applicable to concrete block masonry infilled steel frames. Height to length panel aspect ratios were varied from 0.5 to 1.5 to reflect how other parameters were affected by these values. Eight different types of parameters were studied. The method of applying horizontal load was found to have little effect. Isolation gaps between panel and beam reduced both the stiffness and strength of the infilled frame. While panel-to-column ties generated an increase in peak load, local stress concentrations caused by the ties resulted in additional deterioration of the panel. Strength was found to vary with mortar joint bond strength, with the effects being more significant at higher aspect ratios. Increasing beam stiffness increased strength for low aspect ratio frames, and increasing column stiffness had a similar effect for high aspect ratio frames. Gravity loading was beneficial in increasing shear resistance up to a limit where it caused crushing of the masonry infill. The increases in strength of infilled frames were found to be disproportionate to increases in the strength of the masonry.Key words: masonry, steel, infill, frame, analytical, variables, shear, strength, deflection, interaction.
Nonlinear dynamic behaviour of guy cables in turbulent winds
Authors: Sparling Bruce F , Davenport Alan G
Published: April 2011

Large amplitude cable vibrations are difficult to predict using linear theory due to the presence of sag in the suspended profile. A numerical study was therefore undertaken to investigate the dynamic behaviour of inclined cables excited by imposed displacements. To model the nonlinear nature of cable response, a time domain finite element approach was adopted using nonlinear catenary cable elements. Two types of horizontal displacement patterns were enforced at the upper end of the guy. In the first phase of the study, harmonic displacement histories with a wide range of forcing frequencies were considered. In the second phase, random enforced displacements were used to simulate the motion of a guyed mast in gusty winds. The influence of aerodynamic drag and damping forces was investigated by performing analyses under still air, steady wind, and turbulent wind conditions. It was found that nonlinear coupling of related harmonic response components was significant at certain critical frequencies, particular when the excitation was harmonic and acted in the plane of the guy. Positive aerodynamic damping was shown to effectively suppress resonant and nonlinear coupling response.Key words: cables, structural dynamics, wind loading, finite element method, nonlinear analysis, guyed towers.
Measurements of laboratory rates of concrete expansion and their comparisons with field rates
Authors: Hefny A , Lo K Y , Adeghe L
Published: April 2011

The R.H. Saunders dam is one of over one hundred concrete dams, worldwide, suffering from structural and operational problems due to the expansion of concrete resulting from alkaliaggregate reaction. A laboratory test methodology for measuring the residual expansion rate in these dams with simulation of field environment has been developed. This paper describes the test principles and method of interpretation of the different tests developed. Results of various expansion tests performed on samples recovered from the R.H Saunders dam (Canada) are presented. Results showed that the expansion rates measured in laboratory are consistent with those measured by extensive instrumentation in the field (in situ rebar tests, levelling data, stress meters, and in situ overcoring data). It is believed that the test methodology developed provides the necessary and inexpensive tools for measuring the stress-dependent residual expansion potentials in concrete dams. It would also have an impact on the design of remedial measures and the prediction of future performance because of the reliability and versatility of the test method.Key words: dams, concrete, expansion, alkalis, aggregate, reaction, cement.
Composite reliability model for local scour around cylindrical bridge piers
Authors: Yanmaz A Melih , Cicekdag Ozgur
Published: April 2011

Bridge scour is an extremely complex phenomenon because of the random characteristics of sediment laden flow in close proximity to piers and abutments. This occurrence leads to high uncertainties and unavoidable risk in bridge pier and abutment design. In this study, a composite reliability model is developed for the reliability assessment of bridge pier scour using static resistance  loading interference. Based on the physical interpretation of the phenomenon and a statistical analysis of the available information, the relative maximum scour depth (corresponding to the minimum required relative pier footing elevation) and the linear combination of the relative approach flow depth and flow Froude number are defined as the system resistance and external loading, respectively. By examining a set of laboratory and field data, a two-parameter bivariate lognormal distribution is found to represent the joint probability density function of resistance and loading. Reliability expressions are developed in terms of resistance. Use of the model is illustrated in a practical application in which a relationship is obtained between the reliability and safety factors under various return periods. This information is of importance in decision making.Key words: reliability, bridge pier, scour, resistance, loading, safety factor, return period.
Effect of grain size on local channel scour below a sluice gate
Authors: Kells J A , Balachandar R , Hagel K P
Published: April 2011

In this study, the effect of grain size on the dynamics of local scour processes is discussed in the context of the erosion that takes place downstream from a submerged sluice gate. Four gradations of non-cohesive bed material were used to study the scour process for various tailwater depth and flow rate conditions. The sand gradations included three sizes of uniformly graded sand and a fourth size, which was obtained by mixing the three uniform sands in equal proportions by weight. A total of 36 tests was carried out, each for a period of 24 h. An equilibrium scour condition was not attained over this time period for any of the tests, although a sense of similarity in the bed profiles is observed in the region close to the sluice gate. The present results indicate that the depth and the area of scour are highly dependent on the bed grain size, both increasing as the grain size is reduced. As well, it was found that the tests with a mixed (i.e., graded) sand bed resulted in less scour relative to those in which a uniformly graded sand of similar grain size was used. Moreover, the maximum scour depth increases with increases in the discharge and the tailwater depth. Finally, it was found that the location of the point of maximum scour depth, as measured from the upstream end of the erodible sand bed, moved downstream with an increase in either the discharge or tailwater depth and upstream with an increase in the grain size.Key words: grain size, grain size distribution, local scour, scour dynamics, sluice gate, tailwater depth, video image data acquisition.
Effects of simulated water level management on shore erosion rates. Case study: Baskatong Reservoir, Québec, Canada
Authors: Saint-Laurent Diane , Touileb Bachir N , Saucet Jean-Phillippe , Whalen André , Gagnon Benoit , Nzakimuena Tonino
Published: April 2011

This study was carried out as part of a feasibility study on the construction of a hydroelectric generating station at Mercier dam at the outlet of the Baskatong reservoir in Québec. The study dealt mainly with a comparison of the current and future bank erosion rates of the reservoir. Given the year of impounding of the Baskatong reservoir, i.e., 1927, it was possible to track bank erosion rates using field surveys and photogrammetric and numerical analyses. It was noted that in certain areas, such as Du Diable Bay and Windigo Bay, the Baskatong reservoir banks were substantially affected by erosion. Estimates indicate that the banks have receded by about 10 to 15 m over a 20-year period. The banks most affected by erosion are those containing sandy material of fluvioglacial or glaciolacustrine origin with bluffs greater than 2 m in height and characterized by the longest fetches. In one section of Windigo Bay, banks had receded by about 30 m in 20 years. Wave action is the main factor responsible for bank erosion, especially in areas highly exposed to long fetches. In fact, there is a correlation between bank erosion rates, fetch distribution, and the erosive energy of waves. It has been noted that receding banks with the highest erosion rates are linked to the greatest wave erosion energy. Based on the values obtained using simulated reservoir water levels, while taking into account the future construction of a new generating station, bank erosion rates appear to be comparable to those measured under actual conditions, though erosion rates could increase by about 2830% in the areas most affected by erosion at the present time.Key words: bank erosion, waves and fetch, erosion rates estimated, Baskatong Reservoir, Québec, Canada.
Comportement sismique d'un système formé de murs couplés tronqués et d'un cadre
Authors: Chaallal O , Malenfant P , Nollet M -J
Published: April 2011

This paper presents results of a numerical investigation on the nonlinear seismic behavior of a reinforced concrete system made of truncated coupled shear walls (CSWs) and a frame. The objective of the study is twofold: (a) examine the seismic behavior of CSWframe systems with setbacks and (b) verify the adequacy of the National Building Code (NBC) as far as the design of such systems. The study considers two types of CSWs, coupled and partially coupled, two Canadian seismic zones, 4 and 6, six different levels of setbacks, and 10 historic seismic records encompassing a wide range of frequency content. Results of the study show that the CSWframe system with no setback offers a satisfactory seismic behavior with regards to the sequence of plastification and the ductility demand. For the truncated systems, the NBC recommendations that the static method is not adequate is justified. Also, in the presence of setbacks, the columns show a higher degree of plastification with a possibility of formation of plastic mechanism (soft story). The ductility demand is also higher and can exceed the accepted practical limit in certain cases.Key words: coupled shear walls, frame, reinforced concrete, setback, seismic behavior, code.
The August 17, 1999, Kocaeli (Turkey) earthquake  damage to structures
Authors: Saatcioglu Murat , Mitchell Denis , Tinawi René , Gardner N John , Gillies Anthony G , Ghobarah Ahmed , Anderson Donald L , Lau David
Published: April 2011

The 1975 Turkish code provisions are first reviewed to provide the background for design and detailing of structures prior to the earthquake. The performance of reinforced concrete and masonry structures is described indicating many of the deficiencies in design, detailing, and construction execution. The behaviour of precast concrete structures, steel structures, and industrial facilities is also presented. The provisions of the 1997 Turkish building code are summarized and a description of new construction provides evidence of both excellent and poor construction practice. Some examples of retrofitting of damaged structures soon after the earthquake are also presented.Key words: seismic design, earthquake, Kocaeli, structures, codes, concrete, precast concrete.
Using claims prediction model for road safety evaluation
Authors: Leur Paul de , Sayed Tarek
Published: April 2011

Road safety analysis is typically undertaken using traffic collision data. However, the collision data often suffer from quality and reliability problems. These problems can inhibit the ability of road safety engineers to evaluate and analyze road safety performance. An alternate source of data that characterize the events of a traffic collision is the records that become available from an auto insurance claim. In settling an auto insurance claim, a claim adjuster must make an assessment and determination of the circumstances of the event, recording important contributing factors that led to the crash occurrence. As such, there is an opportunity to access and use the claims data in road safety engineering analysis. This paper presents the results of an initial attempt to use auto insurance claims records in road safety evaluation by developing and applying a claim prediction model. The prediction model will provide an estimate of the number of auto insurance claims that can be expected at signalized intersections in the Vancouver area of British Columbia, Canada. A discussion of the usefulness and application of the claim prediction model will be provided together with a recommendation on how the claims data could be utilized in the future.Key words: road safety improvement programs, auto insurance claims, road safety analysis, prediction models.
Proving WATFLOOD: modelling the nonlinearities of hydrologic response to storm intensities
Authors: Cranmer A J , Kouwen N , Mousavi S F
Published: April 2011

This paper examines the effects of modelling the nonlinearities of hydrologic response to various storm intensities. Radar rainfall data, remotely sensed land use and land cover data, measured streamflows, and meteorological data were incorporated into the distributed flood forecasting model WATFLOOD to synthesize runoff hydrographs for three significant warm weather rainfall events occurring in 1995. The watershed selected for study was the 288 km2Duffins Creek drainage basin in southern Ontario. The effects of scaling radar rainfall amounts to match regional storm intensities on the synthesized streamflow hydrographs were examined. Computations and analysis were performed in agreement with widely accepted hydrologic principles and assumptions. The observed and synthesized hydrographs were compared using the unit hydrograph method. The observed and composite unit hydrographs matched extremely well in terms of shape, timing, and peak flow magnitude. These results indicated that WATFLOOD is capable of accurately modelling the nonlinear rainfallrunoff processes for increasing rainfall intensities with respect to peak flow, basin lag, and time to peak flow. However, the arbitrariness of assessing the effective rainfall and base-flow separation for the unit hydrograph method can lead to uncertainties in computing peak flow magnitudes. The grid element size and number and the drainage areas above streamflow gauges are of critical importance to the accuracy of the model.Key words: hydrology, watershed model, flood forecasting, hydrological modelling, model validation, unit hydrograph, nonlinear response.
Évaluation de l'état du béton par la technique d'analyse spectrale des ondes de Rayleigh
Authors: Hassaim M , Rhazi J , Ballivy G , Khayat K
Published: April 2011

The evaluation of concrete deteriorations is essential to optimize the costs and ensure that the required retrofits are durable. A study undertaken on many experimental concrete specimens has shown that an analysis of the dispersion of Rayleigh waves enables differentiation between concrete of different mechanical properties, description of the evolution of these properties with respect to depth, and detection of defaults in the concrete mass. The study of the different monitoring and processing parameters associated with this technique reveals that the choice of the type of emission source must be accomplished with respect to the thickness of the material under study, and that the distance between the emission source and the sensors as well as the distance between sensors do not have any effect on the Rayleigh wave speed profile. A new monitoring configuration is proposed to improve the experimental procedure.Key words: concrete, deterioration, nondestructive tests, spectral analysis of Rayleigh waves.[Journal translation]
Environmental road and lot drainage designs: alternatives to the curb-gutter-sewer system
Authors: Li James , Orland Robert , Hogenbirk Tom
Published: April 2011

Traditionally, road and lot drainage systems have been designed to convey storm runoff away as quickly as possible to reduce localized ponding. This drainage concept, using curb-gutter-sewer systems, has led to downstream flooding, erosion, water-quality degradation, reduced groundwater recharge and stream baseflow, and aquatic habitat destruction. This paper examines the pros and cons of curb-gutter-sewer systems and qualitatively compares various forms of open ditch - swale drainage alternatives with the conventional curb-gutter-sewer drainage system. These open ditch - swale drainage alternatives not only provide drainage functions but also promote infiltration, trap sediments, and reduce flow velocity along the drainage path. Thus, they can reduce erosion, enhance runoff quality, and increase groundwater recharge. However, they usually require a wider right-of-way than the conventional curb-gutter-sewer systems and may not be suitable for sites with steep topography or erosive soils. For sites that are suitable for the application of these alternative drainage systems, their environment functions make them more attractive than the conventional curb-gutter-sewer system.Key words: drainage systems, storm water, curbs, gutters, sewers, ditches, swales.
Verification of a transient input, two-dimensional, river mixing model
Authors: Putz Gordon , Smith Daniel W
Published: April 2011

A two-dimensional river mixing model capable of handling unsteady input conditions is evaluated in this study. The numerical model utilizes a streamtube representation of the river and a calculation grid which is optimized to eliminate errors associated with advective transport calculations. The application of the modelling procedure to natural river systems is evaluated by comparing model output with the results of tracer studies conducted on the North Saskatchewan, Peace, and Slave rivers. The study results represent a far more extensive field verification of this modelling procedure than had been previously reported by other authors.Key words: river mixing, mixing zones, tracer tests, water quality modelling, mixing coefficients.
Road bridges functional failure costs and benefits
Authors: Brito J de , Branco F A
Published: April 2011

The economic feasibility of a road bridge network depends on its structural costs and functional benefits, which must be predicted in a long-term economic analysis. Nevertheless, road bridges are frequently built according to a lowest possible initial cost design, as long as the design service level is guaranteed, thus neglecting their long-term behaviour. In this paper, a global economic analysis, designed to be used in long-term economic studies related to concrete bridges management, is presented. Taking into account a rationalized costs and benefits analysis, the technique helps the user in decision making and improves the network's investment policies at several levels: building new facilities, maintaining and repairing the existing ones, and upgrading existing levels of service. The analysis of the functional costs and benefits is described in some detail and is illustrated with a bridge case study. These parameters are the most important ones within an economic analysis and allow an estimation of the functional service life of the bridges.Key words: bridges, management systems, economic studies, long-term costs, benefits, functional failure.
Analysis of three-layer beams with non-identical layers and semi-rigid connections
Authors: Chui Ying H , Barclay David W
Published: April 2011

An explicit solution is presented for three-layer beams with non-identical and semi-rigidly connected layers. Exact designer-usable equations for calculating mid-span deflection due to bending deformation and interlayer slip of a simply supported layered beam subjected to a uniformly distributed load and a point load applied at mid-span are also given. Calculated results agree well with the results from finite element analyses and from tests.Key words: layered beam, semi-rigid connection, explicit solution.
Seismic performance of ductile and nominally ductile reinforced concrete moment resisting frames. II. Analytical study
Authors: Filiatrault André , Lachapelle Éric , Lamontagne Patrick
Published: April 2011

This paper is the second of two companion papers on the evaluation of the level of protection offered by ductile and nominally ductile reinforced concrete structures. In the first paper, experimental results obtained from shake table tests of two half-scale reinforced concrete moment resisting frames were reported. The first structure was designed as a ductile frame (force reduction factor R = 4) according to current Canadian standards; and the second structure incorporated only nominally ductile details (R = 2). This second paper deals with the dynamic modelling of the two structures. A simple nonlinear time-history dynamic analysis model is presented and its predictions are compared with the shake table test results. It is shown that inelastic deformations in beam-column joints have a major influence on the seismic response of the structures. Approximate modelling of these joint deformations, based on equivalent rotational springs, can provide a good correlation between numerical and experimental results.Key words: dynamic analysis, moment resisting frames, earthquakes, reinforced concrete, seismic.
Construction quality management - present and future
Authors: Battikha Mireille G , Russell Alan D
Published: April 2011

This paper reviews past work in construction quality management by examining its major components in the context of a study framework derived from ISO 9000. Emphasis is placed on determining the state-of-the-art and exploring the roles that information technology already plays as well as could play in improving the quality management function. The authors elaborate on several dimensions of the quality management view of a project in terms of how it would interact with the physical, process, cost, and as-built views of a project, which are essential to the quality management function as well as to other project management functions. This is done in a way that reflects the authors' vision of the kind of support that a computer system could offer for the tasks of identifying, predicting, analyzing, and solving quality problems in a preventive mode.Key words: construction quality management, ISO 9000, problem prevention, problem prediction, computer system.
Development and field applications of silica fume concrete in Canada: a retrospective
Authors: Thomas MDA , Cail K , Hooton R D
Published: April 2011

The effects of silica fume on the properties of plastic and hardened concrete are now fairly well-established. If properly used, silica fume imparts significant improvement to the strength and durability of concrete; and the availability of this material together with high-range water reducers (superplasticizers) has been largely responsible for the development of high-strength and high-performance concretes. Silica fume has been used in the Canadian cement and concrete industry for over 15 years. Early use was driven by economy, since concrete of a given strength grade could be produced at lower cementitious material content (and cost) if silica fume was incorporated in the mix due to the initial low selling price of the material. The construction boom of the mid to late 1980s saw the exploitation of high-strength silica fume concrete for high-rise construction. By the 1990s, concerns over the deteriorating infrastructure had shifted the focus to concrete durability and silica fume was finding applications in high-performance concrete. Today, silica fume is perhaps the material of choice for engineers designing concrete to withstand aggressive exposure conditions. This paper documents the major developments in the use of silica fume in Canada and discusses the wide range of applications for which the product may be used to beneficial effect.Key words: blended cement, Canada, concrete, high-performance, silica fume.
Simulation of the construction of cable-stayed bridges
Authors: Abraham Dulcy M , Halpin Daniel W
Published: April 2011

Cable-stayed bridges are ideal for spanning natural barriers of wide rivers, deep valleys, or ravines, and for pedestrian bridges crossing wide interstate highways. Modern construction of cable-stayed bridges makes use of the segmental balanced cantilever techniques and involves many repetitive cycles of placing the concrete segments (both cast-in-place and precast) and supporting cables. It provides a fertile area for the application of computer simulation techniques for the planning and analysis of the process, particularly for studying the interaction of resources used in the construction phase and also for assessing the productivity of the construction processes. This paper employs MicroCYCLONE, a microcomputer-based simulation program, for the modeling and simulation of the construction of two cable-stayed bridges: the Dame Point Bridge in the state of Florida, U.S.A., and the Tsukuhara Bridge in Hyuougo, Japan. The paper will also provide a brief explanation of the suspended long traveler method used on the Tsukuhara Bridge, the simulation models developed to analyze the construction processes, and the results of sensitivity analyses.Key words: simulation, modeling, construction, cable-stayed bridges, resources, productivity, balanced cantilever construction.
State-of-the-art of three-dimensional highway geometric design
Authors: Hassan Yasser , Easa Said M , Abd El Halim A O
Published: April 2011

Geometric design is an important phase in the highway design process that is directly related to traffic safety. Highway elements should be jointly designed to account for such design criteria as sight distance, vehicle stability, driver comfort, drainage, and aesthetics. Intuitively, such a design should be based on a three-dimensional (3-D) analysis. This paper reviews the current practice and research work related to each design criterion with emphasis on the conformity with the 3-D nature of the highway. Current standards are based mainly on a two-dimensional (2-D) analysis that does not guarantee a satisfactory design. Recently, several research efforts have been expended in the 3-D highway analysis with sight distance being the most researched area. Analytical models and computer software have been developed to accurately model 3-D daytime and nighttime sight distances. Roads designed using current 2-D standards may compromise safety or economy. Different models are currently available to simulate the forces acting on a vehicle in 3-D. These models show that the point-mass formula for modelling vehicle dynamics in the current standards can be inaccurate. Current standards contain recommendations for drainage of surface water, but explicit quantitative coordination of combined alignments is lacking. Furthermore, research is still needed to study the effect of alignment coordination on highway aesthetics and driver's perception of information.Key words: highway geometric design, three-dimensional analysis, sight distance, vehicle dynamics, drainage, highway aesthetics.
Single-angle compression members welded by one leg to a gusset plate. II. A parametric study and design equation
Authors: Temple Murray C , Sakla Sherief SS
Published: April 2011

Single-angle compression members are complex members to analyze and design. The two generally accepted design procedures, the simple-column and the beam-column approaches, in general, underestimate the load-carrying capacity of single-angle compression members welded by one leg to a gusset plate fixed to a rigid support. One of the reasons is that these approaches do not properly account for the end constraint provided by the gusset plate. The effective length factor can be adjusted, but this is difficult to do as the end restraint is not easy to evaluate in many practical cases. Another reason is that these approaches are not based on a rational understanding of the failure mechanism of these members. An experimental program confirmed that the finite element method can be used, with a reasonable degree of accuracy, to predict the behavior and load-carrying capacity of single-angle compression members welded by one leg to a gusset plate fixed to a rigid support. The finite element method was used to study some 1800 different combinations of parameters. It was found that out-of-straightness, residual stresses in the angle section, Young's modulus of elasticity, and the unconnected gusset plate length do not have a great effect on the load-carrying capacity. The most significant parameter is the gusset plate thickness with the gusset plate width being the second most important parameter. An empirical design equation is proposed.Key words: angles, buckling, columns (structural), compressive resistance, design equation, gusset plates.
Equivalent area of voided slabs
Authors: Jaeger Leslie G , Bakht Baidar , Tadros Gamil
Published: April 2011

In order to calculate prestress losses in the transverse prestressing of voided concrete slabs, it is sometimes convenient to estimate the thickness of an equivalent solid slab. The Ontario Highway Bridge Design Code, as well as the forthcoming Canadian Highway Bridge Design Code, specifies a simple expression for calculating this equivalent thickness. This expression is reviewed in this technical note, and a simple alternative expression, believed to be more accurate, is proposed, along with its derivation. It is shown that the equivalent solid slab thickness obtained from consideration of in-plane forces is also applicable to transverse shear deformations, provided that the usual approximations of elementary strength of materials are used in both cases.Key words: axial stiffness, equivalent area, shear deformation, transverse prestressing, voided slab, slab.
Pre-denitrification and pre- and post-denitrification treatment of high-ammonia landfill leachate
Authors: Shiskowski D M , Mavinic D S
Published: April 2011

This bench-scale study investigated the nitrogen-removal capabilities of two different biological process configurations treating methanogenic-state landfill leachate containing up to 1200 mg N/L of ammonia. The first configuration was a pre-denitrification system known as the modified Ludzack-Ettinger (MLE) process. Large clarifier sludge recycle flows, set to yield clarifier recycle ratios of 7:1 and 8:1, were evaluated as a means to reduce effluent NOx concentrations. A pre- and post-denitrification system, known as the four-stage Bardenpho process, was the second configuration evaluated. The MLE systems (20 day aerobic solids retention time (SRT)) were capable of producing effluent containing about 50 mg N/L of ammonia and 200-235 mg N/L of total inorganic nitrogen (ammonia + NOx) when treating leachate containing approximately 1200 mg N/L of ammonia. In contrast, effluent from the four-stage Bardenpho system contained less than 1 mg N/L of ammonia and 15 mg N/L of NOx, when treating 1100 mg N/L ammonia leachate. An aerobic number 1 SRT of 20 days (total aerobic SRT approximately equal to 40 days) was used with aerobic number 1 and clarifier sludge recycle ratios of 4:1 and 3:1, respectively. The ammonia-removal potential of both systems was clearly demonstrated but each system also showed certain disadvantages, characteristic of each process.Key words: ammonia-N, anoxic denitrification, leachate treatment, nitrification, pre-denitrification.
Designing skid resistance testing programs using videotaped road inventory data
Authors: Innes J David , Wilson F R , Goguen Denis R
Published: April 2011

It is generally accepted that road skid resistance should be carefully monitored. However, system-wide testing programs are generally expensive in terms of both manpower and equipment costs. Programs that test only road sections where the road surface is either inadequate or of marginal quality would be more economical than one in which all roads are tested, particularly where a significant proportion of the road surfaces in the system are clearly adequate. This paper examines the potential for using videotaped road inventory data to identify road sections that are either slippery or of marginal quality in terms of skid resistance. It reports on research conducted which examined the ability of individuals to identify inadequate road sections and discriminate these road sections from those with good surfaces by using VHS and super-VHS road inventory videotaped images. Videotaped records of road sections were evaluated by a panel. Their responses were then compared with skid resistance test data. A statistical analysis showed no satisfactory level of agreement between measured data and video evaluations for the VHS records. A second series of tests was conducted using super-VHS technology. The results of the second series of tests showed much better agreement. The research provided promising results and it would appear that videotaped road inventory data could be used as part of a protocol that could be developed to identify the sections that should be field tested as part of a system-wide skid resistance monitoring program.Key words: highway safety, skid resistance, program design, pavement characteristics, video evaluation.
A comparison of methods for computing the discharge through hydroelectric turbines
Authors: Doering John C , Hans Pamela D
Published: April 2011

The economic and efficient operation of a hydroelectric generating station requires an accurate description of the head-power-discharge relationship for each turbine. Of the information required to determine this relationship, absolute discharge is the most difficult to measure and the most susceptible to measurement error. For low-head hydroelectric plants, the velocity-area method is often used. This method consists of traversing an array of current meters across the intake to obtain a grid of velocity measurements. The location of the metering points is central to the accuracy of the discharge estimate. The codes governing the performance testing of hydraulic turbines require the metering plane to be located in conditions that cannot be met for low-head hydroelectric plants. In spite of this, the codes are still applied. In this paper a densely spaced array of Ott meter data, collected according to the German (DIN) code, are used to examine the velocity profiles at the entrances of low-head hydroelectric turbine. In addition, these data are interpolated using cubic splines to estimate the time-averaged velocities required to compute discharge according to ASME (PTC-18) code. Interpolated data are also used to examine an alternative method of metering low-head plants based on Gauss-Legendre quadrature integration. The velocity profiles observed are significantly different from those assumed by the German and ASME codes to determine metering locations, which raises questions about the applicability of these codes to low-head plants. The results indicate that a Gauss-Legendre quadrature integration of a 4 × 5 grid of metering points estimates discharge more accurately than the German code, which requires a 7 × 12 grid. The suggestion is the location, and not simply the number of metering points, is central to the accuracy of a discharge estimate through a low-head hydroelectric plant.Key words: low-head hydroelectric turbine, performance testing, head-power-discharge relationship, Ott meter, Gauss-Legendre quadrature integration.
Torsional motion of buildings during earthquakes. I. Elastic response
Authors: Humar J L , Kumar P
Published: April 2011

Analytical studies are carried out on the elastic torsional response of single- and multi-storey building models subjected to earthquake motion. Effects of both the natural and accidental torsion are considered. The results of analysis are compared with the design provisions of the National Building Code of Canada (NBCC). It is shown that the NBCC provisions for the design of resisting elements on the flexible side are overly conservative. On the other hand, provisions for the design of elements on the stiff side are conservative in some situations and inadequate in others. Modifications to the design provisions are suggested which give design forces closer to the results obtained from a dynamic analysis, and are at the same time simpler than the existing provisions. It is shown that the ratio of the uncoupled torsional and translational frequencies is an important parameter governing the torsional response and it would be a good practice in design to achieve a value greater than 1 for this ratio.Key words: earthquake response, natural torsion, accidental torsion, elastic torsional response, design for torsion.
Reliability analysis of a telecommunication tower
Authors: El-Fashny Kamal , Chouinard Luc E , McClure Ghyslaine
Published: April 2011

This study presents a structural reliability analysis of a microwave tower subject to wind and freezing-rain hazards. The tower (name code CEBJ, owned by Hydro-Québec) is a 66 m tall, three-legged, steel lattice structure located in the James Bay area. The reliability analysis is performed conditionally with respect to wind speed and ice thickness accretion, and the results are integrated over the domain of wind and ice values using their joint probability distribution. This approach makes it possible to perform sensitivity analyses with respect to various assumptions on the joint probability distribution function of the climatological variable, without having to repeat the detailed coupled reliability - structural analysis of the tower. The probability distribution functions assumed for the wind speed and the ice thickness accretion on the tower members are both extreme-value type I (Gumbel) distributions. Adopting a weakest link model, the failure of the tower is assumed to occur when any of the members fails either in tension, compression, or global buckling. Without loss of generality, the proposed procedure can be applied with more refined probability distribution functions.Key words: reliability, telecommunication towers, wind, ice.
Stirrup distribution across the beam width in tension lap splices
Authors: Pacholka K , Rezansoff T , Sparling B F
Published: April 2011

The influence of the distribution of transverse confining steel on the strength of tension lap splices was investigated experimentally in this study. Beam specimens contained three lap-spliced No. 35 bars placed in one layer. Either two or three stirrup legs were placed across the beam width to provide splitting confinement. Both configurations were designed to provide similar stirrup resistances for intercepting horizontal bond splitting. The effectiveness of the different stirrup configurations was compared by investigating the performance of beams subjected to static, fatigue, and fully reversed inelastic loading. Twenty-three full-size beam specimens were tested with the lap splice placed symmetrically within a maximum moment, zero-shear region. Specimens were constructed and tested in six different series (concrete batches). Within each series, the total bond resistance, as evaluated on the basis of CSA A23.3-94, was similar even though the lateral distribution of transverse steel was varied. Nine specimens were tested under monotonically increasing (static) loading to failure, six specimens were subjected to fatigue load cycling between 25% and 75% of their ultimate static strength, and eight specimens were subjected to fully reversed inelastic load cycling. Test results for six similar specimens from a previous study were also included in the current investigation analysis. Test results indicated that using three vertical stirrup legs across the beam width to provide a more uniform distribution of stirrup confinement significantly enhances post yield ductility under fully reversed inelastic load cycling. Meanwhile, specimens tested under static loading showed that CSA A23.3-94 provisions provide a consistent and conservative prediction of lap-splice strength for the specimen configurations investigated, regardless of the distribution of stirrup confinement across the beam width. Finally, the performance of fatigue specimens indicated a slight improvement with the use of the three-leg stirrup configuration. However, this result does not agree with previous observations made at the same institution where it was suggested that stirrup confinement intercepting vertical splitting plays a more significant role in defining fatigue resistance.Key words: reinforced concrete, bond, confinement, lap splices, stirrups, static loading, fatigue load cycling, inelastic load reversal.