bluuebunny/crossref_metadata_2025 huggingface dataset:
Road contact stresses and forces under tires with low inflation pressure
Authors: Douglas Robert A , Woodward W DH , Woodside A R
Published: April 2011

Many field trials have been undertaken to demonstrate the benefits of reducing the inflation pressure of the tires of heavily loaded haul vehicles, but few carefully controlled laboratory studies have been performed. An earlier full scale laboratory study indicated that tire inflation pressure had far less effect on subgrade strains for unpaved, single-layer granular road structures than the tire loading itself, so attention was directed to the behaviour of the granular base at the tire tread - road surface interface. In the present paper, the results of full scale tests performed using a laboratory apparatus designed to measure the dynamic vertical, transverse, and longitudinal contact forces under tires with varying loads and inflation pressures are reported. Vertical contact forces were observed to be highly non-uniform, both across and along the contact patch.Key words: central tire inflation systems, CTI, model study, haul trucks, unbound roads, unpaved roads, access roads.
Damage detection in framed buildings
Authors: Escobar J Alberto , Sosa J Jesús , Gómez Roberto
Published: April 2011

The transformation matrix method for damage detection in structural elements of frame buildings, expressed as the loss of stiffness, is proposed and evaluated. The method, which allows the locating and assessing of the damage magnitude of structural elements by considering the contribution of each of them to the overall performance of the structure, is applicable to two- and three-dimensional building frames of several storeys and bays with one or several damaged elements. Effects of uncertainties in the experimental measurements of the dynamic characteristics and in the precision of the numerical representation of the structure on the method proposed are evaluated. A three-dimensional frame model with different simulated damage states and a reinforced concrete plane frame model damaged using an earthquake record as excitation are studied. Results show the good agreement between the estimated damage computed with the proposed method and the true value of damage.Key words: damage detection, transformation matrix, structural damage, damage assessment.
Local strain on a leachate collection pipe
Authors: Brachman R WI , Moore I D , Rowe R K
Published: April 2011

Local strain measurements opposite gravel contacts and around a single isolated perforation are reported for a high-density-polyethylene pipe (320 mm outside diameter, 32 mm thick) typical of that commonly used as part of the leachate collection system in municipal solid waste landfills. Emphasis is given to examining the localized effect of coarse gravel contacts on pipe strain and the strain distribution around the perforation. The laboratory testing featured a cylindrical volume of soil with the pipe located in the middle with radially compressive stresses applied along the outer perimeter of the backfill. Two different backfill materials were used. When tested with medium sand backfill the pipe response was essentially uniform, indicative of the near-continuous support and loading provided by the sand. Large variations in local pipe strains were measured with coarse gravel backfill, such as that used in landfill leachate collection systems. Local bending induced by the discontinuous support and loading from the coarse gravel resulted in variations in circumferential and axial strains of over 40%. The local bending effects were not sufficiently large to produce circumferential tension in the pipe tested. A multiplication factor of 1.5 is suggested to account for increases in compressive strain from the coarse gravel. Measurements of surface strain around an isolated 32 mm diameter perforation revealed that a complex three-dimensional response is induced by the presence of the hole. Maximum strains near the hole were found to be 2.7 times larger than those distant from the perforation.Key words: leachate collection pipes, HDPE pipes, leachate collection systems, landfill design.
Design capacities of joints with laterally loaded nails
Authors: Smith Ian , Craft Steven T , Quenneville Pierre
Published: April 2011

Capacities of joints with laterally loaded nails may be predicted using "European yield" type models (EYMs) with various levels of complexity. EYMs presume that a nail and the wood on which it bears exhibit a rigidplastic stressstrain response. Consideration is given in this paper to the "original" model published by K.W. Johansen in 1949, an empirical approximation proposed by L.R.J. Whale and coworkers in 1987, and a curtailed and "simplified" model proposed by H.J. Blass and coworkers in 1999. Predictions from the various EYMs are compared with experimentally determined ultimate capacities of single and double shear joints. Experiments covered a range of combinations of member thicknesses and two nail sizes. The impact of modelling assumptions is illustrated in the context of the Canadian timber design code. Suggestions are made regarding the necessary level of complexity for nailed joint models used in design.Key words: timber, joints, nails, yield model, ultimate limit state, design.
Evaluation of aramid and carbon fibre reinforced polymer composite tendons for prestressed ground anchors
Authors: Benmokrane Brahim , Zhang Burong , Chennouf Adil , Masmoudi Radhouane
Published: April 2011

This paper presents the tension and bond properties of commercially available Aramid fibre reinforced polymer (AFRP) and carbon fibre reinforced polymer (CFRP) rods and their uplift and sustained loading behaviour as ground anchor tendons. Variables for the tests were tendon type and constituent, grout type, and bond or fixed anchor length. Test results indicated that the tension properties of fibre reinforced polymer (FRP) rods were close to the reported data. The surface geometry of FRP rods and the properties of filling grouts influenced the pullout behaviour and bond strength of grouted FRP rods. CFRP Carbon Fiber Composite Cable and Leadline anchors had a higher uplift capacity but lower creep displacement than AFRP Arapree and Technora anchors. The tested CFRP monorod and FRP multirod anchors with a 1000 mm fixed anchor length exhibited an acceptable uplift behaviour according to existing codes. Creep behaviour appeared to control the long-term uplift capacity of prestressed FRP ground anchors. The recommended working load for post-tensioned FRP ground anchors is 0.40 fpu for AFRP rods and 0.50fpu for CFRP rods, where fpu is the ultimate load or strength of the anchor tendon.Key words: FRP, tendon, bond stress, anchorage, grouted anchor, fixed anchor length, free anchor length, slip, creep.
Methodology for off-line assessment of advanced traffic signal control systems
Authors: Alkadry Abdulkader , Khan Ata
Published: April 2011

For the assessment of the effectiveness of major investments in advanced signal control systems prior to their implementation, it is necessary to quantify performance improvement and emission reduction. Owing to the complex nature of a traffic network, reliable estimates cannot be obtained from the use of handbook type of methods. Furthermore, reliance on the experience of other sites may not be justified because of a wide variation in results. This paper describes an off-line optimization-simulation methodology for the study of the effectiveness of advanced traffic control and its application to a real world case study, the central business district of Syracuse, New York. The methodology used incorporates TRAF-NETSIM and TRANSYT. It is well suited for off-line estimation of the measures of effectiveness of advanced signal control systems. Results show that advanced signal control has the potential to cause a highly significant improvement in user service and at the same time emissions can be reduced.Key words: traffic control, congestion, user service, delay, emissions, simulation, optimization.
Évaluation du facteur de qualité sismique au barrage de Carillon (Québec)
Authors: Giroux B , Chouteau M , Laverdure L
Published: April 2011

The seismic attenuation in concrete has seldom been studied, although it is an important parameter for survey design. In this paper, the seismic Q factor is estimated from data measured at the Carillon dam. Three methods were used for this study: amplitude decay yielding a value of 5.1 ± 1.6, spectral ratio giving a value of 8.3 ± 3.5, and a value of 7.5 ± 14.9 was obtained from the rise-time technique. These values are weak compared with what is generally observed in rocks, and slightly lower than values obtained on laboratory concrete samples. However, the average P wave velocity measured on the investigated area is 4081 ± 95 m·s1, an indication of the good quality of the material. Consequently, this strong attenuation could be attributed on one hand to energy loss, and on the other hand to scattering caused by the intrinsic cementaggregate composition of concrete. It is also possible that an inadequate sensor coupling had the effect of reducing the observed Q value. Key words: seismic attenuation, concrete dams, microseismic monitoring, coupling.
Corrosion control strategies for the Halifax regional distribution system
Authors: Maddison Linda A , Gagnon Graham A , Eisnor John D
Published: April 2011

Corrosion in drinking water distribution systems is an important issue for many water utilities because it can lead to water losses, increased headloss, and deterioration in water quality. The objective of this investigation was to evaluate the effectiveness of different corrosion control strategies for maintaining water quality in the Halifax regional distribution system. The corrosion control methods investigated at the pilot scale were lime addition, polyphosphate addition, and pH adjustment with NaOH. The strategies were evaluated with both pilot- and full-scale distribution systems. The pilot-scale system used in the investigation consisted of four 1.5-m sections of 100-year-old cast-iron pipe. Water flowed continuously through the pipe section for the first phase of the pilot-scale investigation. For the second phase of the pilot study, water was allowed to stand in the pipe for 1, 3, 6, and 12 h, which was intended to represent a no-flow or dead zone in the distribution system. Eight sampling points were used in the full-scale portion of the investigation. The hydraulic retention times of the sampling point ranged from 1.5 to 55 h. Both the lime and polyphosphate treatments provided similar performance during the pilot-scale continuous flow and standing periods. However, lime addition significantly increased post-filtered turbidity levels, which resulted in excessive deposition of insoluble material during the standing periods. At full scale, polyphosphates provided better corrosion protection than pH adjustment with NaOH. Based on both pilot- and full-scale data collection, polyphosphate was considered as the preferred corrosion control strategy for the Halifax regional distribution system.Key words: corrosion, water distribution system, corrosion control, polyphosphates, cast iron.
Contamination of a calcareous soil by battery industry wastes. II. Treatment
Authors: Wasay S A , Parker W J , Van Geel P J
Published: April 2011

This study evaluated treatment of a soil that was heavily contaminated by the disposal of waste from a Pb battery industry. The site was of interest from a remediation point of view, since the soil contained substantial quantities of calcareous material. Treatment involved extraction of the metals from the soil using aqueous solutions of EDTA (ethylenediaminetetraacetic acid). The impact of pH, EDTA concentration, and reaction time on the extent of leaching of Pb was evaluated. The leaching efficiency was found to be independent of pH over a range of values from 4 to 8.2. The leaching of Pb and Ca increased with EDTA concentration with 99% of the Pb removed at an EDTA dosage of 3.2 M/kg soil. The removal efficiencies of Cu, Cr, Cd, Ni, and Zn were consistently less than that of Pb; however, with their lower initial concentrations, acceptable levels were achieved for all metals except Cd. A two-reaction model was successfully used to describe the results of a batch extraction test. The results indicated relatively rapid extraction kinetics for a substantial fraction of the Pb contamination. Treatment of the liquid effluent from the soil treatment process with nano-level filtration indicated that both the EDTA and Pb were consistently removed at efficiencies greater than 98%. The nano-filtration process was not affected by pH over a range of values from 4.8 to 7.6.Key words: soil washing, Pb, EDTA, pH effect, kinetic, leachate treatment.
Estimating coefficients in one-dimensional depth-averaged sediment transport model
Authors: Guo Qing-Chao , Jin Yee-Chung
Published: April 2011

Various coefficients in sediment transport models must be accounted for. Models based on depth-averaged equations and sediment carrying capacity formula contain some coefficients: α, k, and m. At the present, no widely acceptable method has been developed for determining the values of these coefficients. The focus of this paper is in the development of semi-theoretical formulas for estimating these coefficients such that, in practical applications, the uncertainty involved in selecting coefficients is minimized. Model verification shows that the coefficients obtained from the proposed formulas give a good simulation of the channel bed deformation. In addition, Rouse's equation for sediment concentration distribution will become solvable because the reference concentration can be determined from the derived expression for α. The simulated concentration profiles obtained by solving the Rouse's equation and α formula agree reasonably well with the measured data.Key words: depth-averaged model, sediment transport, sediment-carrying capacity.
Développement de modèles de queues et d'invariance d'échelle pour l'estimation régionale des débits d'étiage
Authors: Hamza Abdelaziz , Ouarda Taha BMJ , Durrans S Rocky , Bobée Bernard
Published: April 2011

This paper proposes a methodology for the regional analysis of drought flows. This approach lies on the combination of two procedures. (i) The simple scale invariance method for regional series of drought flows, based on the analysis of the relation moments-surfaces or the relation quantiles-surfaces, explains the spatial variability of drought processes by their indexation on a series of scale parameters, essentially the size of the drainage basin. This procedure principally aims at delimitating homogeneous regions, and this characterizes the first condition of a regional estimation. (ii) Frequency analysis of minimum flows, with the approach using tail conditional models, consists in adjusting a probability distribution to values that are smaller than or equal to some given threshold. As a fact, this procedure gives some more weight to the lower part of the distribution by defining a priori a level of censure, mainly a threshold ui called ceiling value. This procedure establishes the second condition of a regional estimation, that is, the determination of a regional estimation model. This methodology has been applied to analyze drought flow characteristics of 187 hydrometric stations scattered in the province of Quebec. Results have shown that the first to the sixth order non-central moments follow a simple scale invariance with respect to the area of the watershed. As a result, analysis of the residuals of these six moments has allowed classifying hydrologically similar watersheds. On the basis of the results from the analysis on the residuals of the sixth moment, the province has been divided into two homogeneous regions. The behaviour of the minimum flows from these different regions has shown that they, too, followed a simple scale invariance.Key words: regionalization, flow, drought, scale invariance, tail model, non-central moment.[Journal translation]
Étude comparative de modèles phénoménologiques décrivant le comportement au jeune âge du béton. Partie 2.
Authors: Charron Jean-Philippe , Marchand Jacques , Bissonnette Benoît , Gérard Bruno
Published: April 2011

A comparative study of phenomenological models used to describe the behavior of concrete at early age was realized. The main objective of this review is to evaluate the ability of various models to predict the autogeneous shrinkage and the basic creep of concrete. The report also proposes some improvements to these models. This constitutes the second part of a series of two complementary papers.Key words : concrete, early age, phenomenological models, thermal deformation, autogeneous shrinkage, restrained shrinkage, basic creep, basic relaxation, induced stress, maturity.
Étude comparative de modèles phénoménologiques décrivant le comportement au jeune âge du béton. Partie 1.
Authors: Charron Jean-Philippe , Marchand Jacques , Bissonnette Benoît , Gérard Bruno
Published: April 2011

A comparative study of phenomenological models used to describe the behavior of concrete at early age was realized. The main objective of this review is to evaluate the ability of various models to predict the autogeneous shrinkage and the basic creep of concrete. The report also proposes some improvements to these models. This constitutes the first part of a series of two complementary papers.Key words: concrete, early age, phenomenological models, thermal deformation, autogeneous shrinkage, restrained shrinkage, basic creep, basic relaxation, induced stress, maturity.
Performance measurement indices for simulated construction operations
Authors: McCabe Brenda , AbouRizk Simaan M
Published: April 2011

This paper describes the development of indices useful in automating the experimentation process of a computer simulation. Simulation methodologies have been developed to model construction systems, but most of these systems require the experimentation process to be carried out manually. In achieving optimum performance, one has to repeat an exhaustive number of experiments. The indices can be used to automate this process, as they are indicators of bottlenecks in the system that can be tracked through the simulation output. They are based upon user-defined performance guidelines for the resources. Where a performance index falls outside the acceptable range, remedial action may be taken. Belief networks, a probabilistic form of artificial intelligence, were used to automate the analysis of the indices to determine the most likely causal factor of poor performance.Key words: construction engineering, computer simulation, performance indices, belief networks, performance improvement.
A decision support system for rehabilitation of sewer pipes
Authors: Shehab-Eldeen Tariq , Moselhi Osama
Published: April 2011

The condition of sewer pipes in North America has severely deteriorated, over the last few decades, creating a need for rehabilitation. Sewer rehabilitation methods are numerous and are constantly being developed, benefiting from emerging technologies. The implementation of these methods is driven by the need to improve quality and to reduce cost and project duration. One of the rapidly expanding fields in the sewer rehabilitation industry is trenchless technology. Due to the large number of methods associated with emerging new technologies in this field, selecting the most suitable method can be a challenging task. Selection in this environment, without a computerized tool, may also suffer from the limited knowledge and (or) experience of the decision-maker and could result in overlooking some of the suitable methods that could do the job at less cost. This paper describes a recently developed system for rehabilitation of concrete and clay sewer pipes and focuses primarily on two of its components: (i) the database management system (DBMS) and (ii) the decision support system (DSS). The system can assist municipal engineers and contractors in selecting the most suitable trenchless rehabilitation technique that specifies job conditions and user requirements. An example application is presented to demonstrate the use and capabilities of the developed system.Key words: pipe defects, rehabilitation, sewer pipes, database management systems, decision support systems, multi-attribute utility theory.
A study on flow past a suspended bluff object in an open channel
Authors: Krampa-Morlu F N , Balachandar R
Published: April 2011

Detailed velocity and erosion measurements in the near wake of a flat plate with a gap between the plate and the channel bed in an open channel are presented. A "wall jet" like flow (confined to the wall region) is observed to interact with the wake flow behind the body. Two axial stations downstream of the body were chosen to obtain the velocity profiles in the near wake region. The span-wise velocity profiles across the wake at two distances from the channel bottom were also obtained. This yielded information in the development of the "wall jet" like flow and also provided some sense of the velocity components in the near wake. At mid-section of the gap, the streamwise mean velocity attains its peak value at one body width. The velocity measurements across the wake exhibit the cause of erosion. Erosion measurements were simulated on an erodible sand bed of D50 = 0.59 mm grain size. The erosion patterns obtained show symmetry about the centerline of the plate. A ripple-like pattern was observed with deeper scour holes generated towards the edge of the wake. Flow separations from the lower corners and the sides of the plate account for this typical nature of the erosion pattern.Key words: velocity profile, local scour, wake flow, wall jet flow.
Role of synthetic fibers in delaying steel corrosion cracks and improving bond with concrete
Authors: Haddad Rami H , Ashteyate Ahmed M
Published: April 2011

An experimental study was conducted to investigate the bond behavior between corroding reinforcing steel and surrounding synthetic fiber reinforced concrete. Pullout concrete and fiber reinforced concrete specimens were prepared at concrete cover to steel bar diameter ratios of 3.1 and 3.7 with three embedded lengths of 100, 200, and 300 mm. Fiber reinforced concrete was prepared using polypropylene at 0.15% and 0.30% or nylon fibers at 0.3% by mix volume. After moist curing for 90 days, pullout specimens, originally contaminated by up to 11 kg/m3 NaCl, were subjected to a special treatment to accelerate corrosion in steel. The bond stressslippage relationship was evaluated at different corrosion levels. The findings indicated that the use of fibers delayed initiation of cracking, due to steel corrosion, and improved the ultimate bond strength at cracking and post-cracking stages. The percentage improvement in ultimate bond strength at the latter stages reached as high as 52% and 87%, respectively. It was noticed that, prior to cracking, corrosion of steel bars resulted in an increase in bond strength, regardless of the concrete cover to bar diameter ratio used, or whether fibers were used or not. After cracking (due to steel corrosion), pullout specimens prepared with polypropylene fibers showed better resistance than that of corresponding ones with nylon fibers.Key words: fibers, reinforced concrete, corrosion, cracking, bond strength, slippage.
Experimental determination of masonry beam-column behaviour
Authors: Liu Yi , Dawe J L
Published: April 2011

An experimental program consisting of 36 reinforced concrete masonry wall specimens comprised of 400 × 200 × 150 mm standard units in two series of tests was carried out to investigate the behaviour of masonry walls under combined axial and lateral loading. W2R series specimens had a single layer of vertical steel, and W4R series specimens had a double layer of vertical steel. Test results show that the effective wall stiffness, (EI)eff, differs from currently specified code values in regions where compression failure tends to predominate. Overall test results presented graphically in the form of lateral load versus deflection, axial load versus moment, and (EI)eff versus eccentricity ratio, e/t, indicate that the current Canadian masonry design code underestimates the effective stiffness of walls with eccentricity ratios e/t < 0.4.Key words: beamcolumn, masonry, reinforcement, experimental, rigidity, moment magnifier.
The August 17, 1999, Kocaeli (Turkey) earthquake  lifelines and preparedness
Authors: Gillies Antony G , Anderson Donald L , Mitchell Denis , Tinawi Rene , Saatcioglu Murat , Gardner N John , Ghoborah Ahmed
Published: April 2011

In the weeks following the Kocaeli earthquake small teams of Canadian researchers had the opportunity to visit the heavily damaged regions, primarily the provinces of Koecali (Izmit) and Sakarya (Adapazari). Amongst other observations, information was gathered on the performance during the earthquake of regional lifelines. The visits by the team members were staggered between August and October, which provided the opportunity to observe the recovery and reinstatement of the systems in the short term. Performance during and post-earthquake of regional lifelines are reported in this paper. Comments are made on the state of preparedness with some suggestions for enhanced preparedness in Canada.Key words: Turkey earthquake, highway, hospital, railway, water, search and rescue, communications.
Design method for bolted connections loaded perpendicular-to-grain
Authors: Quenneville J HP , Mohammad M
Published: April 2011

A new design approach to evaluate the resistance of bolted timber connections loaded perpendicular-to-grain is presented in this paper. The design method consists of calculating the resistances of the ductile failure modes, based on the original European yield model, and that of the splitting mode, and of using the smallest of the two. The splitting calculations are adapted from the wood resistance calculation for timber rivet connections. The new design method is based on the assumption that the bolted connection is forming a cluster considered to be equivalent in dimension to a cluster of timber rivets. The rivet design equations were modified to reflect the fact that bolts extend to the full thickness of the wood members, whereas rivets do not. In this paper, the research program is described, results are presented and the alternative design approach is proposed to predict the failure modes and the ultimate strengths of steelwoodsteel, woodwoodwood, and woodsteelwood bolted connections.Key words: connections, strength, design, bolt, connection, prediction, failure, perpendicular-to-grain.
Structural performance of sliplined watermain
Authors: Zhao Jack Q , Daigle Lyne
Published: April 2011

Rehabilitation of a watermain by grouted sliplining is usually carried out when the existing pipe is only partially deteriorated. Although designs that neglect the structural contributions from the existing pipe and the grout are generally conservative, the performance of the rehabilitated pipe needs to be better understood for effective design and management of buried water pipes. Presented in this paper is a practical method for the determination of load sharing and circumferential stresses in a sliplined pressure pipe. The laboratory tests show that the load carrying capacity of a cast iron pipe increases substantially after it is sliplined and grouted. Results also indicate that the eccentricity between the host pipe and the inserted pipe and the direction of eccentricity have an impact on the rupture load of the sliplined pipe. The effects of the host pipe wall thickness and the grout strength are also discussed. Although the method is based on a pressurized watermain, it can be used to assess the load carrying capacity of a non-pressurized pipe such as a sewer pipe. The use of this method is demonstrated through an example.Key words: performance, sliplining, watermain, circumferential stress, load sharing, grout, service life.
Performance of buildings during the 2001 Bhuj earthquake
Authors: Humar Jag Mohan , Lau David , Pierre Jean-Robert
Published: April 2011

The performance of buildings during the January 26, 2001, earthquake in the Kachchh region of the province of Gujarat in India is discussed. A majority of the buildings in the earthquake region were either of load-bearing masonry or reinforced concrete framed structure. Most of the masonry buildings were built with random or coursed stone walls without any reinforcement and heavy clay tile roofing supported on wooden logs. A large number of such buildings collapsed leading to widespread destruction and loss of life. Many reinforced concrete frame buildings had infill masonry walls except in the first storey, which was reserved for parking. As would be expected, the open first storey suffered severe damage or collapsed. Observations of failures confirmed the vulnerability of some structural details that are known to lead to distress. However, an important observation to come out of the earthquake was that masonry infills, even when not tied to the surrounding frame, could save the building from collapse, provided such infills are uniformly distributed throughout the height so that abrupt changes in stiffness and strength did not occur.Key words: Bhuj earthquake, 2001; seismology of Kachchh; earthquake damage survey; performance of buildings; load bearing masonry; reinforced concrete frames; structural details vulnerable to earthquakes.
Chloride penetration into reinforced concrete slabs
Authors: Suryavanshi A K , Swamy R N , McHugh S
Published: April 2011

The overall aim of this paper is to establish the process and amount of chlorides penetrating reinforced concrete elements when exposed to a salt-laden environment. For this purpose, a number of slabs were subjected to 70 cycles of wetting-drying regime with a 4% sodium chloride solution over a period of 2-3 years. To examine the direction of transportation of the chlorides, some of the slabs were partially coated with a surface coating system known to be highly resistant to chloride penetration. The amount and depth of penetration of chlorides in the coated and uncoated parts of the slab were then determined. The results show conclusively that, in large exposed areas of concrete, chlorides diffuse both in the direction of depth and in a direction lateral to the depth of the element. The amount of chlorides and the distance of their lateral diffusion depend on the water-to-cement (w/c) ratio of the concrete and the duration of exposure. Concrete mixes with a high w/c ratio (0.75) are highly conducive to this lateral diffusion of chlorides. Although concrete mixes of lower w/c ratios (0.45 and 0.60) are less conducive to lateral diffusion of chlorides, in practice, all concretes should be considered to be prone to chloride diffusion in both the direction of gravity and the lateral direction because of the effects of cracking. In unprotected concrete, reducing the w/c ratio from 0.60 to 0.45 is far more effective in decreasing chloride penetration than that achieved by reducing the w/c ratio from 0.75 to 0.60. The acrylic-based surface coating system is totally resistant to chloride penetration.Key words: chloride diffusion, concrete slabs, durability, water-to-cement ratio, surface coating, lateral diffusion.
Full-scale test of concrete-steel hybrid bridge girders
Authors: Leeuwen Joost van , Adebar Perry
Published: April 2011

A full-scale laboratory test was conducted on a unique hybrid bridge girder with a reinforced concrete web and steel flanges. Half-width precast concrete deck panels were compositely attached to the top steel flange of a 17.1 m long hybrid girder to construct a "half-bridge" that was tested to study the service load behaviour and the behaviour under increasing load until failure. It was observed that the concrete web of the hybrid girder cracked because of the combination of dead weight and restrained shrinkage. Under the service loads, the concrete web had numerous closely spaced cracks that were reasonably well controlled - the maximum crack width was 0.20 mm. Although there was significant diagonal cracking in the web of the girder, the ultimate behaviour was dominated by flexure. This paper presents the methods used to construct and test the half-bridge, and a summary of the important results. A companion paper presents a detailed analysis and discussion of the test results. Key words: bridges, composite, cracking, girder, hybrid, reinforced concrete, structural design, tests.
Flexural behaviour of concrete-steel hybrid bridge girders
Authors: Adebar Perry , Leeuwen Joost van
Published: April 2011

The experimental results from a full-scale test are compared with analytical predictions in order to investigate the behaviour of a hybrid bridge girder with a reinforced concrete web and steel flanges. A linear analysis indicates that restrained shrinkage had a significant influence on initial cracking of the concrete web. The longitudinal strains, predicted by a nonlinear flexural analysis accounting for shrinkage and construction stages, compare well with the strains measured during the test. The average widths of the flexural cracks at the service load level are predicted using an empirical average crack spacing approach. The modified compression field theory is used to predict the diagonal cracking of the web due to combined shear and bending moment. A rigorous nonlinear analysis indicates that the effects of creep, load-cycles, and shear deformation must be accounted for in predicting the displacement of the girder. Finally, sectional strength calculations indicate that the distributed longitudinal reinforcement in the web contributes significantly to the flexural capacity of the hybrid girder. Key words: bridges, composite, cracking, girder, hybrid, reinforced concrete, structural design, tests.
Directional effects of earthquake-induced sloshing in rectangular tanks
Authors: Isaacson Michael , Ryu Chung-Son
Published: April 2011

The influence of the direction of earthquake motions on the hydrodynamic loads on a fluid-filled rectangular tank and on the associated amplitudes of the water surface elevation is investigated. A superposition of the closed-form solution for motion parallel to a pair of sides is used to develop analytical results for an arbitrary direction of motion. The resulting solution is used to examine the effects of motion direction on the maximum force on the tank for both harmonic and earthquake-induced motions. For a harmonic motion, the highest loads occur for a motion parallel to a pair of sides, whereas the highest elevations generally occur for an intermediate direction of motion. For an earthquake-induced motion, both the highest loads and the highest elevations occur for a motion parallel to a pair of sides. An example application is provided, and the implication of the results on the design of rectangular tanks is indicated.Key words: added mass, damping, earthquakes, hydrodynamics, reservoirs, sloshing, tanks.
Application of inflatable dam technology – problems and countermeasures
Authors: Tam Paul WM
Published: April 2011

The history of the use of inflatable dams has been a long one in Hong Kong. The first three inflatable dams were constructed in the sixties as an integral part of the Plover Cove Water Supply Scheme. Up to December 1996, a total of 16 inflatable dams had been constructed. The use of rubber as a construction material has been subject to much skepticism. There are many reasons for this and one of them is clearly the problem of durability. Despite the many problems, rubber dams have been successfully implemented in Hong Kong. Most of the rubber dams in Hong Kong had been constructed by the Agriculture and Fisheries Department, Hong Kong Government, for the replacement of polluted agricultural weirs which were still in use. A rubber dam is inflatable and deflatable; when it is inflated, it serves as an agricultural weir (low-level dam) and when it is deflated it functions as a flood mitigation device. This note reviews the problems associated with the application of the technology in Hong Kong. Some countermeasures are suggested.Key words: inflatable dams, flooding, flood mitigation, rubber, weathering, vandalism.
Stochastic modelling of water temperatures in a small stream using air to water relations
Authors: Caissie Daniel , El-Jabi Nassir , St-Hilaire André
Published: April 2011

Stream water temperature is a very important parameter when assessing aquatic ecosystem dynamics. For instance, cold-water fishes such as salmon can be adversely affected by maximum summer temperatures or by those exaggerated by land-use activities such as deforestation. The present study deals with the modelling of stream water temperatures using a stochastic approach to relate air and water temperatures in Catamaran Brook, a small stream in New Brunswick where long-term multidisciplinary habitat research is being carried out. The first step in the modelling approach was to establish the long-term annual component (pattern) in stream water temperatures. This was possible by fitting a Fourier series to stream water temperatures. The short-term residual temperatures (departure from the long-term annual component) were modelled using different air to water relations, namely a multiple regression analysis, a second-order Markov process, and a Box-Jenkins time-series model. The results indicated that it was possible to predict daily water temperatures for small streams using air temperatures and that the three models produced similar results in predicting stream temperatures. The root mean square error (RSME) varied between 0.59°C and 1.68°C on an annual basis from 1990 to 1995, with the warmest year (1994) showing the highest RMSE. Although 1992 was an exceptionally cold summer (coldest in 30 years), good predictions of stream water temperature were obtained, with an RMSE of approximately 1.24°C. Of the three models, the second-order Markov process was preferred based on its performance and its simplicity in development.Key words: small stream, water temperature, model, stochastic, root mean square error, Markov process.
Un critère de rupture multiaxial pour matériaux fragiles
Authors: Aubertin Michel , Simon Richard
Published: April 2011

Most brittle materials show little straining at failure and an ultimate strength that depends upon loading geometry. The surface that defines failure in stress space has a characteristic shape that may be defined by an appropriate mathematical criterion. In this paper, the authors present a simple multiaxial criterion formulated from two quadric functions. Under conventional triaxial compression, the MSDP criterion reduces to the Mises-Schleicher criterion at low mean stress and it takes the shape of the conical Nadai-Drucker-Prager criterion at higher mean stress. The MSDP criterion can be expressed from the three principal stresses or from the usual invariantsI1, J2, and J3. It includes four characteristic parameters, each having a particular significance regarding material properties. The validity of the criterion is shown using experimental results taken from the literature on rock, concrete, and grey cast iron.Key words: failure, brittle materials, rock, concrete, cast iron.
Construction project scheduling by ranked positional weight method
Authors: Tam Paul Wing Ming , Dissanayake Pujitha Bandara Gamagedera
Published: April 2011

Construction projects are commonly scheduled by the critical path method or its similar methods, with the assumption that resources are unlimited. The ranked positional weight method, which may be used for project scheduling and resource allocation for both constrained and unconstrained resource scheduling, is found to be relatively easy in application. In construction, the availability of resources is sometimes limited and this leads to an extension of project duration. The critical path method and similar approaches cannot provide an answer in this scenario. A bridge construction project is used to illustrate how the method can be applied.Key words: scheduling, resource allocation, ranked positional weight method.
Critical review of CSA A23.3-94 deflection prediction for normal and high strength concrete beams
Authors: Sherif Alaa G , Dilger Walter H
Published: April 2011

The purpose of this paper is to critically review the provisions of CSA A23.3-94 for the deflection calculations of normal and high strength reinforced concrete beams. Comparison is made with the provisions of CEB-FIP MC 90 and EC 2 which is similar to the MC 90. Both short- and long-term deflections are discussed. Tests from the literature are used to assess the calculation methods suggested by the codes. These methods are the effective moment of inertia approach, the mean curvature approach, and the bilinear method. A parametric study is carried out to investigate the effect of the level of loading, shape of bending moment, and reinforcement ratio on the predicted deflections.Key words: code predictions, deflections, long term, reinforced concrete beams, short term.
Stiffness and energy degradation of wood frame shear walls
Authors: Shenton III Harry W , Dinehart David W , Elliott Timothy E
Published: April 2011

Tests have been conducted on wood frame shear walls to characterize the degradation of stiffness and energy dissipation that occurs under cyclic loading. A total of eight walls were tested, four sheathed in plywood and four sheathed in oriented-strand board. The tests were conducted in accordance with a draft test procedure recently proposed by the Structural Engineers Association of Southern California, which is based on a sequential phased displacement command input. The results indicate that effective stiffness decreases linearly with continued cycling at the same displacement and decreases with increasing amplitudes of displacement. Furthermore, the energy dissipation capacity of the wall decreases by 15-20% with the first cycle at a given amplitude, then decreases slightly with continued cycling at the same amplitude. The changes in effective stiffness and energy dissipation are generally independent of the type of sheathing for loads less than the wall ultimate, suggesting that the wall performance under cyclic loading is influenced more by the fastener and frame behavior. The results presented should be useful for design and for verifying hysteretic models of the shear wall behavior.Key words: cyclic, dynamic, energy dissipation, experimental, seismic, shear wall, stiffness, testing, timber, wood frame.
A field test for evaluating high performance concrete covercrete quality
Authors: DeSouza S J , Hooton R D , Bickley J A
Published: April 2011

Since in most deterioration mechanisms fluid ingress plays an important role, the surface skin of concrete provides the initial resistance to such factors as de-icer salt penetration, freeze-thaw resistance, and sulphate attack. Surface durability testing must evaluate resistance to the predominant mechanism of initial fluid ingress: capillary absorption or sorptivity. The primary focus of this study was to develop a test device suitable for nondestructive field use to evaluate the durability of covercrete by determining the rate of absorption of concrete, including high performance concrete. This type of testing device must be simple to use, easily handled in the field, portable, and inexpensive. This particular device allows for ease of operation and accommodates a wide range of surface applications such as vertical, horizontal, or sloped surfaces, and smooth or rough finishes, while providing quick, consistent, and meaningful results. The development of this apparatus was based on principles presented in the British Initial Surface Absorption Test BS 1881, Part 5: 1970, since it focuses on water absorption. Tests of this nature, however, are very sensitive to the in situ moisture content of the surface concrete, as it will drastically alter the rate of absorption. In this paper, the field rate of absorption equipment is described and both calibration and field data are presented.Key words: sorptivity, nondestructive testing, durability, ISAT.
Three-dimensional dynamic response of guyed towers to wind turbulence
Authors: Sparling B F , Davenport A G
Published: April 2011

The three-dimensional dynamic response of a guyed tower subjected to turbulent buffeting was investigated analytically in this study. Nonlinear dynamic response was determined in the time domain using Newmark's method to perform a step-by-step integration of the governing equations of motion. A simulated windstorm containing both alongwind and acrosswind turbulences was generated using a second-order autoregressive process. It was found that the fluctuating response in the acrosswind direction was similar in magnitude to that in the alongwind direction, with the relative size of the alongwind and acrosswind components depending on wind direction. Resultant bending moments in the mast were increased significantly by the acrosswind motion, leading to larger peak leg loads. Peak mast displacements and shear forces, on the other hand, appeared to be less sensitive. Dynamic guy fluctuations and axial forces in the mast were also investigated.Key words: guyed tower, dynamic response, wind loading, wind simulation, structural analysis, finite element analysis.
Slab-column edge connections subjected to high moments
Authors: El-Salakawy E F , Polak M A , Soliman M H
Published: April 2011

This paper presents test results of eight large-scale reinforced concrete flat plate edge connections. The test specimens consisted of two identical series. Each series consisted of four specimens, two with openings, in the vicinity of the column, and the other two without openings. One of the specimens without an opening contained shear studs as shear reinforcement. The tests were designed to study the effect of high moment-to-shear ratio on the punching shear behaviour of the slab-column edge connections with openings. Each series was subjected to a different moment-to-shear ratio. The test parameters were the location of openings around the column, the shear reinforcement, and the moment-to-shear ratio. The openings in the specimens were square with the sides parallel to the sides of the column. The square dimension of the openings (150 × 150 mm) was 60% of the square column dimension. The slabs contained typical flexural reinforcement (ACI 318-95 and CSA A23.3-94) with the additional reinforcement added on the sides of the openings (equivalent to that interrupted by an opening). The design procedures in the Canadian and American codes (CSA A23.3-94 and ACI 318-95) are discussed and compared with the test results.Key words: columns, edge connections, flat concrete plates, punching shear, shear strength, high moments, openings, failure, shear reinforcement, reinforced concrete.
International competitiveness of the Canadian construction industry: a comparison with Japan and the United States
Authors: Momaya Kiran , Selby Kenneth
Published: April 2011

Competitiveness can be a useful indicator of the long-term health of an industry. Whereas competitiveness has been studied at the corporate and national levels, its usefulness at the industry level has not been explored. The research objective is to develop a model to evaluate competitiveness at the industry level. Motivated by persistent problems of the Canadian construction industry, an attempt is made to quantify its international competitiveness. The industry is compared with its counterparts in Japan and the United States. Competitiveness is defined, the different dimensions of competitiveness are illustrated, and the need to quantify competitiveness is discussed. A multicriteria hierarchical model was developed and tested using both statistical and survey data. Salient findings of the research and conclusions are presented.Key words: international competitiveness, industry performance, strategic management, Canadian construction industry, Canada, Japan, United States.