Canadian Journal of Civil Engineering
0315-1468
1208-6029
Canada
Cơ quản chủ quản: National Research Council of Canada , Canadian Science Publishing
Lĩnh vực:
Civil and Structural EngineeringEnvironmental Science (miscellaneous)
Các bài báo tiêu biểu
A spectral density approach for modelling continuous vertical forces on pedestrian structures due to walking Existing walking models used for vibration serviceability assessment of structures carrying pedestrians are typically based on measurements of single footfalls replicated at precise intervals. This assumed perfect periodicity allows walking forces to be modelled as a Fourier series based on the walking pace and its integer multiples. This paper examines real continuous walking forces obtained from an instrumented treadmill and the effect of their random imperfections through time simulations of structural response and shows that there are significant differences between responses due to the imperfect real walking forces and the equivalent perfectly periodic simulation. These differences are most significant for higher harmonics where the simulated vibration response is overestimated. As a realistic representation of imperfect walking is an auto-spectral density function, the random character naturally leads to a stochastic approach to treatment of pedestrian loading applied in the frequency domain. The approach can be used for single pedestrians as well as crowd loading where correlation between pedestrians as well as statistics of their pacing rates is used.Key words: vibration, coherence, loading, footbridges, gait, floors, pedestrians, spectral density.
Tập 31 Số 1 - Trang 65-77 - 2004
Analysis of masonry structures: review of and recent trends in homogenization techniquesThis article is one of a selection of papers published in this Special Issue on Masonry. The mechanics of masonry structures have been underdeveloped for a long time in comparison with other fields of knowledge. Presently, nonlinear analysis is a popular field in masonry research and homogenization techniques play a major role despite the mathematical and conceptual difficulties inherent to this approach. This paper addresses different homogenization techniques available in published literature, aiming at defining a first catalogue and at discussing the advantages and disadvantages of the different approaches. Finally, special attention is given to a micromechanical based model and a model based on a polynomial expansion of the microstress field. These seem promising and accurate strategies for advanced structural analysis.
Tập 34 Số 11 - Trang 1443-1457 - 2007
Use of steel slag aggregate in asphalt concrete mixes There are three major steel-manufacturing factories in Jordan. All of their by-product, steel slag, is dumped randomly in open areas, causing many environmentally hazardous problems. This research was intended to study the effectiveness of using steel slag aggregate (SSA) in improving the engineering properties of locally produced asphalt concrete (AC) mixes. The research started by evaluating the toxicity and chemical and physical properties of the steel slag. Then 0%, 25%, 50%, 75%, and 100% of the limestone coarse aggregate in the AC mixes was replaced by SSA. The effectiveness of the SSA was judged by the improvement in indirect tensile strength, resilient modulus, rutting resistance, fatigue life, creep modulus, and stripping resistance of the AC samples. It was found that replacing up to 75% of the limestone coarse aggregate by SSA improved the mechanical properties of the AC mixes. The results also showed that the 25% replacement was the optimal replacement level. Key words: steel slag aggregate, asphalt concrete, Superpave, indirect tensile strength, fatigue, rutting, creep.
Tập 34 Số 8 - Trang 902-911 - 2007
Prévision hydrologique par réseaux de neurones artificiels : état de l'art Artificial neural networks (ANN) are a novel approximation method for complex systems especially useful when the well-known statistical methods are not efficient. The multilayer perceptrons have been mainly used for hydrological forecasting over the last years. However, the connectionist theory and language are not much known to the hydrologist communauty. This paper aims to make up this gap. The ANN architectures and learning rules are presented to allow the best choice of their application. Stochastic methods and the neural network approach are compared in terms of methodology steps in the context of hydrological forecasting. Recent applications in hydrology are documented and discussed in the conclusion.Key words: artificial neural networks, hydrological forecasting, stochastic models, multilayer perceptrons.
Tập 26 Số 3 - Trang 293-304 - 1999
Fatigue damage analysis in asphalt concrete mixtures using the dissipated energy approach An asphalt concrete damage–energy fatigue approach based on the concept of change in dissipated energy is presented in this paper. The damage–energy based fatigue approach is simple and based on a sound theoretical background. The central concept of the energy approach is the energy fatigue curve, which is based on two key elements, namely the plateau value (PV) and the number of load cycles to true failure (Ntf ). The plateau value represents the constant value of the percentage of dissipated energy that produces damage to the material under cyclic loading. Failure is defined as the number of load cycles at which this percentage of dissipated energy begins to increase rapidly, indicating instability. Flexural fatigue testing was used to test hundreds of asphalt concrete beams, mainly under controlled-strain testing conditions. It was found that PV is highly dependent on the initial loading conditions, stress, strain, and dissipated energy. As a result, it can be used conveniently in pavement design. The number of load cycles to 50% reduction in initial stiffness was found to be highly correlated with the new failure point (Ntf ). Using the dissipated energy concepts in fatigue analysis makes it possible to account for damage accumulation in a straightforward manner.Key words: fatigue of asphalt concrete, dissipated energy, damage, energy ratio.
Tập 33 Số 7 - Trang 890-901 - 2006
Duration of load and probability of failure in wood. Part I. Modelling creep rupture Two models are considered for the study of wood creep rupture behaviour and the associated load duration effects on strength. Both are damage accumulation models. In model I, the damage rate is expressed as the product of a stress-dependent factor and a damage-dependent factor. In model II, the damage rate is given as the sum of a stress-dependent term and a damage-dependent term. Both models consider a stress threshold below which the damage rate vanishes. For each model, stress histories corresponding to two types of tests are considered: a step function load test and a ramp load test. The predictions of the models for these two cases are used to obtain model parameters by fitting constant and ramp load test data. Data used correspond to small, clear specimens of Douglas-fir in bending. As an application, the problem of residual strength in a ramp load test after a time of constant load is discussed.
Tập 5 Số 4 - Trang 505-514 - 1978
An overview on the activation of reactivity of natural pozzolans Natural pozzolan is one of the oldest construction materials. Lime-pozzolan cements have been used for several thousands of years and have an excellent reputation for their durability. Pozzolans are being widely used as a cement replacement in Portland cement concrete. The use of pozzolans has the advantage of lower costs and better durability, but the disadvantage of a longer setting time and a slower early strength development. Different techniques have been tried to increase the reactivity of natural pozzolans to overcome these disadvantages. This paper has reviewed various methods used to activate the pozzolanic activity of natural pozzolans. All activation methods can be classified into three catalogues: thermal, mechanical, and chemical activation. A comparison based on strengthcost relationship indicates that the chemical activation method is the most effective and cheapest one.Key words: activation, reactivity, natural pozzolans, pozzolanic reaction, calcination, elevated temperature curing, chemical activators, strength, cost.
Tập 28 Số 5 - Trang 778-786 - 2001
Shear strength of reinforced concrete beams with a fiber concrete matrix The purpose of this study was to investigate the influence of fiber reinforcement on the shear capacity of reinforced concrete (RC) beams. Both steel and synthetic fibers at variable volume fractions were investigated. Two series of tests were performed: structural tests, where RC beams were tested to failure under an applied four-point load; and materials tests, where companion fiber-reinforced concrete (FRC) prisms were tested under direct shear to obtain material properties such as shear strength and shear toughness. FRC test results indicated an almost linear increase in the shear strength of concrete with an increase in the fiber volume fraction. Fiber reinforcement enhanced the shear load capacity and shear deformation capacity of RC beams, but 1% fiber volume fraction was seen as optimal; no benefits were noted when the fiber volume fraction was increased beyond 1%. Finally, an equation is proposed to predict the shear capacity of RC beams.Key words: shear strength, fiber-reinforced concrete, RC beam, stirrups, energy absorption capacity, steel fiber, synthetic fiber.
Tập 33 Số 6 - Trang 726-734 - 2006
Flexural strength of large-scale ultra high performance concrete prestressed T-beams
Tập 38 Số 11 - Trang 1185-1195 - 2011
Sustainable waste management: recovery of fuels from petroleum sludge Petroleum sludge is a complex mixture of hydrocarbons, water, metals, and suspended fine solids. The objective of this research was to develop a technique that will lead to the separation of phases ready for further reuse. A study was carried out to investigate a combination of various systems of electrokinetic cells, to which oily sludge, conditioning liquids, and different electrical potentials were applied. The developed electrokinetic phase separation is a new cost-effective technology, which in turn will permit the revitalization of petroleum sludge. This method can significantly reduce the amount of wasted sludge and can recover new fuels free of metals and water. Life cycle analysis of the recovered fuel shows that a new petroleum waste management protocol might reduce emissions of major greenhouse gases such as CO2 , CH4 , and N2 O by 40 026 000, 1057, and 566 kg, respectively, per refinery per year.Key words: oily sludge, electrokinetics, fuel recovery, sustainable management, life cycle analysis.
Tập 32 Số 1 - Trang 164-169 - 2005