摘要:

Three buildings in Montreal were designed for different levels of "ductility" according to the 1990 National Building Code of Canada and the 1984 Canadian Standards Association standard for the design of concrete structures for buildings. Analytical procedures were developed in order to predict the responses of main structural components to the combined loading effects of axial load, moment, and shear. In addition, a hysteretic behavioural model was developed in order to account for strength and stiffness degradation as well as pinching of the hysteretic response. Nonlinear dynamic analyses were carried out on each building for a series of artificially generated accelerograms together with real earthquake records. The results of the nonlinear dynamic analyses enabled an assessment of the performance of different building designs and an assessment of current code requirements.Key words: seismic design, reinforced concrete, detailing, structures, codes.

ISSN:0315-1468    

DOI:10.1139/l91-046

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Spillways for medium and high head dams may be exposed to high velocity flows and the associated destructive phenomenon of cavitation. Cavitation may occur at rough spots in the surface of the chute or tunnel, at local discontinuities in the finished surface such as construction joints, and at locations along critical flow profiles having significant deviations from design specifications. This paper addresses, on the basis of a review of the literature, a method for preventing or reducing cavitation damage on spillways through the use of spillway aerators. While the ability of induced or forced aeration to reduce or eliminate cavitation has been known for many years, it is only in relatively recent times that the aeration mechanism has been used to this advantage on spillways subject to high velocity flow. The recent application of aerators to spillway design is related, in part, to the trend toward higher head dams and larger design unit discharge rates. Design considerations and criteria for spillway aerators are presented in the paper, and the use of physical hydraulic models to make determinations of aerator performance is discussed. The intent of the paper is to provide a document with sufficient detail and scope to be useful as a first resource for spillway design practitioners.Key words: aerator design, air entrainment, cavitation, design criteria, high dam, model – prototype comparison, physical hydraulic model, spillway, spillway aeration.

ISSN:0315-1468    

DOI:10.1139/l91-047

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

An experimental and analytical study was conducted to assess the contribution of the slab to the uplift resistance of interior footings in low-rise buildings. The experimental program involved applying uplift loads to seven laboratory models, each consisting of a column and footing, slab, and backfill material. The analytical study consisted of a linear finite element discretization in which the slab was modeled using plate bending elements. The backfill material was approximated by linear compression springs with spring constants directly related to the experimentally determined modulus of subgrade reaction. It is concluded that the current design practice of ignoring the strength of the slab in calculating the uplift resistance of footings is very conservative. Based on the experimental results, an empirical equation is suggested for determining the uplift capacity of the slab.Key words: footings, low-rise buildings, uplift resistance, wind forces.

ISSN:0315-1468    

DOI:10.1139/l91-048

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Atlantic Canada is a relatively sparsely populated region with a few large urban centres and many small communities. Many of these communities rely on secondary treatment plants for treatment and disposal of domestic wastes. However, with a generally low tax base and a small pool of technically qualified personnel, maintenance on the plants is often of low quality so that their performance deteriorates after a few years of operation. In this paper the argument is advanced that ocean outfalls provide a more satisfactory means of treating and disposing of domestic wastes in such cases. Details are provided to confirm the low level to which some plants perform; and the design, installation, and postconstruction monitoring of a small ocean outfall are described to show the advantages of this alternative.Key words: ocean outfalls, marine treatment, waste disposal, pollution, environment.

ISSN:0315-1468    

DOI:10.1139/l91-049

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The complex real-time reservoir operation model consists of flow forecasting, reservoir operations planning, and multiobjective modules. In the present paper the original reservoir operations planning module based on a linear programming (LP) formulation is substituted with a goal programming (GP) formulation. The advantage of applying goal programming instead of linear programming lies in the smaller input data requirement, and simpler model formulation. The LP approach requires two-dimensional information while the GP approach needs only one-dimensional information. The impact of change of the operations planning routine on the results of the complex model is observed and commented on a case study. The application of GP instead of LP is found viable, in certain cases even advantageous, giving a better overall objective function value.Key words: reservoir operation, optimization.

ISSN:0315-1468    

DOI:10.1139/l91-050

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The design of practical asphaltic roads and runways in Canada's north is very difficult due to the harsh environmental conditions under which the material needs to be placed in the field, the severe temperature loads to which the pavement is exposed, and the difficulty and (or) cost of obtaining appropriate materials. This paper summarizes the current state-of-the-art in terms of the selection of materials and the design of mixes for the construction of asphaltic pavements in Arctic and sub-Arctic climates. It is shown that the temperature susceptibility of the asphalt cement, the curing rate of cutback liquid asphalts, and the transport of asphalt emulsions at low temperatures are the main problems associated with selecting a binder material. Emulsions appear to be the best suited for use in cold climates, but there is little experience with their use in the far north. In addition, it is indicated neither standard nor the modified Marshall nor the Hveem tests provide ideal tests for selecting the optimum binder content, the degree of curing, the required aerating, or the amount of mixing water for designing asphalt mixes.Key words: asphalt pavements, northern roads, mix design, material selection.

ISSN:0315-1468    

DOI:10.1139/l91-051

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A consistent, four-moment-based approach for quantifying time and economic risks is presented. The goal is to produce a computationally economical approach that can be used to explore the time and economic feasibility of various strategies for executing and sequencing major work packages that describe an engineering project. A three-level hierarchy of variables is used, starting with time, cost and revenue performance at the work package/revenue stream level to net present value and internal rate of return at the project decision level. The treatment of correlations between primary variables at all levels of the hierarchy is included. A modified form of the probabilistic network evaluation technique (PNET) algorithm is presented for quantifying time uncertainty. Use of limiting values (0, 1) of the PNET transitional correlation provides bounds for all decision variables. A comparison with Monte Carlo simulation of a case study is presented to demonstrate the validity and the computational economy of the analytical approach.Key words: economic risk quantification, large engineering projects, probability analysis, moment analysis, Monte Carlo simulation.

ISSN:0315-1468    

DOI:10.1139/l91-052

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

This paper summarizes the results of a study conducted to evaluate the behaviour of recycled asphalt pavements with respect to low-temperature cracking. For this purpose, a recycled mix consisting of 45.2% reclaimed materials and 54.8% virgin materials as well as a virgin control mix were used in the research program. In the design of both mixes, their initial properties were kept as close as possible to each other to allow for a proper comparison between recycled and virgin asphalt pavements. Using mix properties that were determined experimentally in the laboratory, thermal stresses resulted from drop in temperature and the expected cracking temperatures were determined for both mixes. An experimental analysis based on laboratory tests that consider the pavement properties only as well as a more complete theoretical analysis based on a finite element computer program known asFETABwere included in this study. The program incorporates subgrade parameters, as well as pavement properties and thickness. Using these variables as inputs to the program, the expected performance of recycled and virgin asphalt pavements of various thicknesses and resting on different types of subgrade, with respect to low-temperature cracking, was studied. The results of the study indicated that recycled asphalt pavements would perform better than virgin asphalt pavements of similar initial properties.Key words: asphalt, finite element, low-temperature cracking, reclaimed, recycled, thermal stresses.

ISSN:0315-1468    

DOI:10.1139/l91-053

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A pilot-scale study was conducted to evaluate the treatment performance of an upflow anaerobic filter (AF) on a slaughterhouse effluent. The effluent flow rate through the AF was changed for seven treatment trials, and performance was evaluated by the amount of COD removed. The COD removals ranged between 37% and 77% and were related to the reciprocal of the hydraulic retention time, in accordance with the Young and McCarty empirical model. The COD removals in this study were less in comparison to other similar AF studies, and factors attributed to this included low solids retention time and reactor design. The average removals of total coliforms, fecal coliforms, fecal streptococci, and standard plate count densities through the AF were 29%, 18%, 95%, and 65% respectively. The average methane content of the biogas was 71%. The methane yields ranged between 0.19 and 0.23 (m3 STP/kg COD removed). Tracer results showed that effluent flow through the AF was predominately completely mixed.Key words: anaerobic filter, slaughterhouse effluent, media, indicator microorganisms, treatment, methane.

ISSN:0315-1468    

DOI:10.1139/l91-054

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

There is no Canadian policy for the management of health and safety in the public interest. Both lives and resources are lost as a result. Limited life-saving resources ought to be spent efficiently in the public interest. If the life expectancy at birth is the measure of safety overall, then account must be given of the efficiency of any safety program, policy, project, or regulation in terms of the years of life in good health saved and the cost incurred. A comparison is made of 26 programs implemented in the United States, and it is shown that they collectively waste several thousand lives per year; 95 cents on the dollar is wasted. An absolute upper cost limit is established, which no life-saving program can exceed without consuming more human time than it returns. Some elements of a rational safety policy, and some concrete steps that ought to be taken now towards its implementation, are suggested.Key words: risk, management, public interest, health, safety, life, human development, index, efficiency, ethics, profession, accountability.

ISSN:0315-1468    

DOI:10.1139/l91-055

出版商:NRC Research Press    

年代:1991

数据来源: NRC