摘要:

In the more populous watersheds of southern Quebec eutrophication of surface waters is a current problem, linked to excessive nutrient loadings from various municipal, industrial, and agricultural sources. A simple mathematical model has been developed to identify the optimal strategies for controlling nutrient loadings at various points in a river basin; for this optimization the key water quality parameter is phosphorus and the objective is to meet a fixed water quality criterion (0.06 mg total phosphorus per litre) at minimum cost.The potential utility of the model in a water management context has been demonstrated in a case study of the Yamaska River, Quebec, which drains regions of intense agricultural activity and is also subject to phosphorus pollution from numerous point sources of municipal and industrial origin.

ISSN:0315-1468    

DOI:10.1139/l82-067

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Due to rapidly rising costs for conventional sewage collection and treatment systems, there has been a reemergence of alternative approaches to wastewater management in small communities.Alternative systems are generally those that employ either septic treatment and ground disposal or soil absorption. The careful exploitation of the capability of the natural systems to assimilate community wastewater is the underlying principle behind the alternative approach, which can offer significant cost savings over conventional systems.The widespread occurrence of malfunctions of existing wastewater disposal systems in rural and urban-fringe areas leads to a requirement for improved maintenance of the systems. The septic system has been relegated to the role of country cousin in the field of wastewater management; this is due to a historic confusion between central and noncentral systems and the type of management that is applied to them.The Government of Nova Scotia, recognizing the need to develop and test alternatives, commissioned a study in 1978 to investigate the feasibility of municipal wastewater management for rural and urban-fringe areas of Nova Scotia. The study has demonstrated that such an approach is practical, with some limitations.Should land use planning continue to rely on building site approval criteria that are based solely on physical constraints for on-site sewage disposal? As the issues of protection of resource lands and the use of marginal lands for building become more critical, the physical and management systems applied to alternative wastewater management strategies will continue to gain importance in the fields of engineering and planning.

ISSN:0315-1468    

DOI:10.1139/l82-068

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The paper deals with the calculation of longitudinal moments and transverse shear in multi-spine box-girder bridges. Results from three-dimensional analyses by the well tested finite strip method are used to establish the limits of validity of the grillage analogy method and the orthotropic plate method. These methods are shown to give accurate results provided that, for the orthotropic plate method, the number of spines is not less than three.Since transverse shear is mainly responsible for transferring loads from one spine to another, the flexural ridigity of the deck slab, and hence the slab thickness, has little influence on the distribution characteristics of a bridge; this is demonstrated with specific examples. Thus it is shown that a multi-spine bridge with at least three spines can be idealized as an articulated plate, i.e., a specific orthotropic plate in which the transverse flexural rigidity is assumed to be negligible.The behaviour of multi-spine box-girder bridges can be characterized by a single dimensionless parameter, with the help of which a simplified method can be developed to calculate longitudinal moments and transverse shear.

ISSN:0315-1468    

DOI:10.1139/l82-069

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The present allowable stresses for lumber and the associated adjustment factors stated in Canadian Standard CSA-086 are based upon tests conducted using small clear wood specimens. Recent comprehensive tests in which full-size lumber specimens were used (in-grade testing) showed that the present allowable stresses cannot be confirmed and also that new adjustment factors need to be developed.This paper deals with the effect of moisture content on the strength properties. Tests were conducted and reported dealing with: bending, stiffness, tension, compression parallel to grain, compression perpendicular to grain, and shear. From these tests it was possible to make specific recommendations for a new set of moisture content adjustment factors, to be used in design, that more realistically reflect the behaviour of lumber.

ISSN:0315-1468    

DOI:10.1139/l82-070

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Solution of problems in water distribution networks usually proceeds in one of two ways: (1) analysis of flows in the links, or (2) analysis of the head at the nodes. In the former case, which is somewhat commoner and has certain computational advantages, the user is usually required to generate input data by defining the set of independent loops in the circuited network in addition to the usual node and link characteristics. Such methods are acceptable for analysis where the topology of the network remains constant. A method is presented here that allows the node and loop equations to be generated automatically from a very simple data file defining nodal stipulations and link characteristics. The equations are reduced to a small set of simultaneous equations involving only the nonbasic or redundant variables. This greatly reduces the memory requirements and also speeds solution of the equations. Either an iterative linear approximation or the Newton–Raphson method may be used to solve the simultaneous equations. The approach is useful in design and optimization studies since it allows links to be deleted and/or restored with automatic generation of the necessary equations. The method may also be used with microcomputers or even pocket computers since the order of the system of equations to be solved is reduced to the number of loops in the system.

ISSN:0315-1468    

DOI:10.1139/l82-071

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

It is argued that the essence of all reservoir storage models, whether deterministic or stochastic, is the continuity and dynamic equations, both in a very simplified form. The proliferation of storage models is traced to unrecognized redundancies arising as a consequence of language barriers, specialized jargons, and limited knowledge and understanding of published work. Examples of some redundancies are shown in detail and the effective identity of models involving reservoir routing, rule-curve regulation, and any type of operation policy is demonstrated.

ISSN:0315-1468    

DOI:10.1139/l82-072

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The Atrium on Bay is a retail and office complex of about 130 000 m2built in downtown Toronto. Two advanced concrete technology concepts were used on the project.For the columns, the age at which the specified compressive strength was required was specified at 90 days instead of 28 days. In addition, the incorporation of a pozzolanic material was specified for the concrete. Column sizes and the amount of reinforcement were based on the 90-day strength, thus reducing their size and the amount of reinforcement required. This also significantly reduced the cost of the concrete.For the concrete slabs, accelerated construction was achieved by the use of a mix with good early strength gain and by a pullout testing system to confirm early strength. The same testing system was used to check in-place strength at later ages.Keywords: column design, column cost, 90-day strength, pozzolanic, pullout testing, in-place strength, accelerated programme, fly-ash.

ISSN:0315-1468    

DOI:10.1139/l82-073

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

An experimental investigation of the static behaviour of cropped-web joints is presented. The joints involve round hollow structural section chords and round hollow section webs with ends cropped in the plane of the joint. Such joints have the advantage of low fabrication cost compared with that of joints with profiled webs. Tests of 61 isolated joints with Pratt-type configurations are reported. The measured deformations at the joints are described. Equations obtained using multiple regression analysis to relate the strengths and flexibilities of the joints to various parameters are presented. The strengths of the joints were found to be acceptable. The flexibilities of the joints were found to be only one third to one half as large as those for comparable square-chord joints.

ISSN:0315-1468    

DOI:10.1139/l82-074

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Some components of the wastewater management systems used in northern Canada have undergone significant changes within the last ten years. The natural and imposed constraints are reviewed with special emphasis on the wastewater characteristics. Wastewater collection through the use of butt-welded polyethylene pipe, individual line service connections, and truck collection are discussed. Improvements in the disposal of undiluted and moderately, conventionally, and greatly diluted wastewater are outlined. The problems and improvements underway with greywater treatment and disposal are important for the improvement of living conditions. Also, current efforts to increase water conservation are noted.Keywords: cold regions engineering, wastewater treatment, sewage collection, sewage disposal, water conservation.

ISSN:0315-1468    

DOI:10.1139/l82-075

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Recent work has focussed attention on the increasing complexity of structural codes of practice. The question arises: how should a proposed code provision, which might embody a simplification, be assessed? It is suggested that decision theory can be used in making such an assessment. This is explored by means of an example, namely a reinforced concrete portal frame. The analysis focussed on the limit state of cracking and various strategies for the analysis of the frame were considered. For instance, one strategy considered the frame as uncracked; others included assumptions regarding cracking. The frame was analysed using a computer program, in which the frame was discretised and realistic models of material behaviour were incorporated. A Monte Carlo procedure was followed, taking into account uncertainties regarding loading, material properties, and the position of steel reinforcement. Utility functions were developed; these were a function of the action taken and the (random) crack width. The most simple action, i.e., treating the frame as uncracked, gave the maximum expected utility. The basic approach should prove useful for other problems related to code formulation.

ISSN:0315-1468    

DOI:10.1139/l82-076

出版商:NRC Research Press    

年代:1982

数据来源: NRC