摘要:

Composite beams incorporating ribbed and cellular metal deck have been used as the floor system in building construction now for many years. In addition it has been demonstrated that composite action can be achieved between solid concrete slabs and open-web joists.It is demonstrated that good composite action can be achieved between open-web joists and slabs incorporating ribbed metal deck. It is shown that the mode of failure of a composite open-web joist is influenced by the degree of shear connection. In addition it is shown that are spot welds as well as studs can provide an effective shear connection.

ISSN:0315-1468    

DOI:10.1139/l78-001

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This commentary provides background to the requirements found in Section 4Sawn lumberof CSA Standard 086-1976Code for the engineering design of wood.

ISSN:0315-1468    

DOI:10.1139/l78-002

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This paper contains a brief outline of a transportation planning model developed for the purpose of providing detailed analyses of commuter traffic. It sets out to model the movement of automobile, transit and pedestrian traffic taking into account the interaction between and within each of the traffic components. The model is most appropriately applied to areas of high traffic activity, such as the central business district of a metropolitan area or arterial streets of a region-wide network during peak demand.

ISSN:0315-1468    

DOI:10.1139/l78-003

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This paper discusses the origin and concepts of kinetic model equations and standard specifications used to size a biological treatment system (size of aeration tank and aeration requirements). They are shown to yield very similar calculations for a domestic type of waste water, but may yield much different values if the waste water behaves differently than domestic waste. The kinetic model approach, therefore, should be considered more flexible and superior in its ability to yield appropriate design values.

ISSN:0315-1468    

DOI:10.1139/l78-004

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Aeration has been used successfully in northern Canada and other cold regions for treating domestic and industrial waste waters by aerated lagoons, extended aeration package units and conventional activated sludge plants. Many of these installations used diffused aeration because this system has shown several advantages over mechanical surface aeration. The advantages of using diffused aeration in cold regions for oxygenation as well as for mixing are discussed in this paper.The parameters affecting the efficiency of oxygen transfer and the mixing of the tank contents are identified and the influence of varying these operating parameters on the performance of diffused aeration systems under cold climatic conditions is discussed. Equations showing the influence of temperature, airflow rates, submergence and tank geometry on the overall oxygen transfer coefficient are presented.A process of aeration, employing counter-current flow of air bubbles and waste water, is shown to result in increased contact time and therefore higher oxygenation efficiencies. A typical example for designing a diffused aeration system in cold regions has been worked out.

ISSN:0315-1468    

DOI:10.1139/l78-005

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Large urban centres in Canada and the United States are finding it increasingly difficult to locate and develop natural aggregate sources for use in concrete. The study reported herein was therefore undertaken to investigate the possibility of producing aggregates from discarded concrete control test cylinders, normally sent to waste dumps after testing.A series of 2.2-ft3(0.062-m3) concrete mixes were made covering the low, medium and high strength levels. Two sets of mixes were made at each strength level, one set consisted of a control mix and a mix made using coarse aggregate prepared from recycled concrete and reference fine aggregate; the second set consisted of a control mix and a mix using fine aggregate prepared from recycled concrete and a reference coarse aggregate. Cylinder and prism specimens were cast from each mix to determine mechanical properties of concretes at various ages and to study the durability of concrete after exposure to freeze–thaw cycling.The analyses of the test results have shown that satisfactory concrete can be made with aggregates prepared from recycled concrete. At lower water–cement ratios, strengths of the two types of concrete are comparable.The durability of concrete made with aggregates prepared from recycled concrete is comparable to the durability of concrete made with reference aggregates.

ISSN:0315-1468    

DOI:10.1139/l78-006

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The thermal discharges from various sources that occur during winter may prevent ice formation at the free surface. In order to predict the extent of the free surface without ice, numerical models of thermal discharges should take into account: (1) the particular heat transfer at the free surface that occurs during winter time and (2) the nonlinear relationship between density and temperature for water near 0 °C. This article indicates a method of modifying existing models and presents some results obtained from a modified buoyant surface jet model.

ISSN:0315-1468    

DOI:10.1139/l78-007

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Forced vibration analysis of two dimensional bridge deck structures involves complex mathematical procedures and therefore analysis is often based on beam idealization of equivalent plates. This simplification yields close agreement only for long span bridges where plate action is relatively insignificant. However, such a concept of beam idealization cannot be successfully utilized in the case of short span bridges where plate action is predominant and where the determination of the distribution of dynamic deflections and amplification factors at critical sections of such plates is of prime concern. The principal objective of the present investigation is the forced vibration analysis of longitudinally stiffened, simply supported orthotropic bridge decks utilizing a new concept of interconnected beam idealization. The theoretical analysis deals with determination of amplification factors and dynamic deflections along critical sections of the plate treated as a series of interconnected beams. The aspect ratios of the plates under investigation as series of interconnected beams are designed to cover a wide range of plate to beam transition. The theoretical analysis is supplemented by an extensive experimental programme.In conclusion, it is seen that this concept of interconnected beam idealization not only takes into account the plate action of the deck structure but also reduces greatly the complexity of mathematical formulation. A good comparison between the theoretical and the experimental results indicates that this concept can be used to advantage for analysis and, within certain limitations, for design purposes.

ISSN:0315-1468    

DOI:10.1139/l78-008

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

An extensive literature review and a study of unpublished documents were undertaken to summarize information on the performance, design and operation of "northern" extended aeration waste water treatment plants. This information was compared with that for 'non-northern' plants and National Sanitation Foundation (NSF) plants, the latter providing an indication of optimum performance.The study revealed that the northern plants generally performed more poorly than their non-northern counterparts and much worse than the NSF plants.Reasons for poor performance of the northern plants were related to design and operation deficiencies. The most frequently observed conditions indicating design errors were organic and hydraulic overloading. The most common operating errors were failure to scrape hopper-type clarifiers and failure to maintain sludge returns operative.Very few design and operating problems relating specifically to northern plants were identified since many of the smaller plants were encapsulated for freeze protection.

ISSN:0315-1468    

DOI:10.1139/l78-009

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The use of cheap, locally available peat as a treatment method for landfill leachate was investigated by passing leachate through plexiglass columns filled with an amorphous-granular peat. Preliminary adjustment of pH showed that reducing pH to 4.8 dramatically reduced adsorption. Increasing the pH to 8.4, metal removal was increased owing to filtration of precipitated metals. The best adsorption of metals occurred at the 'natural' pH of 7.1. Manganese was found to be the limiting pollutant. At the 0.05 mg/ℓ maximum acceptable manganese concentration 94% of the total metals were removed, requiring 159 kg of peat per 1000 ℓ of leachate.Resting the peat for 1 month did significantly increase removal capacity.Desorption of some contaminants occurred when water was percolated through the peat. The desorption test effluent was not toxic to fish although iron, lead and COD (chemical oxygen demand) exceeded acceptable values.Chemical pretreatment using lime and ferric chloride achieved significant iron, manganese and calcium removals. Chemical pretreatment followed by peat adsorption offered no advantage other than reducing toxicity to fish.Peat treatment alone was effective in reducing concentrations to a level that was non-toxic to f

ISSN:0315-1468    

DOI:10.1139/l78-010

出版商:NRC Research Press    

年代:1978

数据来源: NRC