摘要:

The paper describes the design and construction of a steel cantilever dam on the Yukon River, approximately 24 km upstream of Whitehorse. The dam can retain 2.4 m of water to store a volume of 1.02 × 109 m3for use at the Whitehorse Hydroelectric Power Plant. Although the dam is small by today's standards, its design and construction posed several interesting problems, which were overcome by an innovative structure that was built on a pervious foundation, without the benefit of cofferdams, without diversion and with little obstruction to the flow of the river.The design concept has not previously been used in Canada and utilizes a combination arrangement of H-section piles, interconnected with Z-sheet pile sections to form a continuous steel wall. Alternate H-piles extend above this wall to provide openings for vertical lift gates and to support a prefabricated steel deck. The pile driving equipment worked from this deck when driving subsequent piles. Prefabricated gate guides were positioned between the extended H-piles and held in place with tremie concrete.The dam was constructed in approximately half the time and at about half the cost that would have been required for a conventional concrete structure.

ISSN:0315-1468    

DOI:10.1139/l78-019

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A method for analysis of interconnected shear walls is described that accounts for the torsional stiffness caused by non-uniform warping. Floor to floor, plane wall members are idealized as part of the input to a three-dimensional frame analysis program. Where walls in different planes intersect, constraints that ensure common vertical displacements are imposed. These constraints appear in the computer input as special types of 'members'; however, within the solution, the Lagrange multipliers method is used to process the constraint equations. A frontal method that handles the constraints efficiently along with members and loadings is used to organize the analysis.The use of this method of analysis is simple and versatile relative to comparable methods. Most arrangements of shear walls that form open cross sections can be analyzed in conjunction with frames and other walls. Location of the shear centre of groups of walls and their torsional properties are not required.Analysis results are compared to experimental results and the results of other methods of analysis. The accuracy of the proposed method depends upon the number of storeys in the model because force transfer between adjacent wall segments occurs only at floor levels; in reality, a continuous transfer of force occurs through the height of the walls. In the opinion of the authors, using the proposed method for buildings of 20 or more storeys would certainly provide adequate accuracy for design.

ISSN:0315-1468    

DOI:10.1139/l78-020

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Laboratory tests were conducted on a full scale prototype of a segment of a bridge superstructure of cold-formed steel box girders in composite construction with a reinforced concrete slab. The results indicate that such a superstructure has adequate ultimate load carrying capacity, is effective in distributing concentrated loads laterally, and that the specially-formed shear connectors (lugs) are quite successful in shear transfer; furthermore, the design parameters can be predicted by means of ordinary analytical methods. Based on the field performance of a similar superstructure for a bridge over the Slate River and on the laboratory test results, refinements in the design that should lead to further economies for this type of construction are suggested.

ISSN:0315-1468    

DOI:10.1139/l78-021

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Concrete and steel–concrete composite beam-slab type and box-girder bridges are analyzed using the finite strip method, a variation of the powerful finite element method. The results obtained are used to determine the effective width of the compressive flange of the bridge girders. A study of a wide range of bridge models resulted in an empirical relationship that is in good agreement with the design criteria set down in the composite road bridge design code of the Federal Republic of Germany.The empirical relationship presented in this paper is intended to supplant the effective width specifications in current American and Canadian design codes, which in general lead to conservative designs.

ISSN:0315-1468    

DOI:10.1139/l78-022

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The performance of a steel–concrete composite box-girder bridge is examined through a series of live load field measurements. This paper describes the measurement program and the results obtained, as well as comparisons wherever possible between the observed values and those obtained from beam theory calculations and bridge code equations. It was found that the measured strains were generally much lower than the design values and that for bridges with asymmetrical cross sections, a beam theory calculation using bridge code live load distribution formulas can lead to nonconservative results.

ISSN:0315-1468    

DOI:10.1139/l78-023

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Ice jam initiation by a simple partial surface obstruction in a channel was studied experimentally in laboratory flumes using polyethylene, paraffin, as well as real ice parallelepipeds, as model ice floes. The important dependent parameter under study was the critical surface concentration of floes at the gap in the surface obstruction at which floes would form a stable arch across the gap and an ice jam would be initiated. This critical floe concentrationCg* was found to be independent of the ratio of gap width to flume width and to be a decreasing power function of the ratio of floe size to gap width. In additionCg* was found to be independent of the approach flow Froude number for flow velocity less than the critical submergence velocity of an ice floe, for artificial model floes, but to increase with increasing Froude number when real ice floes were used. This difference and other quantitatively different results depending on whether natural ice blocks or plastic blocks were used as model ice floes were tentatively attributed to differences in floe material characteristics, mainly interparticle friction force and surface tension property, the latter affecting significantly the critical submergence velocity of thin plastic blocks as compared to that of natural ice floes of the same size and density.

ISSN:0315-1468    

DOI:10.1139/l78-024

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Many aspects of the action of calcium chloride in concrete are ambiguous, controversial, or incompletely understood. Examples include: (a) the restrictive definition of calcium chloride as an accelerator; (b) the lack of clarity in prescribing the dosage for practical applications; (c) the classification of calcium chloride as an antifreezing agent; (d) the misconception regarding corrosion of reinforcement in the presence of CaCl2; (e) the divergence of opinion on the mechanism of action; and (f) incomplete understanding of the changes in the intrinsic properties of cement containing calcium chloride. This paper attempts to deal with these aspects citing typical examples.

ISSN:0315-1468    

DOI:10.1139/l78-025

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The St. Marys River connects Lake Superior with Lake Huron. It contains many navigation improvements that make it an important commercial shipping route. The operation of ships in winter tinder a federal (USA) program to extend the navigation season has led to troublesome ice movements and accumulations. To help conteract these effects, two ice booms with a 250 ft (76 m) wide navigation opening between their adjacent ends were installed at the southerly outlet from the harbor at Sault Ste. Marie, Michigan and Ontario.The ice booms contained six force measuring devices. Records of these forces and pertinent data on the weather, water levels, ship passages, and ice conditions were kept the following winter of 1975–1976.The ice booms reduced the harbor ice losses to an acceptable level and provided much information about their interactions with the ice cover and the ships. Ship and environmental effects kept the ice behind the west boom broken-free from shore and moveable much of the winter. The maximum force measured in the west boom was 88 000 lb (391 kN) and the maximum in the east boom was an impact load of about 160 000 lb (712 kN). The forces associated with ship passages averaged 25 000 lb (111 kN).

ISSN:0315-1468    

DOI:10.1139/l78-026

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The use of air bubbler systems to suppress ice formation is a technique that has been applied in a variety of situations with varying degrees of success. In 1974, two-dimensional line source bubbler systems were analyzed by G. D. Ashton in an effort to make available a tool that may be used in the design of a bubbler installation. That analysis was a steady-state evaluation of the melting rate of an ice cover above a bubbler system predicted on the basis of the input variables (depth, air discharge rate, water temperature). In actual operation, however, a bubbler 'sees' changing conditions such as diurnal and longer-term weather conditions, varying water temperatures and depletion of the available thermal reserve.The simulation presented herein uses the steady-state analysis developed earlier by Ashton and steps it in time with each new condition determined from the results of the previous time step. In this sense the analysis herein may be considered quasi-steady.Results of the simulation are presented for an example case for a winter in Superior, Wisconsin, and illustrate the variation in width of open water area with changing weather conditions with good comparison to field observations.

ISSN:0315-1468    

DOI:10.1139/l78-027

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The natural heat dissipating abilities of Canadian water resources are examined in order to determine their variability both spatially and temporally. The cooling performance is expressed in terms of the surface heat exchange coefficientKand the equilibrium temperatureE. The computational procedure, reflecting some adjustments to recognize Canadian conditions, is shown to satisfactorily reproduce water temperatures in two Canadian lakes of moderate size.Examination of data from 115 stations across Canada reveals that three regions are particularly suited to heat dissipation, namely southern Saskatchewan, southern Ontario, and parts of the Maritimes. Considerable variability is apparent in bothKandE, both within a year and from year to year.Several examples are used to demonstrate how the information compiled in this paper can be used during the preliminary screening stage of power plant siting investigations.

ISSN:0315-1468    

DOI:10.1139/l78-028

出版商:NRC Research Press    

年代:1978

数据来源: NRC