摘要:

A labyrinth weir is an effective and economical means of providing increased spillway capacity under some restricted operating conditions. This type of weir is particularly suited to reservoir sites where a low head to high discharge relation is required, the topography restricts the spillway width, and a self-operating structure is highly desirable for emergency operation. Over the past few decades, labyrinth weir spillways have been constructed throughout the world. Definitive guidelines and theoretical procedures pertaining to hydraulic design of this type of weir are not completely established. The designer is confronted with the use of empirical methods for determining spillway configurations which require careful design and verification by use of a hydraulic model. This paper describes the design and hydraulic model study conducted for a labyrinth weir arrangement proposed for the South Heart Dam in northern Alberta. The model study permitted the designers to adopt a more efficient two-cycle weir for the same spillway width as opposed to an initially proposed three-cycle labyrinth weir.Key words: labyrinth weir, spillways, weirs, floods, hydraulic structures, hydraulics.

ISSN:0315-1468    

DOI:10.1139/l90-001

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Recent research on the interconnection of double angles has raised questions with regard to the forces and moments to be transmitted by connectors. It is proposed that when buckling of back-to-back angles occurs in the plane of symmetry, the connector should be termed aninterconnectorand can be designed for small forces and moments. When buckling occurs in a plane at right angles to the plane of symmetry, the connector should be termed abattenand designed for the shears and moments specified for battens in the applicable standard.Key words: angles, battens, buckling, columns (structural), interconnectors.

ISSN:0315-1468    

DOI:10.1139/l90-002

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Slurry erosion tests were performed on various types of repairing mortars in order to determine the factors influencing the abrasion-erosion resistance of some mortars. An in-house built apparatus was used, which produced a slurry jet that impinged the surface of mortar specimens with an incidence angle of 45° and a velocity of 18.5 m/s. The results showed that the epoxy mortars were the most erosion resistant compared with cementitious grouts and polymer-modified cement-based mortars. The erosion of mortars is controlled by the wear of the binder (epoxy or cement paste), and a strong relation exists between the erosion resistance of the mortar and the absence of microporosity in the binder. The results also suggest that to minimize the exposed areas of the binder, well-graded, i.e., small- and large-size, sand particles should be used.Key words: abrasion, erosion, repair mortars, cementitious grouts, polymer-modified cement-based mortars, epoxy mortars, hydraulic structures.

ISSN:0315-1468    

DOI:10.1139/l90-003

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Results are presented from an investigation on the compressive strength and durability of concretes containing substitute materials at a 50% replacement level (by mass) of Portland cement. Seven fly ashes (sub-bituminous, bituminous, and lignitic), together with limestone and an inert material (silica flour), were used as replacement materials. Durability studies included freeze–thaw testing (ASTM C666A), scaling resistance (ASTM C672), and abrasion resistance (ASTM C944). The air void system was assessed using the modified point count method of ASTM C457. The results indicate that although concretes with a 50% replacement level of cementitious material did not perform as well as the control concretes with no replacement, such concretes were able to meet minimum durability requirements. As anticipated, air-entrainment is the overriding factor that allows concrete to meet freeze–thaw durability requirements. In the context of this study, compressive strength does not appear to be a significant factor in freeze–thaw durability. Results indicated that concretes with compressive strengths of less than 10 MPa will still pass the freeze–thaw test, provided an adequate air void system is in place. Abrasion resistance tends to increase with compressive strength but not in all the cases.Key words: concrete, fly ash, compressive strength, durability, mineral admixtures.

ISSN:0315-1468    

DOI:10.1139/l90-004

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The factors contributing to the line haul transportation costs of very large trucks operating on the Ontario highway system are calculated from fundamental tractive resistance equations and tractive effort characteristics for two "weigh-out" commodity types and representative haul routes. These calculated costs are compared with some observed costs and earlier analyses to check the validity of the models. The theoretical models are then used to assess the impact on operating costs of a variety of truck parameters which include truck type and tire pressures. The pavement damage created by the different truck types are estimated and the damage costs compared with the savings in line haul transportation costs. It is concluded that the pavement damage impacts of different truck types should be carefully compared with potential line haul transportation cost savings to ensure that allowable truck configurations are economically efficient with respect to both public and private costs.Key words: highway engineering, pavement damage, pavement cost, truck operating cost, vehicle weights.

ISSN:0315-1468    

DOI:10.1139/l90-005

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The water temperature beneath river ice covers has an important influence on the heat flux to the overlying ice cover and on ice melt. Measurements of water temperature beneath the Liard River ice cover showed that prior to spring breakup, the water temperature was always between 0.0 and 0.025 °C, with important cross-channel and diurnal variations. The lowest temperatures were controlled by the bed heat flux and frictional heating, while variations above these minimum values were explained by changes in solar radiation. Using measurements of these heat fluxes, in conjunction with measurements of ice and bed roughness, water depth and velocity, and slope, a simple method which assumes the similarity between heat and momentum transfer was able to accurately predict water temperatures beneath the ice cover. During breakup when the river had both ice-free and ice-covered sections, water temperatures rose to a few degrees above 0 °C. When this water entered an ice-covered reach, the water temperature declined rapidly to near 0 °C within 10 km. This temperature decay was predicted from measurements of the initial temperature, ice and bed roughness, and water depth.Key words: water temperature, ice, thermal regime, ice melt.

ISSN:0315-1468    

DOI:10.1139/l90-006

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Models are developed for the gross vehicle weight and axle weight distributions of laden trucks as a function of governing weight limits. The models are based on truck weight surveys conducted in Manitoba between 1972 and 1986, a period of changing weight limits. They are developed for 2-axle trucks, 3-axle trucks, 5-axle (3-S2) tractor-semitrailers, 7-axle (3-S2-2) A-trains, and 7-axle (3-S2-S2) B-trains. The models can provide important input to the analysis of pavement loadings (and costs), given particular weight limits or changes in weight limits. They can also provide useful input to estimates of the relative benefits of alternative weight limit regimes.Key words: truck weights, weight limits.

ISSN:0315-1468    

DOI:10.1139/l90-007

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Fillet welded connections are frequently loaded eccentrically in shear with the externally applied load in the same plane as the weld group. While some current design tables are based on ultimate strengths, methods of analysis that incorrectly mix inelastic and elastic approaches are still used. These methods give conservative and variable margins of safety. Design standards generally use a lower-bound approach basing strengths on the longitudinal value neglecting, conservatively, the increase in strength for other directions of loading. The factored resistance of fillet welds, as a function of the direction of loading, is established based on ultimate strength expressions developed herein and using geometric, material variations, and test-to-predicted ratios reported in the literature. Factored resistances of eccentrically loaded fillet weld groups are established. These are basesd on the method of instantaneous centres, ultimate strengths, and the load–deformation expressions developed herein that are functions of the angle of loading. Also, statistical data on geometry, material variations, and the comparison of predicted strengths with the full-scale test results of others are used. Tables of design coefficients giving factored resistances for various eccentrically loaded fillet welded connections are developed. The coefficients, on the average, are essentially the same as those in current design tables.Key words: connections, design tables, eccentric, fillet welds, limit states, ultimate strength.

ISSN:0315-1468    

DOI:10.1139/l90-008

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A pilot-scale (300 L) evaluation of waste-activated sludge digestion by a cyclical aerobic–anoxic mode of operation was undertaken at ambient liquid temperatures (14–17 °C). Three experimental runs were conducted over a 2-year period. The first run compared the aerobic–anoxic process to a conventional, continuously aerated, digestion process. During the second run, the aerobic–anoxic digester was compared to a lime-supplemented conventional aerobic process. The third run compared two aerobic–anoxic digester units, operating at reduced (50 and 25% of normal) aeration rates during the aerobic period. In addition, basic data from batch tests are outlined and discussed. Results from the various experimental runs indicated numerous potential advantages for the aerobic–anoxic mode of digester operation. The main advantage was that turning the air on and off resulted in volatile solids reduction efficiencies similar to that in the continuously aerated systems. In addition to the potential for significant savings in aeration costs, another benefit of the intermittent aeration mode of operation involved improved supernatant quality of the final, settled effluent.Key words: aerobic digestion, anoxic, intermittent aeration, lime, pilot-scale, Redox potential, sludge, solids reduction.

ISSN:0315-1468    

DOI:10.1139/l90-009

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

This paper describes the techniques used in the planning and design of a system of passing lanes for the Trans-Canada Highway in Yoho National Park. The techniques, which include a traffic simulation model, were developed to allow the evaluation of the impact of low-cost operational improvements such as passing lanes on the level of service. The traffic simulation model allowed the investigation of a wide range of highway alternatives in addition to changes in traffic flow, traffic stream characteristics, and vehicle performance characteristics. The passing lane designs described in the paper are based on the concept of incorporating passing lanes within the existing highway cross section. The design concept has evolved from the experimental passing lane project in Banff. In addition to geometric design, signing, and road marking guidelines, warrants for bicycle lanes on the Trans-Canada Highway are also presented.Key words: highway planning and engineering, two-lane highways, traffic simulation model, level of service, passing lanes, Trans-Canada Highway.

ISSN:0315-1468    

DOI:10.1139/l90-010

出版商:NRC Research Press    

年代:1990

数据来源: NRC