摘要:

The new Ontario Highway Bridge Design Code (OHBDC) is based on limit states theory and therefore uses a load and resistance factor format. This paper deals with the development of the basis for the timber bridge design provisions (OHBDC). Three structural systems are considered: sawn timber stringers, laminated nailed decks, and prestressed laminated decks. The latter system has been successfully used in Ontario for the last 7 years.The acceptance criterion in calculation of load and resistance factors is structural reliability. It is required that bridges designed using the new code must have a reliability equal to or greater than a preselected target value. Reliability is measured in terms of the reliability index. The safety analysis is performed for a structural system rather than for individual members. The live load model was developed on the basis of available truck survey data. Material properties are based on extensive in-grade test results. Numerical examples are included to demonstrate the presented approach.Key words: bridge deck, design code, prestressed timber, reliability, reliability index, stringers, structural safety, timber bridges.

ISSN:0315-1468    

DOI:10.1139/l86-001

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The problem of the behaviour of lumber at the low end of the strength distribution is slowly being unravelled. It appears that this lumber behaves more like a brittle material than had been previously assumed. This paper describes a test program in which matched samples (N = 88) of lumber were tested using different loading systems. It was found that the systems in which energy was stored in the testing machine gave apparent strengths that were lower than those obtained in a deformation-controlled setup. Since failure is caused by crack growth, it is postulated that the available stored energy is the cause of the observed strength differences. The difference between the two systems was found to be strength dependent (larger for the weaker pieces), and at the 5th percentile amounted to about 30%. The implications for the development of characteristic strength and design data are outlined.

ISSN:0315-1468    

DOI:10.1139/l86-002

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The petrographic study of numerous concrete structures in Quebec has revealed the extent of postconstruction chemical reactions. Those reactions between the aggregates, which form 70% of the volume of the concrete, and the cement paste result in early deterioration and undesirable mechanical deformation of the structures. From this study, it appears that the coarse aggregates can react in three different ways: (a) by peripheral reaction, which is the case for massive granitic rocks, (b) by bulk swelling, as illustrated by the Potsdam orthoquartzite, and (c) by formation of silica gel veinules within the aggregate, as shown by some Trenton limestone. Considering these three mechanisms, it is easy to understand why certain aggregates react rapidly, that is within a few months, whereas others show signs of distress only after scores of years. Using the three rock types cited above, we have also tried to evaluate existing concrete standards and their capability to detect the most important pathologies encountered in concrete.Key words: concrete, aggregate, alkalis, disintegration, expansion, testing, durability.

ISSN:0315-1468    

DOI:10.1139/l86-003

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The beginnings of engineering education in Canada, in the mid-19th century, are described. The development of engineering programs in 10 of Canada's universities is outlined. The activities of a number of pioneers in engineering education are described, and the curricula for several of the early civil engineering programs are presented.Key words: history, education, civil, engineering.

ISSN:0315-1468    

DOI:10.1139/l86-004

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Aluminum sulphate (alum) and ferric chloride are commonly employed to aid phosphorus removal in wastewater treatment. Previous studies have indicated that these chemical coagulants produce sludges that adversely affect anaerobic digestion. The objective of this study was to assess the magnitude of the effects chemical coagulants have upon methane generation in anaerobic digestion. Methane production was monitored and concentrations of aluminum or iron present during batch digestion of chemically precipitated sludge were measured.Both alum and ferric chloride addition to activated sludge produced a sludge that demonstrated reduced methane production in batch anaerobic digestion. Neither metal inhibited methanogenesis of an acetate supplement, suggesting that chemical toxicity was not a likely explanation for overall reductions in methane formation. Considering the experimental results and the findings of others, reduced methane generation is most likely caused by physical isolation of degradable substrate by the coagulant floc, which causes an overall reduction in conversion of sludge volatile solids to methane.

ISSN:0315-1468    

DOI:10.1139/l86-005

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

To compute the water-surface profiles in steady-state, gradually varied flows in open channels, an algorithm is presented that allows calculation of the flow depths and discharges at all sections of a parallel-channels system simultaneously instead of by the presently used trial-and-error computations. This algorithm is accurate, efficient, and suitable for computer solution. As compared to other methods, it may be used directly for computing flows in parallel channels without necessitating graphical plots or other trial-and-error manual computations. A procedure is outlined so that the resulting matrix for a parallel-channels system may be banded in order to increase accuracy and to reduce computer time and storage. A parallel-channels system is solved for illustration purposes and the results are compared with those obtained by the fourth-order Runge–Kutta method.Key words: backwater profiles, computer algorithms, gradually varied flows, mathematical models, Newton–Raphson method, open-channel flows, parallel channels, water surface profiles.

ISSN:0315-1468    

DOI:10.1139/l86-006

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

To evaluate the seismic torsional effect on multistory buildings, the concept of eccentricity is extended from single-story buildings to multistory buildings by defining the locations of the centers of rigidity at each floor. A practical procedure to locate the centers of rigidity and hence floor eccentricity is introduced. This procedure depends on the use of plane frame computer programs only and is suitable for use in design offices. The seismic torsional provisions in the National Building Code of Canada 1985 (NBCC 1985) explicitly emphasize that the code provisions apply to buildings where the centres of rigidity lie on a vertical axis only. By means of examples, it verifies the claim of NBCC 1985. Also, it shows that, for buildings with centers of rigidity scattered from a vertical axis, the code procedure may or may not apply. Therefore, one should interpret the condition of centers of rigidity located along a vertical axis to be a sufficient, but not a necessary, condition for the NBCC 85 code provisions to be applicable. Until the necessary conditions are known, dynamic analysis remains the most reliable method to assign the torsional effects to various portions of the building.Key words: building code, center of rigidity, dynamic analysis, eccentricity, irregular, multistory, seismic, torsion.

ISSN:0315-1468    

DOI:10.1139/l86-007

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The purpose of this paper is to test a recently proposed model of road classification for use by provincial highway agencies. The proposed model to be tested is intended to classify roads according to temporal volume variations, road use characteristics, such as trip purpose, and trip length distribution. The proposed model, which was developed by using Alberta highways data, is applied to Saskatchewan highways to evaluate its classification results. For the purpose of this study, a total of 31 permanent automatic traffic recorder sites in Saskatchewan is investigated. The application of the model to Saskatchewan highways results in six main groups according to the trip purpose and trip length distribution characteristics. The paper defines and discusses these classes in detail and compares them with the existing classification of Saskatchewan highways. The model produces similar road classes for Alberta and Saskatchewan highways. The similarity of road classes for the two provinces has implications for a standard classification of provincial highways.Key words: highway classification, road use, traffic, transportation, traffic volume patterns.

ISSN:0315-1468    

DOI:10.1139/l86-008

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

This paper presents a computer simulation model, PORTSIM, that was developed for the grain terminals of the Port of Thunder Bay. In addition to simulating ship arrival and grain loading characteristics, the model incorporates two distinct features of the port. These features are the movements of ships between berths to load different grades of grain and the impact of the rail-side operation on port performance.The paper first reviews existing simulation models and presents an overview of the operations of the port. Model details are then presented and include its logic and structure, design of experiments, measures of performance, and model input/output. In particular, the model provides several measures of performance, including average waiting time of ships, average queue length, berth utilization, port throughput, and maximum queue length. These measures are useful in assessing future improvements in the port. Some practical applications of the model and areas of future expansion of its capabilities are discussed.Key words: port, grain terminals, simulation model, ship arrival, grain loading, performance measures, practical applications.

ISSN:0315-1468    

DOI:10.1139/l86-009

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

This paper concerns the analysis and testing of 10 cantilever composite beams incorporating ribbed metal deck, representing the positive moment beam–column connections in an unbraced steel frame with composite floor beams. The positive moment beam–column connections arise from lateral forces on the unbraced frame. The effective widths of the slabs for strength and stiffness calculations have been determined from analysis. Agreement between the calculated strain distributions across the concrete slab width and the corresponding measured strain distributions was attained. Use of the calculated effective widths of the slab for strength together with a concrete strength ofgave good agreement with the measured positive ultimate moment capacities of the cantilever composite beams subjected to upward end test loads.

ISSN:0315-1468    

DOI:10.1139/l86-010

出版商:NRC Research Press    

年代:1986

数据来源: NRC