摘要:

As a result of the reconstruction of the Lachine Canal in the 1840s, waterpower became available within the city of Montreal. This power source was a strong stimulus to Montreal's rapid industrialization starting in the 1850s. However, the efforts of the Commissioners of Public Works of the Province of Canada to balance the competing demands of shipping and manufacturing resulted in many problems. The civil engineers, who designed and built the canal, were drawn into an unresolved conflict with other engineers who were interested in utilizing waterpower. Engineers were also in conflict with a variety of non-engineers over the building of waterpower installations and factories. This case study of waterpower on the Lachine Canal demonstrates the opportunities and conflicts for engineers in mid-nineteenth century Canada.Key words: waterpower, industrialization, turbine, hydraulic engineering, canal, Montreal, Lachine Canal.

ISSN:0315-1468    

DOI:10.1139/l93-048

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The limit states design version of the 1989 Canadian code for engineering design in wood (CSA-086.1-M89) is, for the most part, reliability-based. This paper discusses the methodology employed in the calibration procedure and the reliability levels adopted. Particular emphasis is given to the results obtained for duration of load and system (load sharing) strength adjustment factors, to serviceability limit states, and to the design of columns. Final comments address the impact of the new code in comparison to the traditional working stress design procedures.Key words: code, design, reliability, timber construction, wood.

ISSN:0315-1468    

DOI:10.1139/l93-049

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This paper summarizes some Canadian experimental results for duration of load effects in wood, and discusses the theoretical framework utilized for their interpretation and implementation in design guidelines. The theory is based on a model for accumulation of damage, and it is used in the context of reliability assessment of a structure under load over its service life. The paper also compares results from other theoretical approaches. Finally, the background to currently recommended design adjustment factors for duration of load is discussed.Key words: fatigue, load duration, reliability, timber construction, wood.

ISSN:0315-1468    

DOI:10.1139/l93-050

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The difficulties associated with developing reliable roadway failure prediction models are due to the lack of sound theoretical analyses to assess the true causes of pavement distress. Low-temperature cracking and stripping may be two of the causes of pavement distress that are difficult to predict. This paper introduces a simple mechanistic approach that describes the response of the asphalt–aggregate system to temperature changes. The concept recognizes the thermal incompatibility between asphalt cement and aggregate. Owing to the considerable difference in the coefficients of thermal expansion of aggregate and asphalt, the asphalt matrix will attempt to contract more than the aggregate during thermal cooling. An analytical model was derived to estimate the thermally induced stresses resulting from differential thermal contraction. The experimental investigation, which is part of a study investigating adhesion, verified the findings of the analytical approach. Findings from this study explained field and laboratory observations made earlier by other investigators. These observations were associated with asphalt concrete low-temperature performance and its resistance to stripping.Key words: differential thermal contraction, asphalt matrix, localized damage, stripping.

ISSN:0315-1468    

DOI:10.1139/l93-051

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This paper considers energy dissipation by jet diffusion in drop shafts used in urban stormwater systems, using the theory of circular turbulent jets. It presents experimental results on the decay of the maximum velocity in the jet forD/din the range of 5 to 15, whereDis the diameter of the chamber anddis the diameter of the jet at the water surface in the diffusion chamber. It was found that whenD/dis small, the decay of the velocity in the jet is appreciably larger than that in a jet in a large stagnant ambient.Key words: jet diffusion, drop shafts, stormwater systems, turbulent flow.

ISSN:0315-1468    

DOI:10.1139/l93-052

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The performance characteristics of truck weigh stations are presented. Seasonally operated scales and random inspection sites are found to be at least 3 and 8 times respectively as effective in detecting violations as continuously operated permanent scales with no alternative bypass routes. The availability of alternative bypass routes reduces truckers' perceived probability of detection at permanent weigh scales by at least 5%. Higher perceived probabilities are associated with high inspection rates.Queuing theory is employed to study the impact of two alternative manpower levels on the performance of con tinuously operated permanent weigh scales. For the level of truck traffic volume considered, it is found that, theoretically, there is no significant delay to truck traffic through such weigh scale stations irrespective of the manning strategy. It is concluded that it is feasible to maintain minimal staff at the scales and redirect human resources to increase inspection capacities of other methods.The queuing model for the permanent scale operations represents a rare practical example of a classicM/Ek/1 model where thekstages in the service time Erlang distribution are real and not necessarily imaginary.Key words: permanent scale, effectiveness, enforcement, violation, inspection, arrival time, service time.

ISSN:0315-1468    

DOI:10.1139/l93-053

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The present paper outlines a numerical model for predicting the wave field in a harbour with partially reflecting boundaries, and describes laboratory tests undertaken to assess the model. The numerical model is based on linear diffraction theory and involves the application of a partial reflection boundary condition. By utilizing a wave doublet representation of the fluid boundaries instead of the usual wave source representation, the extension is made to general harbour configurations that include breakwaters. Numerical results are compared with known solutions for specific reference configurations. Laboratory measurements have been made of the wave field within a particular harbour model having portions of the boundary corresponding to different degrees of wave reflection. A comparison with the numerical predictions is summarized and highlights the importance of adequately modelling the partial reflections within the harbour.Key words: breakwaters, coastal engineering, harbours, waves, wave diffraction, wave reflection.

ISSN:0315-1468    

DOI:10.1139/l93-054

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

It is now well established that concrete deck slabs of slab-on-girder bridges subjected to concentrated loads develop an internal arching system provided that certain conditions of confinement of the concrete are met. Because of this arching system, the deck slab, being predominantly in compression, fails in punching shear rather than in flexure. This aspect of deck slab behaviour, coupled with the corrosion problems associated with steel reinforcement in concrete, has prompted the authors to investigate the feasibility of fibre-reinforced concrete decks that are entirely devoid of steel. Through tests on a small number of half-scale models, it has been established that fibre-reinforced concrete slab with inexpensive non-ferrous fibres is indeed feasible, provided that the top flanges of the steel girders are connected just below the deck by transverse steel straps and the concrete deck is joined to the girders and diaphragms by shear connectors. The straps and shear connectors together provide the restraint necessary for development of the internal arching system in the slab, whilst the fibres control cracking due to the effects of shrinkage and temperature in the concrete. This paper describes the exploratory model tests and presents their results.Key words: deck slab, fibre-reinforced concrete, internal arching, punching shear, slab-on-girder bridge.

ISSN:0315-1468    

DOI:10.1139/l93-055

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Floor joists consisting of 38 × 89 mm top and bottom chords connected by galvanized steel V webs are often used in the construction of low-rise buildings where long spans are required. An experimental and theoretical program was undertaken to evaluate the performance of such joists when used in conjunction with plywood sheathing attached to the top chord to form a truss floor system. A finite-element analysis procedure for sandwich beams with faces of unequal thickness was adapted in order to predict the load-deflection curves of full-scale floor systems. The experimental program involved the testing of double-block shear specimens to determine the modulus of rigidity of the core, shear specimens to evaluate the performance of the adhesive, and four floor sections to evaluate the performance of the floor system when subjected to uniformly distributed loads. The results indicate that a modulus of rigidity can be determined from the double-block shear specimens, the adhesive performed well under a variety of environmental conditions, the sand wich beam analysis can be used to predict the load-deflection curve of the truss floor system, and the floors performed well when subjected to uniformly distributed loads.Key words: adhesive, floors, floor joists, floor trusses, metal V webs, timber.

ISSN:0315-1468    

DOI:10.1139/l93-056

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Stepped spillways have become a popular method for handling flood releases. The steps significantly increase the rate of energy dissipation taking place on the spillway face and reduce the size of the required downstream energy dissipation basin. The compatibility of stepped spillways with roller compacted concrete and gabion construction techniques results in low additional cost for the spillway. This paper presents a review of recent developments for the design of stepped spillways, provides a discussion of the effects of air entrainment, and presents new calculation methods that take into account the effects of flow aeration on the flow characteristics and the rate of energy dissipation.Key words: stepped spillway, air entrainment, dam, spillway, energy dissipation.

ISSN:0315-1468    

DOI:10.1139/l93-057

出版商:NRC Research Press    

年代:1993

数据来源: NRC