摘要:

Aquatic weeds growing in irrigation conveyance systems of the earth-lined, open-channel type retard the flow and reduce the efficiency of the systems. The aquatic weed infestations, consisting of both submerged and emergent vascular plants and algae, also reduce system capacity and may result in increased seepage and spill losses. The flow retardance effects and their impacts on the performance of the irrigation conveyance system are evaluated using a modified version of the irrigation conveyance system simulation (ICSS) model developed at the University of Calgary.Key words: aquatic plants, irrigation conveyance systems, efficiency, performance.

ISSN:0315-1468    

DOI:10.1139/l88-001

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Application of computer-aided design (CAD) in civil engineering is most effective when the entire design process, from design and analysis to construction, is integrated. Owing to the complexity of civil engineering projects, complete integration of design has not been achieved as yet. However, even partial integration considerably improves the reliability and efficiency of the design process. This is illustrated in the paper through a case study on the application of CAD in the structural design of the Ontario Domed Stadium. The Ontario Domed Stadium, currently being constructed on a site near the Toronto harbour, will have a seating capacity of 55 000. A unique feature of the stadium is its fully retractable roof. The proposed roof has four separate steel space truss panels, three of which move along tracks and one of which is fixed. To handle the large volume of data involved in the design and analysis of the roof structure, generation of data files containing information on the geometry and topology of the roof structure was automated as much as possible. Special interfaces were developed to transfer this data to application programs for structural analysis, design, and production of working drawings. Computer graphics played a vital role in the design process, assisting in data generation, visual check of geometry and deflected shapes, and seating layout.Key words: computer-aided design, CAD, computer graphics, Ontario Domed Stadium, sight line studies, solids modelling.

ISSN:0315-1468    

DOI:10.1139/l88-002

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The Hong Kong Government invested HK$1760 million (US$225 million) to build a 24 km trunk road with a dual 3-lane carriageway from Sha Tin to Fanling in the eastern New Territories to serve the new towns and also to cater to the increase in cross-border traffic with China. The section Tai Po Bypass, which is 2.9 km long, required the construction of four viaducts ranging from 116 to 242 m long with columns up to 30 m high. The original design of these bridges adopted precast prestressed concrete beam construction. An alternative design using the incremental launching method to construct these bridges was proposed by the contractor with a saving of HK$10 million in contract costs. Specialist subcontractor and consultants from overseas were involved in the design and construction of these launched bridges, which were the first to be constructed in Hong Kong. With the effort of engineers from four continents, this project was completed ahead of schedule, and the road system was open to traffic in September 1985.Key words: prestressed concrete, alternative design, incremental launching.

ISSN:0315-1468    

DOI:10.1139/l88-003

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The paper discusses the problems of wind loading of urban transit vehicles in the context of the overturning problem. It is shown that vehicles will respond to gusts of the order of only a few seconds in duration. The available aerodynamic information for vehicle shapes is reviewed, as is the nature of the wind environment in urban areas. The implications of these data are placed in a simplified probabilistic perspective that suggests that the risk of overturning can become very significant if a number of factors are unfavourable. While the details of assessing the risks more precisely are described and have been developed in detail elsewhere, they cannot be applied to this problem until better information for particular cases is developed. Better data on both vehicle aerodynamics and the wind statistics for actual vehicle routes are needed.Key words: urban transit vehicles, overturning, wind loading, aerodynamics, wind engineering.

ISSN:0315-1468    

DOI:10.1139/l88-004

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Tests and analyses were conducted to characterize the physical, chemical, exothermic, and leaching properties of solid residues from bubbling bed atmospheric fluidized bed combustion units. The residues were produced during the combustion of eastern Canadian high-sulphur bituminous coals (4–8% sulphur) in a bed of eastern Canadian limestone. The residues were highly buffered and composed primarily of calcium and sulphur salts. They were exothermic and swelled considerably when contacted with water. Leachates generated during 20-cycle serial batch leaching tests were highly alkaline with high total dissolved solids concentrations, primarily calcium and sulphate ions. Column leaching test results and field observations suggest reactions may continue to occur over several months until the residues eventually solidify. The residues have properties that are unique, in comparison with conventional pulverized coal combustion wastes.Key words: fluidized bed combustion, ash, leaching.

ISSN:0315-1468    

DOI:10.1139/l88-005

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The performance of a river flow forecasting model employing a Kalman filtering algorithm was evaluated for increasing forecast lead times. The expected decrease in forecast accuracy was quantified and a decrease in forecast precision was noted for increased lead times. The merits of external estimates of meteorological inputs to the model were evaluated through an examination of different forecasting options. It was revealed that even noisy estimates of meteorological events improved the flow forecasts.Key words: forecasting, Kalman filter, real time, precipitation, snowmelt.

ISSN:0315-1468    

DOI:10.1139/l88-006

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Dynamic forces were measured during walking, running, and jumping, using an instrumented platform. The results are expressed as sinusoidal force amplitudes normalized by the subject's weight and are plotted versus frequency. The maximum dynamic loads for walking were found to be nearly twice as large as those recommended in the 1983 Ontario Highway Bridge Design Code or the British Standard BS5400, and those for running or jumping, more than six times as large.Responses of footbridges are calculated using a simple formula based on the dynamic loading due to one person, the response of a simple span at resonance, and limited duration of excitation. Good agreement was obtained with the measured response of two 17 m experimental spans subjected to human excitation, for both the first and second harmonics of the step rate. The resonant vibrations of the spans can be substantially reduced by resonant dampers.Key words: footbridges, dynamic loads, dynamic response, design criteria, resonant dampers.

ISSN:0315-1468    

DOI:10.1139/l88-007

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A study is made on the seismic behaviour of highway bridges with lead–rubber base isolation. The system of base isolation is considered as a bilinear spring. Single- and two-span highway bridges subjected to representative strong earthquake ground motion records were analyzed. The effect of various parameters such as the isolator's stiffness, pier stiffness, and pier eccentricity on the system response was evaluated.It was found that the use of base isolation shifts the fundamental frequency of the bridge system towards the longer period. Proper design of the base isolation tends to reduce the design forces on the bridge piers and is accompanied by larger displacements. Simplified design guidelines are adequate as long as the bridge system can be represented by a single degree of freedom model. The reduction in pier stiffness of a two-span bridge may increase the displacement and the force transmitted to the abutment. The increased forces at the abutments are accompanied by reduction in the shear force transmitted to the pier. Increased displacements and forces may also result when the location of the pier departs from the centre and unequal spans are created. In this case, the maximum displacements and forces occur at the abutment adjacent to the long span.Key words: dynamic, seismic, response, highway, bridges, earthquake, base isolation, design.

ISSN:0315-1468    

DOI:10.1139/l88-008

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The Greater Vancouver Regional District distributes drinking water that displays several attributes of an aggressive water: low pH, low alkalinity, and high dissolved oxygen. A study, consisting of two experimental sessions, was conducted at the University of British Columbia to examine the effects of pH adjustment on internal corrosion of residential cast-iron and copper water distribution pipes.Because of its aggressive nature, this water accelerates the corrosion of water pipes, which not only increases maintenance costs, but also encourages high levels of metal in the water. This last finding was confirmed by a preliminary survey wherein, after one month's sampling of six dwellings, it was found that the recommended maximum level of 1.0 mg/L was exceeded in 67% of the morning cold water first-flush samples.Adjustment of pH with hydrated lime, Ca(OH)2, was used for corrosion control. Cast-iron and copper samples were exposed to pH-adjusted water for varying lengths of time, in two flow-through experimental systems (gravity-fed and system-pressure-fed).Although the corrosion rates were different for the two experimental sessions, analysis of the pH-related corrosion rates variation led to the same two findings. The corrosion rates of cast iron were 10 times those of copper; the increased pH enhanced these cast-iron corrosion rates by approximately 15%. However, a pH increase reduced copper corrosion by as much as 68%. The effects of increased pressure on corrosion were different for both metals; a higher pressure greatly enhanced cast-iron corrosion but had little effect on copper corrosion.Key words: aggressive water, cast iron, corrosion, copper, lime, pH adjustment, water pipes.

ISSN:0315-1468    

DOI:10.1139/l88-009

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The spatial and temporal patterns of water distribution pipe failure in the City of Winnipeg are examined. The failures are shown to be strongly clustered in space, where 22% of the total failures examined occur within 1 m of another failure and 46% occur within 20 m of another failure. A strong temporal clustering is also apparent, with 42% of all failures that occur within 1 m of another found also to occur within 1 day of the initial failure in the group. An exponential decrease in the marginal rates of failure with respect to both the temporal and spatial interval parameter is also observed. Earlier failures in a particular location appear to be an important key to assessing potential failures in that vicinity. These results suggest that a fruitful area for further examination for the reduction of failure rates is the change in the ground conditions resulting from an initial leak and its subsequent repair.Key words: failures, groupings, marginal rates, pipes, space, time, water distribution, Winnipeg.

ISSN:0315-1468    

DOI:10.1139/l88-010

出版商:NRC Research Press    

年代:1988

数据来源: NRC