摘要:

The seismic provisions for the National Building Code of Canada are based on assumptions that seismic source zones can be defined within which earthquakes are distributed uniformly according to a magnitude/frequency-of-occurrence relation, and that a set of attenuation relationships hold for the earthquake magnitudes and distances that dominate the selected risk level of 10% probability of exceedence in 50 years. These assumptions appear to be reasonable at the probability level used for the average structures included in the code. However, attempts of extending the calculations to significantly lower levels of probability for special structures may invalidate the original assumptions, because the dominant contribution ranges of magnitudes and distances are outside of the intended scope of the ground-motion relations. Moreover, the basic assumption that earthquakes are uniformly distributed over large source zones is seriously compromised.

ISSN:0315-1468    

DOI:10.1139/l86-093

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The objective of this long-term research project was to demonstrate the feasibility of removing nitrogen from highly nitrogenous wastewater by (a) blocking the nitrification process at the intermediary nitrite level through the action of free ammonia and (b) subsequently reducing the nitrite to nitrogen gas. The success of such a process could lead to substantial reductions in nitrogen removal costs.Two identical bench-scale activated sludge systems were operated for 147 days, in the initial phase. Each system was composed of four equal-sized, completely mixed cells in series. The free ammonia concentration was highest in the first cell of each system. It averaged 2 mg NH3-N/L in the first system and 5 mg NH3-N/L in the second. Nitrite buildup, in excess of 80% of the oxidized nitrogen present, was induced and sustained for around 2 months in all cells of the second system, after which time a steady decline occurred. Nitrite buildup could not be sustained in the first system. Average chemical oxygen demand (COD) for nitrite reduction was 40% lower than that for nitrate reduction. The nitrification rate for the ammonia oxidizers was similar for both systems. The presence of up to 100 mgnitrite in system 2 caused no discernible inhibition. Subsequent runs proved that nitrite accumulation could not be sustained indefinitely, owing to acclimation to free ammonia levels as high as 22 mg NH3-N/L. Periodic resting and flushing may be required; further research is being pursued along these lines.Key words: biological treatment, denitrification, nitrification, nitrite, nitrogen removal, nitrogenous wastewater.

ISSN:0315-1468    

DOI:10.1139/l86-094

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The requirements for the interconnection of starred angle compression members contained in North American standards vary greatly from those of European standards. The North American standards, which require only one interconnector for any starred angle made with equal leg angles, are the most liberal. The British standard, on the other hand, is the most conservative.A theoretical study of "slender" starred angles indicates that the buckled shape changes when the number of interconnectors is increased from one to two. There is a corresponding increase in the critical load. The addition of more than two interconnectors has no significant effect on the critical load. An extensive experimental program verified these results. The experimental program also included starred angles that could be classed as being of "intermediate" length.The paper recommends that two interconnectors be used, one at each of the third points, in all starred angle compression members made with equal leg angles.Key words: angles, buckling, building (codes), columns (structural), design, interconnector, starred angle.

ISSN:0315-1468    

DOI:10.1139/l86-095

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The Speedvale Experimental Basin, a 210 ha watershed on the outskirts of Guelph, Ontario, was established in 1965 as an International Hydrological Decade project for the purpose of studying impacts of urbanization on hydrologic response. A relatively extensive hydrologic database regarding precipitation, streamflow, soil moisture, and groundwater has been assembled for the preurbanization period from 1966 to 1974 and for the period of ongoing development from 1975 to 1982. The study area, located physiographically within the Guelph Drumlin Field, was used for mixed agricultural purposes prior to 1974. During 1975 and 1976, 155 ha of the basin were serviced for development for light industrial and commercial usage, dramatically altering the configuration of the drainage system. The major alteration was the installation of a stormwater conveyance system, consisting of a large-diameter storm sewer (2.5 and 3.0 m) and a network of open drainage ditches outletting through ditch inlet catch basins into a main drainage channel.With the changes in land use in the basin have come changes in both volumetric and time distribution aspects of hydrologic response. Changes in the response include (i) an increase in the mean annual runoff coefficient by a factor of 1.5, (ii) an increase in the average annual maximum instantaneous discharge by a factor of almost 3.0, (iii) a change in the time of the annual peak flow from occurring solely in the spring runoff period to occurring throughout the various seasons, (iv) a change in the seasonal pattern of monthly runoff coefficients, with the greatest change observed in the summer and lesser changes observed in the other seasons, (v) a 3-fold reduction in unit hydrograph lag time, and (vi) a 3.5-fold increase in unit hydrograph peak discharge.Key words: urbanization, hydrology, surface water runoff, streamflow, watersheds.

ISSN:0315-1468    

DOI:10.1139/l86-096

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

This study fits into the scheme of research work being carried out to control stormwater rejects. Its main objective is to represent, with the help of a water quality index, the deterioration of the quality of the Saint-Charles River, caused by the combined sewer overflows of Quebec City, Canada, during a rainstorm. The proposed quality index has been applied to evaluate the recreational use of the river.The overall results obtained in the case of a 20 mm rain show index values that characterize a water of poor quality. Moreover, within the region of the combined sewer overflow, a minimum delay of 24 h is necessary to allow the water quality of the Saint-Charles River to return to the level where it was at the dry period, which generally has a value less than the critical value for recreative use.Key words: water quality index, urban runoff, water pollution, nonpoint source of pollution, water quality, water use, environmental impact, pollution control.

ISSN:0315-1468    

DOI:10.1139/l86-097

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Some of the present Canadian rules for designing steel beam–columns can be improved if different formulations are used for designing against in-plane failure and out-of-plane buckling. An extension of the present use of nonlinear elastic analysis methods allows a common formulation for the in-plane strengths of braced and unbraced beam–columns, and generally leads to predictions that are more accurate than the present forms. Two alternative methods are developed for improving the design rules for estimating the out-of-plane strengths of beam–columns. The first of these retains the present familiar form, while the second uses a new form that will lead, in some cases, to significant economies. A method is also proposed for combining the separate formulations for the in-plane and out-of-plane strengths in order to estimate the biaxial bending resistances of beam–columns.Key words: beams, buckling, columns, flexure, steel, structural design, structural engineering, torsion.

ISSN:0315-1468    

DOI:10.1139/l86-098

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

In terms of structural failure, drift loads at changes in roof elevation are the most important snow load. In this paper, present building code provisions and recent research results are reviewed. The mechanics of snow drift formation as well as the parameters that influence these drifts are discussed in depth. Finally, a new empirical relationship for peak drift height and drift load is presented. The input parameters for the new empirical relationship are the width, length, and height of the upper level roof, the elevation difference between the upper level roof and snow on the lower level roof, and the ground snow load. Comparisons with case history measurements indicate that the new empirical relationship is a marked improvement over existing relationships.Key words: snow, loads, roof, drift, fluid mechanics, building codes.

ISSN:0315-1468    

DOI:10.1139/l86-099

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Breakup of the Liard and Mackenzie rivers near Fort Simpson, N.W.T., was monitored from 1978 to 1984. In each year, ice jams ranging in length from 10 to 22 km formed at the Liard River mouth. Although the thickness of some of the jams exceeded 5 m, the volume of ice within the accumulations represented less than 20% of the ice contained within the pre-breakup ice cover of the Liard River main stem. The composition and thickness of the ice jams was related to whether breakup was a 'thermal' or 'mechanical' event. The majority were mechanical breakups and produced much thicker jams and higher water levels than did thermal breakups.Stage–discharge rating curves were developed for the site using two appoaches based on the equilibrium jam theory. The first employed jam parameters calculated for the 1983 jam and the second used a simplified approach suggested by S. Beltaos. Both approaches predicted stage increases of approximately 4–8 m above that which would result from similar discharge under open water conditions. Furthermore, the first approach resulted in a coefficient of internal friction of 1.06, supporting the suggestion that this parameter may have a mean value of 1.2.Key words: floating ice, floods, ice jams, ice breakup.

ISSN:0315-1468    

DOI:10.1139/l86-100

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Trip distribution models attempt to capture two effects and these are changes in the overall scale of travel between some base year and forecast year as well as fundamental changes in commuting structure. The paper begins with a very brief discussion of observed commuting changes in the Toronto region between 1971 and 1981 using the census journey-to-work data. The abilities of a doubly constrained gravity model to emulate interzonal commuting flows in 1971 and 1981 are examined as well as its ability to forecast 1981 flows. These explanatory and forecasting capabilities are compared with those of a Fratar-type trip distribution model. The trip interchange residuals for both model types are isolated and interpreted in terms of the changes in spatial structure that have occurred in the Toronto region over the analysis period. It is concluded that the forecasts provided by the Fratar model are much superior to those of the aggregate doubly constrained gravity model. Both model types have difficulties in emulating shifts in commuting structure that are due to fundamental changes in living and working patterns by the various socioeconomic groups.

ISSN:0315-1468    

DOI:10.1139/l86-101

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Wood-frame walls with low and high water vapour permeance insulating sheathings were tested in a climate simulator with respect to moisture and thermal performance. Exfiltration of moist interior air through the walls was simulated by pumping moist air into wall cavities from the warm side of the climate simulator where the walls were tested. It was found that ventilation slots in extruded polystyrene sheathing did not improve the drying ability of the walls. Incomplete filling of wall cavities with glass-fibre batt insulation, the presence of ventilation slots, and temperature difference across the walls had, if at all, a very small effect on thermal performance. The ability of glass-fibre-board insulating sheathing to store water condensed from exfiltrating air was improved by installing the sheathing with the spun-bonded polyolefin membrane facing the cold side.Key words: exterior walls, insulating sheathing, air exfiltration, condensation, thermal resistance, workmanship.

ISSN:0315-1468    

DOI:10.1139/l86-102

出版商:NRC Research Press    

年代:1986

数据来源: NRC