摘要:

Samples were taken from 72 high-rise apartment suites (6 suites in 12 individual high-rise towers) and 60 single-family houses located within the Greater Vancouver Regional District. The influence of the following factors on trace metal concentrations in 1-L first-flush drinking water samples and “running” hot water samples was investigated: building height, location, plumbing age, type of plumbing, and type of building. Results of this survey show that with the exception of building height, all factors had a correlation with one or more of the trace metals investigated. The trace metals examined were lead, copper, iron, and zinc. Lead was influenced primarily by building type, copper by plumbing age and type of plumbing, and iron by location. Elevated lead levels were associated with high-rise samples. New copper plumbing systems resulted in high copper levels. Highest iron levels in the drinking water were measured in the East Vancouver location. Zinc did not show a distinct correlation with any of the factors investigated. Brass faucets were the primary source of zinc in tap water. They also contributed substantially to the lead detected in the 1-L first-flush sample. Metal concentrations measured in the high-rise and house samples were compared with the U.S. Environmental Protection Agency's (USEPA) maximum contaminant levels (MCLs) and the proposed “no-action” level for lead. In high-rise samples, the 0.01 mg/L “no-action” level proposed for lead was exceeded in 43% of the samples, and 62% of the samples exceeded the current 1.0 mg/L MCL standard for copper. In single-family house samples, these values were 47% and 73%, respectively. The average lead concentrations were 0.020 mg/L for all high-rise samples and 0.013 mg/L for house samples. Regulatory levels stated above would still be exceeded in 6% of the cases for lead and 9% of the cases for copper, even after prolonged flushing of the tap in a high-rise building. In all cases associated with single-family houses, flushing the cold water tap for 5 minutes was successful in achieving compliance levels.Key words: aggressive water, compliance, corrosive, drinking water, first-flush, GVRD, high-rise, single-family house, trace metals, USEPA.

ISSN:0315-1468    

DOI:10.1139/l91-111

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The present paper describes the sloshing of a liquid in a rigid circular cylindrical tank subjected both to harmonic and to irregular base motion. Initially, the boundary value problem for the case of an inviscid fluid and a harmonic base motion is solved on the basis of linearized potential flow theory. The case of energy dissipation of a real fluid is then treated by a simple extension to this, which involves an assumption of dissipation at the free surface and a corresponding modification to the free surface boundary condition. In order to treat earthquake-induced motions, this solution is then extended to (i) the stochastic response to a base motion which describes a stationary random process; (ii) the time-domain response to a specified base acceleration record; and (iii) a simplified method of estimating maximum forces using a modal analysis and involving earthquake response spectra. The estimation of hydrodynamic damping is briefly considered, and example applications are provided.Key words: added mass, cylinders, damping, earthquakes, hydrodynamics, sloshing.

ISSN:0315-1468    

DOI:10.1139/l91-112

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The effect of gradation of armour stones and the amount of rounded stones in the armour on dynamically stable breakwaters was assessed in a two-dimensional wave flume. A total of 52 series of tests were undertaken at the Coastal Engineering Research Laboratory of Queen's University, Kingston, Canada using irregular waves. Profiles of the structure during the various stages of reshaping were measured using a semiautomatic profiler developed for this study. Four gradations of armour stones were used, giving a range in uniformity coefficient of 1.35–5.4. The volume of stones and the initial berm width required for the development of a stable profile, along with the extent to which the toe of the structure progressed seaward, were chosen as representative parameters of the reshaped breakwater. The results indicated that the toe width formed as a result of reshaping and the area of stones required for reshaping were dependent on the gradation of the armour stones. The initial berm width required for reshaping was also found to be dependent on the gradation and the percentage of rounded stones in the armour.Key words: breakwaters, dynamic stability, hydraulic models, stability, armour stones.

ISSN:0315-1468    

DOI:10.1139/l91-113

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The concept of schifflerization of 90° equal-leg angle is presented and its application in triangular-base latticed steel towers is explained. The similarities and differences between schifflerized angles and regular 90° angles are discussed. The current design practice for schifflerized angles is reviewed and its limitation is highlighted. A design method which includes the effect of the torsional-flexural buckling mode of failure is proposed. For ready use of designers, the factored axial compressive resistances of schifflerized angles are tabulated for both the present and proposed design methods.Key words: buckling, compressive resistance, design criteria, schifflerized angles, stability, standards, steel, struts, towers, guyed towers.

ISSN:0315-1468    

DOI:10.1139/l91-114

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Ice control structures placed in the streamwise direction of a river were analyzed to determine the effectiveness in reducing ice jam thicknesses. The theory describing the thickness for “wide” river ice jams was modified to analyze these longitudinal types, providing the computational verification that ice jam thicknesses could be reduced where the mode of ice cover thickening is internal collapse. These longitudinal structures appear to provide a new tool for modifying the river ice regime at freeze-up and possibly at breakup. By decreasing the ice jam thicknesses, which leads to lower stages, the structures have the potential for decreasing ice jam flood levels. The structures' ability to function is independent of the flow velocity and these structures should perform in rivers with velocities greater than the usual limitation of roughly 1 m/s associated with conventional cross-channel ice booms. Other possible applications include controlling ice movement at outlets from lakes, enhancing river ice cover progression, or even restraining the ice cover at breakup. A U.S. patent application has been filed jointly by the author and the U.S. Army Corps of Engineers.Key words: river ice, ice jams, ice control, hydraulic structures, ice booms.

ISSN:0315-1468    

DOI:10.1139/l91-115

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Design criteria of a pilot plant for treating secondary municipal effluents using filamentous, bioflocculating micro-algae were evaluated. Using a sequential batch reactor, the best removal rate of ammonia nitrogen was reached for 25% draw volume; at 20–22 °C, up to four cycles per day could be achieved giving a removal efficiency of approximately 2 g of N per day and per square meter of basin (200 mm deep) with negligible nitrogen residual; increasing the water level by increments of 200 mm (from 200 to 600 mm) increased the N removal efficiency in a way similar to an increase in the number of renewals per day on a 200 mm deep basin. The dominant micro-algae (Chlorhormidium) was heavily influenced by the water temperature.Key words: micro-algae, municipal wastewater, water treatment, ammonia nitrogen, removal rate, removal efficiency.

ISSN:0315-1468    

DOI:10.1139/l91-116

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

This paper evaluates the earthquake-resistant design provisions of the 1990 edition of the National Building Code of Canada (NBCC 1990) for asymmetric building structures subjected to combined lateral shear and torsional dynamic loadings arising from earthquake base excitation. A detailed parametric study is presented, evaluating the dynamic edge displacement response in the elastic range, for the side of the building which is adversely affected by lateral–torsional coupling. A series of buildings is studied, with realistic ranges of the fundamental natural period, structural eccentricity, and uncoupled frequency ratio. These buildings are evaluated under base loadings arising from a total of 45 strong motion records taken from earthquakes in North America, Mexico, Europe, the Middle East, and Southern Pacific, categorized according to site soil conditions and the ratioa/vof peak ground acceleration to velocity. The latter parameter together with the uncoupled lateral period are found to influence strongly the combined dynamic edge response, with the greatest forces on edge members arising from earthquakes with higha/vratio in structures with natural periods below 0.8 s. In this case the NBCC 1990 loading provisions significantly underestimate the elastic dynamic response. For buildings with periods longer than 0.8 s, the conservatism of the base shear provisions leads to overestimation of combined dynamic edge response in asymmetric systems, and this is also true in the short-period range for buildings subjected to ground motions with lowa/vratio. The NBCC 1990 provisions are reasonably conservative for short-period systems subjected to ground motions with intermediatea/vratio.Key words: earthquakes, seismic, design, response, spectra, base, shear, torsional, provisions.

ISSN:0315-1468    

DOI:10.1139/l91-117

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

An experimental investigation was conducted at the structural laboratory at Memorial University of Newfoundland to examine the behaviour of high-strength concrete two-way slabs. It was evident that a new mechanical model is required to predict the punching shear capacity of such slabs. The experimental results of the tested slabs with regard to deformations, strains, ultimate capacity, and modes of failure were examined. Based on the test results, a mechanical model was adopted and developed for high-strength concrete slab applications. The formulation takes into account the actual behaviour of the high-strength concrete and steel. The proposed model gives a fairly good agreement between the predicted and experimental punching loads.Key words: deflections, deformations, failure mechanisms, flat concrete plates, high-strength concrete, loads (forces), mechanical model, punching shear, reinforced concrete.

ISSN:0315-1468    

DOI:10.1139/l91-118

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The results for nine sites with different characteristics subjected to earthquakes of varying intensity and frequency content are presented in the form of base shear coefficients, base shear coefficient ratios (surface to rock), and foundation factors. They indicate that large amplifications can be expected at structural periods close to the site periods, especially for low intensity excitation. Comparisons are made with the provisions of the National Building Code of Canada (NBCC) 1990. They show that, depending on the site and the nature and level of the excitation, the expected base shear can be well in excess of the values specified by the NBCC.Key words: seismic, design, code, soil, site, response, amplification, base, shear.

ISSN:0315-1468    

DOI:10.1139/l91-119

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Results of a parametric study on site response effects due to seismic strong ground motions are used in this paper to develop a new "dynamic foundation factor" for the National Building Code of Canada. In order to capture the effect of the site resonance, the proposed dynamic foundation factor,F*, is given as a function of the ratio between the fundamental period of the building and the site period,T/Ts(i.e.,F* spectra in terms ofT/Ts). The parametric study results suggested that the proposedF* spectra be dependent on four different classes of soil deposits. These classes aredeep cohesive(class 1),deep cohesionless(class 2),shallow cohesive and cohesionless(class 3), anddense sand(class 4). For classes 1 and 2, theF* spectra are independent of the ratio of peak acceleration to peak velocity,av, of the seismic ground motion. For classes 3 and 4, however, theF* spectra are an increasing function of the ratioa/v. A scaling multiplier is introduced to take into account the influence of level of intensity,v. The proposed dynamic foundation factor is compared with the National Building Code of Canada 1990 foundation factor. Finally, actual sites are used to check the validity and consistency of the proposed dynamic foundation factor.Key words: seismic, foundation factor, soil, site, amplification, building, shear, force, period, spectra.

ISSN:0315-1468    

DOI:10.1139/l91-120

出版商:NRC Research Press    

年代:1991

数据来源: NRC