摘要:

The use of biofiltration ozonation followed by biofiltration in drinking water to improve the physicochemical and biological qualities of drinking water can promote the development of macro-invertebrates in filters colonized by bacteria. The passage of invertebrates in filtered water should be avoided both from an aesthetic point of view and from the potential of bacteria growth support on their surface. This paper focuses on the development of two simple methods to estimate the population of members of the naidid family from the class of oligochaetes in biofilters and in water. The first method involves a naidid column trap used to concentrate naidids present in the effluent of biofilters. During the study, the concentrations of naidids recorded in the biofilter effluent studied varied from 0 naidid per m3in cold water (1°C) to 20 naidids per m3in warm water (22°C). The second method enumerates naidids in a sample of biofilter media taken using a core sampler. Typical naidid densities encountered ranged from the limit of detection (1 naidid per 4 mL) in cold water (1°C) to 25 naidids per mL in warm water (25°C) at the surface of the biofilter. Statistical analyses done on the second method have shown that samples taken at the surface of the filter media at depths between 0 and 200 mm were statistically different from those taken at deeper levels and represented the maximum naidid densities measured in the biofilter studied.Key words: drinking water, biofiltration, population of naid

ISSN:0315-1468    

DOI:10.1139/l00-005

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The provisions for the design of steel beam-columns in CSA Standard CAN/S16.1-94 are reviewed and changes are proposed to provide more consistent reliability in the next edition, CAN/CSA-S16-2001. The in-plane strength interaction equations have been checked using plastic-zone finite element analysis based on realistic residual stress patterns and initial imperfections. The same overall format is maintained.P-&dgr; effects have been found to be negligible for members in sway frame. The interaction equation for checking the in-plane strength of sway beam-columns has been modified by taking the factorU1as 1.0 for members in unbraced frames. For weak-axis bending, a new factor &bgr; accounts for the effect of the distributed plasticity on stability. The concept of the notional load for sway buckling, also used in Australia and in Eurocode 3, is now applied for all load combinations and not just as a minimum. The upper limit onU2of 1.4 is removed. Examples are given illustrating these changes. A re-analysis of the local buckling experiments of other researchers on Class 2 sections, using a widely accepted buckling criterion, shows that no distinction need be made between Class 1 and 2 section beam-columns, i.e., Class 2 sections are treated as Class 1 sections. The changes in total do not increase the complexity of the standard, but reflect better the behaviour of beam-columns. The standard is aligned more closely with the best international practice.Key words: analysis, beam-column, buckling, compact, design, interaction equation, resistance, stability, steel, sway.

ISSN:0315-1468    

DOI:10.1139/l00-003

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A high concrete strength can be achieved by lowering the water/binder ratio and a high workability by adding a higher dosage of superplasticizer. However, a high-performance concrete with both high strength and high workability cannot be produced by just these means because lowering the water/binder ratio leads to lower workability and there is a limit to the increase in workability that can be attained by adding superplasticizer. To produce a high-strength, high-workability concrete, the concrete strength needs to be increased without lowering the water/binder ratio. This can be done by adding condensed silica fume. In this study, a series of trial mixing aimed at developing high-strength, self-consolidating concrete (mean cube strength >80 MPa and needs no compaction for consolidation) was carried out. Several mixes suitable for making such high-performance concrete have been developed and it was found that the addition of condensed silica fume may, under favourable conditions, increase not only the strength but also the workability of the concrete mix. Based on the trial mix results, charts for the design of high-strength, high-workability concrete mixes made of the studied constituents are presented.Key words: condensed silica fume, high-strength concrete, self-consolidating concrete.

ISSN:0315-1468    

DOI:10.1139/l99-091

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The research for habitat comfort conditions goes through a better knowledge of the thermal behavior of materials for building surfaces subject to thermal perturbations. This paper presents a general method for the simultaneous identification of the thermal diffusivityaand of the surface transfer coefficients, one for the irradiated faceh0and one for the non-irradiated facehe, of a single-layer or multi-layer building surface. The experimental technique used, which is called box method, is based on the exploitation of the experimental thermograph of the non-irradiated face. The results of the identification are given for several construction materials (hollow brick, plaster, cork). The noteworthy influence of the number of parameters to identify is also exposed.Key words: Construction and insulation materials, measure and identification, thermal diffusivity, thermal loss coefficients.

ISSN:0315-1468    

DOI:10.1139/l00-011

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Conventional greensand treatment for the removal of iron and manganese from groundwater is not quite appropriate for waters with a high content of iron and manganese. In this pilot study, different modifications to this process were tested to improve treatment performances for water with a high concentration of iron and manganese: addition of a settling tank, use of sand and anthracite covered with manganese oxides, and aeration. Different oxidants and oxidation sequences were also tested. Results show that the presence of a high quantity of iron significantly improves removal of manganese. These results also confirm that manganese oxidation can be realized with free chlorine inside a filter bed other than greensand, provided that the excess of free chlorine is sufficient. Within the conditions studied, the target area for filtration performances can be attained for every treatment sequence tested and for a filtering aid dose ranging from 0.25 to 0.5 mg/L. Although groundwater aeration leads to better settling performances, it also accelerates head loss in the filtering bed when a filtering aid is present.Key words: groundwater, iron, manganese, pilot study, treatment, separation.

ISSN:0315-1468    

DOI:10.1139/l00-012

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Several masonry structures, built over the past centuries, have to be restored to ensure their structural integrity and their conservation. Important research and development projects have been initiated by Public Works and Government Services Canada to rehabilitate some of these structures, such as the Rideau canal locks, by using a cement-based grouting technique. By following grouting pressures and flow rates, the stability of the structure is protected and the efficiency to fill openings is assured by using microfine cement-based grouts with admixtures. However, cement grout penetration cannot be observed with precision during the injection. The project described in this paper presents the grouting treatment of a Rideau canal lock sill wall that had to be demolished and reconstructed. The penetration of two different grout mixes was observed by removing the front row of blocks, piece by piece. A second phase of this study was conducted in the laboratory to compare the penetration of different grouts in a reconstructed granular material which simulated the lock's interior walls.Key words: restoration, masonry, grouting, groutability, cement grout, colloidal agent.

ISSN:0315-1468    

DOI:10.1139/l00-041

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The deformation of a high-pressure sluice gate under an orthogonal water pressure load of 0.539 MPa (i.e., 55 m water height), acting upon the upstream side of a gate leaf, was studied numerically and experimentally. The sluice gate was installed at the end of a water-release tunnel in the Nan-Hwa Reservoir, Nan-Hwa, Taiwan, R.O.C. The numerical results obtained using the ANSYS 5.5.2 finite element program agreed reasonably well with the experimental data. The deformation of this high-pressure sluice gate under water pressure loads of 0.736 MPa (i.e., 75 m water height) and 0.931 MPa (i.e., 95 m water height) was predicted by ANSYS 5.5.2. The research reported here may provide a method for establishing a safety monitoring system for any high-pressure gate and provide engineers with useful information to evaluate the possibility of increasing the capacity of an existing reservoir.Key words: sluice gate leaf, finite element method (FEM), strain gauge, water pressure.

ISSN:0315-1468    

DOI:10.1139/l00-015

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The purpose of this study is to compare three modeling approaches used for the prediction of daily natural flows 1-7 days ahead. Linear black-box models, which have been commonly used for modeling flows, constitute the first approach. The second approach, a linear type in the context of our application, is less known in the water resources field and is identified by the term diffusion process. The third approach uses models called neural networks, which have gained interest in many fields. All these approaches were tested on 15 watersheds from the Saguenay - Lac-Saint-Jean hydrographic system, located in the province of Quebec, Canada. Because the watersheds possess different physical characteristics, the models were tested under several runoff conditions. In this article, the focus is on results; all approaches along with their conditions of use have been detailed elsewhere in the literature. The results obtained showed that neural networks constitute, for almost all the watersheds studied, the best approach to forecast daily natural flows. The more flexible structure of neural networks allows a best reproduction of complex runoff conditions. However, neural networks are more sensitive to outliers present in observed natural flow series, which are used as inputs in the three models tested. In practice, to model flows at specific periods of the year, it seems preferable to establish seasonal models. If a neural network has an inadequate structure for the period under consideration, then it may produce less convincing results than the other two modeling approaches tested in this study.Key words: forecasts, flows, black-box model, diffusion process, neural network.

ISSN:0315-1468    

DOI:10.1139/l00-016

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

An experimental investigation of 15 cyclically loaded extended end plate connections was undertaken to assess the significance of some design parameters. The parameters investigated were beam size, bolt layout, end plate thickness, use of extension stiffeners, welding process, and weld preparation. Eleven of the 15 full-scale test specimens were designed to confine failure to the end plate and four were designed to develop the plastic moment capacity of the beam. Of the beam sizes tested (W360×51, W460×97, and W610×125) the W460×97 beam connections provided the most ductility. The relaxed bolt configuration provided more energy dissipation and connection ductility. The use of extension stiffeners improved the ability of the end plates to dissipate energy and increased the connection rotation at yield. An increase in end plate thickness results in an increase in the connection flexural strength. No significant difference in behaviour was observed between the connections fabricated using the shielded metal arc welding process and those fabricated using the flux-cored arc welding process. Bolt bending and loss of preload were observed in all the test specimens. End plate thickness prediction equations proposed by various researchers were evaluated by comparing predicted plate thickness with plate thickness used for the test specimens. New prediction equations that use yield lines in close agreement with those observed in the test specimens are proposed. The proposed prediction equations are able to predict the thickness of the end plate to within 13%. The proposed prediction equations are applicable to stiffened and unstiffened end plate moment connections with various bolt layouts. Extended end plate moment connections showed good potential for use in seismic zones.Key words: cyclic loading, energy absorption, extended end plates, moment connections, steel, yield l

ISSN:0315-1468    

DOI:10.1139/l99-080

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Six series of tests were carried out to have a better understanding of the stability and efficiency of a coagulation-flocculation process with chemical sludge recycling. The tests consisted in sequential sludge recycling in 100-L pilot reactors. Other tests were performed to examine the stability following wastewater loading variations. Results showed that stability was reached immediately during the first recycling sequences. Furthermore, to obtain improved results compared with those of a classical coagulation-flocculation process, the flocculant concentration must be increased according to the sludge recycling load. Results also revealed that recycling sludge does not absorb wastewater load variations. Consequently, the implementation of sludge recycling in a wastewater treatment plant would not cause effluent degradation or entail major changes in a normal plant operation routine. The predominant coagulation-flocculation mechanisms that explained the increase in efficiency, in comparison with the classical process, were identified as enmeshment and sweep flocculation. Finally, the recycled sludge produced were conditioned and dewatered in a fashion similar to that of a classical process.Key words: recycling, sludge, preformed flocs, coagulation-flocculation, treatment, wastewater, stability.

ISSN:0315-1468    

DOI:10.1139/l00-047

出版商:NRC Research Press    

年代:2000

数据来源: NRC