摘要:

With the advancement of knowledge in drinking water and health impacts related to it, requirements for drinking water have progressively become more stringent. Removal of particulate matter causing turbidity has also been found to be an effective means for removal of microbial contaminants such asGiardia. The conventional treatment process most effective at removal of small particulates is filtration. Presented is a two-phase pilot-scale study used to select new filter media for the Rossdale Water Treatment Plant in Edmonton, Alberta. The study was necessitated by more stringent turbidity guidelines which existing filters would have difficulty achieving. The design and planning of the study had to consider constraints posed by upgrading of an existing filter facility which dictated the media depth and the allowable bed expansion during backwashing. Phase I involved a screening test of four types of media. Based on the phase I results, a crushed quartz and a dual-media consisting of anthracite and sand were selected for more detailed study in the second phase involving investigation of the effects of filtration rate (3.5–12.5 m/h). Filter performance was analyzed using different statistical methods. Factorial experimental concepts were used to study significant effects. Results from both phases indicated that crushed quartz consistently provided the best effluent quality, while the dual-media provided longer filter runs.Key words: water treatment, constant rate filtration, turbidity standards, filter media, crushed quartz, statistical analysis.

ISSN:0315-1468    

DOI:10.1139/l95-123

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Recently, the study of processes and of non value-adding tasks at the process level has enjoyed a renaissance in the manufacturing sector because of the emphasis on total quality management and the work of W. Edwards Deming and others. Interest by the construction industry in the study of processes at this level has been negligible. In order to achieve better quality in construction, the industry must become more process oriented and involved in the study of resource interaction. The CYCLONE modeling system provides an environment for flow charting and studying the interaction of resources within a construction process. The DISCO program which is integrated with the CYCLONE modeling system provides a graphical modeling and simulation environment which facilitates the analysis of construction operations using simulation techniques. The CYCLONE modeling format and the DISCO program interface constitute a foundation upon which improved process design and efficiency can be established.Key words: construction management, simulation, flow modeling, computer methods, construction processes.

ISSN:0315-1468    

DOI:10.1139/l95-124

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Concrete aging is a problem that affects more and more service structures. Detailed knowledge of their state is necessary prior to rehabilitation. Sonic tomography, a relatively new, nondestructive global auscultation approach allows to reconstitute the internal image of the structure. Transmitted sonic wave velocity in the material is the parameter considered. The relative variation in wave propagation velocity in the material provides information about changes in the structure, and therefore the state of degradation. Two hydraulic concrete structures were studied. The principle and the experimental procedure of this method are explained.Key words: structure, concrete, degradation, auscultation, nondestructive test, sonic tomography

ISSN:0315-1468    

DOI:10.1139/l95-125

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This paper describes the assessment of waves and wave effects with respect to the design of a jetty at Plymouth, Montserrat, in the eastern Caribbean Sea. A previous jetty was destroyed in 1989 by Hurricane Hugo, and a critical part of the new jetty's design relates to the effects of waves. Particular attention is given to the establishment of design wave conditions. This includes both hurricane and non-hurricane conditions and requires a consideration of wave shoaling and refraction, as well as wave breaking in the vicinity of the jetty. The prediction of design wave loads includes the calculation of drag and inertia forces and an assessment of impact loads due to waves on the underside of the jetty and waves breaking onto the deck.Key words: coastal engineering, coastal structures, hydrodynamics, wave forces, wave impact, waves.

ISSN:0315-1468    

DOI:10.1139/l95-126

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The ultimate limit state design for composite skew bridges with slab-on-I-steel girders requires a reliable prediction of their ultimate load capacity. In this paper, the results from a yield-line analysis of prototype composite bridges subjected to OHBDC truck loading are presented and compared with the results from a nonlinear finite element analysis of such prototype skew bridges. The favourable comparison between the two sets of results indicates that the collapse loads of skew composite bridges can be reliably and readily predicted by the yield-line method of analysis. Equations useful for the design and analysis of skew bridges are given. The experimental results from five composite bridge models tested to failure verify and substantiate the analyses. Results of the ultimate loads of six other skew composite bridge models with punched-to-failure deck slabs are also shown. A general and simplified method relating OHBDC truck loading to the collapse load predicted using the yield-line analysis is presented.Key words: analysis, bridges, composite, design, failure patterns, finite element, models, skew, yield-line.

ISSN:0315-1468    

DOI:10.1139/l95-127

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Flexible corrugated metal pipes are commonly used as an alternative to concrete bridges for small and medium sized streams. If these flexible culverts are improperly designed they can fail dramatically. One cause of failure is uplift at a submerged inlet. With the pipe flowing partly full, the weight of the pipe and the net force due to the internal water pressure may be less than the buoyant force acting on the submerged pipe; this may result in an upward bending moment. This paper describes an experimental study of the hydraulic forces inside culvert inlets. The tests were carried out on a plexiglass pipe with projecting and flush inlets. The effect of the flow separation on the pressure fluctuation at the inlet was investigated in this study. The internal pressures for the case with a headwall were found to be significantly higher than for the projecting inlet. The formation of a scour hole at the upstream end of the inlet increased the uplift potential. Internal pressure profiles were integrated to determine the internal load distributions on culverts with different inlet treatments.Key words: culvert, projecting inlets, headwall inlets, uplift failure, scour, hydraulic loading.

ISSN:0315-1468    

DOI:10.1139/l95-128

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In this paper, an experimental study of the behavior of 102 mm shear plates subjected to tensile load is presented. The design requirements for shear plate connectors specified in the last three editions of the Canadian wood design standards (1980, 1984, and 1989) are also reviewed and compared with the experimental results. In the experimental study, 83 specimens were tested with shear plate end distances of 80, 145, 210, and 275 mm. Specimens were either 64 or 89 mm thick. Results for all tests were analyzed and 5th percentile resistance values were obtained for each end distance value, assuming a two-parameter Weibull distribution. Results show that connections using 102 mm shear plate connectors behave in a brittle manner when loaded in tension. It is also shown that the member thickness affects the tensile resistance of shear plates in thin members with small connector end distances and that it appears to impose a limit on the resistance for thin members with large connector end distances. Finally, it is shown that the 75% minimum limit on a member net area adjacent to a connector unit (clause 4.3.7.2 of O86.1-M89) is conservative for members with small connector end distances.Key words: wood, shear plate, end distance, resistance, thickness.

ISSN:0315-1468    

DOI:10.1139/l95-129

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A simple hand method of estimating member bending moments in flexibly connected multistorey frames is presented in this paper. The method allows for semirigid joint action and can be used in conjuction with any of the current rigid methods of frame design. The load factor at elastic instability of flexibly connected frames can be obtained by the proposed method. Also, a procedure for calculating a linearized approximation of the joint stiffnesses in a multistorey frame subjected to vertical and horizontal loads accounting for the nonlinearity of the joint's moment–rotation characteristic is included. Comparison of the prediction of the proposed method with an accurate analysis shows that the proposed method leads to an accuracy that is satisfactory for design purposes.Key words: columns, frames, semirigid connections, steel, structural design.

ISSN:0315-1468    

DOI:10.1139/l95-130

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The main goal of this paper is to present a technique to improve the specification of discharge at the open boundaries of a hydrodynamic numerical model. Generally, two dimensional models need boundary conditions using imposed values of water level and (or) velocity components. Although these conditions are satisfactory in most situations, they are not sufficient for open channel flow modelling, in which the discharge is set up according to the upstream hydraulic head. The integral form, needed by finite element modelling, is useful to generate explicit boundary terms that, adequately used, allow the introduction of discharge boundary conditions at open borders of the application domain. The theoretical aspects of this approach are first detailed and, to check the validity of the development and to evaluate the reliability of the model as a design tool, the numerical results are compared with observations on an experimental installation. The results allow to conclude that the proposed model offer a wide range of applications and a high level of accuracy and that it can be considered as a useful aid for hydraulic design.Key words: hydrodynamics, free surface flow, modelling, finite elements, discharge law, boundary conditions, numerical-experimental comparison.

ISSN:0315-1468    

DOI:10.1139/l95-131

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Composite steel–concrete bridges remain one of the most common types built. Proper design of new bridges and evaluation of existing bridges requires accurate prediction of their structural response to truck loads. The American Association of State Highway and Transportation Officials has traditionally applied a load distribution factor for both moment and shear. The Ontario Highway Bridge Design Code (OHBDC) considers several parameters in establishing load distribution factors for moment. However, the method is limited to bridges with skew parameters less than a certain value specified in the code. The presence of skew reduces the longitudinal moments in the girders. However, it also causes high concentration of shear in the girder closest to the obtuse corner and reduces shear concentration in the girder closest to the acute corner as well as in the interior girders. Therefore, shear should be considered in the design of such bridges. In this paper, the influence of skew on the shear distribution factor is investigated. The influences of other factors such as girder spacing, bridge aspect ratio, number of lanes, number of girders, end diaphragms, and intermediate cross-beams are presented. An experimental program was conducted on six simply supported skew composite steel–concrete bridge models. Results from a finite element analysis showed excellent agreement with the experimental results. An extensive parametric study was conducted on prototype composite bridges subjected to OHBDC truck loading. The parametric study included more than 400 cases. The data generated were used to develop empirical formulas for shear distribution factors for OHBDC truck loading and also for dead load. An illustrative example is presented.Key words: bridges, codes of practice, composite, distribution, reaction, reinforced concrete, shear, skew, structural engineering, tests.

ISSN:0315-1468    

DOI:10.1139/l95-132

出版商:NRC Research Press    

年代:1995

数据来源: NRC