摘要:

The drop inlet spillway consists of a vertical riser open at the top and connected to a horizontal conduit or tunnel at the bottom. A 90° change in direction is required at the connection between the riser and the conduit. In the interests of simplicity a square bend, sometimes called a miter bend, is often used for small unimportant structures. This type of bend produces separation zones and large eddy losses (bend loss). At the other extreme is the fully curved bend, commonly used for large shaft spillways. A properly designed curved bend will eliminate separation and minimize head loss. However, layout and forming for construction of a curved bend for a tunnel is complicated and expensive because the elbow surface is of double curvature.In this paper the results of hydraulic tests on five bend designs are presented. It was found that a simplified design with only an inside curve performed almost as well as the fully curved bend. It is suggested that the proposed design will meet the requirement for many low head drop inlets where use of the fully curved bend is not warranted but the square bend is not satisfactory.

ISSN:0315-1468    

DOI:10.1139/l83-001

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A modified two-dimensional mathematical model has been developed to simulate the dispersion of soluble degradable and nondegradable pollutants discharged from multiple industrial outfalls along a large river. This model takes into account the effects of depth and velocity variations in both longitudinal and lateral directions, the removal rates of degradable organic trace pollutants, the lateral convection of mass, and the effect of jet mixing and dilution at the outfalls. It can also accommodate the rapid convergence or divergence in stream width and the influence of an island and of flow diversion on pollutant dispersion.The model was validated by using phenol as a pollutant and comparing the computed values with the field data collected by the Ontario Ministry of the Environment. The application of this model to the simulation of organic pollutant levels in the St. Clair River due to discharges from multiple sources is demonstrated in this paper.Keywords: degradable pollutants, dispersion; jet mixing, pollutant transport, multiple outfalls, nondegradable pollutants, St. Clair River.

ISSN:0315-1468    

DOI:10.1139/l83-002

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A designer-oriented iterative method for the evaluation of effective length factors in braced frames is described. The formulae used in the method have been expressed in terms of effective length factors because designers use this parameter, rather than the values of critical buckling loads, in the analysis and design of columns. The method takes into account the reduced stiffness of restraining members due to the presence of significant axial forces and also allows for the stabilizing effect of tension members. Application of the method is demonstrated by numerical examples.Keywords: braced structures, buckling of continuous columns, frame buckling, truss buckling, effective length factors, accurate stability functions, linear approximations of stability functions, structural stability.

ISSN:0315-1468    

DOI:10.1139/l83-003

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The trend towards slender and lighter structures has shifted the emphasis in design from strength to stability and deflection criteria. Approximate methods have been suggested in design codes to complement the traditional methods and to compensate for secondary effects.In this paper a procedure is outlined whereby the effects of axial forces are automatically accounted for. The method is first described by formulating the stiffness of an element in its deformed position. It is then shown that any existing computer programme can easily be modified to incorporate the axial force effects on the deformation and overall stability of the system. Numerical examples are provided and shortcomings of the approximate methods are discussed. A computer programme named CALTOP is developed that is capable of predicting results for linear as well as nonlinear behaviour of a given structure. It also indicates the critical (instability) load of the system.Keywords: axial force effects, buckling, building codes, columns, computer programme CALTOP, deformations, displacements, elastic, frames, critical loads, matrix analysis, moments, nonlinear analysis, safety, stability, stiffness matrix, structures.

ISSN:0315-1468    

DOI:10.1139/l83-004

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A model, entitled HSS, for selecting the sequence in which trains are to be humped in a rail hump yard, was applied to the Canadian National Railways' Taschereau Yard in Montreal. Based on the promising results of an eight-train pilot study, two separate case studies were performed. The first study compared FIFO and HSS in sequencing the 57 trains that arrived during a 24-h period. The other compared current operations and HSS in sequencing the 169 trains that arrived during a three-day period. Both showed improvements using HSS, with estimated time savings of about 3 and 0.6 h per car at Taschereau Yard, and corresponding estimated inventory savings of about $4000 and $700 per day, respectively.Keywords: humping, HSS, sequencing, railcars.

ISSN:0315-1468    

DOI:10.1139/l83-005

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Extensive field observations have been made on 104 sites where concrete was being placed. A variety of concrete operations and transport equipment was studied. The mean volume being placed each hour and each man-hour has been determined. Variations in productivity have been established throughout the day. The duration and nature of delays in the placing operation have been determined and allocated to three categories: concrete trucks, transport equipment, and manpower.

ISSN:0315-1468    

DOI:10.1139/l83-006

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The behaviour of energy-absorbing friction joints in vertical connections was studied using a model on a shaking table. By varying the slip force in the joints it was shown that there is an optimum value that maximizes the energy dissipation and minimizes the stress for a given seismic intensity.Results given by nonlinear time history dynamic analysis are compared with values from the tests. A proposed approximate method for the calculation of the optimum slip force is given that agrees well with the other values obtained.Keywords: seismic response, tall buildings, friction joints, energy dissipation, earthquake resistant structures, model tests, dynamic analysis.

ISSN:0315-1468    

DOI:10.1139/l83-007

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Results of the tests carried out on eight 45 × 45 × 3 mm and eight 65 × 65 × 4 mm concentrically loaded cold-formed single angles with hinged end conditions are presented. The nominal slenderness ratios of the test specimens varied from 90 to 250. Experimental failure loads are compared with loads calculated in accordance with North American and European specifications. A finite element computer program, which takes into account the effect of the initial out-of-straightness, was developed to predict the flexural failure loads of cold-formed angle sections. The out-of-straightness of the test specimens was measured. Load–deflection curves were obtained experimentally and theoretically. The magnitude and distribution of residual strains were also determined.

ISSN:0315-1468    

DOI:10.1139/l83-008

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

In this paper, two methods of analysis used to determine the factored moment resistance of composite beams are compared. The first method is the one recommended by Standard CAN3-S16.1-M78 (1980 revision). The second method gives the ultimate moment resistance which is multiplied by a "global" performance factor to obtain the factored moment resistance. An elaborate statistical analysis where the variability of the strength parameters has been taken into account was carried out to determine this "global" performance factor. The proposed value is based on the results of 12 420 computer analyses.The authors believe that the second method of analysis is more coherent. Moreover, that method is similar to the method used to determine the flexural strength of reinforced concrete beams. Since one of the objectives of code writing committees is to produce consistent standards, the second method seems more appropriate. (An English version of this paper is available upon request.)

ISSN:0315-1468    

DOI:10.1139/l83-009

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The breakup of ice along the Mackenzie River between Fort Simpson and Fort Good Hope was studied in 1979, 1980, 1981, and 1982. This paper describes the 1980 and 1981 observations. An aircraft dedicated to this task was used to make over 40 observation flights during those two breakup seasons in which more than 20 major ice jams were observed during their formation, stationary position, and breakup. Although the paper is based on experience gained during only 4 years, it was found that all observed jams displayed the same major characteristics; hence it appears that general descriptions of ice melting, breakup, and jamming for the section of the Mackenzie River under investigation are possible. Although there could be additional variations, these are expected to be minor.The paper describes the ice melting process prior to any ice movement. The ice jamming process as it takes place along the Mackenzie River is discussed as well as the various parameters that affect this process. Several secondary factors that influence the detailed character of the jams are also addressed.

ISSN:0315-1468    

DOI:10.1139/l83-010

出版商:NRC Research Press    

年代:1983

数据来源: NRC