摘要:

In the 1985 edition of the National Building Code of Canada (NBCC) the intensity of the specified snow load at any location on a roof is obtained by multiplying the ground snow load for the building locale by a series of factors. These factors reflect the overall reduction in average snow loads on roofs as compared with that on the ground, the effect of exposure to wind, the effect of roof slope, and the effect of drifting, sliding, creep, and drainage.The four loading cases for the design of curved roofs suggested in the Commentary on snow loads accompanying the 1980 NBCC were examined by determining, for roofs of circular cross section, the variation across the span of load intensity, shear force, and bending moment for a wide range of spans, ground snow loads, and roof edge slopes. The purpose of the examination was to fully describe known inconsistencies arising from these loading cases.A new case for drift loading was developed (case III) that, when used with "full" or "uniform" loading and with the unbalanced loading developed for the 1977 NBCC (case II), eliminates or at least reduces the inconsistencies. With this new loading case and the derivation of a formula to define when to switch from loading case II to the new case III the designer now has to consider only one unbalanced loading condition rather than three as before.A simplified method for establishing specified load intensities, shear forces, and bending moments, suitable at least for preliminary design, is also presented.Key words: bending moments, curved roofs, drifts, load intensity, shear force, snow load factors, wind.

ISSN:0315-1468    

DOI:10.1139/l85-051

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The present paper provides a review of recent research on various nonlinearities that arise in ocean wave interactions with offshore structures. These include nonlinearities associated with the incident waves alone, the response of slender structural members to waves, and the nonlinear diffraction problem involving wave interactions with large structures. Emphasis is given to areas of current research into two particular nonlinear problems. One concerns an investigation into alternative approximations to the Morison equation for flexible structures and the other concerns the numerical simulation of nonlinear wave diffraction around large structures.Key words: diffraction, hydrodynamics, nonlinear flow, ocean engineering, offshore structures, waves.

ISSN:0315-1468    

DOI:10.1139/l85-052

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A numerical model to simulate the performance of both rectangular and circular primary clarifiers is presented. The proposed model is restricted to those mean steady flows that are isothermal, of neutral density, low in solids concentration, and nearly two-dimensional.The strip integral technique is used to reduce the partial differential equations of continuity, momentum, and mass transport to a set of ordinary differential equations. The resulting set of equations is numerically integrated using a fifth-order, Runge–Kutta method.The full numerical model contains a hydrodynamic submodel and a transport submodel. The hydrodynamic submodel predicts the velocity field and dispersion characteristics within the clarifier, which are prerequisite for the transport submodel.The model, as presented here, was used to simulate the circular tanks used in the cities of Windsor, Ontario and Waterloo, Ontario. The predicted concentration profiles and removal efficiency were in good agreement with the measured values.Key words: numerical model, primary clarifiers, strip integral technique, transport model, concentration profiles, removal efficiency.

ISSN:0315-1468    

DOI:10.1139/l85-053

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The MOBED and HEC-6 models of river flow were compared in this study. The comparison consisted of two steps. In step one, the major differences between the models were identified by examining the theoretical base of each model. In step two, the predictive capabilities of the models were compared by applying the models to identical data sets. The data set comes from the South Saskatchewan River reach below Gardiner Dam and relates to the degradation process that has taken place since the creation of Lake Diefenbaker. Comparison of model predictions with measurements reveals that MOBED has predictive capability superior to that of HEC-6 and that use of HEC-6 as a predictive tool requires an extensive model calibration by the adjustment of Manning's 'n' and the moveable bed width.Key words: computers, models, sediment transport, river hydraulics erosion.

ISSN:0315-1468    

DOI:10.1139/l85-054

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The 465 m span Annacis cable-stayed bridge, currently under construction near Vancouver, British Columbia, will be the longest cable-stayed span in the world when it is completed in 1986. As this bridge is partially founded on soft delta deposits and is located within 80 km of a seismic source zone, its design has required careful consideration of earthquake effects. This paper reports the seismic analytical and design approaches adopted for the foundations and superstructure of the bridge. Details covered include dynamic modelling of the subsoil layers, correlation of measured surface accelerations with those predicted by computer modelling from nearby rock accelerations, earthquake risk analysis, assessment of the soil liquefaction potential, compliance of deep piles and pier translation during ground shaking, dynamic modelling of the superstructure, ductility and displacement demands in the superstructure, and details for construction.Key words: bridges, earthquake.

ISSN:0315-1468    

DOI:10.1139/l85-055

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

CAPDET is a computer program for estimating construction and operation costs of wastewater treatment plants. A validation study of the model was carried out in order to assess its capabilities for predicting these costs for Canadian conditions. The validation was performed using data from existing full-scale facilities located in Ontario, Québec, and other provinces. The validation study identifies problems in applying the model to Canadian conditions and formulates precise recommendations to account for them. Key results of the validation study were that construction costs can be predicted by the model to within ±20% of the actual costs and operation and maintenance costs to within ±30%.Key words: wastewater treatment plants, construction costs, operation and maintenance costs, CAPDET, computer program.

ISSN:0315-1468    

DOI:10.1139/l85-056

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The development, by Butler and Kulak, of equations for the calculation of fillet weld resistance with relation to the angle of load application has improved the understanding of the limit states behavior of welded connections. For the design of welded connections subjected to shear and moment, Dawe and Kulak developed a method of analysis based on the principle of instantaneous center of rotation, which accounts for the actual load–deformation characteristics of the weld. Due to its complexity, the method of Dawe and Kulak requires the use of a computer. In order to make the method more attractive to the designer, Neis suggested some simplifying assumptions and at the same time criticized the work done by Dawe and Kulak. In the discussions that followed the publication of his results, various researchers expressed diverging opinions on several matters related to the theories.Since the proposed methods were based on the results of only 8 laboratory tests done by Dawe and Kulak, we have carried out a series of 24 tests. The results of these tests were compared with the theoretical ultimate loads obtained from the methods of Dawe and Kulak and Neis, and demonstrate that the proposed methods are adequate as long as they are used within certain limits and respect certain conditions.

ISSN:0315-1468    

DOI:10.1139/l85-057

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

In this paper, the authors deal with the stability of columns braced by girt–diaphragm systems used as cladding in low industrial buildings. The main characteristics of this system are presented and past research, conducted at Cornell University, is reviewed. A new approach based on the finite element method is presented, as well as a series of tests used to validate the proposed method.Key words: diaphragm, finite elements, girt, column, stability.

ISSN:0315-1468    

DOI:10.1139/l85-058

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Dispersion experiments were conducted in four river reaches under both open-water and ice-covered flow conditions. The data were used to obtain the transverse mixing coefficient and to investigate which dimensionless mixing coefficient should be used for ice-covered flows. The results also demonstrate that the sinuosity of a river reach affects the value of the mixing coefficient and can thus be used to guide the selection of mixing coefficient for natural streams.

ISSN:0315-1468    

DOI:10.1139/l85-059

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

In 1981, the City of Québec signed a protocol with the Québec Ministry of Environment permitting the study of the impact of combined sewer overflows (CSO) during rain periods on the St-Charles River. One of the main study objectives was to characterize CSO, both quantitatively and qualitatively. Five main drainage basins, representative of the study area, were selected and sampled during nine rain events. Certain appraisals were made to explain the importance of the water quality variations during rain events in combined sewers, dry weather period influence on runoff quality, and "first-flush" phenomenon. Two principal conclusions have been drawn from these data: (1) the major part of the pollutant load routed through a combined sewer network during a rain event is generated by surface runoff and dragging of sewage deposits and (2) the overall water quality of CSO doesn't seem to vary much from one basin to another, even if the percentages associated with different types of land use (residential, commercial, industrial, etc.) are different.Key words: urban runoff, combined sewer overflow, rainfall, quality, concentration, load.

ISSN:0315-1468    

DOI:10.1139/l85-060

出版商:NRC Research Press    

年代:1985

数据来源: NRC