摘要:

The National Building Code of Canada requires buildings to be designed to carry uniformly and nonuniformly distributed snow loads and the "Commentary on Snow Loads" inSupplement No. 4 to the National Building Code of Canadagives detailed design information. This paper discusses the material given in the 1977 commentary and supplements it with examples and photographs.

ISSN:0315-1468    

DOI:10.1139/l80-001

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The carrying capacity of simply supported rectangular plates under uniaxial, in-plane compressive loading is investigated. The ultimate load is determined as the load corresponding to the intersection of an elastic loading line and a rigid–plastic unloading line. An attempt is made to formulate a plastic roof mechanism for the rectangular plate; the square buckle pattern mechanism for long plates is obtained as a special case. The effective width method is re-examined and is shown to give good agreement with experimental evidence. The recommendations of CSA S136-1974 are briefly reviewed in the light of the results obtained.

ISSN:0315-1468    

DOI:10.1139/l80-002

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Investigations with three laboratory-model aerated lagoons proved that incompletely mixed (or aerobic–anaerobic) aerated lagoons can be rationally designed by using the Wehner–Wilhelm equation or Thirumurthi chart, which graphically depicts that equation for applications in biological wastewater treatment. Whereas the biological factors (such as temperature and wastewater quality) are delineated by a first-order biochemical oxygen demand (BOD) removal coefficient (K), the physical–hydraulic regimes (such as mixing pattern and depth–width ratio of lagoon) are represented by a dispersion index. The key to the design is the standard BOD removal coefficient (Ks), which is evaluated to be 0.29/day for municipal wastewater at a standard temperature (T) of 20 °C and organic load (L) of 20 g∙m−3∙day−1. When the actualTandLof a lagoon, however, are other than the standard values, appropriate corrections should be assigned toKsto obtainK. Two equations for such corrections are provided.Two companion papers of previous studies demonstrated the successful application of the same method for designing waste stabilization ponds and completely mixed (aerobic) aerated lagoons; the present study accomplishes the same for incompletely mixed lagoons. An example design is included; the technique, however, needs to be verified by investigating the actual, field lago

ISSN:0315-1468    

DOI:10.1139/l80-003

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The 14 in. (0.36 m) forcemain followed an overall convex pipeline profile for 4000 ft (1200 m) and would be subject to negative surge problems associated with pump shutdown. The forcemain couplings failed three times near the pumphouse and the failure was thought to be related to waterhammer effects. The sequence of breakages is reviewed. A series of pressure recordings were then made over 14 days on the repaired forcemain, leading up to and including the final failure. These pressure recordings were digitized and subjected to power spectral analysis. The power spectra pointed out several significant events that were not evident from the pressure record alone.These included the fact that the original breakdown in the forcemain occurred several days prior to its ultimate failure and discovery on the surface. It was also determined that the break in the system was due to the apparent merging of the primary waterhammer wave with an existing but gradually changing lower frequency wave. This second wave was associated with rigid column motion and gradually increased its frequency. The resultant wave superposition collected sufficient energy at one point to cause the ultimate failure of the evidently already damaged forcemain system.Power spectral analysis proved useful as a method for analyzing waterhammer effects in a forcemain complicated by column separation, leakage, and vapour pocket collapse, and may be a useful way of monitoring the performance of longer pipelines.

ISSN:0315-1468    

DOI:10.1139/l80-004

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A detailed statistical analysis to give ratios of mean to nominal values and associated coefficients of variation (based on raw data collected from Canadian mills on the strength and geometric properties of rolled W shapes, welded W shapes, and class H hollow structural sections) is presented. By relating the tested capacity (based on physical tests performed by others) to the predicted capacity (based on the design equations in CSA standard S16.1-1974,Steel Structures for Buildings—Limit States Design), the professional ratio and its associated coefficient of variation were determined for steel columns as a function of the slenderness ratio, as well as for laterally supported and laterally unsupported steel beams, enabling the performance factor to be determined for these members over the entire range of behaviour. A serviceability criterion for steel bridges is presented.

ISSN:0315-1468    

DOI:10.1139/l80-005

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Because the governing mathematical equations for water distribution networks are nonlinear, many computerized methods of solution have been proposed as the "best" method of solving these equations. A comparison of some of the more popular methods indicates that little difference exists between the methods, although a slight overall edge is available with the Newton–Raphson technique. The exponential increase in computer model cost with increasing network size is demonstrated. The utility of network schematization models is documented, particularly as employed in design studies.

ISSN:0315-1468    

DOI:10.1139/l80-006

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The ultimate capacity of eccentrically loaded fillet-welded connections was experimentally determined by Dawe and Kulak. They proposed an analysis technique for such connections based on an assumption of rigid body rotation of the connection plate about the instantaneous center and the use of weld group load–deformation curves. The Canadian Institute of Steel Construction (CISC) published factored resistance tables for such connections based on this theory. Unfortunately, the theory and design tables can be subjected to the following criticisms : (1) the theory is complex and cannot be easily used for design purposes unless design tables are available; (2) the results from a modified theory were apparently used for comparison with the eight laboratory test results; and (3) the CISC design tables were obtained by using an analysis procedure that does not appear to satisfy all of the design code limitations given by CSA-S16.1-1974.In this paper the author examines the statical behavior of such connections. This study indicates that the overall effect of the last two points is not too serious. The author presents explicit equations approximating the factored load resistance. The use of these equations obviates the first criticism.The design equation developed in this study is very simple; it may be applied with ease in any system of units since it is essentially nondimensional; and it satisfies the specifications of the design code.

ISSN:0315-1468    

DOI:10.1139/l80-007

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

This paper, for river engineers and their environmental counterparts, presents and explains the origin and potential of four-dimensional charts that smooth most of the world's numerical data obtained from the equilibrium dimensions of sand rivers, gravel rivers, and laboratory flumes. These charts aim to provide a practical service comparable with that provided by factual plots on the comprehensive classic three-dimensional Stanton friction-factor diagram for circular pipes and clean Newtonian fluid. In the river problems, especially, the existence of different phases (whose transitions are not susceptible to formulation), the inadequacies of textbook theories even for simple phases, and the unavoidable imperfections of both field and laboratory measurements combine to prevent responsible design. The remedy is a graphing of total information backed by references from which its reliability and practicability can be assessed.The references have been chosen to contain principal information in the forms of: (i) usable photos, graphs, and tables; (ii) explanations free from specialized mathematics and speculative arguments; and (iii) papers with discussions, authors' replies, and further useful references (since a major reference list would be too long for this paper). Because condensation has had to be extreme the authors will be glad to attempt answers to discussions and questions on the subject matter, its practical applications, and its implications in teaching and research.

ISSN:0315-1468    

DOI:10.1139/l80-008

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The effects of gravity loads acting on column and wall deviations from plumb in core-braced buildings have been investigated and expressions for the forces involved have been published in previous papers. The predictions obtained from the design expressions, as applied to two typical core-braced buildings, are compared in this article with corresponding actions resulting from wind and earthquake loads.This investigation aims at separating the effects that are significant in design from those that are small enough to be neglected. A set of simple rules to account for the out-of-plumb effects in buildings is presented as a possible complement to the existing recommendations on stability in the Canadian standard for steel construction CAN3-S16.1-M78.

ISSN:0315-1468    

DOI:10.1139/l80-009

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A study is made of the behaviour of open web steel joists having both top and bottom chords connected to a column when the end is subjected to negative bending moments. Six tests are described, three of which examine the behaviour with typical standard connections as detailed and supplied by manufacturers; the other three involve modifications to these connections in an attempt to minimize connection eccentricity. It is shown that the eccentricities inherent in the standard connections examined can have a significant influence on the behaviour and strength of a joist, whereas if the eccentricities are eliminated, reasonably predictable behaviour, based upon the member resistances under axial loads, can be achieved. These results are examined in relation to tie joists, which are designed to be simply supported under gravity load but have the bottom chord extended and attached to a column, and also in relation to joists designed as framing members.

ISSN:0315-1468    

DOI:10.1139/l80-010

出版商:NRC Research Press    

年代:1980

数据来源: NRC