摘要:

The deformation response of floating ice sheets under high intensity, short duration loads is examined. Using a rigid-plastic theory, together with a Tresca yield criterion, expressions are derived for the total time of response and the final deformed configuration of floating ice sheets. The influence of the magnitude of the impact load and the load-contact radius on the various design quantities such as deflection profile and stress distribution is discussed. Based on the results derived, a design method is presented to find the safe thickness of a floating ice sheet to sustain a given impact load. The method is illustrated with a numerical example.

ISSN:0315-1468    

DOI:10.1139/l81-054

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Experiments have been conducted on high strength prestressing and bridge wires (zinc-coated) to assess their susceptibility to stress-corrosion cracking (SCC). The wires were subjected to various stress levels and corrosive environments. Loss of ductility and reduction in the ultimate strength of these materials are determined. A criterion is then proposed to evaluate the susceptibility to stress-corrosion by means of an index based on the observed mechanical properties of the wires. Further experiments were carried out on another high-strength bridge wire to validate the proposed approach.Based on the experimental and field observations, the proposed method could be applied to select the type of wire used in pre- or post-tensioned concrete construction or in other applications to ensure better protection against SCC.

ISSN:0315-1468    

DOI:10.1139/l81-055

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

This paper describes a system in operation at the University of British Columbia for structural analysis using interactive computer graphics. The three major components of such a system are a central processing unit, some graphics hardware, and software. The central processing unit should allow fast interactive use of the graphics hardware to eliminate long time delays for the designer. The minimum graphics hardware is a storage tube terminal for the display of vectors and diagrams. The addition of a hard copy unit will relieve the designer from the inevitable pressure of an interactive system and provide time to study the results of an analysis. Finally, a tablet provides for fast input and alteration of data, both geometric and numerical. These three pieces of graphics equipment, terminal, tablet, and copy unit, form an efficient input-output system.Software programs are of two varieties. The first will produce a common data bank via the tablet or generators. The second will draw from that bank for a variety of analyses such as linear, elastoplastic, second order, or dynamic. In all cases the analysis programs plot on the screen scale diagrams of axial, shear, moment, and deflection for instant hard copy. This integrated system of hardware and software provides an efficient analysis tool for both students and practising engineers.

ISSN:0315-1468    

DOI:10.1139/l81-056

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Within the context of studies concerning water inflow forecasts for some Quebec watersheds, a deterministic hydro-meteorological model, the SSARR (streamflow synthesis and reservoir regulation), was used for Lake Memphremagog near Magog. The low discharge capacity at the outlet of the lake and the obligation to regulate water levels, imposed both by an international agreement and by the wish to protect the environment, had made essential an accurate assessment of runoff during the spring thaw and periods of heavy rain. The results were so conclusive that tests are currently being carried out to prepare forecasts for eight other watersheds in Quebec. [Traduit par la revue]

ISSN:0315-1468    

DOI:10.1139/l81-057

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A preliminary investigation was made of the effect of frazil ice on arrays of lines positioned in flowing water under winter conditions. It was found that the lines would provide a stable basis for forming an ice cover on many stream reaches that would normally remain open because of high velocity and shallow depths.Tests were conducted in a refrigerated flume and in small mountain rivers. Flume depths varied from 2 – 22 cm and river depths varied from 33–50 cm. Average flow velocities had a range of 0.08–0.84 m/s in the flume and a range of 0.6–0.8 m/s in the rivers. Frazil ice would grow on a line quite rapidly achieving a diameter of 32 mm in 15 min, on a 3.2 mm dia, line in the flume. In the river, overnight accumulations reached 20 cm in depth. A few drag force measurements were made which yielded an average shear drag coefficient of 0.16.The results suggest methods of increasing our control over ice.

ISSN:0315-1468    

DOI:10.1139/l81-058

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A 58.27 × 4.57 × 3.04 m wave flume has been constructed and calibrated. The maximum wave height that can be generated in regular waves is 0.7 m at a water depth of 1.8 m. Random wave spectra have also been modelled in the flume for prototype wind speeds up to 25 m/s. The maximum significant wave height that can be generated at a 1 m water depth is 20 cm.A series of tests performed to verify design curves presented by Gilbert, Thompson, and Brewer show good agreement with the predicted values. The Pierson-Moskowitz spectrum was modelled between wind speeds of 5 and 25 m/s at suitable scale factors ranging from 1:50 to 1:150. All analysis was carried out in real time by means of an on-line computer.

ISSN:0315-1468    

DOI:10.1139/l81-059

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

An ultimate strength theory is developed for double chord rectangular hollow section (RHS) K-joints that accounts for both perfectly plastic and strain hardening material characteristics. The parameters that are investigated are chord depth–width ratio, eccentricity, chord preloading, and diagonal–chord angle. Interaction curves are presented that relate the diagonal and chord axial forces for different combinations of the parameters. It is shown that joints may suffer significant reductions in strength with an increase in eccentricity for the case when shear capacity of the chord's webs does not govern overall strength.Various detailing alternatives are investigated to improve joint capacity for prescribed weldment lengths. These include altering the diagonal–chord angle and the chord depth–width ratio.

ISSN:0315-1468    

DOI:10.1139/l81-060

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Inadequate end-point facilities in office buildings for shipping and receiving freight are partly due to a lack of understanding of the urban goods movement problem by architects and engineers and partly due to inadequate municipal freight facility by-laws. The problems created by inadequate freight facilities impose a wide range of environmental, social, and economic impacts on an urban area. Because of the magnitude and extent of these impacts engineers involved with the planning, design, and approval of office buildings must take an increasingly comprehensive view of the range of factors that should be considered in the design and operation of office building freight facilities.This paper is based on a recently completed study of urban freight facilities conducted by the Department of Civil Engineering of The University of Calgary for the City of Calgary Transportation Department. The study included measurement of arrival rates and service times of delivery trucks, couriers, and service vehicles at office buildings in Calgary. These measurements, in addition to a survey of existing freight facilities in central business district office buildings, formed the basis for the development of a proposal to revise existing zoning by-laws regarding freight facilities. The primary deficiency of existing Calgary by-laws is that they overstate the need for delivery vehicle facilities by a factor of two for larger office buildings and neglect the space requirements for couriers and service vehicles. The paper includes a comparison of freight facility by-laws for office buildings in a number of selected Canadian cities.

ISSN:0315-1468    

DOI:10.1139/l81-061

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A rotating biological contactor (RBC) unit in series with a septic tank for primary solids removal and sludge storage was monitored for 21 months. The results of that monitoring are summarized in this paper. The treatment configuration produced an effluent that met federal guidelines of 20 mg/L for BOD5, and 25 mg/L for suspended solids. When solids were allowed to accumulate in the septic tank beyond 12 months, there was a marked increase in loading of the RBC with a resultant decrease in effluent quality. A linear relationship could be shown between clarified effluent BOD5and applied BOD5. The data from this monitoring program suggest that surface area requirements of RBC units utilizing septic tanks for primary solids removal are three times those utilizing conventional primary treatment. When high levels of nitrate were in the unit, feed denitrification occurred concurrently with carbonaceous oxidation.

ISSN:0315-1468    

DOI:10.1139/l81-062

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The entire roadway of the approach viaduct was replaced with minimal disruption to traffic. The design, tolerant of errors and maximizing prefabrication, achieved quick replacement. Foundations were rotated by inserting hinges and cutting through the mass concrete piers. Plans were prepared for replacing the suspended structure of the main spans without disrupting Monday to Friday traffic. Design criteria are given for limit states of old steel, buckling of rivetted compression members, fatigue resistance of welded tubular construction, and temporary obstructions in the roadway. The effects of turbulence on aerodynamic stability led to the use of solid guard rails. Problems associated with progressive replacement of the suspended structure are discussed. The importance of public information during reconstruction is emphasized.

ISSN:0315-1468    

DOI:10.1139/l81-063

出版商:NRC Research Press    

年代:1981

数据来源: NRC