摘要:

A new system of composite columns is developed using lipped cold-formed steel channels with embossments and cast-in-place concrete. The combined action of the embossments and the channel's lips leads to very good bond between the steel and the concrete. It has been found that by replacing the standard longitudinal reinforcing bars by cold-formed steel sections of equal area, the structural performance of the columns remains almost unchanged, while considerable savings are achieved in time and material of construction. The present paper outlines the main characteristics of the proposed columns and provides an approach for their analysis and design, which is verified experimentally.Key words: columns, composite structures, concrete (reinforced), construction, cold-formed steel.

ISSN:0315-1468    

DOI:10.1139/l87-047

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The object of this paper was to use a nonlinear plane stress finite element procedure to predict the behaviour of simply supported reinforced concrete beams with a large opening, under mid-span static loading. In the finite element analysis, parabolic isoparametric elements were used in conjunction with the discrete bar formulation. A smeared cracking approach was included and concrete under different states of stress was modelled by using individual models that were incorporated to represent a biaxial state of stress. Reinforcing steel was modelled by using a uniaxial elastoplastic strain-hardening curve. Test results showed that the above approach was found to be satisfactory in predicting the load–deflection curves, crack patterns, and ultimate loads for this type of beam.Key words: beams, cracking, endochronic theory, finite element method, load deflection, nonlinear analysis, openings, reinforced concrete, ultimate load.

ISSN:0315-1468    

DOI:10.1139/l87-048

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

For several years it had been noted in the field that in the absence of an accepted, rational standard method for testing impact-placed zero-slump piling concrete, a variety of strength levels were produced from the same sample of fresh concrete depending upon which of a variety of test methods happened to be used. Finally, in 1977 the Canadian Standards Association published a standard method. This method subsequently proved ambiguous and impractical in practice to many field engineers.This paper presents the results of a laboratory and field study conducted during 1985 directed at the rational development of a practical test method to realistically predict the appropriate concrete strength,, to be used in the calculation of the structural load-carrying capacity of this type of pile.Key words: zero slump, impact piles, energy input, vibration, compaction, concrete strength.

ISSN:0315-1468    

DOI:10.1139/l87-049

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Partially prestressed composite concrete sections are analyzed for the stress and strain changes due to a normal forceNor a bending momentMor a combination of the two. One general approach is presented, which can be used for any of the three loading cases on composite or noncomposite sections. The applied forcesNandMare assumed of such magnitude to produce cracking. The distribution of stress existing before the application ofNandMmust be determined a priori.Key words: analysis, composite section, cracking, loads (forces), precast concrete, prestressed concrete, stress, strain, tension stiffening.

ISSN:0315-1468    

DOI:10.1139/l87-050

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Near the water surface, dispersion and transport were extensively measured in the coastal regions of Lake Ontario using dye patches and clusters of water sail and surface drogues. The measurements were carried out for 6–8 h. Each method produced different measurements of dispersion magnitudes with the largest dilution occurring for the dye, followed by sail drogue clusters (40% of the dye's value) and then surface drogue clusters (25% of the dye's value). Both the sail and surface drogues measured the two-dimensional dispersion. The mean surface dispersion was about 50% less than the dispersion 1.5 m below the water surface. The dilution characteristics decreased as the water surface was approached. The sail dispersion was about half of the dye-dispersion data. It was not known how much of the difference was attributable to the dye being three-dimensional and affected by dispersion in the vertical direction; consequently, as time progressed, the dye patch was measuring dispersion at greater depth than the water sail drogues, which were set for a depth 1.5 m below the water surface. The statistical increase of the variance with time was computed for each method of measuring dispersion, and the results were compared. A method for predicting dilution envelopes for a location using the path lines of the drogue-cluster centroids or center of mass of the dye patch was developed for both a batch release and a continuous discharge. These dilution envelopes are based entirely on Lagrangian data for both the velocity and dispersion estimates.Key words: lake, dispersion, drogue clusters, dye, surface streaking.

ISSN:0315-1468    

DOI:10.1139/l87-051

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Two posted bridges, with pin-connected steel trusses, were recently proof tested in Ontario. This paper presents some results of the tests and draws conclusions, which are also applicable to other similar structures. It is concluded that, unlike other bridge types, this type of bridge does not possess reserve strengths beyond those ascertained analytically. An experimental procedure is given in the paper using which the ratio of dead loads in the two components of a tension chord can be readily determined. This paper also describes a procedure by which equivalence between the test and design vehicles is established, thereby providing a basis for determination of the posting loads.Key words: bridge evaluation, bridge testing, pin-connected truss, posting load, proof test, through truss, steel truss, tension chord.

ISSN:0315-1468    

DOI:10.1139/l87-052

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This paper outlines the results of tests performed to study the effect of strain gradient, strain history, and initial precracking on the efficiency of confinement in reinforced-concrete columns. To this end, five reinforced-concrete specimens with closely spaced ties have been tested under combined flexure and axial load.Two of the specimens were used as control specimens, subjected only to a strain gradient. The remaining three specimens were precracked using different loading schemes and then tested under a combination of flexure and axial load. Two of these specimens were tested with repeated loading.The test results revealed that precracking lowered both the flexural rigidity and the ultimate capacity of the specimens. No significant differences were observed due to the type of loading used to initially crack the specimens. Repetition of loading did not seem to affect the ultimate capacity of the specimens.Comparison of the test results with four analytical models for confined concrete showed that the models that predicted the behaviour of the control specimens accurately, overestimated the capacities of the precracked specimens. The Thompson and Park concrete model accurately predicted the behaviour of the specimens tested with repeated loading.Key words: reinforced concrete, confined concrete, confinement, columns, cyclic loading, precracked column, experimental.

ISSN:0315-1468    

DOI:10.1139/l87-053

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This paper reports a study on the comparisons between the behaviours of braced steel building frames with friction joints and with eccentric bracing, under seismic forces. Nonlinear time-history dynamic analysis is used. Friction damping is shown to be of particular merit.Key words: bracing, damping, ductility,dynamics,earthquakes,eccentric; energy dissipation,friction, hysteresis loops,response,steel frames, time history.

ISSN:0315-1468    

DOI:10.1139/l87-054

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The Vancouver Advanced Light Rapid Transit (ALRT) System consists of 21.4 km (13.3 miles) of grade-separated guideway between the cities of Vancouver and New Westminster. Of the total length, 16.6 km (10.3 miles) are elevated, 1.3 km (0.8 miles) are in tunnel, and 3.5 km (2.2 miles) are at grade. There are 15 stations and a maintenance and vehicle storage facility. The system uses linear induction motor driven, light-weight driverless cars which are automatically controlled from the operations center located in the maintenance facility.The guideway beam concept was developed in concrete with the requirement that direct track fixation be used without a second pour. The beams are post-tensioned, following erection into two- and three-span continuous structures, encastre at the internal supports, with single pot bearings at the expansion ends.During construction the management for the project was provided by a joint project organization (JPO) consisting of the system contractor, Metro Canada Ltd., and the owner, B.C. Transit. The JPO was formed part way through the project to reduce duplication of effort and improve communication and coordination.Quality assurance for all materials and construction was critical to the successful completion and operation of the system. To ensure quality, the JPO instituted a detailed quality assurance (QA) and quality control (QC) program, implemented through the construction management team.Production of the precast guideway beams for the project was undertaken by two separate contractors. The initial contractor produced the beams for the 1 km prebuilt or demonstration phase, requiring 74 beams. The second contractor produced the remaining and major portion of the elevated guideway beams, for phase 2, amounting to an additional 1040 beams. Information obtained from phase 1, the prebuilt section, was used to modify the structural design, equipment requirements, and production and construction methods for phase 2.The cost of the transit system including 114 vehicles and all operation and control equipment was budgeted for a maximum expenditure of $854 million of which approximately $240 million was for civil works for the guideway, stations, and maintenance yard.Construction of the guideway began in August 1983 and was completed in December 1985. The guideway began operation January 1, 1986 on time and on budget.Key words: transit, automated, design, construction, guideway precast, concrete, quality assurance.

ISSN:0315-1468    

DOI:10.1139/l87-055

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

When planning for the treatment and disposal of domestic wastes, coastal communities have a number of options. Like inland towns, they may utilize full treatment allied with traditional methods of disposing of the treated liquid and solid end products. At the other extreme, it would be possible to consider discharge of untreated wastes directly to the ocean through a submerged outfall. As a compromise, some combination might be used with the final design incorporating a degree of on-land treatment together with a submerged outfall.In this paper, the environmental problems and benefits of discharging domestic wastes through a submerged ocean outfall after minimal on-land treatment are compared with those of a totally land-based treatment plant. Water-quality standards attainable by both systems are enumerated, and other environmental problems are taken into account. Consideration is also given to biological, chemical, and bacterial effects; and aspects of aesthetics and health are discussed. Financial and economic viewpoints merit considerable discussion but are generally outside the scope of this paper and are mentioned only briefly. Regulations governing discharges in Canada, the United States, and Europe are discussed and considered in light of the evidence presented.Key words: outfall, dilution, pollution, treatment, sewage.

ISSN:0315-1468    

DOI:10.1139/l87-056

出版商:NRC Research Press    

年代:1987

数据来源: NRC