摘要:

This paper reports the findings of a physical model study of backwaters generated in the vicinity of the Queen Street bridge crossing of the North Thames River in the town of St. Marys, Ontario. Flood profiles generated in the physical model are compared with those observed in the field and with "HEC-2"-generated profiles. Certain limitations of the HEC-2 model, in regards to bridge hydraulics, are identified. The physical model is also used to compare several flood protection alternatives for the town, for both the 100- and the 500-year flows. Floodline delineation was based on both physical model and HEC-2 simulations. The former were adopted for the reach simulated by the physical model, with the latter being employed for the reaches upstream of the physically modelled reach.Key words: physical model, numerical model, bridge backwater, floodline delineation.

ISSN:0315-1468    

DOI:10.1139/l89-001

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The object of this paper is to share the experience gained from a 4-year rehabilitation program on a section of the F. G. Gardiner Expressway in Toronto. The paper describes the latex-modified shotcrete repairs at locations of rusting strands at beam soffits and the conversion of original simply supported spans into continuous beams with the resulting elimination of nearly three fourths of the expansion joints. The benefits of continuity, reduction of expansion joints, new reinforced deck slab, and new drainage system are discussed and essential cost figures are provided.Key words: concrete, prestressed, bridge, rehabilitation, expressway, transportation, urban, shotcrete, continuity, expansion joint, composite deck, epoxied dowels, drainage.

ISSN:0315-1468    

DOI:10.1139/l89-002

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Ice pressure ridges in the southern Beaufort Sea near Tuktoyaktuk were surveyed in April 1986. Sail cross-section profiles and ice-block dimensions of ridges of extreme heights were measured at several locations along the outer edge of the landfast ice. Statistical distributions of sail heights as well as correlations between sail dimensions and between ice block dimensions are obtained. Geographical distribution of sail dimensions and longitudinal changes along individual ridges are examined.Key words: ridges, landfast ice, sea ice, ridge sails, ridge statistics, Beaufort Sea.

ISSN:0315-1468    

DOI:10.1139/l89-003

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A statistical analysis is performed to evaluate the base shear provisions in the 1985 edition of the National Building Code of Canada (NBCC 1985). Three sets of real earthquake records are selected to represent seismic ground motions with low, normal, and high peak acceleration to velocity (a/v) ratios. Single degree of freedom stiffness degrading systems are used as structural models; three damage indicators are employed to measure structural damage. The yield strength of the systems is specified in two different ways: (a) a single seismic response factor is used, irrespective of thea/vratios of the input ground motions; (b) three different seismic response factors are used in the short-period range, depending upon thea/vratios of the input ground motions, as suggested in NBCC 1985. A comparison of the statistical results of the three damage parameters for the systems designed with these two methods of strength specification indicates that the NBCC 1985 base shear provisions provide consistent control over structural damage when the structural systems are subjected to ground motions with differenta/vratios.Key words: earthquakes, ground motions, response spectra, stiffness degrading systems, seismic design, base shear, yield strength, inelastic response, damage parameters.

ISSN:0315-1468    

DOI:10.1139/l89-004

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Proposals from Cornell University for seismic design of lap splices, where the strength provided to the lap splice by the concrete confinement is considered insignificant, were evaluated. The concrete confining the splice length is assumed to deteriorate after high-intensity (inelastic) reversed load cycling so that the performance is mainly dependent on the amount of transverse reinforcement provided to confine the lap splice. Lap lengths of 30–40 bar diameters are proposed, along with heavy transverse reinforcement. Longer lap lengths are considered to be less effective. By contrast, for static loading the concrete confining the splice is known to play a major role in transferring load between the bars along the splice.The current program consisted of testing six reinforced concrete beams under fully reversed cycled loading. The three similar beams in each of the two series contained equal stirrup confinement (number of stirrups) along the lap length to satisfy the Cornell University recommendations for seismic loading for the measured reinforcing yield strength, while the splice length was varied. Splices were located in the bottom face of the test beams and were positioned in a region of maximum moment to ensure severe stressing. Each series of specimens exhibited only small strength gains with increasing splice lengths; however, the performance, when evaluated on the basis of the ductility achieved and the hysteretic energy absorbed prior to failure, was superior with long splices. Since the main reinforcement in the test beams was loaded past yielding, large increases in deformation capacity resulted in only small increases in load.Full reversal inelastic load cycling is very detrimental to the concrete that confines the splice region when compared to static (monotonic) loading or one-directional repeated loading to failure. Splice failure loads under reversal loading in the current study were below predicted static strengths for the same beam configurations, and with the longer lap lengths, static failure would have been flexural rather than in the splice.Key words: reinforced concrete, beams, splices (lap), confinement, seismic design, cycled loading, ductility, strength.

ISSN:0315-1468    

DOI:10.1139/l89-005

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

This paper examines the importance of base flexibility on the nonlinear behaviour of coupled shear walls subjected to pseudo-static lateral loading. The classic continuum method is adopted, with the base flexibility modelled by effective rotational and vertical elastic stiffnesses,KθandKv, respectively. Since the magnitudes of these stiffnesses depend on the properties of the supporting soil and also on the characteristics of the foundation itself, different soils as well as the type of foundation are considered. The latter consists of separate footings under each wall as well as a single combined foundation under the coupled walls. In general, the results show that base flexibility becomes especially important for the overall lateral stiffness at all load levels, whereas internal stresses are affected in only the lower portion of the structure for service loading.Key words: shear walls, coupled, nonlinear, continuum method, flexible bases, separate footings, combined foundation.

ISSN:0315-1468    

DOI:10.1139/l89-006

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Closer collaboration of the traditional disciplines of architecture, structural engineering, and mechanical engineering is required at the design stage to better deal with the complexity of modern buildings, and to maintain the cost of energy low while providing a suitable indoor environment during the life of the building.The availability of personal computers and the development of interactive software provide more opportunities for an integrated approach to building design. This approach is useful in determining the impact of one subsystem on the performance of another subsystem and on the overall performance of the building. An example of such an integrated approach is presented in this paper, which determines the impact of a structural system (hollow core slab) and its mass on the energy consumption of the building.Key words: building design, computers, energy.

ISSN:0315-1468    

DOI:10.1139/l89-007

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The magnitude and relative importance of atmosheric (air–ice) and hydrothermal (water–ice) heat fluxes to intact and fragmented river ice covers are studied for the case of a thermal breakup. Based on field measurements obtained from the Liard River, the atmospheric sources are shown to be dominant during the period of intact ice cover. Radiation was the primary heat source, but its effect was reduced by a granulation of the decaying columnar ice which increased the cover albedo to that comparable for melting snow. The hydrothermal heat input, even with frazil ice entrained within the flow, was comparable to that from atmospheric sources under low melt conditions. The hydrothermal heat flux dramatically increased with the arrival of the breakup front because of a rapid rise in water temperature and an increase in subsurface ice roughness. Higher surface roughness and lower albedo of the fragmented ice also increased the atmospheric heat fluxes, but these were small relative to the hydrothermal heat input near the leading edge of open water.Key words: floating ice, ice breakup, ice jams, ice melt.

ISSN:0315-1468    

DOI:10.1139/l89-008

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Estimation of loss of prestress is an essential part of the design of permanent or temporary prstressed anchors since stability of the retained structure must not be compromised. Findings of a field study on long-term behaviour of prestressed anchors are presented herein: different lengths of anchors in solid rock were injected with cement grout or epoxy resin. Load variation in the anchors with time indicated two distinct stages of loss of prestress: an initial stage of rapid loss of prestress and a second stage of very minor and uniform loss ending about 6 months after prestressing. Our study also showed that restressing anchors after a period of time reduces subsequent prestress loss and that overdimensioning of the injected length does not.Key words: rock, prestressed injected anchor, grout, loss of prestress, creep, relaxation.

ISSN:0315-1468    

DOI:10.1139/l89-009

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A method of two-dimensional modelling for the analysis of symmetrical structures subjected to eccentric transverse loading is presented. The three-dimensional behaviour of the structure is decomposed into separate translational and twisting behaviour under the respective transverse and torque loadings. A two-dimensional model is formed and analyzed for each mode of behaviour and the results are combined to represent the total behaviour of the structure. The method is suitable for structures consisting of bents parallel to the direction of transverse loading. The bents can be of any type and may vary in their properties over the height.Key words: structural analysis, symmetrical structures, two-dimensional model.

ISSN:0315-1468    

DOI:10.1139/l89-010

出版商:NRC Research Press    

年代:1989

数据来源: NRC