摘要:

The problems associated with freezing and thawing of the subgrade soil underneath highway and airfield pavements in countries with cold winters like Canada are well known. In the southern parts of Canada, the subgrade can be protected from freezing by a thick layer of granular material or a thin insulating layer. In northern regions, layers of granular materials or insulation can maintain the subgrade in a frozen condition.Previous studies have shown that extruded polystyrene foam is effective as an insulating material. However, the effect of this material on the physical behavior of pavements has not previously been investigated.To study the effect of a thin insulating layer on the curling deformation and thermal properties of rigid pavements two concrete slabs were cast in the field. One slab was laid over a 1½ in (4 cm) thick layer of styrofoam, while the second slab was cast over a 1½ in. (4 cm) thick layer of sand without insulation. A 10 in. (25 cm) subbase layer of compacted gravel was used underneath both slabs.Both slabs were instrumented from surface through foundation to determine the temperature distribution and to establish the curling behavior of the slabs. Periodic readings were taken during one warm and one cold weather period. The results derived from these readings have indicated that insulation reduces curling deformation of pavement slabs and does not significantly effect temperature gradients across their thickness.

ISSN:0315-1468    

DOI:10.1139/l75-022

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The use of a fluorometric method for the determination of residual aluminum salts used as coagulants in water treatment has permitted evaluation of the influence of some factors, particularly temperature, on the hydrolysis of these salts. The yield of hydrolysis is lessened by low temperatures and aluminum ion is more sensitive than aluminate ion. This new method is suggested for detecting abnormal working of water treatment plants.

ISSN:0315-1468    

DOI:10.1139/l75-023

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A long horizontally curved, post-tensioned concrete highway bridge, continuous over 12 spans, is described. Particular emphasis is placed on a number of original and unorthodox design concepts which make the structure unique.

ISSN:0315-1468    

DOI:10.1139/l75-024

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

This paper describes the present method of deriving allowable stresses for wood. While this method has served adequately in the past its relevance to ‘limit states design’ is questioned and several of its shortcomings are pointed out.An alternative method of obtaining characteristic values for the strength properties of wood is suggested. A pilot investigation was carried out to ascertain the amount of work involved in obtaining the necessary data. It would appear possible and practical to derive the characteristic values needed for ‘limit states design’ based upon ‘in-grade testing’.It is suggested that such a method could result in improvements in the present grading rules and a more efficient use of our timber resource.

ISSN:0315-1468    

DOI:10.1139/l75-025

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A procedure is presented for analyzing steel frames with any combination of pinned connections, fixed connections, connections with any specified flexibility characteristics, or any of seven commonly used connection types. A method is outlined for expressing, in a nondimensional form, the moment–rotation characteristics for all connections of a given type. The dimensionless relationships are listed for the commonly used structural steel framing connection types. The incorporation of connection deformations into a linear structural analysis, by modifying the stiffness matrix and fixed-end-force vectors for each member, is demonstrated.An iterative nonlinear analysis procedure is described in which repeated modifications are made to assumed flexibility characteristics for all connections in a structure. When a suitable set of connection flexibility characteristics has been arrived at, a single analysis is performed to determine the correct structural deflections and internal forces.

ISSN:0315-1468    

DOI:10.1139/l75-026

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

This paper describes a pilot study of the development of a national commodity flow model for Canada. The aim is to develop a modelling capability that can estimate the commodity movement implications of probable changes in development and in the transport system. The model described in this paper concentrates on estimating the implications of alternative development patterns. The basic inputs to the model are spatially disaggregated allocations of population and of employment by industry sector. The principal outputs from the model are the annual tonnages of freight on each link of each modal transport network. Data inputs to the model and the model parameters are derived principally from information collected and published by Statistics Canada.The structure of the model is similar to the model structure used in urban transport planning studies. It proceeds from the estimation of commodity productions and consumptions, through the estimation of commodity distributions patterns and modal split by mode to network assignment.Preliminary results from the commodity flow model using a 1971 data base are described along with a very limited appraisal of the model outputs using independent information on Canadian commodity flows. Plausible results were obtained from the model and the assembly of an improved data base should lead to a well-developed national commodity flow model for Canada. Such a model may then be used to examine the freight movement implications of alternative patterns of urbanization in Canada and to evaluate alternative transport supply decisions for the various modes of transport.

ISSN:0315-1468    

DOI:10.1139/l75-027

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Simplified analyses of wall-beam frames, based on previously determined equivalent member stiffnesses, are given. The analyses are based on two approaches: (i) using the methods of difference calculus and (ii) using the continuum method, commonly used in shear wall analysis, in which the beams connecting the columns are replaced by a continuous connecting medium. It is shown that the analyses using difference and differential calculus are equivalent if an approximation of the column bending is introduced. Comparison of the proposed approximate methods with exact skeletal analysis shows excellent agreement. One conclusion of practical importance is that many analyses applied to shear walls, and available in the literature, may be applied to wall-beam frames as well. It is suggested that in many cases it is possible in practice to neglect the column bending stiffness altogether and details of an analysis based on this assumption are also given.

ISSN:0315-1468    

DOI:10.1139/l75-028

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Urban transportation studies cost roughly 1 dollar/capita with approximately 50% of the expenditures consumed in the collection of data on travel habits. Many small cities, those 50 000 population and under, have limited budgets for data collection and analysis. In addition, the conventional urban transportation planning process is not only expensive but may be out of scale in terms of the order of magnitude of transportation decision-making in small cities.The simplified traffic forecasting process suggested in this paper requires a minimum amount of data collection and relies to some extent on travel parameters taken from cities of similar size and characteristics. Thus, the problem of costly home-interview surveys is avoided in addition to the fact that the model can be quickly updated by hand. The simplified model is based on the premise that travel time does not affect trip distribution to any extent due to the fact that significant differences in travel times between short and long trips are not perceived by the trip maker. The model was applied to the town of Fort McMurray which is the residential and operations base for the development of Alberta's Tar Sands. Comparisons of model output with traffic counts show that the simplified model gives reliable results.

ISSN:0315-1468    

DOI:10.1139/l75-029

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

This presentation, taking the form of a state of the art report, considers several aspects of the behavior of tall and squat shear walls. In particular the problems of brittle and ductile failure modes, diagonal tension, construction joints, alternating plasticity, sliding shear, stiffness degratation, and strength loss under reversed cyclic loading are discussed. The behavior of coupled shear walls is examined in some detail and the problems related to the components of this structure are reviewed. The principles rather than techniques of design for earthquake resistance are stated. Wherever possible the issues are studied against the background of experimental evidence. The material presented indicates that carefully detailed shear walls, designed to possess an intelligent hierarchy in their failure mechanisms, can be made to possess the properties so desirable in earthquake resistant structures.

ISSN:0315-1468    

DOI:10.1139/l75-030

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A simplified method of analysis is presented for the determination of dynamic properties of single-story structures founded on flexible foundations. The general equations for natural frequency, mode shapes, and modal damping are applied to structures founded on an elastic half-space and on piles. The results of parameter studies, including the effects of hysteretic soil material damping, are presented for these two cases.

ISSN:0315-1468    

DOI:10.1139/l75-031

出版商:NRC Research Press    

年代:1975

数据来源: NRC