摘要:

This article describes the change in the basic properties of standard concrete subjected to 12 h freeze–thaw cycles. Basic properties considered are resistance to compression and other parameters describing concrete behavior in axial compression with axial and transverse expansion. Although 300 freeze–thaw cycles have relatively little effect on standard concrete (without air entrainment), results show that the basic property most affected by slow freeze–thaw cycles is compressive strength and not modulus of elasticity. Furthermore, nondestructive testing indicates that only the residual axial elongation allows detection of minor concrete deterioration. Finally, the authors put forward a theory that the presence of air that has been entrained in the concrete, even though specific air entrainment agents have not been used, explains the observed minor deterioration of standard concrete subjected to slow freeze–thaw cycles. [Journal translation]

ISSN:0315-1468    

DOI:10.1139/l80-050

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A theoretical and experimental analysis of curvilinear flow in open channels is presented. The pressure head coefficient and pressure force coefficient used to account for curvature effects utilizing the energy approach and the momentum approach, respectively, are shown to be related by a simple expression. By virtue of this expression and the relative ease with which the pressure force coefficient is usually obtained, the energy approach can now be readily applied to analyze curvilinear flow problems. Verification of this expression is based on curvilinear flow experiments conducted on simple bottom openings and on available data for the limiting case of a free overfall.

ISSN:0315-1468    

DOI:10.1139/l80-051

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

This paper describes the field tests and analysis of a massive bridge pier that is subjected to the action of dynamic ice forces. The field results indicate that the pier has a natural frequency of 8.9 Hz and a damping ratio of 0.19 in the fundamental mode of vibration. By using these dynamic characteristics, the response of the pier to dynamic ice forces was analyzed. This analysis confirms that the pier is capable of responding in full to short duration peak ice forces.

ISSN:0315-1468    

DOI:10.1139/l80-052

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The results are reported of static tension tests and impact bend tests on studs and push-out tests on stud shear connectors with the stud welds made on bare steel and through 20 and 18 gage (0.953 and 1.27 mm) wipe coated galvanized decking at temperatures ranging from 20 to −40 °C. Welding procedures, qualified on the basis of static tension tests, are developed for welding studs over this temperature range. Increased heat input is required to obtain satisfactory welds, both for decreased temperature and increased thickness of galvanized decking. Impact bend tests do not provide a satisfactory criterion for the rejection of stud welds in the field at temperatures below −5 °C. The angle of bend is a function of the test temperature and not the temperature at which the qualified weld was made. Static tension tests at room temperatures form an adequate basis for qualifying stud welding procedures.

ISSN:0315-1468    

DOI:10.1139/l80-053

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Performed laboratory studies on aerobic digestion of activated sludge show that an initial concentration of solids might be effective in reducing digester volume required for sludge stabilization, and lowering the rates of associated nitrification. Therefore, the input solids concentration may be a controlling factor for unwanted nitrogen transformation.The experimental results obtained in the batch and semicontinuous digestion studies indicate similar trends but differ enough to prevent the use of the batch experiment data for the design of continuous flow digesters.

ISSN:0315-1468    

DOI:10.1139/l80-054

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The principal relationship between concrete and rebars when cracks form in reinforced concrete (RC) and prestressed concrete (PC) structures is presented. Mainly for better understanding, crack formation in concrete is compared with that of other materials such as wood or soil.Cracks in RC and PC structures are almost unavoidable and are more often caused by restraint forces than by loads. Cracks are harmless for serviceability and durability if crack width is limited to hair cracks up to 0.2 or 0.3 mm. Although it has been proved that cracks up to 0.4 mm wide do not increase corrosion of the embedded steel, engineers have to strive to limit crack width primarily to get a good appearance from concrete structures.References are given to completed RC and PC structures having a maximum crack width of less than 0.2 mm and structures without expansion joints up to a total length of 140 m.

ISSN:0315-1468    

DOI:10.1139/l80-055

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

It is the objective of the present study to determine the general behaviour of an estuary under the reduction of its freshwater discharge. A unidimensional mathematical model, using the finite differences method, has been set up for this purpose. Although this model is very simple and not costly, the output results are quite good. The influence of a reduction of the freshwater discharge upon the tide propagation and the salinity distribution within the estuary is studied. The Koksoak River (now called the Kuujjuaq), which flows into Ungava Bay, has served as model for the present work.One of the goals of the study was to verify if simple geometries, having linear and exponential variations along the river, could be used in the mathematical study of the Koksoak River. Although the present field data are not complete and precise enough to obtain satisfying results of the case under study, i.e., the Koksoak River, general trends are clearly put forward with respect to the comparison between the simulated canals and the river itself. Further field measurements are expected to improve results, which would then predict more accurately the behaviour of this estuary.

ISSN:0315-1468    

DOI:10.1139/l80-056

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The experimentally observed behaviour of five, one-twelfth scale, wide-flange single-cell composite steel–concrete box girders with both box- and trough-shaped steel sections is described and compared with the behaviour predicted by a folded plate analysis.The folded plate method accurately predicts the elastic strains in such girders when subjected to uniformly distributed load but seriously underestimates the elastic deflections.No significant differences were observed between the structural behaviour of composite box girders with a closed box steel section and girders with a trough-shaped steel section.Aspects of the design of single-cell composite box girders where existing standards result in satisfactory structural behaviour are identified. Tentative design guides are proposed for some aspects of the design of such girders where no guidelines appear to exist at present.

ISSN:0315-1468    

DOI:10.1139/l80-057

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A procedure for numbering the computation points along a system of waterways is presented for the implicit finite difference solution of open channel unsteady flow problems. In a multichannel system, with each branch watercourse being treated as one-dimensional, application of the proposed numbering procedure will produce a narrow diagonally banded coefficient matrix of simultaneous equations. An existing IBM programme, GELB, can thus be employed to solve the simultaneous equations resulting in a significant reduction both in computer storage requirements and computing time.The tailrace system of Portage Mountain Development on the Peace River, British Columbia, Canada, is a Y-shaped channel to which the proposed procedure was first succesfully applied.

ISSN:0315-1468    

DOI:10.1139/l80-058

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

An experimental and theoretical investigation of the statical behavior of cropped-web joints is reported. The joints have square hollow structural sections as chords and circular hollow structural sections with longitudinally oriented cropped ends as webs. Such joints have the advantage of low fabrication cost compared with that of sawn-or profiled-web joints. Tests of 32 isolated joints with Pratt- or N-truss configurations are reported. The measured strain distributions at the joints are described. Equations obtained using multiple regression analysis to relate the strengths and stiffnesses of the joints to various parameters are presented. The strengths of the joints are found to be acceptable and comparable to those of similar sawn-web joints with small gaps between the webs. The stiffnesses of the joints are also found to be acceptable, provided that the chord walls satisfy certain dimensional criteria.

ISSN:0315-1468    

DOI:10.1139/l80-059

出版商:NRC Research Press    

年代:1980

数据来源: NRC