摘要:

Upsurges and downsurges are calculated and plotted for a simple pump discharge line provided with an air chamber. Basic parameters such as pipeline constant, air chamber parameter, pipe wall friction, and orifice resistance are used. The results of this paper can be used to determine the necessary volume of the air chamber. Computer studies indicate that the assumption of the rigid water column and the concentration of pipe friction at the pump end of the pipeline yields reasonably good results at the pump end; however, because of these assumptions, large errors in estimation of both upsurges and downsurges occur at the midpoint and particularly at the quarter point of the pipeline. Pipe friction has a substantially different effect on surges than that of the orifice resistance; these two effects should therefore be considered separately. A differential orifice is recommended and considered; this orifice should have a low resistance to flow out of the chamber.

ISSN:0315-1468    

DOI:10.1139/l77-040

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The basic information needed for the selection of appropriate bridge systems of short and medium spans is given. The options in the longitudinal and transverse sense and in the choice of the supports are described. Then, by means of the Sasselli Viaduct (in project), the application to a selection problem is demonstrated.

ISSN:0315-1468    

DOI:10.1139/l77-041

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Numerous old concrete structures showing signs of disintegration are found in the Beauharnois–Valleyfield area located to the southwest of Montreal.After a short examination of some of the structures, evidences of alkali–silica reactivity appear to be related to sandstone aggregates belonging to the Potsdam group. This rock type, although common in the state of New York and in the provinces of Quebec and Ontario, is only very rarely used as an aggregate owing to its hardness and abrasion. Nevertheless, when available from important excavation sites it has sometimes been used as an aggregate with ordinary alkali-rich cements.The products of the chemical reactions between the siliceous aggregates and the cement were studied with a polarizing microscope, a scanning electron microscope, an electron microprobe, and a thermobalance and differential thermoanalyser.During these studies superposed layers of silica gel of variable composition were found and secondary minerals were also identified. The Na/K ratio was found to increase in the more recent layers of silica gel suggesting that sodium could have been added within the structures as winter de-icing salts.The hypothesis is put forward that even if a low alkali cement is used with this Potsdam sandstone, alkali–silica reactivity could still occur in the presence of alkalies from external sources.

ISSN:0315-1468    

DOI:10.1139/l77-042

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

An analysis for wood diaphragms is presented taking into account the deformation of the connections. The load–deformation characteristics for the connectors are assumed to be nonlinear. A numerical example is presented and comparisons are made with experimental results on a 20-ft by 60-ft (6-m by 18-m) plywood and decking roof diaphragm. The agreement between the test results and the predictions of the analysis is shown to be good.

ISSN:0315-1468    

DOI:10.1139/l77-043

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

An analysis of truss-plate connections is presented, taking into account the nonlinear character of the load–deformation relationship. The connection is considered as ‘continuous’ because of the high density of teeth, and connector properties are derived from those for a single tooth. Parameters considered in the analysis include the actual shape of the connected area, gaps between connected members, the buckling capacity of the plate, and its yielding in tension and shear. Good agreement is shown in a comparison between theoretical and experimental results using a single connection under eccentric loading.

ISSN:0315-1468    

DOI:10.1139/l77-044

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The results of a study on longitudinal shear strength of Douglas fir, based on Weibull's theory of brittle fracture, are implemented in a design method. Design formulae are given and required parameters are calculated for several common configurations of beams and loadings. A method for extending the results to other species is proposed.

ISSN:0315-1468    

DOI:10.1139/l77-045

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The Hsiang–Reilly method, a discrete Bayesian model discrimination technique, is used to select the best model of several alternative models to describe data relating observed BOD exertion as a function of time. Use of this approach avoids the need for linearization of equations and results in distributed probability estimates of the parameter magnitudes rather than simply point estimates. A case study application to the raw influent and primary effluent of the Waterloo Pollution Control Plant is included. The results indicate that although a three-parameter model often gives a better fit to observed BOD data than the two-parameter first-order model, differences between the BOD-progression curves for the models are often so small as to be insignificant. In view of these small differences, and considering that none of the proposed models could adequately describe observed deviations from the exponential BOD curves, the use of the first-order equation to describe BOD-progression relationships for the Waterloo Pollution Control Plant appears to be justified.

ISSN:0315-1468    

DOI:10.1139/l77-046

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Ice conditions on the St. Marys River hamper winter navigation between Lake Superior and Lake Huron. Vessel movements in the river during winter months lead to changes in the river ice regime and affect local ferry service across the river. A hydraulic scale model of a 7300-m length of the waterway extending downstream from the Soo Locks was used to compare alternatives for relieving these effects. Methods for representing ice behavior were a key element in the model study.An arrangement of ice booms with an open ship passage which does not impede navigation was developed and recommended on the basis of model tests. That boom arrangement was installed at the end of 1975 and proved to be highly effective under the ice conditions experienced in the 1975–1976 and 1976–1977 winter seasons.

ISSN:0315-1468    

DOI:10.1139/l77-047

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The organization and bookkeeping routine are described for a basic frontal program which is suitable for frame analysis of large structures using a minimum of computer core capacity and auxiliary storage. This displacement method analysis automatically partitions the stiffness matrix of an idealized structure in a manner similar to substructuring. Space frame, plane frame, grid and truss members can be mixed in one input and the program automatically will take advantage of these modelling assumptions. Joint numbering has no effect on efficiency. However, for an efficient solution, a physical sequence of the members in the structure must be used as the sequence for presenting the idealized members to the solution routine; therefore, the solution can be visualized to progress as a ‘wavefront’ moving through the structure. The analyses of three structures are outlined and the time required for each part of their solution is listed; a maximum of 15% of the solution time was used for frontal bookkeeping. The penalty for using a frontal method rather than a band matrix algorithm is small, if any, because for many problems, the frontal bookkeeping time can be offset by a reduction in the time required for solving the equations.

ISSN:0315-1468    

DOI:10.1139/l77-048

出版商:NRC Research Press    

年代:1977

数据来源: NRC