摘要:

An experimental program, exploratory in nature, has been carried out to investigate the effect of interface gap on the load–slip behaviour of joints fabricated with multiple nails. In total, 320 joint specimens have been tested. Modification factors are developed to account for the effects of number of nails and interface gap on the overall load-carrying capacity of joints with multiple nails. The current practice for the design of nailed joints is that a joint fastened together with multiple nails in a row, regardless of the interface characteristics of that joint, carries lateral load equal to the product of the lateral-load capacity of the corresponding joint with a single nail and the number of nails in a row of the joint. The findings of this investigation indicate this practice to be somewhat of an overestimation of the overall capacity of the joint.Key words: design, interface gap, interface friction, joint slip, loads (forces), modification factors, multiple fasteners, nailed joints, stiffness, structural engineering, tests, timber construction.

ISSN:0315-1468    

DOI:10.1139/l85-011

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The results of the full-scale testing, previously carried out, of 75 light wood trusses are analysed to evaluate their compliance with strength and serviceability requirements. Size effects were studied considering span length and chord size. Test data were grouped into 15 case studies according to span lengths, chord size, and mode of failure. For the study of a strength limit state, the safety index, β, was calculated for a range of values of the ratio of maximum lifetime to nominal snow load. For the study of a serviceability limit state, the safety index was calculated for a range of values of allowable mid-span deflection as a function of the span. A size effect was observed for both span length and chord size. Short-span trusses with small chords exhibited acceptable levels of safety when their strength safety index is compared with recommended target values. Long-span trusses with large chords, with an improved heel joint detail, exhibited values of β slightly below target values. All trusses showed acceptable levels for the safety index for the serviceability limit state.Key words: safety index, serviceability, size effect, strength, structural reliability, wood trusses.

ISSN:0315-1468    

DOI:10.1139/l85-012

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

This paper presents the results of an experimental investigation on the behaviour of steel column base connections. The connection is effected by means of a steel base plate welded to the lower end of the column and attached to the concrete footing with two or four anchor bolts. The testing program comprised 15 specimens. The measured moment–rotation curves were used to determine the fixity factors of the base connections, taking into account the presence of an axial compression load.The results indicate that the compression force in the column significantly increases the flexural stiffness of the base connection and that the rotational restraint offered by the column base is sufficient to be considered in design. The results also show that the method of analysis used to determine the ultimate moment capacity of the base connection is conservative.Key words: steel column, column base connection, moment–rotation curve, anchor bolt, flexibility factor, fixity factor.

ISSN:0315-1468    

DOI:10.1139/l85-013

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Maximum pressure head drops and rises resulting from pump failure and subsequent check valve closure are calculated and plotted for a simple pump discharge line at pump end, midpoint, and three-quarter point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, and pump inertia constant are accounted for in the analyses. Computer studies indicate that pipe friction, pipeline constant, and pump inertia have a major effect on pressure head drops and rises.Studies indicate further that whereas for large pump inertia the pressure head rise or drop at the midpoint is only moderately larger than one-half of the rise or drop at pump end, for small pump inertia this difference is much greater. For very small pump inertia, the pressure head drop or rise at midpoint approaches the values at pump end. This increase in pressure head drop and rise for very small pump inertia is even more pronounced at the three-quarter point.

ISSN:0315-1468    

DOI:10.1139/l85-014

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The nearly 100 year record of spring flood peaks on the Red River at Winnipeg, Manitoba, shows a clustering of high annual peak flows that is possibly, but not likely, due to chance. A similar degree of clustering has been observed in other long-term geophysical records. It can be measured by means of the Hurst statistic. Clustering increases the uncertainty in the parameters of the probability distribution of peak flows estimated from the record. As such it profoundly affects the weight that must be given to the unusually high historical floods that preceded the period of record, in particular the 1826 and the 1852 floods. Incorporating this historical information in the probability analysis requires a time series model that tends to produce the appropriate degree of clustering. A fractional noise model was adopted for this purpose. Bayes' theorem was then used to update the distribution parameters, obtained from the record, with the additional information about the historical floods. The result shows the flood risk to the City of Winnipeg and the Red River Valley to be substantially higher than was estimated by conventional methods that assume serial independence of the peak flows.Key words: Red River floods, flood risk, historical floods, Hurst phenomenon, fractional noise, Bayesian probability distribution, Bayesian updating, time series.

ISSN:0315-1468    

DOI:10.1139/l85-015

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Improving the fatigue strength of welded joints may be economically interesting in many situations, especially in those cases where high-strength steels are used. However, widespread use of a method is, in many cases, restricted by a lack of knowledge of its reliability. Previous work has focused only on the effectiveness of improvement methods to increase fatigue strength; cost studies and quality control instructions are rarely given.In this report, several methods for structural steel are summarized. A review of existing test results shows that improved connections made from a high yield strength steel reveal a higher percentage improvement than mild steel connections using the same improvement method. In addition, improved joints may be sensitive to the applied stress ratio. Finally, the most efficient method depends on the type of welded joint.Residual stress methods have relatively inexpensive application costs whereas some grinding methods are very costly. Quality control depends upon fabrication, loading, and environmental conditions. Examination of four types of fillet-welded joints has identified several methods that require further research. A three-dimensional finite element study of these joints predicts that at crack locations, under service loading, a very small plastic zone is formed. Therefore, residual stress methods may remain effective under variable-amplitude load conditions.Key words: structural steel, welded joints, fatigue, improvement methods, fillet welds, finite element analysis.

ISSN:0315-1468    

DOI:10.1139/l85-016

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The renovation or replacement of existing steel bridges in North America is a topic of increasing importance. Because most older structures used riveted connections, rather than the bolted or welded connections that are common today, information on the fatigue life of riveted connections is required for a proper evaluation of the structure.The study reported herein provides a summary and evaluation of the existing data on the fatigue strength of riveted connections, and reports on the results of fatigue tests on some highway bridge members taken from service. Fatigue tests were also carried out on new material containing unfilled holes, both as a reference for riveted connections (rivets with zero clamping force) and with respect to new work in which misplaced holes might be present. The beneficial effect of filling misplaced holes with high-strength bolts is noted.Key words: bolts, failure, fatigue, holes, steels.

ISSN:0315-1468    

DOI:10.1139/l85-017

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The impact of alternative subdivision standards on the design of stormwater management systems is explored with a view toward quantifying such impacts. The combined drainage flow (piped plus overland) for reduced standards (e.g. smaller lot sizes, road widths) for the ease study analyzed is shown to be comparable to the flow emanating from a conventional design standards system, in terms of both peak flow and total volume, and the quality of the drainage water from the reduced standards system is acceptable. A comparison of stormwater-related cost savings shows that the "per lot" costs for the reduced standards system are approximately 50–70% of those associated with the conventional designs.Key words: stormwater management, subdivision design, storm sewers.

ISSN:0315-1468    

DOI:10.1139/l85-018

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The dynamic response of a guyed tower to irregular waves has been studied by the finite element method. Hydrodynamic interaction is taken into account by the added water mass concept, and the fundamental frequencies are determined using (i) a lumped-parameter two-dimensional beam model and (ii) a three-dimensional truss finite element model. The effect of the mooring guy lines is simulated using one-dimensional boundary elements. The example structure analyzed is the Exxon test guyed tower erected in water of 89.3 m depth in the Gulf of Mexico. The measured wave height – time history reported by Exxon is used to determine the wave forces. Irregular wave forces are computed using the linearized Morison's equation. The nonlinearity of the mooring system is computed using an iterative technique in which the cable configuration is corrected using successive solutions. The tower response in terms of offset-time history to wave forces is determined for both linear and nonlinear cable behaviour. The computed frequencies and the responses agree reasonably well with the available measured values.Key words: guyed tower, irregular wave forces, linear and nonlinear mooring cable stiffness, dynamic response.

ISSN:0315-1468    

DOI:10.1139/l85-019

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The design of prestressed concrete bridges using standard CPCI (Canadian Prestressed Concrete Institute) girders is generally done by trial and error, requiring extensive computation. This study will use a linear programming mathematical model to establish preliminary design charts for such cases and to obtain the required prestressing force after losses for a given CPCI bridge interior girder with different spans and spacings. The bridge is designed to carry the MS200-77 loading, and the design conforms with the Canadian Standards Association CAN3-S6-M79 for design of highway bridges. The bridge considered is single-span, with a castin situconcrete deck acting compositely with the prestressed girders under live load. The linear programming model is also used to determine the design criteria that will control the design for the cases investigated, and to perform the parametric study to evaluate the effect of variations in deck thickness, girder concrete strength, and prestressing losses on the value of the required prestressing force.Key words: bending moment, concrete, girders, highway bridges, linear programming, load, prestressing, span.

ISSN:0315-1468    

DOI:10.1139/l85-020

出版商:NRC Research Press    

年代:1985

数据来源: NRC