摘要:

The beam–column interaction equations of the Canadian Standards Association Standard CAN3-S16.1-M84 "Steel structures for buildings — limit states design" are reviewed and areas of concern in the formulations are addressed. The interaction equations developed for the 1989 edition of the standard, CAN3-S16.1-M89 "Limit states design of steel structures," and the methods of dealing with the areas of concern in the previous standard are presented. The new standard requires that at least an approximate second-order geometric analysis be carried out. For frames dependent on the frame stiffness for lateral stability, no longer is the traditional method, using effective length factors greater than one, allowed. Unlike the current American Institute of Steel Construction "Load and resistance factor design'' (AISC LRFD) specification, two sets of interaction equations, one for in-plane member strength and the other for out-of-plane stability, are used. This results in considerably less unnecessary conservatism. In both sets of interaction equations, the component of the moment due to translation is increased by the second-order effects. The "double ω" problem has been resolved and the minimum sway effects for the gravity loading case have been increased substantially to guard against sidesway buckling. A design example using the new standard is given. By means of a series of analytical examples, the requirements of S16.1-M89 are compared with the traditional method of S16.1-M84. For frames with direct-acting bracing, S16.1-M89 gives interaction values about 1.15 times those of the previous standard with a coefficient of variation of 0.08, while for unbraced frames the corresponding values are 0.98 and 0.07. The S16.1-M89 values reflecting greater rigor in a number of areas are considered the more valid. The S16.1-M89 standard would give comparable results to the AISC LRFD specification for class 1 sections when out-of-plane behaviour governs. The latter specification does not specifically cover cross-sectional strength and in-plane behaviour as does S16.1-M89.Key words: beam–column, stability, strength, bending, compression, standards.

ISSN:0315-1468    

DOI:10.1139/l90-100

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

During periods of rain, combined sewer systems carry urban runoff water to sewage works. Urban runoff water is different, however, from household wastewater — the usual influent of wastewater treatment systems — especially the flow and the concentrations of suspended solids and metals. The purpose of the research described herein was to examine potential effects of runoff water on a treatment system to find out if major damage to the system is likely to result from input of urban runoff. The literature on urban runoff and on qualitative, toxic, quantitative, and hydraulic shocks was reviewed, and the knowledge gained was applied to a case study based on real data collected from metropolitan Quebec City (Canada) in June 1985. Experimental data indicate that the recorded variations in flow and in quantities of suspended solids, organic matter, and nutrients in the combined system following various rain events would not dramatically affect operation of a wastewater treatment system. The same conclusion applies for the increase in concentrations of copper and zinc. Further research on qualitative shock and the impact of the increase in the concentration of lead is required.Key words: biological treatment, waste waters, quality, concentration, rainfall, urban runoff waters, shock loads, toxics. [Journal translation]

ISSN:0315-1468    

DOI:10.1139/l90-101

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A new nondestructive test for estimating the compressive strength of concrete and mortar at early ages is described in this paper. The pin penetration test was used to relate the early age strength of hardened concrete and mortar in the laboratory. It was found that the pin penetration tester can be used successfully, under laboratory conditions, to determine the compressive strength of concrete cylinders and mortar slabs at early age from 10 hours up to 28 days. For concrete and mortar cylinders, slabs, and cubes with a compressive strength of up to 27.6 MPa (4000 psi), the pin penetration readings were found to be linearly related to the compressive strength. The tester was also used successfully in the field to determine the compressive strength of a concrete floor slab in a new building in order to post-tension the strands and remove the forms. The building was constructed in winter under severe climatic conditions.Key words: early age, strength evaluation, concrete slabs, form removal, nondestructive tests, mortar testing, pin penetration test.

ISSN:0315-1468    

DOI:10.1139/l90-102

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A study was conducted to evaluate the effect of gauge length on the short-term performance of visually graded Select Structural and No. 2 kiln-dried nominal 38 × 89 mm spruce-pine-fir lumber in tension parallel-to-grain. The short-term tensile strength properties of three groups of lumber, matched for modulus of elasticity and having gauge lengths of 2642, 3683, 4877 mm, were obtained from test results where the effect of gauge length was isolated from the effect of grade. The performance of the lumber was evaluated by first-order second-moment reliability analyses. In the analyses, the lumber was treated as single tension members under uniform tensile stress along the member length, undergoing snow load conditions at various locations in Canada. The results indicate that the performance factor for Select Structural spruce-pine-fir lumber in tension parallel-to-grain should be multiplied by a factor of 0.92 to adjust for doubling the length from 2500 to 5000 mm to achieve a common reliability index of 3.0. The effect of doubling the length from 2500 to 5000 mm on the performance of No. 2 spruce-pine-fir lumber appears to be negligible.Key words: length effect, tensile strength, lumber, performance factor, reliability index.

ISSN:0315-1468    

DOI:10.1139/l90-103

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

This paper presents the results of an experimental study on the development of a simple yet efficient technique allowing for the long-term measurements of strains and stresses in working concrete dams. The proposed technique consists of installing a cylindrical concrete inclusion instrumented with vibrating wire gauges embedded into the concrete. The 140-mm cylinder is slipped into a 152 mm diameter hole, which is drilled into the dam and then filled with cement grout. This technique, which was tested in the laboratory on instrumented concrete blocks, has shown that it is now possible to measure the deformation variations in a working dam. The inclusion can be instrumented for both bidimensional and tridimensional cases. The volume of the cylinder makes room for a sufficient number (4–8) of vibrating wire gauges. Moreover, during the drilling process, the technique of overcoring makes it possible to determine the initial total stresses. This technique can also be used to instrument heavily loaded rock structures such as mine pillars or underground gallery walls. Current observations show that this technique, contrary to plastic inclusions, can be considered appropriate for permanent structures.Key words: vibrating wire gauges, strain gauges, instrumentation, strain measurements, long term, concrete dams, rock slopes, rock pillars, mines, underground excavations.

ISSN:0315-1468    

DOI:10.1139/l90-104

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Spreadsheets are among the most common microcomputer programs used by engineers because they provide an easy means of formulating equations in algebraic format. By introducing appropriate stiffness equations with numerical values representative of material properties, boundary conditions, and loading, spreadsheet templates can be developed to model specific structural systems. These equations are mutually dependent and may be solved using the iteration techniques that are part of the spreadsheet program. A common structural problem that is difficult to solve without a special computer program is the analysis of a slab arbitrarily supported on elastic beams and columns. The use of readily available spreadsheet programs to solve this problem is demonstrated. Equations for slab bending and for beams with finite flexural and torsional stiffnesses are derived using finite difference operators. These equations are then recast into a form more convenient for an iterative solution. The use of these equations is demonstrated with numerical examples.Key words: analysis, convergence criteria, deflections, finite difference, plates, spreadsheets.

ISSN:0315-1468    

DOI:10.1139/l90-105

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Timber bridges are still commonly used by several North American railroads. For short spans, they offer an attractive alternative to other types of bridges, as they are economical, faster to construct, and easy to maintain. Current design practices do not allow an independent consideration of the effects of the dynamic loads in sizing the bridge components, because very little information is available on the subject. Dynamic tests were carried out at two timber railroad bridge sites under the passage of trains at speeds varying from crawl, i.e., 1.6 km/h (1 mph), to 80.5 km/h (50 mph). The loads at wheel–rail interfaces, the vertical displacements, and the accelerations were measured at several locations on the bridge spans, the bridge approaches, and the normal track sections. The maximum values of the dynamic load factors obtained were 1.50, 1.65, and 1.85 for bridge, bridge approach, and normal track, respectively; and the corresponding maximum values of the dynamic displacement factors obtained were 1.30, 1.00, and 1.20. The main objective of this paper is to describe the experimental work and the influence on the measured values of the train speed and other factors.Key words: railroad, timber, bridge, wheel–rail interfaces, load, deflection, frequency, load factor, dynamic displacement, track modulus.

ISSN:0315-1468    

DOI:10.1139/l90-106

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

In the 1970s, it was reported that there were approximately 3700 track kilometers of timber railroad bridges in the United States and Canada. For short spans, they offer an attractive alternative to other types of bridges, as they are economical, faster to construct, and easy to maintain. Current design practices do not allow an independent consideration of the effects of the dynamic loads in sizing the bridge components, because very little information is available on the subject. Dynamic tests were carried out in 1986 on timber bridge spans at two test sites using test trains consisting of a locomotive unit, two loaded hopper cars, and a caboose. This paper gives a brief description of the analytical approach employed for determining the dynamic response of timber bridge spans under railway vehicles travelling at a constant speed. The model comprises a multi-degree-of-freedom system with each vehicle having bounce, pitch, and roll movements. Two parallel chords, each having its distributed mass lumped at discrete points, were used to idealize the bridge spans. A computer program developed on this basis was used to predict the loads at the wheel–rail interfaces and the vertical displacements at the discrete points on the spans. The predicted loads at wheel–rail interfaces and the maximum vertical displacements were found to be in agreement within about 20% and 16% respectively of the measured values. The program was utilized to study the effect of speed and other factors on the dynamic response of open-deck and ballast-deck bridges.Key words: analytical approach, timber railway bridge, railway locomotive and cars, constant speed, wheel–rail interface, loads, displacements, accelerations, dynamic response.

ISSN:0315-1468    

DOI:10.1139/l90-107

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A geographic information system (GIS) supporting a flood hydrograph prediction software package is described. The hydrograph prediction method is based on the convolution of excess rainfall with a synthetic unit hydrograph, derived by the Soil Conservation Service runoff curve number and a regional dimensionless unit hydrograph method, respectively. The GIS uses a raster method to store the following data: land use and land cover, soil type, rainfall intensity–frequency–duration statistics, runoff curve numbers (CN), regional dimensionless unit hydrograph, and regional lag-time relationship. The GIS has also the capability of computing a number of watershed and hydrologic parameters required for predictions, such as a watershed average rainfall and CN value, area, centroid, stream length, etc. Most of the data for such computations are input from a digitizer. Substantial time and cost savings are possible once the data base has been created. Application of the system is illustrated by an example of predicting flood frequency curves for selected watersheds in Alberta's Rocky Mountain foothills.Key words: geographic information system, flood hydrograph, curve number, hydrologic simulation, flood frequency.

ISSN:0315-1468    

DOI:10.1139/l90-108

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The standard CAN3-S16.1-M84 "Steel structures for buildings — limit states design" recognizes three sets of assumptions in the analysis, design, and construction of steel buildings. In two of them the connections are assumed to be either fully rigid (continuous construction, clause 8.2) or completely free (simple construction, clause 8.3.1). In the third type of construction, termed here as "special simple construction" (clause 8.3.2), the beam-to-column connections are assumed to be completely free (pinned) to resist gravity loads and are assumed to be rigid to resist the lateral loads due to earthquake or wind. Such connnections are designed for moments due to lateral loads only, and thus they are more flexible and may yield at ultimate load levels. This paper illustrates the analysis and design of two (one 5-storey and the other 10-storey) office buildings assumed to be located in Hamilton, Ontario, on the basis of special simple construction. Using realistic connection behaviour, the influence of connection flexibility and strength on the performance of these buildings is studied. In the nonlinear static analysis, the buildings have been subjected to gravity loads and incremental lateral loads until failure. For comparison purposes, the building frames were also analysed and designed, based on continuous construction assumptions. The results showed increased drifts and decreased overall strength due to connection flexibility and strength. Thus, the system based on continuous construction structurally performs better than the system based on special simple construciton. As far as the economy is concerned both systems appear to be equivalent.Key words: building design, steel structures, flexible connections, analysis, wind load, earthquake load, strength.

ISSN:0315-1468    

DOI:10.1139/l90-109

出版商:NRC Research Press    

年代:1990

数据来源: NRC