摘要:

It is shown in this article that neural networks can be used to predict wind pressure profile for a structure, provided that informative experimental data are initially available to train the network. Utilizing this technique, wind load profiles are obtained for various cylindrical and spherical air-supported membrane structures. The experimental results obtained by the authors have been used as the training set for the network to recognize the pattern. This method can be very effectively applied to other similar problems.Key words: neural network, wind pressure, structures, air-supported, cylindrical, spherical.

ISSN:0315-1468    

DOI:10.1139/l95-053

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This paper concerns the incorporation of steel fibres in singly reinforced high strength concrete beams without stirrups failing under the combined effect of flexure and shear. A new equation for predicting the shear strength of reinforced high strength concrete beams is developed. This equation shows a good correlation with own test data of 16 reinforced high strength concrete beams with and without steel fibres and numerous published experimental data for beams with concrete compressive strength up to 140 MPa. The flexural capacity of reinforced high strength concrete beams is also investigated. The existing ACI method for predicting the flexural strength of steel fibre concrete composites is slightly modified to be applicable for high strength concrete. Based on the proposed equations, an analytical model is developed for predicting the relative flexural capacity, i.e., the ratio of the moment with shear interaction to the pure flexural moment.Key words: high strength concrete, steel fibre, shear strength, flexural strength, stirrups, web reinforcement.

ISSN:0315-1468    

DOI:10.1139/l95-054

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Lightweight floors for residential or commercial applications may exhibit annoying levels of vibration under occupancy loading. This paper presents an experimental and analytical study of the vibrational response of wood floors to impact produced by occupants. The results show that, for the analysis of this type of floors, it is necessary to consider the coupled dynamical system of floor and occupants. It is also shown that occupants may be modelled with simple oscillators, and that the dynamic analysis of the coupled system can produce close agreement with tests. Acceptability criteria are used to study design guidelines, combining the variability in floor stiffness with the variability in human tolerance to vibrations. Floors considered use 2 × 8 SPF joists and I-joists.Key words: vibrations, serviceability, occupancy loads, wood floors, reliability.

ISSN:0315-1468    

DOI:10.1139/l95-055

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Capping of contaminated sediment with clean granular material is a commonly used mitigative measure. The capping material is often dispersed from the end of a pipeline or dumped down a chute. Such methods require special equipment that is sometimes costly. The possibility of using a hopper barge to place the material was thus explored. Laboratory tests were conducted to study bottom distribution of granular material placed in this way. Distribution is determined at the moment of impact. To identify the mechanisms at work at the moment of impact, tests were conducted with different bottom slopes. Experimental results indicate that distribution of the granular material can be described by the turbulence created by an impinging jet. This turbulence is estimated, using a digital model, the results described in a second paper.Key words: dredging, capping, seacoast.[Journal translation]

ISSN:0315-1468    

DOI:10.1139/l95-056

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The capping of contaminated sediments is a way to isolate them. From experimental results presented in the previous article, and with an impinging jet model, the formation of the mound at the bottom and the risks of resuspension associated with the disposal operations are predicted.Key words: dredging, capping, impinging jet.

ISSN:0315-1468    

DOI:10.1139/l95-057

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Because of the difficulties in applying current earthquake requirements in the National Building Code of Canada to existing buildings, a document "Guidelines for the seismic evaluation of existing buildings" has been developed to provide alternative criteria. The Guidelines are based primarily on similar U.S. documents with changes to suit Canadian seismicity and practice. The basis of the document is earthquake damage experience as it relates to life safety, and the methodology is based on the identification of deficiencies of the building from a master list known from earthquake experience to result in life-threatening failures. Potential deficiencies are checked against evaluation criteria which are based on the NBC/CSA seismic limit states design using a load reduction factor of 0.6. The paper provides a background on those features which differ substantially from the NBC requirements.Key words: existing buildings, seismic evaluation, procedure, criteria.

ISSN:0315-1468    

DOI:10.1139/l95-058

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The foundation failure of a small earth dam, 4.1 m in height, has created a large breach through the overburden foundation, down to the bedrock, and has produced the complete loss of the Beloeil Lake reservoir. The geological nature of the dam foundation was complex; its resistance to internal erosion has changed with time due to seepage forces. The design of the dam foundation treatment was marginal. In this paper, the conditions of the dam prior to failure are given, the probable causes of the accident are presented, and the environmental consequences are reported. Such a case history of a dam failure illustrates the necessity to have a thorough knowledge of the foundation conditions of existing dams even for a very small water retaining structure. That accident demonstrates also the need for a continuous and effective surveillance program. Damages consist mainly in overburden erosion and sediment transportation through a remote area without any loss of human life.Key words: earth dam, foundation, failure, environment, rehabilitation, dam safety, surveillance.

ISSN:0315-1468    

DOI:10.1139/l95-059

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Canadian codes allow the design of concrete deck slabs of slab-on-girder bridges by taking account of the internal arching action that develops in these slabs under concentrated wheel loads in particular. Provided that certain prescribed conditions are met, a deck slab is deemed to have met the design criteria if it is provided with a top and a bottom layer of steel reinforcement with each layer consisting of an orthogonal mesh of steel bars in which the area of cross section of the bars in each direction is at least 0.3% of the effective area of cross section of the deck slab. For deck slabs of bridges having skew angles greater than 20°, the codes require the minimum amount of reinforcement to be doubled in the end zones near the skew supports. Model testing has shown that need for such an increase can be eliminated by providing composite end diaphragms with high flexural rigidity in the horizontal plane. The proposed concept is tested on a model of fibre-reinforced concrete deck without steel reinforcement in which deficiencies in the confinement of the deck slab readily manifest themselves in form of a bending, rather than punching shear, failure.Key words: highway bridges, bridge decks, deck slabs, skew deck, skew bridges, fibre-reinforced concrete decks.

ISSN:0315-1468    

DOI:10.1139/l95-060

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The effect of ammonia loading and operating temperature on the treatment of high ammonia, methanogenic, landfill leachate was investigated. Two single-sludge, nitrification–predenitrification systems were operated in parallel: one with a 10-day aerobic solids retention time, and the other with a 20-day aerobic solids retention time. The study consisted of two phases: an ammonia loading phase and a cold temperature phase. From the first phase, it was found that, at an influent leachate ammonia level of up to 1500 mg N/L, both systems produced an effluent of < 1 mg NH4-N/L and approximately 170 mg NOx−-N/L. Aerobic nitrite and anoxic "free" ammonia were both observed to increase as the ammonia loading was increased. When the influent ammonia was raised from 1500 to 2000 mg N/L, nitrification in both systems failed. During the second phase, the temperature was decreased from 20 to 10 °C while maintaining the leachate ammonia level at 1500 mg N/L. Aerobic nitrite accumulation and rising aerobic BOD5were observed to begin at 14 °C. When the temperature was dropped from 12 to 10 °C, nitrification failed in both systems. In both cases, nitrification was re-established at 10 °C, by ceasing to waste solids and by stopping methanol addition.Key words: ammonia, biological, denitrification, landfill, leachate, nitrification, temperature, treatment.

ISSN:0315-1468    

DOI:10.1139/l95-061

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

It is common practice in most Canadian provinces to permit right turns on red at signalized intersections. At intersections with a high volume of pedestrian traffic, the opportunity to turn right on red may be critical to satisfy right turn demand. However, in order to properly time the traffic control signal display at a signalized intersection, the saturation flow rates for each lane or lane group of the intersection must be known. Six signalized intersections were studied in Kingston, Ontario, where saturation flow rates for right turns were measured as a function of conflicting through traffic. From these measurements, estimations of the gap size required for a right turn movement were made. A regression analysis resulted in the production of a simple equation for estimating right turn on red saturation flow rates. It was found that the gap acceptance behaviour of drivers varied both spatially and temporally.Key words: saturation flow rates, signalized intersections, capacity, gap acceptance.

ISSN:0315-1468    

DOI:10.1139/l95-062

出版商:NRC Research Press    

年代:1995

数据来源: NRC