摘要:

Construction of the Santa Isabel hydro project in central Bolivia was completed in 1973. The project includes a penstock, with the lower half comprising an unusual hyperstatic design with no expansion joints and anchors at alternate bends. The penstock was designed for a static head of 864 m plus 15% waterhammer. It burst when filled with water on March 16th, 1973 at a head of 735 m. Cause of the failure was attributed to an improper weld at an unsupported bend in the hyperstatic section of the penstock. Construction of a second parallel penstock was completed and commissioned in March 1981. This paper describes the work undertaken to guard against a repetition of the 1973 failure, compares the isostatic design (with expansion joints) of the upper half of the penstock with the hyperstatic design of the lower half of the penstock, outlines design procedures, and describes construction methods used for installation of the second penstock.

ISSN:0315-1468    

DOI:10.1139/l82-001

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Precast panel shear walls are investigated for conditions simulating progressive collapse. The latter are simulated by assuming ineffective panels at various levels within the structure. The analysis is performed by an efficient finite element substructuring procedure for both static and seismic loadings, and by a simple rigid-cantilever approximation for static loading only. The principal interest concerns the magnitude and distribution of design forces in vertical and transverse ties which, in the finite element analysis, are modelled by discrete connectors along horizontal and vertical joints. For static loading the results evaluate the accuracy of the simple cantilever design procedure, whereas for seismic loading the magnitude and distribution of connector forces resulting from local panel failure are examined. In particular, it is shown that failure of an exterior panel leads to unexpectedly large concentrations of shear force in the vertical joint, something that is not adequately predicted by the simplified cantilever analysis.

ISSN:0315-1468    

DOI:10.1139/l82-002

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The amount of energy consumed in urban transportation is directly related to the number of vehicle-kilometres of travel. To reduce vehicle travel, strategies are needed to tackle its two components: the number of vehicle trips and their length. This study deals only with the second component.At present, various energy conservation strategies are being studied. The most important of these are: (1) improving the technical efficiency of the automobile by producing cars that are more fuel efficient and encouraging car pools — this can be effective in the short and medium term; (2) improving the urban transit system to increase the public transit modal share — this can also be effective in the short and medium term; (3) planning the urban structure in such a way as to reduce the number of vehicle-kilometres of travel — this can be effective in the longer term.In this study, an attempt is made to channel the growth in employment among the zones of an urban region in such a way as to provide maximum access opportunity with minimum travel requirements. The gravity model is used to simulate the pattern of trips to work and a performance measure is developed to evaluate the overall performance of the urban system. Calgary, Alberta, has been taken as a case study area in this analysis and a computer-aided investigation has been carried out to handle the allocation technique using a method of incremental maximization.The results of the study, when compared with the growth strategy proposed by the City of Calgary Planning Department, indicate that some savings in fuel consumption can be achieved by planning the location of future employment growth.

ISSN:0315-1468    

DOI:10.1139/l82-003

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

An analytical expression was developed to define the incipient drawdown of a thermocline into a submerged intake equipped with a circular cover. The critical discharge at the incipient drawdown was expressed in terms of dimensionless variables defining the thermal structure of the surrounding water body and the geometric properties of the intake structure.The relationship was verified by laboratory experiments and by field data.

ISSN:0315-1468    

DOI:10.1139/l82-004

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A study is made of the accuracy of the static code provisions on torsional effects, with special reference to the National Building Code of Canada of 1977. A uniform frame type monosymmetric 12-story building is used as an example. The static story torque is compared with the dynamic torque computed using the response spectrum technique as outlined in Commentary K of the Code. It has been found that for a building with uniform eccentricity, the static code torque estimate is good if the effect of sympathetic coupled torsional–lateral resonance is small. At the sympathetic coupled resonance, the static code torsional provision underestimates the story torque by a factor of approximately two. Also, it is shown that for buildings with large eccentricities, sympathetic resonance is unlikely to occur and the current Code requirement of doubling the computed torque for design is a very conservative requirement.In addition, the eccentricity expression given in the 1980 Code is used to estimate the story torques for eccentrically set-back buildings and its accuracy is checked with a response spectrum technique. It is concluded that for irregular structures, such as eccentrically set-back buildings, a dynamic analysis is the only reliable procedure for the estimation of the torque loading on the building.

ISSN:0315-1468    

DOI:10.1139/l82-005

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A description of the design and practical application of a new precast concrete building is presented. The system combines two basic structural components: a modular ribbed panel of size 10 × 20 ft (approximately 3 × 6 m) in plan, and a three-dimensional H-shaped module of up to 10 × 40–45 ft (approximately 3 × 12–15 m) in plan and 8–12 ft (approximately 2.4–4 m) in height.It is designed for speedy erection of multistorey buildings. The main feature of the system is the simplicity of connections. Large-size, H-shaped modules are erected by stockpiling them one on top of another with simple bearing connections located at mid-height of the supporting columns or walls. The spaces between module stockpiles are filled with modular ribbed panels. In some areas panels are omitted, thus open spaces are created to accommodate staircases or elevator shafts where required. The panels are simply supported on continuous edge brackets that are formed along the entire perimeter of the modules.This system was used in the design of a large building complex recently erected in Edmonton, Alberta. It combined a four-storey hotel, eight-storey office tower, and covered courtyard, all situated above a two-storey underground parkade.A description of the building, production of modules and panels, erection, and some details of the connections are discussed in the paper.

ISSN:0315-1468    

DOI:10.1139/l82-006

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The direct analysis to determine the transverse distribution of moments in stiffened bridge decks using the differential equation approach becomes laborious, especially in the preliminary design process where several trials are often required to determine the relative dimensions of slab and stiffeners for achieving optimum structural efficiency of the deck. The majority of design charts and tables available to the engineer during the preliminary design process assume absolute dimensions of slab, stiffeners, diaphragms, and their spacing, and thus are more suitable for detail design. This study deals with the development of design charts that express governing parameters in dimensionless form, and with the rapid evaluation of rigidity parameters and critical moments. Such design charts and tables are ideal for carrying out several trial sections to find the most economical structural system during the preliminary design process. The theoretical work is supplemented by a limited experimental programme and good agreements are found.

ISSN:0315-1468    

DOI:10.1139/l82-007

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Theturbulence model has been used to calculate the velocity distributions for a large number of channel flows with different top and bottom boundary roughnesses. The resulting distributions are used to review the standard procedures for stream gauging of ice-covered flows. It is found that the average of the velocities atandof the depth is indeed very nearly equal to the overall mean velocity. Examination of the velocity profiles shows that the profiles deviate from the logarithmic distribution for about 40% of the flow depth. Other flow properties, such as the location of the maximum velocity and the mean velocities in the top and bottom layers, are also examined.

ISSN:0315-1468    

DOI:10.1139/l82-008

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The ultimate strength of reinforced masonry compression members subjected to axial or eccentric vertical loads is the main concern of the paper. As an initial step, the literature is reviewed so as to arrive at reasonable assumptions relating to the stress–strain properties of the material; these are necessary to define the load–moment interaction curve for a short column or wall. A method that can account for the weakening effect of slenderness is also discussed. These two fundamental components of the procedure are then judged relative to experimental test data. Axially loaded walls are modelled quite well but the theory is conservative for walls tested eccentrically. Although the inclusion of a strain gradient factor and consideration of nonlinear behaviour would improve analytical predictions for the latter case, these extra factors are not applied to the results due to a lack of definitive knowledge relating to the latter.

ISSN:0315-1468    

DOI:10.1139/l82-009

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The paper describes a design method for structures consisting of a heavily loaded masonry wall supported by a steel beam, taking account of the composite tied-arch behaviour of the wall and beam. The design approach is based on the assumption of triangular distributions of vertical stress at the wall–beam interface, the length of the distributions being a function of the beam-to-wall relative stiffness. In the design method the beam flexural stiffness is calculated to give an adequate distribution of the interface stress so that the maximum stress in the wall does not exceed allowable limits. The beam is also designed with flexural and shear strengths sufficient to resist the bending moment, tie force, and shear forees applied by the normal and shear interface loadings. Experimental evidence is cited to support the assumptions and the resulting design method.

ISSN:0315-1468    

DOI:10.1139/l82-010

出版商:NRC Research Press    

年代:1982

数据来源: NRC