摘要:

Major waste products from fertilizer manufacture are calcine and so-called phosphogypsum, calcium sulphate. The oxidation and leaching of calcine produces a liquid with a high acidity and hence is acid generating. Disposal of phosphogypsum, an acid-bearing waste, is normally effected by construction of a tailings impoundment, similar in nature to those utilized for tailings disposal in the mining industry.This paper addresses the general chemistry, pollution potential, and chemical attack potential of both calcine and phosphogypsum and the impact these have on their disposal. The similarities and differences in the design philosophy for acid-bearing and acid-generating waste facilities are then discussed.Key words: phosphogypsum, acid sludge, fertilizer manufacture, water pollution, waste disposal, calcine, sulphuric acid manufacture.

ISSN:0315-1468    

DOI:10.1139/l87-001

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The comparison of measured dynamic characteristics or response of large structures with that of an appropriate finite element model with all its underlying assumptions often reveals discrepancies. This may be due to improperly determined parameters, such as interstory stiffness, mass of different stories, and the modulus of elasticity of the concrete, as well as the inadequacies of the model.The measured dynamic response generally occurs in one of three forms: time response, frequency response, and modal data. For time response data, either in free vibration or for a known input, parameters are estimated by proper adjustments to match more closely the measured motion. For steady-state frequency response, a sinusoidal load (or synchronized loads) is input mechanically and the response, both in amplitude and in phase, is measured for different frequencies of excitation. Damped resonant frequencies, the associated modal damping ratios, and the corresponding mode shapes are the measured quantities for modal data.The finite element models used for civil engineering structures often incorporate a large number of degrees of freedom. Measured response is sparse and usually limited to the lower frequency range. A procedure for estimating these parameters must be able to allow for the small amount of data and must utilize efficient numerical algorithms to determine the best parameters. Nonlinear least squares, within a Bayesian framework, is such a method. It can be applied to time-history data, steady-state response, and modal characteristics. This method is used to determine aerodynamic coefficients of a scale model of a suspension bridge deck from free response data in a wind tunnel, stiffness parameters from frequency measurements of a 5-story steel building frame loaded by mechanical exciters on the roof, and stiffness parameters from modal data of a 12-story reinforced concrete frame, as obtained from transient wind observation of lateral accelerations.

ISSN:0315-1468    

DOI:10.1139/l87-002

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A full-scale load test to failure of a 34-year-old three-span continuous reinforced concrete highway bridge located in southern Alberta is described. The opportunity to load test the structure to failure occurred as a result of the scheduled demolition of the bridge.Load was applied to the structure in two phases. In the first phase, precast concrete sections were placed at the centre of the middle span until a load of approximately 1900 kN was reached. At this load level a mid-span deflection of 28 mm was measured for the interior span. Additional load was applied by jacking the ends of the bridge at the abutment supports. Loading continued until a maximum deflection of 157 mm was reached at mid-span. Significant cracking as well as crushing of the compression flange at mid-span were evident. On removal of load at mid-span, a residual deflection of 118 mm was observed indicating that the bridge had been loaded well into the postyield range without collapsing.Results of the test are presented in the form of plots of load vs. deflection, reactions vs. deflection, mid-span moment vs. deflection, and deflection profiles at various loading stages. In addition the calculated flexural capacity is compared with measured values.Key words: highway bridge, load test, reinforced concrete.

ISSN:0315-1468    

DOI:10.1139/l87-003

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A case study is presented describing the sump model test of a wet well in an existing sewage pumping station at the Regional Municipality of Ottawa–Carleton Green Creek Pollution Control Centre in Ottawa, Ontario. The purpose of the test was to determine whether the existing sump could accommodate projected flow increases of up to 83% associated with the proposed expansion of the plant. It was anticipated that the (low increases could cause the formation of localized flow disturbances such as vortices and eddies, which might induce unacceptable cavitation and (or) vibrations in the proposed new larger pumps. The sump model was constructed entirely of Plexiglas to facilitate flow visualization enhanced by a dye tracer. Of particular interest was the use of a laser Doppler anemometer to measure velocity distributions at critical locations such as the pump intakes. This provided a significant improvement in accuracy and convenience over more conventional velocity-recording devices such as a pitot tube or hot-wire anemometer. The methodology and considerations in the selection of the model scale are described.Key words: model, sump, similitude, vortices, pumps.

ISSN:0315-1468    

DOI:10.1139/l87-004

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Historically, sewage treatment in Sweden shows a development towards the construction and use of package plants. These package plants, however, present several problems associated with flow and temperature.Year-long studies of chemical precipitation using slaked lime in stabilization ponds have demonstrated an overall reduction of organic matter (as COD (chemical oxygen demand)) of about 75% to a level somewhat below 100 mg/L, and a reduction of total phosphorus of 90% to approximately 0.7 mg/L as P. These values were reached under ordinary operating plant conditions. No efforts to optimize the process were made. Chemical precipitation treatment using slaked lime has shown good bacterial reduction at the high pH values obtained.Two tracer studies using Rhodamine B dye have demonstrated the appearance of strong short-circuiting flows in pond systems and the inserting of simple baffle walls in the pond has been recommended. Dewatering the sludge in the ponds by natural freezing has proven to be an excellent process, as the time for collecting sludge can be chosen almost arbitrarily during the year.The lack of design guidelines, especially with respect to detention time, is rather obvious. The conventionally used design criteria for pond surface area design have proven to be inadequate.Key words: sewage treatment, stabilization ponds, chemical precipitation, phosphorus removal, tracer, sludge treatment.

ISSN:0315-1468    

DOI:10.1139/l87-005

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Many inspections of the pavements of orthotropic steel bridge decks show longitudinal cracks above the connections of the deck plate to the main girders and ribs. By using a simplified model for analysing the behaviour of the pavement and comparing the theoretical results with damage records, the ultimate resistance of the pavement is defined, and minimum stiffness requirements for orthotropic decks are derived. These serviceability limit states have been included in a recent draft of the German steel road–bridge code DIN 18809.Theoretical studies of the material behaviour lead to proposals for the minimum strength requirements for bituminous pavements, which may be used in conjunction with the results of material tests. This procedure will improve the strength design of bituminous bridge pavements.Key words: bitumen, bridge decks, composite structures, design criteria, durability, limit design method, orthotropic plates, pavements, serviceability limits, specifications, steel.

ISSN:0315-1468    

DOI:10.1139/l87-006

出版商:NRC Research Press    

年代:1987

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 purpose of the study was to determine the value of the rigidity ratio at the column base (GL). The connection is made of a steel base plate welded to the lower end of the column and attached to the footing by means of two or four anchor bolts. It is generally admitted that this type of connection behaves like a hinge and it is recommended to useGL = 10.0 to evaluate the effective length factor of the column.The test results indicate that for weak-axis buckling a conservative value of the rigidity ratio is GLY = 0.50 and for strong-axis bucklingGLX = 1.50, if there is no relative displacement of column ends. The effective length of the column is therefore reduced. A design example shows that the column strength is increased by approximately 30% for slenderness ratios currently met in practice.Key words: steel column, column base connection, moment–rotation curve, buckling.

ISSN:0315-1468    

DOI:10.1139/l87-007

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Studies have shown that the MS-200 loading model in the Canadian Standards Association standard CAN3-S6-M78 for design of highway bridges no longer represents modern-day heavy trucks in Canada. For the new edition of the CSA-S6 code, based on the limit states philosophy, a new loading-truck model was developed based on the Council of Ministers' loading, which is the legal load limit for interprovincial transportation in Canada. The loading model, designated as the "CS-Wloading truck," provides the flexibility to adopt a multiple-level loading system appropriate to various jurisdictions.The live-load factor was determined from a statistical approach using data from a truck survey conducted across Canada in seven provinces. Responses in simple-span bridges were determined by running one or more trucks from the survey across the bridge. Based on this study, a live-load factor of 1.60 was determined and CS-600, with a gross weight of 600 kN, was selected as the standard load level. As well, the validity of the truck model and the live-load factors were checked for continuous-span bridges.Key words: highway bridges, design loads, codes and standards, live-load models, load factors, load surveys, vehicle weight regulations.

ISSN:0315-1468    

DOI:10.1139/l87-008

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The importance of beam-to-column connections in determining the load–deformation behaviour of steel building frames has been recognized for more than 70 years. Yet steel design specifications, including Canadian Standard Association standard CAN3-S16.1-M84, still mandate that connections be treated as either "pinned" or "rigid," and prescribe approximate design assumptions accordingly. Structural analysis procedures and tools exist that can account adequately for connection behaviour. What is not complete is the knowledge of the force–deformation behaviour of the various connection types.In this paper, what is known of the force–deformation behaviour of the commonly used connection types is described. The factors influencing that behaviour are outlined. Procedures for modelling connection behaviour and for incorporating it into structural analysis computer programs are described. The effects of connections on the behaviour of the overall structure are described and illustrated with examples. Finally, the areas where additional research is needed are discussed.Key words: connections, steel, structural analysis, columns, semirigid design.

ISSN:0315-1468    

DOI:10.1139/l87-009

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

An emphasis is placed on the importance of understanding the processes responsible for resistance to flow and on the necessity of critically reviewing the assumptions and limitations associated with the methods that are commonly adopted to evaluate resistance to flow in gravel-bed rivers.A commonly applied technique is first presented for estimating the local effective boundary roughness,ks, by the use of data from a vertical velocity profile. Then methods of estimating bulk measures of resistance to flow in a river reach are outlined. Resistance equations in terms of the friction-factor parameter,,are classified into three main types: dimensional power equations, nondimensional power equations, and nondimensional semilogarithmic equations. The results of seven independent studies are considered when recommending tentative equations for each of the three defined classes of resistance equations. The bulk flow equations are considered to be applicable for the case whered/D50is greater than 10, there is no bed-load transport, and the flows are in-bank flows. Finally, a brief summary of the problems of estimating resistance to flow for an ice-covered channel is presented.Key words: resistance, flow, hydraulics, rivers, gravel-bed, velocity, friction factor, equations, Manning, Keulegan, classification.

ISSN:0315-1468    

DOI:10.1139/l87-010

出版商:NRC Research Press    

年代:1987

数据来源: NRC