摘要:

Simplified braking models are used to analyze the braking efficiencies of a range of truck types under a variety of loading conditions and tire–pavement coefficients of friction. These analyses show that while most of the fully loaded trucks are capable of achieving a braking efficiency of 70%, the braking efficiencies of the unloaded or partially unloaded trucks deteriorate substantially. A bobtail tractor, an unloaded semi-trailer with tridem rear axle group and two air-lift belly axles, and a B-train double trailer with rear trailer unloaded have estimated braking efficiencies of 40–50%. The braking distances required by the unloaded and partially loaded vehicles from a 100 km/h operating speed are two to four times longer than those specified in the Canadian geometric design standards. Comparisons of the model-estimated braking distances with those obtained in one set of field tests show that the models are capable of reflecting accurately observed field behaviour. The results presented in the paper demonstrate the need for a systematic review of those highway design standards that are based on the braking capabilities of vehicles using the highway system.Key words: highway geometric design, truck braking efficiency, braking distances, highway safety.

ISSN:0315-1468    

DOI:10.1139/l89-025

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The axle load shifts of four truck types during braking are estimated using theoretical braking models and the implications of these axle load shifts for bridge and pavement design are explored. The truck types examined are a three-axle straight truck, a five-axle tractor semi-trailer, a seven-axle tractor semi-trailer with two air-lift belly axles, and a seven-axle B-train tractor-double trailer, each loaded to legal Ontario limits with weigh-out commodities. Each of the truck types experienced a substantial load transfer to the front steering axles under braking, mainly from the rear tandem axle groups, where the front axle load increase varied from 38 to 48%. The bridge design implications of the load shifts are examined in terms of the Ontario Bridge Formula and the moments induced in simple-span bridges compared with the moments induced by a reference design truck. For the braking model used, the decelerations and associated shifts in axle load do not lead to higher forces for bridge design and evaluation. The pavement damage implications are analyzed in terms of load equivalency functions derived from some load tests conducted at a number of pavement sites across Canada in 1986. These equivalencies increased up to 50% of the static values for the three-axle truck at maximum braking. It is suggested that the major damage implications are at intersections in urban areas and that increased structural sections could be designed to handle the increased equivalencies.Key words: bridge design, pavement design, truck braking, truck loads, pavement damage, bridge damage.

ISSN:0315-1468    

DOI:10.1139/l89-026

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A number of reports on simulations of real-time control of combined sewer system runoff have been published. Most of the control strategies suggested use linear models to calculate discharge routing. We used a nonlinear model for discharge routing and some of our findings differ from those obtained in earlier studies. In particular, it appears that the prediction horizon used for control optimization could be favourably shorter than the time of system flow-through.Key words: combined sewer system overflow, real-time control, nonlinear programming, discharge propagation. [Journal translation]

ISSN:0315-1468    

DOI:10.1139/l89-027

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members.Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

ISSN:0315-1468    

DOI:10.1139/l89-028

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

This paper gives the results of laboratory invstigations to determine the mechanical properties and freezing and thawing durability of concrete incorporating a granulated blast-furnace slag from a Canadian source. A series of fifteen 0.06 m3concrete mixtures were made with water-to-(cement + slag) ratios (W/(C + S)) ranging from 0.70 to 0.45. The percentage of slag used as a partial replacement for normal portland cement ranged from 0 to 100% by weight. All mixtures were air entrained. A number of test cylinders and prisms were cast for determining the mechanical properties and freezing and thawing resistance of concrete.The test results indicate that the ground granulated blast-furnace slag can be used with advantage as a partial replacement for portland cement in concrete at 50% or lower replacement levels, especially at W/(C + S) of the order of 0.55 or lower. At 28 days, irrespective of the W/(C + S) and regardless of the percentage replacement of the cement by the slag investigated, the compressive strength of the concrete incorporating slag is comparable with that of the concrete made with normal portland cement. At all W/(C + S) and at all percentages of replacement, the flexural strength of the slag concrete is comparable with or greater than the corresponding strength of the control concrete. Durability of air-entrained slag concrete exposed to repeated cycles of freezing and thawing is satisfactory as evidenced by the high durability factors achieved.Key words: granulated slag, bleeding, time of setting, concrete, strength, freezing and thawing, shrinkage, creep, abrasion.

ISSN:0315-1468    

DOI:10.1139/l89-029

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Batch studies were conducted to determine the efficiency of Saskatchewan horticultural peat to remove biochemical oxygen demand (BOD), chemical oxygen demand (COD), phosphorus, nitrogen, and indicator microorganisms from septic tank effluent. Results of the studies showed that peat was effective in adsorbing 35–50% of dissolved BOD, COD, and organic carbon from the septic tank effluent and in removing indicator microorganisms to the extent of 45–70%. The studies showed that peat has the potential to be used as a medium for septic tank effluent treatment in areas with high water table and with bedrock at shallow depths. Because of leaching of pollutants from peat in the 2-h batch studies, it is necessary to conduct long-term column studies to observe the length of time up to which leaching continues and to evaluate the performance of a peat filtration system under dynamic conditions.Key words: batch studies, septic tank effluent, treatment, peat, adsorption isotherms, indicator microorganisms.

ISSN:0315-1468    

DOI:10.1139/l89-030

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The effect of the cruciform weld profile and internal defects on the stress intensity factor and the crack growth are investigated using a plane stress, linear, elastic, finite element approach. The stress intensity factors and the propagation and total lives of the cruciform joint with or without internal imperfections are determined for various types of analytical modelling and are compared with the published results. In addition, stress concentration factors, stress intensity factors, and fatigue lives are also determined for various ratios of plate thicknesses under tensile and bending loads.Key words: stress intensity factor, cruciform joint, crack growth, crack initiation, fatigue life, fracture mechanics, compact tension specimen, tensile and transverse loads.

ISSN:0315-1468    

DOI:10.1139/l89-031

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A finite element model which takes account of plasticity and contact for the behavior of bolted steel connections is presented in this study. The mathematical formulation is first presented, followed by the analysis of two bolted connections and a presentation of the results. Future developments and possible applications are finally described.Key words: steel structures, bolted connections, mathematical model, finite element, nonlinear analysis, plasticity.

ISSN:0315-1468    

DOI:10.1139/l89-032

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Nonlinear wave forces on a surface-piercing vertical circular cylinder are considered using a time-stepping method previously developed which is based on Green's theorem. Possible improvements in the efficiency, accuracy, and stability of the method are considered. Results based on this method are compared with those obtained previously using perturbation methods as well as with experimental results. It is found that the time-stepping method adopted here is quite reasonable. Wave force coefficients are given as functions of the governing parameters of the problem and the importance of nonlinear wave effects on the forces is assessed.Key words: hydrodynamics, ocean engineering, offshore structures, waves, wave forces.

ISSN:0315-1468    

DOI:10.1139/l89-033

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Ever since the Government of the Northwest Territories began installing water and sewer service connections in the permafrost areas of the Northwest Territories that are subjected to long and harsh winters, there have been the problems as to how to keep these service connections from freezing. Water and sewere service connections of many types and materials have been installed in permafrost in the Northwest Territories in past years. While not always successful, these have provided invaluable experience and have all contributed to the development of the concept presented in this paper towards the provision of water and sewer connections in the Northwest Territories. This paper presents the current methods for the provision of water and sewer service connections in those communities where the Government of the Northwest Territories is directly responsible for program delivery. The water and sewer service connection details are illustrated in eight concept plans contained in this paper.

ISSN:0315-1468    

DOI:10.1139/l89-034

出版商:NRC Research Press    

年代:1989

数据来源: NRC