ISSN:0315-1468    

DOI:10.1139/cjcecontents00

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The demand for comprehensive environmental assessment of river ecosystem has increased for engineers and scientists. Accurate and versatile water temperature models are required to meet this demand. A number of hydrological models take vegetation and soil characteristics into account, but very few temperature models do. The objective of this paper is to incorporate soil temperature and vegetation as input variables in a deterministic heat budget model. The CEQUEAU hydrological and water temperature model was used to simulate water temperature in Catamaran Brook, a small catchment located in central New Brunswick. The model was modified by incorporating soil temperature as a parameter influencing the temperature of interflow, using the so-called force-restore method. Crown closure was also incorporated in the model as a factor influencing locally advected water using a negative exponential function. The modified model simulated daily water temperatures better than the original model. Root-mean-square error for a period of 5 years decreased from 2.10°C with the original model to 1.77°C with the modified model. Nash coefficient increased from 0.78 with the original model to 0.82 with the modified model. An analysis of residuals showed that the modified model is sensitive to additional parameters such as crown closure, especially for short time scales during periods of higher discharge and during extreme meteorological and hydrological events such as tropical storms.Key words: stream temperature, hydrology, deterministic model, CEQUEAU, forestr

ISSN:0315-1468    

DOI:10.1139/l00-021

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The main objective of this research was to investigate the contribution of pavement characteristics, traffic, and physical and mechanical properties of asphaltic mixtures to highway pavement rutting. A total of 51 pavement sections from the rural highway network in Jordan were selected for a case study. The average rut depths for these sections were measured and three cores were drilled for comprehensive laboratory testing. The investigation was performed using four approaches. The first approach considered pavement characteristics represented by surface thickness, last overlay thickness, pavement age, and subgrade California bearing ratio. The average annual equivalent single axle load was also included in this approach. The second approach included Marshall test parameters such as stability, flow, stiffness, and Marshall modulus. The third approach dealt with the effect of mixture air voids on rutting. The variables examined in this approach include air void content within the ruts, voids between ruts, voids near the pavement centerline, and the difference between centerline and rut voids. The fourth approach considered the dynamic permanent deformation characteristics of the pavement surface layer represented by the dynamic modulus. Regression analysis techniques were employed to develop statistical relationships between average rut depths and the parameters examined in each individual approach. The combined effect of these significant parameters on pavement rutting was also examined for prediction purposes. Rutting formation was found to be most dependent on the traffic loading, dynamic modulus of the bituminous mixture and its susceptibility to further compaction, and foundation soil strength.Key words: pavement rutting and characteristics, Marshall test, traffic loading, air voids, static creep, dynamic permanent deformation.

ISSN:0315-1468    

DOI:10.1139/l00-037

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The presence of ice in rivers affects hydrodynamic conditions through changes in both the river's boundary conditions and its thermal regime. Therefore, the characteristics of sediment transport and the deformation of the river channel in ice-covered rivers are quite different from those experiencing conventional open channel flow. The variables of ice behavior, ice jamming extent, sediment transport, and deformation of the riverbed during ice periods are interrelated on the basis of both physical arguments and field experiments of river ice jams in the Hequ Reach of the Yellow River. The characteristics of sediment concentration in water, frazil ice, and ice cover are described. Analyses have been made on the mechanism of the evolution of frazil jam and the associated adjustments in the riverbed. It has been found that the evolution of the ice jam and the deformation of the riverbed reinforce each other. The interrelationship between the particular features of evolution of ice jam and deformation of riverbed is summarized here in the form of regression relationships relating the hydraulic parameters of water under ice jams to the deformation-extent of the riverbed and the jamming-extent.Key words: deformation of riverbed, evolution of frazil jam, frazil jam, suspended load, sediment concentration.

ISSN:0315-1468    

DOI:10.1139/l00-038

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Crane selection is a time consuming process that involves extensive data manipulation. Several systems have been developed to assist in selecting cranes and in planning their lifts. These systems lack the support of a comprehensive database to provide information about crane configurations, their lift capacity settings, and rigging equipment. Although crane manufacturers provide data for their cranes, these data are not always consistent and do not follow a standard format. This creates frequent problems for crane users, especially when interpolating the load charts. This requires the users to make decisions based on job conditions and categories of cranes, which can lead to costly mistakes. This paper describes the development of a comprehensive database (called D-CRANE) designed to support efficient selection of cranes. D-CRANE has been developed in collaboration with an industrial partner. It includes operational information about crane geometry, lift configurations, lift capacity settings, accessories, and attachments. D-CRANE has a number of interesting features: (i) powerful graphics capabilities, featuring a multimedia environment and a practical user-friendly interface; (ii) capacity to accommodate different types of commercially available cranes; (iii) powerful storage, sorting, and query routines; (iv) flexibility in using metric and empirical units; (v) capability of operating in a network environment, and (vi) minimum disk storage space. D-CRANE is a relational database designed using entity relation diagram and is implemented using MS-Access database management system. A case example is presented to demonstrate the use and capabilities of D-CRANE.Key words: database management system, crane selection, planning critical and heavy lift.

ISSN:0315-1468    

DOI:10.1139/l00-039

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A comprehensive research program is currently in progress to monitor and study the behavior and performance of the Confederation Bridge. Part of this program is on monitoring short- and long-term deflections to evaluate the deflection prediction techniques employed in the design of concrete structures in general and this bridge in particular. The investigation comprises measurements of parameters related to the materials used in the bridge. This paper presents some field measurements of vertical deflection as well as the results of computer analysis. Short-term deflections are measured at the time of installation of precast units and also in truck-loading tests. After completion of construction, the deflections are measured at specified intervals. The last readings reported in this paper have been taken 27 months after completion of construction. The computer program CPF (Cracked Plane Frames in prestressed concrete) is employed for analysis of the monitored part of the Confederation Bridge. The bridge is modeled as a plane frame in which the nonprestressed and prestressed steels are considered. Several analyses are performed employing the actual time-dependent concrete properties measured in the field and those calculated from the ACI Committee 209 equations and CEB-FIP Model Code. Comparisons are made between the measured and the predicted deflections. The predicted deflections are found to be in close agreement with the measured values, which indicates that the deflection prediction techniques used in design of this bridge are adequate.Key words: computer analysis, concrete bridges, Confederation Bridge, creep, deflections, field measurements, long-term, prestressed steel, segmental construction, short-term, shrinkage, time-dependent.

ISSN:0315-1468    

DOI:10.1139/l00-050

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

This paper summarizes the results of an investigation into the behaviour of truss plate reinforced single and multiple bolted connections in parallel strand lumber (PSL) under static tension loading. Sixty single-bolt connections were tested with bolt and PSL size combinations of 12.7 mm bolts in 38×140 mm specimens, 15.9 mm bolts in 89×140 mm specimens, and 22.2 mm bolts in 133×191 mm specimens. Another sixty multiple-bolt specimens were tested, using the above-mentioned PSL size and bolt combinations. The multiple-bolt connections consisted of two rows of five bolts in the 38×140 mm and 89×140 mm specimens and two rows of two bolts in the 133×191 mm specimens. Each connection was configured according to the Canadian Standard for Engineering Design in Wood (CAN/CSA 086.1-94) in terms of bolt spacing, edge distances, and end distances. All reinforced single-bolt connections had average ultimate strength increases, compared to unreinforced connections, of 3% for the 133×191 mm, 12% for the 89×140 mm, and 37% for the 38×140 mm specimens. Reinforcement had little effect on the strength of multiple-bolt connections in both the 38×140 mm specimens and the 89×140 mm specimens. The reinforced four-bolt connections in the 133×191 mm specimens had a 7% increase in average ultimate strength. Reinforcement significantly improved the ductility in all the connections tested.Key words: timber connections, parallel strand lumber, multiple bolts, reinforcement, truss plates, ductility, composite wood products, testing, experimental, composite struct

ISSN:0315-1468    

DOI:10.1139/l00-040

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Ambient and forced vibration tests were carried out on the Beauharnois Bridge, a unique, 177-m combined suspension and cable-stayed structure near Montreal. A rehabilitation program was completed on the bridge during which the deck was completely rebuilt with an orthotropic slab on two steel trusses. The rehabilitation program also included the addition of two pairs of stay cables on both towers, creating a hybrid suspension system. The paper presents a series of dynamic tests performed to evaluate the dynamic properties and the dynamic amplification factor (DAF) for the rehabilitated bridge. The experimental program involved the measurement of vertical, transverse, and longitudinal acceleration responses of the deck and tower under ambient and controlled traffic loads. Displacement, strain, and integrated acceleration DAFs were computed under different loading conditions. Modal properties were evaluated and used to correlate a three-dimensional finite element model for the bridge, including nonlinear cable behaviour. The paper discusses the experimental setup and the techniques used to evaluate vibration frequencies, mode shapes, and the DAF. Correlation of numerical dynamic properties and experimental results is also presented.Key words: cable-stayed bridge, dynamic amplification, dynamic testing, numerical correlation, modal analysis, suspension bridge.

ISSN:0315-1468    

DOI:10.1139/l00-051

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The paper describes the development of a simple theoretical approach in estimating the capacity of short reinforced concrete (RC) columns under biaxial bending and axial load. The developed approach considers the nonlinear stress-strain relations of concrete and reinforcing steel and does not make the assumption about the limiting strain of extreme compression fiber of concrete. The solution is obtained using a nonlinearly constrained optimization algorithm. The approach was used to estimate the theoretical capacities of many tested RC columns found in the literature. A probabilistic analysis of the modeling errors was carried out using the ratios of the test-to-predicted results. The probabilistic analysis was extended to include two simplified theoretical methods: the reciprocal load method given by Bresler and the failure surface method given by Hsu.Key words: biaxial bending, modeling error, optimization, probability distribution.

ISSN:0315-1468    

DOI:10.1139/l00-054

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

This paper describes results from an evaluation study of the elastic seismic response coefficient introduced in the Canadian Highway Bridge Design Code. The evaluation is conducted by comparing the seismic response coefficient with (i) uniform hazard spectra for selected cities in eastern and western Canada, (ii) spectra of numerically simulated ground motions for sites in British Columbia for scenario earthquakes on the Cascadia subduction zone, (iii) spectra of the 1988 Saguenay, Quebec, earthquake records and selected ensembles of recorded accelerograms from strong earthquakes around the world, and (iv) bridge design spectra of other countries. The results from this study show that the seismic response coefficient of the Canadian Highway Bridge Design Code is conservative in terms of the Canadian seismic hazard, with the exception of (i) sites close to the Cascadia subduction zone and (ii) sites for which the seismic hazard is governed by the effects of strong earthquakes at large epicentral distances.Key words: seismic, response, coefficient, acceleration, spectra, bridge, design, code.

ISSN:0315-1468    

DOI:10.1139/l00-058

出版商:NRC Research Press    

年代:2000

数据来源: NRC