摘要:

Results from an experimental program on the behaviour of high strength concrete-filled steel hollow structural section (HSS) columns will be presented for three types of concrete filling. A comparison will be made of the fire-resistance performance of HSS columns filled with normal strength concrete, high strength concrete, and steel-fibre-reinforced high strength concrete. The various factors that influence the structural behaviour of high strength concrete-filled HSS columns under fire conditions are discussed. It is demonstrated that, in many cases, addition of steel fibres into high strength concrete improves the fire resistance and offers an economical solution for fire-safe construction.Key words: high strength concrete, steel columns, fire-resistance design, high-temperature behaviour, concrete-filled steel columns.

ISSN:0315-1468    

DOI:10.1139/l98-023

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

An experimental program and associated numerical analysis were undertaken to study the shear-lag effect in round hollow structural section (HSS) tension members that are welded to gusset plates at their ends. The connection is made by slotting the tube longitudinally, inserting the gusset plate, and then placing longitudinal fillet welds at the tube-gusset interface. A total of nine specimens with three different tube sizes (HSS 102 × 6.4, HSS 102 × 4.8, and HSS 219 × 8.0) and various weld lengths were tested in the program. Most of the specimens failed by fracture of the tube somewhere between the two gusset plates, and there was considerable ductility prior to fracture. Most importantly, there was no reduction in the effective net area for the tested specimens, even with a weld length as little as 80% of the distance between the welds. Numerical analyses of the connections were carried out using an elastoplastic model and measured material properties. The studies showed that the restraint provided by the gusset plate at the slotted end effectively increases the load-carrying capacity of the tube as compared with that of the unrestrained portion of the member. In the analysis, fracture is assumed to have occurred when the equivalent plastic strain reaches a critical value. The test results are discussed in light of the requirements in the Canadian standard for design of steel structures.Key words: connections, steel, shear lag, finite element analysis, gusset plates, hollow structural section, tension, wel

ISSN:0315-1468    

DOI:10.1139/l98-025

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The development of watersheds complicates the management of hydraulic facilities. Managers are facing economic and social imperatives that are potentially conflicting. Generally, their decisions are based on operational rules established by experience. However, these rules do not ensure that certain minimal conditions be respected and they do not determine future conditions for the river as a whole. Therefore, the communication of these conditions between managers of a same river is difficult. The present paper provides an approach to improve this situation. The real time simulator XSIM, with a graphical interface, has been developed in order to assist managers in control, design, analysis, and information transmission. It is designed based on an intumescence model functioning in an unsteady flow regime. It allows the managers to input the considered operations and provides them with the design conditions in a format adapted to their needs. It ensures the distribution and the availability of the results by creating a web page automatically. Its application to the management of complex sections of a real river is presented in order to illustrate its usefulness for day-to-day management and in emergency situations, such as a sudden flood or the rupture of a dam.Key words: flood, decision aid, management, unsteady flow regime, hydrology, graphical interface, numerical simulation.

ISSN:0315-1468    

DOI:10.1139/l98-035

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In July 1987, a section of the southwest wall of Sault Ste. Marie Lock failed during a locking operation when a portion of limestone facing, 60 m by 8 m, separated from the rubble backing wall. Engineering investigations resulted in the selection of the Recreational Lock Option, involving either downsizing the lock chamber within the existing lock or constructing a new lock as the most viable solutions. A Dry Dock Option, where the lock would be used to store craft during the winter months, was also considered. However, this option was abandoned during the course of testing. The engineering investigations also revealed that the emergency swing dam, constructed upstream of the existing lock to protect the system should the lock gates be damaged or carried away (as happened in 1909), was in poor condition and required rehabilitation in the order of over $0.5 million. A stop log emergency system was proposed as an alternative safety device designed to stop the flow of water through the canal in the event of gate failure. Physical hydraulic model studies were carried out to evaluate the feasibility of using an emergency stop log system. The tests showed that stop logs constructed with solid horizontal web plates top and bottom result in unacceptably high hydraulic downpull forces. Open truss stop logs can be deployed to stop the flow of water through the canal in the event of gate failure. The follower should also be constructed as an open truss such that the areas of steel exposed to the flow at the top and bottom of the follower are minimized. Hydraulic uplift forces that could prevent closure can be reduced by increasing the space between the stop log and the follower. Physical hydraulic model studies of the lock filling-emptying systems are described. The first and preferred option consists of downsizing the existing lock and retaining part of the existing wooden culverts and emptying system, if possible. A new filling port, filling valves, and supply culvert would be constructed upstream. In the event that the existing wooden culverts are found to be unserviceable, a second option was considered. This second option would be to fill in the wooden culverts and then construct a new filling port, filling valves, and supply culvert that would discharge into the lock through the upstream breast wall just above floor level. The existing emptying system would be retained or rebuilt. The third option, if both the filling and discharge culverts have to be condemned, would be to build a new lock. The results of the hydraulic model studies carried out to explore these three options are described.Key words: emergency closure, stop logs, follower, canal, lock, downpull, uplift, crane capacity, filling-emptying system, culverts.

ISSN:0315-1468    

DOI:10.1139/l98-033

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The objective of this study was to examine the feasibility of using a semiautomated computer-vision system to quantify the percentage of voids in mineral aggregates (VMA%) of bituminous mixtures. The system used a hybrid procedure which utilized a digital image analysis scheme and a planimeter surveying instrument. Thirty-nine Marshall specimens were prepared using limestone and gravel aggregates. Values of VMA% were obtained using the ASTM conventional procedure and the computer-vision procedure. To compute VMA% using the computer-vision procedure, normal case photography with uniform scale images was used to map horizontal and vertical cross sections of Marshall specimens. Image domain measurements were corrected for distortion. Spatial filters and image processing operations were used to enhance the aggregate edges. Experimental results showed slight variations between VMA% computed using conventional and the computer-vision procedures. The average differences of VMA% between conventional and the computer-vision procedures were 0.81% and 0.006% for gravel and limestone specimens, respectively. Measurements of VMA% for limestone mixtures were more precise than those for gravel mixtures because of the angular edge shape of limestone particles. Variations in VMA% were due to the anisotropic properties of asphalt mixtures, aggregate distribution in the asphalt mixture, and different shapes of aggregates. Using the computer-vision-based technique, VMA% of horizontal and vertical cross sections were 50% consistent. The existence of fine aggregate in the asphalt mixture affected the accuracy potential of the developed system because a low-resolution camera was used. Increasing the camera resolution and automating the area computation of aggregate are expected to enhance the potential accuracy of the procedure. The proposed method for VMA quantification is anticipated to improve field quality control of hot-mix asphalt (HMA). The use of computer-vision technology with bituminous mixtures can open the doors to a wide variety of applications.Key words: bituminous mixtures, voids in mineral aggregate, computer vision, automation, image processing.

ISSN:0315-1468    

DOI:10.1139/l98-034

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A definition of homogeneous regions in terms of precipitation regime is achieved by the use of principal component analysis (PCA). The method has been shown to be a reliable regionalization tool even though it was applied to a territory showing rather complex physiography and high precipitation variation. Results based on the application of the PCA to the interstation correlation matrix of precipitation have indicated four distinct homogeneous regions. These regional patterns can be explained by the orographic effect and by the circulation of air masses within the study region.Key words: homogeneous regions, rainfall, principal component analysis, orographic effect.

ISSN:0315-1468    

DOI:10.1139/l98-040

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Even for the most well-intentioned companies, the commitment required for the initial drafting of a plan is a real barrier to developing a useful schedule for a construction project. This paper explores how artificial intelligence and expert systems have and can be used for automating the generation of plans and schedules. Findings from a thorough literature review and observations about the general characteristics of projects provide a backdrop to explain the reasoning that has led to the authors' approach to developing a module capable of generating draft plans and schedules. This approach combines expert systems with large building blocks of predefined project scoping, sequencing, and scaling knowledge contained in standard templates and rules. It relies on templates to store much of the reasoning needed to produce a project plan and schedule, and on the use of generalized planning structures as activities. A draft schedule can then be automatically generated by way of a relatively simple rule set that assigns activity property values dealing with physical locations and production rates, as well as other project scale related values. The role of a physical model or view of a project is emphasised.Key words: construction, scheduling, project management, expert system, template, automated schedule generation, rule based, computer integration.

ISSN:0315-1468    

DOI:10.1139/l98-029

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

There is now growing evidence that large-magnitude earthquakes have occurred and could occur again along the Cascadia subduction zone located west of Vancouver Island, Bristish Columbia. Numerical simulations indicate that these earthquakes would produce long-duration ground motions and would thus be capable of inducing a large number of reversals of inelastic deformations in engineered structures. Efforts have now been undertaken to account for this damage potential in building codes. In this paper, inelastic design spectra are developed for Cascadia subduction earthquakes for four sites in British Columbia. These spectra are compared with elastic design spectra that have been developed recently for the same sites based on empirical attenuation relationships for Cascadia events. The approach used to develop the inelastic spectra aims at providing the same level of protection against structural failure for both subduction events and crustal or subcrustal earthquakes. Force modification factors are first determined for structures exhibiting various failure modes and ductility levels when subjected to representative crustal and subcrustal earthquake ground motions. Thereafter, design spectra are developed for the same structures to prevent structural collapse under simulated Cascadia subduction ground motions. The study reveals that the elastic spectra do not reflect adequately the damage potential of Cascadia earthquakes. These elastic spectra generally are unconservative for Tofino and Victoria. For Vancouver and Prince George, the elastic spectra overestimate the demand, especially for short-period structures.Key words: collapse, crustal earthquakes, damage index, design spectrum, ductility, duration, ground motion, subduction zone.

ISSN:0315-1468    

DOI:10.1139/l98-028

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Exchange of synthetic organic contaminants across the air-water interface is a significant process affecting the fate of the contaminants released into the environment. Benzene, toluene, trichloroethylene, and tetrachloroethylene were selected as typical contaminants in this study. The equilibrium distribution of the selected volatile organic compounds between air and water was simulated in the laboratory at the University of Saskatchewan. A gas chromatograph headspace auto sampler system was used to analyze the chemical concentrations. The effect of salinity on the equilibrium distribution of selected organic contaminants between water and air was studied. Concentrations of sodium chloride from 100 to 1000 mol/m3were used to simulate various levels of salinity in water at a temperature of 20°C. Typical seawater was simulated with 3.5% sodium chloride and tested at temperatures from 15°C to 45°C. A modified van't Hoff expression was developed by incorporating a salting-out coefficient to predict the effect of temperature and salinity on the equilibrium distribution. The parameters of the modified van't Hoff model were determined by using the experimental results for selected organic contaminants.Key words: water pollution, volatile organic contaminants, distribution, salini

ISSN:0315-1468    

DOI:10.1139/l98-042

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The main objective of this study is to propose a method for validating the daily net basin supply data to obtain the most reliable values for the management of water resource systems. Based on the regression and exponential smoothing methods, various validating procedures are developed and compared. Results of a numerical application using data from La Grande 3 basin have shown that the simple exponential smoothing method is the most suitable. Further, it has been found that the proposed exponential smoothing has the simplest structure and would require a simple parameter estimation method because it contains only one parameter.Key words: real time validation, net basin supply, forecasting, time series analysis, reservoir management.

ISSN:0315-1468    

DOI:10.1139/l98-036

出版商:NRC Research Press    

年代:1998

数据来源: NRC