摘要:

The growing use of professional construction management has been synonymous with the development of new project delivery systems such as the phased construction approach and the fast-tracking technique. This paper establishes the distinction between these two types of approach which have become increasingly popular for reducing project duration. The paper further illustrates, through a case study, the possible consequences of compressing and overlapping design activities in a fast-track program to expedite project delivery. A delay analysis shows the impact of this accelerated technique on construction activities. The far-reaching effect of mistakes during the early design/engineering phase in a fast-track program is usually underrated. Accelerating a project through fast-tracking is a major decision, and construction professionals often are not aware of its implications. Based on the case study examined in this paper and other fast-track constructions previously analyzed, trouble areas requiring special attention have been depicted and recommendations with regard to the effective use of this technique are presented. It has also been shown that if intensified effort on problem areas is lacking, such a popular accelerated technique could result in unexpected delays.Key words: fast-tracking, phased construction, professional construction management, design management.

ISSN:0315-1468    

DOI:10.1139/l88-068

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The use of hydraulic conductivity (k) of soil material as the sole basis for sanitary landfill liner design is reviewed. On one hand,kmeasurements obtained in the laboratory often vary by several orders of magnitude. On the other, laboratory-measuredkvalues fail to address field behavior, where crack formation before and (or) during landfill operation may control the bulk permeability.A synaerisis shrinkage test (SST) to study the soil shrinkage caused by municipal solid waste (MSW) leachates is introduced. Leachates cause soil shrinkage by reducing interparticle repulsive stresses thereby increasing effective stress. The effective stress concept and double layer theory adequately describe the synaerisis shrinkage phenomenon. A strong correlation was obtained betweenpercent strain, the soil–liquid parameter determined from SST results, and a volume change parameter (free swell difference, FSD) from sedimentation test results. The results provide a basis for a broader approach to landfill liner design. The SST, which supplies information on both volume shrinkage and permeability changes caused by leachate, provides a useful laboratory procedure for evaluating liner materials.Key words: clay liners, shrinkage, leachate, synaerisis, hydraulic conductivity.

ISSN:0315-1468    

DOI:10.1139/l88-069

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Bed configuration is shown to be a relevant parameter of the saltation movement of solid particles in free surface flow. Analytical and statistical results confirm the importance of this parameter on bedload and suspended load.Key words: solid transport, entrainment, bed configuration, calculation formula, compared performance.

ISSN:0315-1468    

DOI:10.1139/l88-070

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A new analytical model for the static analysis of cable-stayed bridges is presented taking into consideration the effect of soil–structure interaction. Bridges having pylons and piers of different degrees of restraint, such as fixed or hinged base pylons, fixed base piers, and pile-supported piers, are analyzed and compared to investigate the effect of these restraints on the response of the entire cable-stayed bridge system. The validity of the assumption of fixed support for pylons or piers is also examined.Key words: bridges, cables, foundation, towers, pylons, piers, piles, caissons, soil mechanics.

ISSN:0315-1468    

DOI:10.1139/l88-071

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The purpose of this paper is to analyze the fatigue crack growth rate in groove weld with backing steel bar. The linear elastic fracture mechanics approach is used. This approach is coded in a special purpose fracture mechanics package FAST. By using FAST, the structure is modeled and analyzed by its finite element module FAST-I, and the cyclic life is estimated by its crack propagation module FAST-II.An example recently studied by Baker and Kulak is investigated by the FAST program. TheS–Ncurve (stress range versus number of cycles to failure) obtained by FAST is compared with the curve presented by Baker and Kulak.Key words: Engineering, finite element, fracture mechanics, fatigue, steel, stress intensity factor, numerical, computer analysis, weld, stress ratio, enriched element.

ISSN:0315-1468    

DOI:10.1139/l88-072

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Serviceability limit states such as fatigue, cracking, corrosion, permanent deformations (kinking), deflection, and vibration are considered. A probability-based approach to develop design criteria is proposed. Load history is represented by load histogram and ADTT (average daily truck traffic) volume. Criteria for the selection of acceptable serviceability levels can be derived from the available test data, bridge surveys, and theoretical studies. Simple format is suggested for the code, with a characteristic value representing load effect and an allowable stress or force representing the structural ability to absorb damage. In the case of deflection and vibration, human perception threshold levels are used as the acceptance criteria.Key words: bridges, damage accumulation, design criteria, limite states, serviceability.

ISSN:0315-1468    

DOI:10.1139/l88-073

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Using the data from Brownlie's update of the Compendium of Solids Transport Data, velocity and sediment discharge equations have been derived using regression analysis. Two velocity equations have been determined, one for the lower flow regime and the other for the upper flow regime. A single equation for sediment discharge covers both flow regimes. The equations provide estimation/prediction of sediment discharge and velocity that are simple to use.Plots of over 3000 test results show the relationship of sediment discharge, velocity, flow depth, energy gradient, and sediment size for the lower and upper flow regimes. Included in the plots are estimation and prediction limits for the velocity and sediment discharge relationships.Key words: sediment discharge, velocity, flow regime, weighted least squares, regression, prediction.

ISSN:0315-1468    

DOI:10.1139/l88-074

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Experiments using artificial dunes show that the friction factor is reduced when the steep face of the dune is on the upstream side, i.e., when the direction is reverse that of normal. Calculations using bedform regime relationships show that this configuration of reverse flow over dune profiles could have existed in the Pitt River, causing the decrease in bed roughness which was found during the calibration runs.Key words: friction factor, dunes, tidal flow, Fraser River, bedform roughness, Pitt River.

ISSN:0315-1468    

DOI:10.1139/l88-075

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This paper summarizes the results of push-out tests conducted on 17 different types of shear connections simulating three distinct components of a composite floor system: (1) an interior beam (perpendicular metal deck), (2) a spandrel beam (perpendicular metal deck), and (3) a girder (parallel metal deck). Each push-out specimen had a layer of 152 × 152 WM9.1 × WM9.1 welded wire mesh at mid-depth of each concrete slab.Two composite beams, each with ribbed shear connections typical of those in two of the types of push-out specimens representing ribbed shear connections in interior composite beams with ribbed metal deck, were tested with third-point loads over a simply supported span. Using the average ultimate shear strengths of the push-out specimens having the same configurations as the ribbed shear connections in the composite beam tests to calculate the ultimate flexural capacities of the composite beams resulted in a very close estimate of the measured ultimate flexural capacities of the composite beams. The average measured static yield strengths of the flanges and webs of the wide-flange sections used in the composite beam tests were included in the calculations of the ultimate flexural capacities of the composite beams.Key words: composite, push-out, ultimate shear, shear stud, ribbed metal deck, deep rib.

ISSN:0315-1468    

DOI:10.1139/l88-076

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This paper reviews the available experimental data regarding the effect of parapet configurations on the wind loading of roofs of buildings of various geometries and under different exposures. Particular reference is given to the recent study carried out by the authors in a boundary layer wind tunnel. This study deals with the effects of wind on a variety of flat roofs with and without parapets when exposed to simulated open country and urban terrains. Geometrical parameters examined include the effect of building height (ranging from 12 to 145 m) and parapet height (0–3 m) on both local and area-averaged roof pressures for a variety of wind directions. Results show that parapets generally reduce the high suctions on roof edges and may slightly increase the suctions on the interior areas of the roof. Roof corner suctions, however, increase significantly for low parapet heights.Additional parapet configurations have been examined to reduce these high local corner suctions. Parapet cuts or slots around corners have proven to be effective in this respect. The effect of one-sided, as opposed to perimetrical, parapet has also been examined. Extensive comparisons of the data and recommendations for the wind load provisions of the National Building Code of Canada (NBCC) and the American National Standards Institute (ANSI) are also made.Key words: building, code, design, loads, pressure, project, roof, wind.

ISSN:0315-1468    

DOI:10.1139/l88-077

出版商:NRC Research Press    

年代:1988

数据来源: NRC