摘要:

A grout for use in pile installation in permafrost is described. The high alumina cement (Ciment Fondu) based grout cures by rapidly evolving heat which maintains it above 0 °C until it hydrates and hardens. The laboratory development program of the mix design along with the cement admixtures which allows the grout to cure at temperatures as low as −10 °C and to remain workable during field use is reviewed. The development of installation procedures for the grout during construction of short range radar foundations is described along with field measurements of the compressive strength and the temperature profiles of the grout after placement in permafrost as cold as −14 °C. The Ciment Fondu grout performed according to the design requirement of hardening without freezing in permafrost colder than −10 °C during the installation of about 2000 piles for part of the short range radar project.Key words: permafrost, grout, laboratory, field, installation procedure, mix design.

ISSN:0315-1468    

DOI:10.1139/l93-011

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

To better understand the behaviour of curved box girder bridges in resisting eccentric design truck loads, and the influence of plan curvature on the structural response, a model study was conducted at the University of Ottawa. In this study, the elastic response of a curved composite box girder bridge model was evaluated experimentally and confirmed analytically using the finite element method. Analytical predictions of both vertical displacements and normal stresses at critical sections compared fairly well with those evaluated experimentally. The isoparametric thin shell element employed in the analysis proved to be versatile and provided an accurate representation of the various structural components of a curved box girder bridge. Despite the eccentric nature of the applied OHBDC design truck loads and the bridge plan curvature, it was evident that in resisting the applied live loads, the girders at critical sections share equal proportions of the applied bending moments.Key words: bridge, curved, cellular, composite, eccentric loads, static, linear, experimental, finite element.

ISSN:0315-1468    

DOI:10.1139/l93-012

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The ability of the creep model of Fish to simulate the observed behaviour of ice and frozen soils in multiaxial stress-strain fields is investigated. The generalization of the original uniaxial creep model is made through the use of several assumptions and the multiaxial model is implemented in an iterative, time-incrementing finite element code. Sample creep parameters for the model are evaluated using previously reported uniaxial creep tests on ice and frozen silt. The finite element code is used to demonstrate the ability of the model to predict different stages of creep deformation in frozen media, by re-simulating some uniaxial creep tests on ice. Pressuremeter tests, plate load tests, and laterally loaded rigid cores (piles considered in cross section) in frozen media are simulated to demonstrate the similarity between the global response of ice and frozen soils predicted by the model and the reported experimental findings. Redistribution of stress predicted by the model is also investigated. The model is seen to possess validity in situations of attenuating as well as accelerating creep of ice and frozen soils.Key words: creep, ice, frozen soils, finite elements, structure–frozen media interaction, numerical prediction.

ISSN:0315-1468    

DOI:10.1139/l93-013

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Sediment rating curves in conjunction with daily flow data have often been used to estimate the total mass of sediment flowing past a given river cross section over relatively long periods of time. Techniques are presented that seek to make the best use of limited noncontinuous suspended sediment concentration data to generate nine partial years of suspended sediment load by means of sediment rating curves for the Kennebecasis River, N.B. (drainage area of 1100 km2). Initially, the data were partitioned in an attempt to improve correlations between concentration and discharge. Such partitioning by season, month, periods of rising stage, and periods of falling stage did not uniformly improve correlations as compared with the correlations for nonpartitioned data. Various combinations of less well-known methods were then used, including a moving intercept method that makes greater use of point concentration observations in time, and correction factor methods for simple power-type relations as suggested by Ferguson and by Duan. In addition, the validity of some of the underlying assumptions for performing ordinary least-squares regression is examined for this data set. Finally, the effect of daily flow averaging on the computed load was examined and found to be small for this basin.Key words: suspended sediment,C–Qrating curves, flow averaging, washload estimates, statistical bias, regression estimates.

ISSN:0315-1468    

DOI:10.1139/l93-014

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Estimates indicate that 30 to 70 percent of cast-in-place concrete cost is attributable to the assembly and stripping of formwork. This wide percentage range is partially due to factors that are not well understood with regard to their influence on productivity. The purpose of this paper is to identify the factors that influence formwork productivity and identify a methodology to evaluate productivity data. Two groups of factors were found to have a great effect on formwork productivity: non-measurable factors such as contract document and measurable factors such as engineering design. This paper discusses the effect of both groups of factors on the productivity of vertical formwork. To quantify the effect of the measurable factors on formwork productivity, a case study of the productivity of a crew of carpenters erecting wall formwork for a three-story underground parking structure is presented and analyzed. Data were collected by physically measuring the daily output of vertical formwork erected and the total daily work hours.Key words: formwork, productivity, construction methods.

ISSN:0315-1468    

DOI:10.1139/l93-015

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

One of the most pressing problems facing Canada is the condition of roadway infrastructure. Making good maintenance decisions requires years of practical experience and judgement. Expert systems have great potential for solving pavement maintenance problems that usually require significant human expertise for solution. Expert systems, also known as knowledge-based systems, have been used as a means for conveying pavement maintenance knowledge gained through research and field experience to individuals responsible for maintaining asphalt pavements. An expert system is defined as an interactive computer program which documents judgement, experience, intuition, and other information in order to provide knowledgeable advice.This paper describes the development ofPMAS, a pavement maintenance advisory system, which can assist highway engineers in planning effective flexible or asphalt concrete pavement maintenance strategies. The system uses two alternative commercial expert system shells. The system questions the user in a multiple-choice format in everyday English and (or) by using pictures. The user responds by selecting one or more of the choices provided by the system. At the end of the consultation session, the system displays the most appropriate maintenance strategy along with its life expectancy.PMASfacilitates the decision-making process and could serve as a consultant for field engineers.Key words: expert system, knowledge-based system, pavement maintenance.

ISSN:0315-1468    

DOI:10.1139/l93-016

出版商:NRC Research Press    

年代:1993

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l93-017

出版商:NRC Research Press    

年代:1993

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l93-019

出版商:NRC Research Press    

年代:1993

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l93-020

出版商:NRC Research Press    

年代:1993

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l93-021

出版商:NRC Research Press    

年代:1993

数据来源: NRC