摘要:

As the spans of cable-stayed bridges increase, the degree of nonlinearity of structural response increases markedly. For future spans greater than (say) 800 m, existing three-dimensional software then becomes very time consuming and costly, and a finite strip approach becomes more attractive and preferable. An improved finite strip method using two types of longitudinal shape functions is developed in this paper for the analysis of girders of such bridges. The nonlinearities due to sag and angle change of the cables are taken into account by means of catenary theory. The substructuring technique and the modified Newton–Raphson iteration method are used for nonlinear solutions. A number of numerical examples are given to show the accuracy and efficiency of this method.Key words: finite strip, continuous structure, cable-stayed bridge, substructuring, catenary, nonlinearity, iteration.

ISSN:0315-1468    

DOI:10.1139/l90-011

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A relatively short highway construction season exists on the Canadian prairies and typically the paving season extends from May to October. Highway engineers and contractors are continually confronted with unfavorable weather conditions during the early spring and latter parts of the fall paving season. During these periods of cooler weather, the decision as to whether or not to allow paving to continue or begin becomes very difficult, since freshly laid pavements cool quickly and proper compaction is difficult to attain. The final density obtained in a pavement depends critically on its initial temperature and cooling rate. This study researches the subject of pavement cooling and investigates the feasibility of cold-weather paving. The results of this study illustrate the significance of the factors affecting pavement cooling and provide information for improving the paving specifications used by Saskatchewan Highways and Transportation. This study also shows that the short paving season which exists in Saskatchewan can be extended under certain conditions. Extension of the construction season into colder weather will provide financial and various other benefits, not only to Saskatchewan Highways and Transportation but also to paving contractors and the general public.Key words: pavement cooling, pavement temperature, computer simulation, compaction, asphalt concrete.

ISSN:0315-1468    

DOI:10.1139/l90-012

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The influence of CaCl2or a chloride-based accelerating admixture on the freeze–thaw resistance of concrete was evaluated. Three air entrained mix designs were investigated using ASTM C666-84, Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing. All mix designs were similar, using cement contents of 340–357 kg/m3of concrete, except for the addition of either 2% calcium chloride or 2% High Early Pozzolith, while no accelerating admixture was added to the control mix. The entire test program was repeated four times with water-to-cement ratio of 0.46 and three times with the ratio of 0.43. For the Pozzolith-accelerated concrete, half the samples were coated with boiled linseed oil in all seven series. For the control (unaccelerated) concrete, half the samples were coated with boiled linseed oil in one series for each water-to-cement ratio. Performance was monitored using the dynamic modulus of elasticity as obtained from transverse resonant frequency measurements. Weight loss of the specimens was also measured. Only the control samples (no accelerators) showed sufficient durability to satisfy the standard of maintaining at least 60% of the original dynamic modulus after 300 cycles of alternate freezing and thawing. Sealing with linseed oil showed inconsistent improvement in the durability in the various test series when defined in terms of the dynamic modulus; however, weight losses were the lowest of all categories and surface scaling was minimal.Key words: concrete, durability, freeze–thaw testing, calcium chloride, admixtures, sealants, air void system.

ISSN:0315-1468    

DOI:10.1139/l90-013

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

In February 1987, the Greater Vancouver Sewerage and Drainage District awarded an $8.5 million contract for the construction of the Iona Outfall submarine section. The contract awarded to the Dillingham–Manson joint venture involved the installation of approximately 3200 m of twin 2.3 m diameter steel outfall, of which 500 m was twin 2.1, 1.8, and 1.4 m diameter steel diffuser sections. The outfall extended from the end of the Iona Jetty into the Strait of Georgia near the mouth of the Fraser River and was 107 m deep at the end of the diffuser. The tender documents suggested a method of installation such that the entire twin outfall pipe was fabricated on an existing jetty complete with flotation pipe and pulled into the water. The contractor submitted an alternative method with the tender and was the successful low bidder. The proposed installation method was to assemble the pipe into nominal 300 m lengths in Dillingham's North Vancouver yard, launch them, tow them to the site, and sink and bolt them together underwater. This paper discusses the more interesting aspects of the project.Key words: construction, pipelines, robotics, sewage treatment, bolted joints.

ISSN:0315-1468    

DOI:10.1139/l90-014

出版商:NRC Research Press    

年代:1990

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l90-015

出版商:NRC Research Press    

年代:1990

数据来源: NRC