Thesis (M.E.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 125-126). Also available via the Internet.

Yes / This paper presents the behaviour of circular concrete-filled double-skin steel tubular (CFDST) stub columns compressed under concentric axial loads. To predict the performance of such columns, a finite element analysis is conducted. Herein, for the accurate modelling of the double-skin specimens, the identification of suitable material properties for both the concrete infill and steel tubes is crucial. The applied methodology is validated through comparisons of the results obtained from the finite element analysis with those from past experiments. Aiming to examine the effect of various diameter-to-thickness (D/t) ratios, concrete cube strengths and steel yield strengths on the overall behaviour and ultimate resistance of the double-skin columns, a total of twenty-five models are created to conduct the parametric study. In addition, four circular concrete-filled steel tubes (CFST) are included to check the dissimilarities, in terms of their behaviour and weight, when compared with identical double-skin tubes. A new formula based on Eurocode 4 is proposed to evaluate the strength of the double-skin specimens. Based on the comparison between the results derived from the analysis, the proposed formulae for the concrete filled double-skin would appear to be satisfactory.

No

No / This paper presents the buckling behaviour and design of axially loaded concrete filled steel elliptical hollow sections. The experimental investigation was conducted using normal and high strength concrete of 30, 60 and 100 MPa. The current study includes both the stub and slender column tests. Based on the existing design guidance in Eurocode 4 for composite columns, the proposed design equations were found to provide an accurate and consistent prediction of the cross section and buckling capacity of the composite concrete filled steel elliptical hollow sections in axial compression.

During the past decades, reactive distillation has received intensive attention due to the well known benefits of integrating distillation with reaction in a single unit. Significant capital savings, improved conversion and selectivity, avoidance of azeotropes, together with heat integration are some of the main advantages of using reactive distillation. Many applications have proven to be economically advantageous by using reactive distillation (e.g. MTBE and TAME synthesis, production of methyl-acetate, manufacture of di-isopropyl-ether, oligomerisation of linear butenes and others). Whereas there are many procedures available for the synthesis of non-reactive columns or reactive-separation systems, the synthesis of reactive distillation columns is still a challenge, due to the complexity and the high number of design parameters involved. Available conceptual design methods generally address three (or four) components and fully reactive columns, but there is still a lack of systematic conceptual design methods for more general column configurations and for multi-component systems. The aim of this work is to develop a methodology to identify promising column configurations and to obtain column design parameters (number of reactive and non-reactive stages, reflux and reboil ratios, feed condition) for a given feed mixture and a set of desired products. A new systematic design method for reactive systems reaching equilibrium allows the analysis of the impact of different configurations (fully reactive or hybrid columns) and feed policies (single- or double-feed columns) on column performance. The methodology is extended to account for kinetically-controlled reactions in synthesis and design of reactive distillation columns. Systems with two degrees of freedom (according to the Gibbs phase rule) were considered for equilibrium reactions, and ternary and quaternary systems for kinetically-controlled reactions. Reactive distillation column designs generated by the methodology are presented as illustrative examples. Their predicted performances are shown to be in good agreement with those predicted by rigorous simulation using HYSYS. The approach can easily be automated and typically generates multiple designs, allowing a design engineer to efficiently compare various design options including hybrid and fully reactive columns, single- and double-feed configurations, and different sets of operating parameters for a given column configuration. The new methodology developed in this work facilitates a stepchange in conceptual design practice, offering a systematic and easy to use tool for the synthesis and design of reactive distillation columns.

The study examines the behavior of pinned-end, centrally loaded columns of monosymmetric and asymmetric cross sections, with emphasis on angle shapes. The investigation covers flexural and flexural-torsional buckling in the elastic and inelastic ranges, which the aim of developing a rational method of predicting the buckling load for cross sections with low torsional rigidity and single or no axes of symmetry. The computer program that was developed takes into account the effect of residual stresses. The properties of the cross section were determined in the laboratory and utilized in the computer model. Full-scale column tests were run to verify the theoretical model. The results shows that equal-legged angles with low width-to-thickness ratio have flexural and flexural-torsional buckling loads that are less than 2% different. It is therefore suitable to continue using a flexural buckling solution for such shapes. This is also true for equal-legged angles with a high width-to-thickness ratio that fail in the elastic range, but in the inelastic range the flexural-torsional buckling load was about 11% less than the flexural buckling load. When the angle is unequal-legged, the flexural-torsional buckling load is always smaller than the corresponding flexural buckling load, in both the elastic and the inelastic ranges. The average difference between the flexural and flexural-torsional load for unequal-legged angle ranges from 3% in the elastic range to 10% in the inelastic range. The average ratio of the experimental results to the minimum of the theoretical results was 0.95 and the coefficient of variation was 0.053. Comparison with the results of other researchers show that it is possible to formulate an empirical formula that can be used in designing columns that are made of monosymmetric or asymmetric cross sections. However, due to the scarcity of data at this stage, it is recommended that the development of such a formula be postponed until additional test data are available. Moreover, in designing any cross section that does not have two axes of symmetry, it is advisable to check the possibility of flexural and flexural-torsional buckling.

No description available.

No description available.

This study is an experimental investigation pertaining to the creep behavior of slender pultruded fiber-reinforced polymeric (FRP) columns subjected to sustained concentric axial loading at elevated service temperatures. Six creep tests were performed on columns having a slenderness ratio of 49 at different combinations of axial load and temperature for a duration of at least 1,000 hours. The axial loads used represented 33%, 67%, and 90% of the critical buckling load for the column selected. For each load level, one test was performed at 22.8℃ (73℉) and one test was performed at 65.5℃ (150℉) Knife-edge end supports were utilized to simulate pinned-pinned boundary conditions. Midheight lateral deflection and axial shortening were recorded incrementally for the duration of the testing. Following termination of the creep tests, the columns were allowed to recover and tested for buckling strength. A semi-empirical model for long-term behavior of concentrically loaded FRP columns at elevated service temperatures is proposed based on experimental results.