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.

Thesis (M.S. in civil engineering)--Washington State University, May 2010. / Title from PDF title page (viewed on June 23, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 90-91).

By using a nonlinear computer analysis, a parametric study is developed in order to examine the accuracy of the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The variables used in the parametric study are: axial load intensity, P/Po; column reinforcement ratio, rho; slenderness ratio, klu; shape of column cross section, flexural stiffness ratio, and distribution of axial loads. In the parametric study, 216 cases of single bay fixed-base portal frames are examined. The higher moment for each one of these frames at failure are then compared with the design moment predicted by the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The Moment Magnifier Method proved to be very conservative when the columns are subjected to high level of axial loads and when the slenderness ratio is increased.

Microreproduction of original thesis. / Thesis (PhD)--Stellenbosch University, 1990. / Some digitised pages may appear illegible due to the condition of the original microfiche copy. / ENGLISH ABSTRACT: see item for full text / AFRIKAANSE OPSOMMING: sien item vir volteks.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.

This thesis studies the uni-axial behaviour of circular double-skinned concrete-filled-steel-tubular (CFST) columns with external confinement in form of external steel rings. Particular attention is paid to the experimental behaviour of double-skinned CFST columns and theoretical model for evaluating the loadcarrying capacity of un- and ring-confined double-skinned CFST columns. Experimental studies on circular double-skinned CFST columns with various spacing of confinement, concrete strength and hollow ratio were conducted and discussed comprehensively. The mechanical properties of double-skinned CFST columns such as elastic stiffness, elastic strength, load-carrying capacity and ductility are presented. From the result, it is found that the elastic stiffness, elastic strength, load-carrying capacity and ductility are enhanced by installing the external steel rings to the outer tube as external confinement. To verify the effectiveness of external steel rings, the Poisson’s ratios of the double-skinned CFST columns are listed and found to be similar to that of concrete so that a perfect bonding is maintained. To emphasis the excellent performance of double-skinned CFST columns with external rings under uni-axial compression, the load-carrying capacity, elastic strength and elastic stiffness are compared to those of single-skinned CFST columns and reinforced concrete columns. To fill up the gap that no design model is provided in Eurocode 4 (EC4) for confined double-skinned CFST columns, a theoretical model based on the force equilibrium condition is proposed for evaluating the load-carrying capacity of both un- and ring-confined double-skinned CFST columns. The model takes into account the composite action between the steel tubes and core concrete. To verify the proposed model, numerous test results obtained by the author and other researchers are used for comparing the theoretical results. According to the above theoretical model above, a parametric study is carried out to investigate the effect of various geometry and material properties on the load-carrying capacity of double-skinned CFST columns. The confining pressure is expressed in terms of geometry and material factors. A simplified design formula is proposed to facilitate the preliminary design of double-skinned CFST columns with and without external confinement. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Not available / text

published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.