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CONTENTS
Volume 5, Number 1, February 2005
 

Abstract
Important characteristics of the previously proposed reduced stiffness method and a summery of its design curves for the buckling of the axially loaded sandwich cylindrical shells is presented. Comparison of the lower bound obtained with FEM analysis with that from the reduced stiffness analysis shows that the proposed reduced stiffness method can provide safe lower bounds for the buckling of geometrically imperfect, axially loaded sandwich cylindrical shells. One of the attractive features of the reduced stiffness elastic lower bound analysis is that it provides safe estimates of buckling loads that do not depend on the specification of the precise magnitude of the imperfection spectra. As a result, designers can readily apply this method without being worried about possible geometrical imperfections that might be generated during fabrication and construction of sandwich cylindrical shells.

Key Words
sandwich shells; reduced stiffness; buckling; lower bound; axial loading.

Address
Mitao Ohga and Aruna Sanjeewa WijenayakarnDepartment of Civil and Environmental Engineering, Ehime University, 3, Bunkyo-Cho, Matsuyama 790-8577, JapanrnrnJames G. A. CrollrnDepartment of Civil and Environmental Engineering, University Collage of London, London WC1E 6BT, U.K.

Abstract
This paper presents an experimental study and its findings of the behavior of circular and square stub columns filled with high strength concrete (=49 MPa) and polymer cement concrete (PCC) under concentric compressive load. Twenty-four specimens were tested to investigate the effects of variations in the tube shape (circular, square), wall thickness, and concrete type on the axial strength of stub columns. The characteristics of CFT stub columns filled with two types of concrete were investigated in order to collect the basic design data for using the PCC for the CFT columns. The experimental investigations included consideration of the effects of the concrete fill on the failure mode, ultimate strength, initial stiffness and deformation capacity. One of the key findings of this study was that circular section members filled with PCC retain their structural resistance without reduction far beyond the ultimate capacity. The results presented in this paper will provide experimental data to aid in the development of design procedures for the use of advanced concretes in CFT columns. Additionally, these results give structural designers invaluable insight into the realistic behavior of CFT columns.

Key Words
polymer cement concrete; CFT stub columns; ultimate strength; failure mode; width-thickness ratio.

Address
Hyun-Sik Kang and Seo-Hyung Lim rnDepartment of Architecture, Jinju National University, KorearnrnTae-Sup MoonrnDepartment of Architectural Engineering, Hanyang University, Seoul, KorearnrnS. F. StiemerrnDepartment of Civil Engineering, University of British Columbia, 2324 Main Mall, Vancouver, B.C., Canada, V6T 1Z4

Abstract
This paper presents the results of a series of tests carried out on hollow and concrete-filled cold-formed steel sections subjected to axial and bending forces. The effects of eccentricity ratio and strength of in-fill on the behaviour of these sections were studied. A total of forty-eight medium sized columns and six beams were tested to failure. Extensive measurements of material properties, strains, axial shortening and lateral deflection were carried out. Interaction of local and overall buckling was observed in the tests. Failure mode observations were local buckling coupled with overall buckling. A description of the specially fabricated end fixtures for applying eccentric loading to the columns and to simulate pinned end condition is also presented. The experimental results of hollow columns are compared with the existing Indian, British and American codes of practice and the results of concrete-filled columns are compared with EC4 recommendations. It is seen that in the case of hollow columns predictions based on British and American codes of practice and in the case of concrete-filled columns predictions based on EC4 recommendations agree reasonably well with the experimental results. From the experiments it is seen that the provision of in-fill substantially increases the ultimate load carrying capacity of the order of one and a half to two times and the increase in strength of the in-filled concrete from a low grade concrete of compressive strength 24.94 MPa to a high grade concrete of compressive strength 33.26 MPa increases the ultimate load carrying capacity by one and a half times irrespective of the eccentricity of loading.

Key Words
column; cold-formed; concrete-filled; buckling; composite.

Address
H. Jane Helena and G. M. Samuel KnightrnCollege of Engineering, Guindy, Anna University, Chennai 600 025, Tamil Nadu, India

Abstract
This paper reports on finite element analysis techniques that may be applied to the study of circular hollow structural sections and related bearing connection geometries. Specifically, a connection detail involving curved steel saddle bearings and a Structural Tee (ST) connected directly to a large-diameter Hollow Structural Section (HSS) truss chord, near its open end, is considered. The modeling is carried out using experimentally verified techniques. It is determined that the primary mechanism of failure involves a flexural collapse of the HSS chord through plastification of the chord wall into a well-defined yield line mechanism; a limit state for which a shell-based finite element model is well-suited to capture. It is also found that classical metal plasticity material models may be somewhat limited in their applicability to steels in fabricated tubular members.

Key Words
tubular truss; truss bearing; pipe bearing; pipe crushing; curved saddles; nonlinear finite element analysis.

Address
B. Kozy and C. J. EarlsrnDepartment of Civil & Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, 15222, U.S.A.

Abstract
Based on the test data of Nippon Steel Corporation, the formulas for calculating mechanical properties of fire-resistant (FR) steel at elevated temperatures have been established. A practical approach for fire safety design of FR steel members, including axially compressed members, flexural members and eccentrically compressed members, is developed in this paper. Compared with the full-scale specimen experiments and FEM numerical analysis, this practical approach for fire safety design of FR steel members is demonstrated to be effective and precise.

Key Words
fire-resistant steel; fire safety; column; beam.

Address
Guo-Qiang Li and Jun DingrnCollege of Civil Engineering, Tongji University, Shanghai, 200092, ChinarnrnY. SakumotornNippon Steel Corp., 6-3, Otemachi 2-Chome, Chiyoda-ku, Tokyo, 100-71, Japan


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