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  • Nonlinear Inelastic Analysis of

    Concrete-Filled Steel Tubular

    Slender Beam-Columns

    by

    Vipulkumar Ishvarbhai Patel, ME

    Thesis submitted in fulfillment of the requirement for the degree of

    Doctor of Philosophy

    College of Engineering and Science, Victoria University, Australia

    January 2013

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns ii

    ABSTRACT

    High strength thin-walled concrete-filled steel tubular (CFST) slender beam-columns

    may undergo local and global buckling when subjected to biaxial loads, preloads or

    cyclic loading. The local buckling effects of steel tube walls under stress gradients have

    not been considered in existing numerical models for CFST slender beam-columns. This

    thesis presents a systematic development of new numerical models for the nonlinear

    inelastic analysis of thin-walled rectangular and circular CFST slender beam-columns

    incorporating the effects of local buckling, concrete confinement, geometric

    imperfections, preloads, high strength materials, second order and cyclic behavior.

    In the proposed numerical models, the inelastic behavior of column cross-sections is

    simulated using the accurate fiber element method. Accurate constitutive laws for

    confined concrete are implemented in the models. The effects of progressive local

    buckling are taken into account in the models by using effective width formulas. Axial

    load-moment-curvature relationships computed from the fiber analysis of sections are

    used in the column stability analysis to determine equilibrium states. Deflections caused

    by preloads on the steel tubes arising from the construction of upper floors are included

    in the analysis of CFST slender columns. Efficient computational algorithms based on

    the Mllers method are developed to obtain nonlinear solutions. Analysis procedures

    are proposed for predicting load-deflection and axial load-moment interaction curves for

    CFST slender columns under axial load and uniaxial bending, biaxial loads, preloads or

    axial load and cyclic lateral loading.

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns iii

    The numerical models developed are verified by comparisons of computer solutions

    with existing experimental results and then utilized to undertake extensive parametric

    studies on the fundamental behavior of CFST slender columns covering a wide range of

    parameters. The numerical models are shown to be efficient computer simulation tools

    for designing safe and economical thin-walled CFST slender beam-columns with any

    steel and concrete strength grades. The thesis presents benchmark numerical results on

    the behavior of high strength thin-walled CFST slender beam-columns accounting for

    progressive local buckling effects. These results provide a better understanding of the

    fundamental behavior of CFST columns and are valuable to structural designers and

    composite code writers.

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns iv

    DECLARATION

    I, Vipulkumar Ishvarbhai Patel, declare that the PhD thesis entitled Nonlinear inelastic

    analysis of concrete-filled steel tubular slender beam-columns is no more than 100,000

    words in length including quotes and exclusive of tables, figures, appendices,

    bibliography, references and footnotes. This thesis contains no material that has been

    submitted previously, in whole or in part, for the award of any other academic degree or

    diploma. Except where otherwise indicated, this thesis is my own work.

    Signature Date:

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns v

    ACKNOWLEDGMENTS

    The author would like to thank his principal supervisor A/Prof. Qing Quan Liang for his

    close supervision, productive discussions and invaluable suggestions throughout the

    period of the research project. The author would also like to thank his associate

    supervisor A/Prof. Muhammad N.S. Hadi of the University of Wollongong for his

    discussions, invaluable suggestions, encouragement and support.

    The research presented in this thesis was carried out in the College of Engineering and

    Science at Victoria University (2010-2013). The author was supported by an Australian

    Postgraduate Award and a Faculty of Health, Engineering and Science scholarship. The

    financial support is gratefully acknowledged.

    The author would also like to thank all staff in the College of Engineering and Science

    and Postgraduate Research Office for their kind assistance. I am grateful to the staff of

    the Victoria University library for their strong support of my enthusiasm to find the

    research articles and reports.

    The author wishes to express his appreciation to his friends and colleagues for their help

    and support.

    Last, but certainly not the least, the author would like to thank his family for their

    support and understanding during three years study.

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns vi

    LIST OF PUBLICATIONS

    Based on this research work, the candidate has written the following papers, which have

    been published or submitted for publication in international journals and conference

    proceedings.

    Journal Articles

    1. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., High strength thin-walled

    rectangular concrete-filled steel tubular slender beam-columns, Part I: Modeling,

    Journal of Constructional Steel Research, 2012, 70, 377-384.

    2. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., High strength thin-walled

    rectangular concrete-filled steel tubular slender beam-columns, Part II: Behavior,

    Journal of Constructional Steel Research, 2012, 70, 368-376.

    3. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Inelastic stability analysis of high

    strength rectangular concrete-filled steel tubular slender beam-columns,

    Interaction and Multiscale Mechanics, An International Journal, 2012, 5(2), 91-

    104.

    4. Liang, Q. Q., Patel, V. I. and Hadi, M. N. S., Biaxially loaded high-strength

    concrete-filled steel tubular slender beam-columns, Part I: Multiscale simulation,

    Journal of Constructional Steel Research, 2012, 75, 64-71.

    5. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Biaxially loaded high-strength

    concrete-filled steel tubular slender beam-columns, Part II: Parametric study,

    Journal of Constructional Steel Research (currently under review).

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns vii

    6. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Numerical analysis of circular

    concrete-filled steel tubular slender beam-columns with preload effects,

    International Journal of Structural Stability and Dynamics, 2013, 13(3), 1250065

    (23 pages).

    7. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Nonlinear analysis of rectangular

    concrete-filled steel tubular slender beam-columns with preload effects, Journal

    of Constructional Steel Research (currently under review).

    8. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Numerical analysis of high-strength

    concrete-filled steel tubular slender beam-columns under cyclic loading, Journal

    of Constructional Steel Research (currently under review).

    Refereed Conference Papers

    9. Liang, Q. Q., Patel, V. I. and Hadi, M. N. S., Nonlinear analysis of biaxially

    loaded high strength rectangular concrete-filled steel tubular slender beam-

    columns, Part I: Theory, Proceedings of the 10th International Conference on

    Advances in Steel Concrete Composite and Hybrid Structures, Singapore, July

    2012, 403-410.

    10. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Nonlinear analysis of biaxially

    loaded high strength rectangular concrete-filled steel tubular slender beam-

    columns, Part II: Applications, Proceedings of the 10th International Conference

    on Advances in Steel Concrete Composite and Hybrid Structures, Singapore, July

    2012, 411-418.

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns viii

    11. Patel, V. I., Liang, Q. Q. and Hadi, M. N. S., Nonlinear inelastic behavior of

    circular concrete-filled steel tubular slender beam-columns with preload effects,

    Proceedings of the 10th International Conference on Advances in Steel Concrete

    Composite and Hybrid Structures, Singapore, July 2012, 395-402.

  • V.I. Patel: Nonlinear Inelastic Analysis of Concrete-Filled Steel Tubular Slender Beam-Columns ix

    PART A:

    DETAILS OF INCLUDED PAPERS: THESIS BY PUBLICATION

    Please list details of each Paper included in the thesis submission. Copies of published papers and submitted and/or final draft Paper manuscripts should also be included in the thesis submission.

    Item/

    Chapter

    No.

    Paper Title

    Publication

    Status(e.g. published, accepted for publication, to be revised and resubmitted, currently under review, unsubmitted but proposed to be submitted)

    Publication Title and

    Details (e.g. date published, impact factor etc.)

    3

    High strength thin-walled rectangular con