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|Title:||Structural behaviour of octagonal concrete-filled steel tubular stub columns under uniaxial compression||Authors:||Zhu, Jiongyi||Degree:||Ph.D.||Issue Date:||2019||Abstract:||Composite steel-concrete construction system has favourable advantages over the traditional systems. It combines the structural and construction efficiency from both the reinforced-concrete and steel construction. Concrete filled steel tube is one of the most popular structural members in composite construction system and cross-section shape is one of the crucial factors to determine its structural efficiency. Commonly used cross-section shapes include circular and rectangular cross-section which have their own advantages and limitations. Circular cross-section can provide the most efficient confinement to enhance the concrete compressive strength while rectangular cross-section can provide better constructability in tube fabrication and in beam-column connection. This thesis targets an innovative cross-section shape - octagonal cross-section, which combines the merits of both circular and rectangular cross-sections. Through experimental investigation, numerical simulation and development of design formulation, the structural behaviour of octagonal concrete-filled steel tubular stub columns under uniaxial compression has been investigated. Experimental investigation on normal strength steel cold-formed hollow tubular stub columns with circular, square and octagonal cross-section shapes under monotonic axial compression was conducted. The measured yield strength ranged from 381 MPa to 477 MPa. Detailed material tests together with residual stress measurements were carried out. Complemented by the validated numerical models, in line with the design methodology of Eurocode 3, a cross-section classification approach designated for octagonal cross-section has been proposed.
Furthermore, experimental investigation on concrete-filled steel tubular (CFST) stub columns in conjunction with the plain concrete counterparts, in circular, square and octagonal cross-section shapes under monotonic axial compression was conducted. Different concrete grades were examined with measured compressive cylinder strengths ranging from 38 MPa to 112 MPa. In line with the design methodology of Eurocode 4, a design method to predict the cross-section axial load resistance of octagonal CFST taking into consideration of confinement effect on concrete core has been proposed. In parallel to the experimental investigations on hollow and CFST specimens, experimental investigation on steel tube confined concrete (STCC) stub columns with circular, square and octagonal cross-section shapes under monotonic axial compression was also conducted. Likewise, different concrete grades were examined with measured compressive cylinder strengths ranging from 38 MPa to 112 MPa. The performance of STCC stub columns and the CFST counterparts with different cross-section shapes has been compared. Comparisons have indicated that the design method for CFST stub column is also applicable for the design of STCC stub column. Based on the abovementioned experimental results, a finite element modelling methodology has been developed and an analysis model of confined concrete in CFST stub columns has been proposed. The developed finite element models can capture the behaviour of non-linear confined concrete in octagonal CFST stub columns and mimic the corresponding load capacity and stress-strain relationship.
|Subjects:||Hong Kong Polytechnic University -- Dissertations
Structural analysis (Engineering)
|Pages:||xxiv, 220 pages : color illustrations|
|Appears in Collections:||Thesis|
View full-text via https://theses.lib.polyu.edu.hk/handle/200/9898
Citations as of May 28, 2023
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