| Author: | Chen, Junbo |
| Title: | Behaviour and design of high strength circular hollow and concrete-filled tubular stub columns under uniaxial compression |
| Advisors: | Chan, Tak-ming (CEE) Chung, Kwok-fai (CEE) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Steel, High strength Tubular steel structures Concrete-filled tubes Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xx, xi-xii, 225 pages : color illustrations |
| Language: | English |
| Abstract: | High strength steel (HSS) has been increasing adopted in constructional industry due to its high strength-to-weight ratio. The application of HSS in tubular members has great potential in structural engineering due to their aesthetic appearance and strong resistance against torsional buckling. Related research and design rules for HSS circular hollow sections (CHSs) and concrete-filled steel tubular (CFST) sections are therefore imperative in order to promote the structural application of HSS. In this study, an experimental programme consisting of 58 tensile coupon tests, residual stress measurements on 2 CHSs, 16 HSS CHS stub column tests and 36 high strength circular CFST stub column tests were carried out. A total of 11 CHSs were considered. The steel tubes were manufactured from Q460, Q690 and Q960 quenched and tempered (QT) steel plates with measured yield strengths varying from 546.5 MPa to 973.3 MPa. As regards the stub column behaviour of high strength CFST columns, three concrete grades with compressive cylinder strengths of 30, 50 and 90 MPa were used to fill the steel tubes. The cold-forming effect and the material variability within the cold-formed CHSs were examined by 58 tensile coupons extracted from both virgin plates and cold-formed tubes. The material properties after cold work of forming were discussed. A new bilinear plus nonlinear strain-hardening constitutive model was proposed for materials with pronounced yield plateau, while an existing model was adopted to describe the stress-strain relationships of cold-formed steels. Residual stress measurements were made on two cold-formed HSS CHSs. A multilinear predictive model for the distribution of membrane residual stresses in cold-formed HSS CHS was proposed and satisfactory agreement was yield when compared to test results. The stub column behaviour and strength of cold HSS CHSs under axial compression were examined. A total of 16 stub column specimens fabricated from different steel plates with mean measured yield strengths ranging from 546.5 MPa to 973.3 MPa were tested. Finite element (FE) modelling on 175 HSS CHSs in seven steel grades was carried out. Based on the test and FE results, it was found the design methods in current design codes, e.g. ANSI/AISC 360-16, AISI S100-16, AS 4100-1998, and EN 1993, are generally appropriate for normal strength steel but become conservative for HSS. A more precise cross-section slenderness limit and a new set of design equations were proposed. It was found that the proposed design equations generally produce more accurate and less scattered strength predictions. The stub column behaviour and strength of high strength circular CFSTs under axial compression were examined. A total of 36 stub column specimens were tested. The steel tubes were fabricated from different steel grades with mean measured yield strengths ranging from 546.5 MPa to 973.3 MPa and three concrete grades with compressive cylinder strengths of 30, 50 and 90 MPa were used. An experimental database composed of 232 high strength circular CFST stub column test results was complied. Based on the test and collected results, it was found the design method in ANSI/AISC 360-16 provides safe but conservative strength predictions. Based on the proposed cross-sectional limit for CHSs, a new set of design equations in conformance with ANSI/AISC 360-16 were then proposed. It was found that the proposed design method gives more accurate and less scattered strength predictions when compared to ANSI/AISC 360-16. |
| Rights: | All rights reserved |
| Access: | open access |
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