| Author: | LI, Shuai |
| Title: | Behaviour of FRP-confined concrete composite stub columns with HSC and ECC under monotonic and cyclic loads |
| Advisors: | Chan, Tak-ming (CEE) Young, Ben (CEE) |
| Degree: | Ph.D. |
| Year: | 2022 |
| Subject: | Fiber-reinforced concrete Composite materials Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xxviii, 295 pages : color illustrations |
| Language: | English |
| Abstract: | Fibre Reinforced Polymer (FRP) confined concrete is widely used in engineering applications. With the effective confinement provided by FRP, concrete can exhibit significantly improved load carrying capacity and ductility performance under compressive loads, compared with unconfined concrete. However, the confining efficiency as well as strength and strain enhancement will decrease with the increase of unconfined concrete strength, due to the increased concrete brittleness. In this study, two types of novel FRP-confined concrete composite columns with the use of high strength concrete (HSC) and engineered cementitious composite (ECC), which are named as FRP-ECC-HSC composite column and FRP-concrete double tube composite column, are proposed to achieve the improved structural performance in comparison to the normal FRP-confined HSC columns. Experimental investigations were firstly carried out on the proposed composite columns under monotonic and cyclic axial compression. A total of 31 FRP-ECC-HSC composite columns and 32 FRP-concrete double tube composite columns with different FRP tube thicknesses and concrete strengths were considered in the test programme. It is found that ECC is effective to obtain a more uniform hoop strain distribution on the outer confining FRP tube, leading to the delayed column failure. Compared with normal FRP-confined HSC columns, both FRP-ECC-HSC composite columns and FRP-concrete double tube composite columns exhibited improved ultimate axial strain, which demonstrates the enhanced column deformability. In order to understand the stress-strain response of ECC under FRP confinement, experimental investigations on the axial compressive behaviour of 18 FRP-confined ECC stub columns were also conducted. Analysis-oriented stress-strain models were developed for FRP-confined HSC and ECC in this study, and then were used to generate accurate concrete properties for the numerical simulations. Mechanical analysis was carried out on the FRP-ECC-HSC composite column to understand the non-uniform stress distribution on the composite column section. Finite element (FE) models were established and validated for the proposed composite columns, followed by the parametric study to investigate the influence of different parameters on the column behaviour. Based on the test results obtained from the current study, design approaches were proposed for FRP-ECC-HSC composite columns and FRP-concrete double tube composite columns under monotonic and cyclic loadings. Design equations of the axial load capacity for the composite columns were proposed with the consideration of accurate confined concrete stresses for the core concrete and ring concrete. Monotonic axial load-axial strain models were developed for the composite columns based on the existing monotonic stress-strain model with considering the newly proposed equations for ultimate compressive strength and ultimate axial strain of confined concrete. Cyclic axial load-axial strain models were developed for the composite columns based on the existing cyclic unloading and reloading models as well as the newly proposed equations for the plastic strain and stress deterioration. This study presents a comprehensive investigation on the compressive behaviour of the proposed novel composite columns and provides analysis and design approaches to the FRP-confined concrete columns with innovative sectional forms. |
| Rights: | All rights reserved |
| Access: | open access |
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