Development of new structural systems using novel and eco-efficient construction materials
| dc.contributor.advisor | Nguyen, Giang D. | |
| dc.contributor.advisor | Thomas, Vincent | |
| dc.contributor.author | Fallah Pour, Ali | |
| dc.contributor.school | School of Civil, Environmental and Mining Engineering | en |
| dc.date.issued | 2021 | |
| dc.description.abstract | Fibre-reinforced polymer (FRP)-confined high strength concrete (HSC) as a structural system, has received significant attention recently due to higher engineering profits compared to normal strength concrete (NSC). To use widely any new construction material or structural element in the construction industry, its mechanical behavior under different loading type should be accurately determined. Although numerous research was performed to predict the mechanical behavior of FRP-confined concrete, most of the models had a poor prediction for the ultimate axial strain which is a key reference parameter in designing procedure. This inaccuracy can be dependent or on experimental data which were used to develop/validate models, either on the understanding of mechanical response of FRP-confined concrete. Examination of existing experimental data needed for developing or validating a model in this study shows that the type of measurement method is one important factor affecting the obtained experimental axial stress-strain curve for FRP-confined HSC specimens. This indicates that a better measurement method should be used to obtain both local and overall deformation of specimens during the test procedure. Investigation on the performance of existing models showed that compressive strength of concrete and hoop rupture strain are two influential parameters in existing models which govern the accuracy of models compared to other parameters. However, hoop rupture strain had a large variability of recorded data in existing experiments, partly due to the use of contact measurement methods, i.e. strain gauges that measure local lateral deformation. In addition, this variability can be dependent on the understanding of mechanical behavior, confinement mechanism and localization characteristics of FRP-confined concrete. The confinement mechanism was examined in this study by investigation of FRP-confined HSC behavior under concentric and eccentric loading condition. A total of 31 specimens with circular and square cross-section were tested under different eccentricity ranging between 0 to 50 mm. The outcome showed that the load-displacement-curves are influenced significantly by eccentricity. The results also illustrated that the ultimate axial stress decreased by increasing eccentricity opposite to ultimate axial strain. The results also indicate the influence of eccentricity on the confinement mechanism. The mechanical behavior and localised failure of unconfined and FRP-confined concrete circular specimens for three structural systems, i.e. plain, ultra-high-strength steel and polyvinyl alcohol fibre-reinforced concrete-filled FRP tubes (CFFT), was investigated using Digital Image Correlation (DIC). A new approach also was developed to correlate the mechanical behavior of FRP-confined concrete with its localization characteristics. This approach is able to determine the onset of localization accurately and quantify the localization evolution. Furthermore, probability density function (PDF) was used in this approach to correlate localization characteristics to the mechanical response of FRP-confined concrete. The localization onset of FRP-confined NSC specimens was found to be earlier than in FRP-confined HSC specimens. Furthermore, the outcome indicated the existence of two types of localization evolution in tested specimens. The results showed that the unconfined and insufficiently confined specimens showed abrupt expansion of shear zone opposite to well-confined specimens by more gradual expansion. The results also indicated that the mechanical behavior of FRP-confined HSC is governed by naturally brittle behavior of HSC and the distribution of strain over specimens’ surface had similar behavior to probability density function. The analysis and quantification of strain evolution showed that Beta PDF function can be used to capture the distribution and evolution of Von Mises strain over specimens’ surface and to correlate localization characteristics to mechanical response of specimens under compression. The intrinsically brittle behavior of HSC influences negatively the mechanical performance of unconfined HSC and FRP-confined HSC. An abrupt behavior in the evolution of localization of HSC specimens and FRP-confined HSC compared to NSC was observed in this study, although FRP jackets limited this brittle behavior. In previous reports it has been found that adding fibers such as steel in concrete wet mix improves the performance of HSC and shows more ductile behavior compared to plain HSC. In this study, ultra-high-strength steel and polyvinyl alcohol fibers were used to improve brittle behavior of FRP-confined HSC. The results showed that these fibers improve the ductility of this structural element by disappearance of temporary lose of strength after transition zone in axial stress-strain curve and higher obtained ultimate axial strain. However, it was observed that ultimate axial stress had a marginal increase by adding used fibers in wet mix of concrete at same normalized lateral stiffness. Additionally, as shown in this study, the lateral behavior of these systems was not altered significantly by adding fibers and approximately similar lateral trend as FRP-confined plain concrete can be obtained. Although the more homogenous crack distribution and localization evolution were observed in these structural elements due to the bridging phenomenon, the characteristics of localization did not change intensively. Finally, to establish better engineering characteristics of studied systems, a correlation between bridging and mechanical performance of specimens was made which shows the detail of bridging occurrence under compressive loading. | en |
| dc.description.dissertation | Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environment & Mining Engineering, 2020 | en |
| dc.identifier.uri | https://hdl.handle.net/2440/133090 | |
| dc.language.iso | en | en |
| dc.provenance | This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals | en |
| dc.subject | Stress-strain curve | en |
| dc.subject | FRP-confined concrete | en |
| dc.subject | steel fibre reinforced concrete | en |
| dc.subject | PVA fiber reinforced concrete | en |
| dc.subject | strain localization | en |
| dc.title | Development of new structural systems using novel and eco-efficient construction materials | en |
| dc.type | Thesis | en |
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