| Author: | Xia, Zhiyu |
| Title: | Structural behavior of FRP-reinforced concrete arches |
| Advisors: | Yu, Tao (CEE) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Subject: | Fiber-reinforced concrete Reinforced concrete construction Concrete arches Structural engineering Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xxxiv, 286 pages : color illustrations |
| Language: | English |
| Abstract: | Arches are a common type of structures that have been extensively used in the field of civil engineering, known for their excellent spanning and load-bearing capabilities. Traditionally employed in tunnel linings and bridges, arch structures are typically designed for a long service life (e.g., more than 100 years). However, steel-reinforced concrete (RC) arch structures often suffer from degradation due to steel corrosion, resulting in massive maintenance and repair costs. To address the durability problem, the use of fiber-reinforced polymer (FRP) bars in substitution of traditional steel rebars has gained increasing applications, particularly for structures exposed to a corrosive environment. This PhD study is concerned with the structural behavior of FRP-RC arches. The study started with preliminary investigations on an FRP-RC arch, which validate the feasibility of such arch structures while elucidating two key challenges that they may face: (1) the use of existing FRP stirrup products, whose horizontal legs take up a significant portion of space in shallow arches, may negatively affect the flexural stiffness/strength and lead to locally weak sections in such arches; (2) the relatively low elastic modulus of glass FRP (GFRP) compared to steel may result in significant load drops accompanied with the opening of major cracks in under-reinforced arches. Furthermore, it was found in the preliminary investigations that the existing simplified theoretical models fail to account for geometric nonlinearity and may thus overestimate the load-bearing capacity of FRP-RC arches. This study was then focused on addressing these challenges so as to facilitate the wide practical applications of FRP-RC arches. Firstly, a novel form of narrow closed FRP stirrups, fabricated via a filament winding process, was developed. The horizontal legs are purposely removed in the novel stirrups to minimize the reduction of concrete area and the resulting local weakening of section capacity, while the use of filament winding method leads to enhanced strength at the bent region of the stirrups compared to the pultruded FRP stirrup products in the market. The effectiveness of the novel stirrups as shear reinforcement of concrete structures were demonstrated in this study by systematic laboratory tests. To mitigate the effects of relatively low elastic modulus of GFRP rebars, it is recommended that GFRP-reinforced concrete arches shall be designed as over-reinforced members to meet the serviceability requirements and to reduce/eliminate the load drops associated with opening of cracks. A systematic experimental study was then conducted on over-reinforced FRP-RC arches with the novel stirrups proposed in this PhD project. The structural behavior of these arches was thoroughly examined, and it was demonstrated that they can sustain a monotonically increasing load without significant load drops upon cracking, and that their load-bearing capacities are comparable to the steel-reinforced concrete arch with a similar reinforcement ratio. Furthermore, to gain a comprehensive understanding of the structural behavior of FRP-RC arches, two advanced predictive methods were developed: one based on one-dimensional (1D) theoretical modeling and the other based on three-dimensional (3D) finite element (FE) simulations. The 1D theoretical model was developed based on an enhanced deflection method, offering a unified approach for handling both small- and large-curvature problems in 1D members, with an emphasis on its applicability to FRP-RC arches and other FRP-enabled arches. The enhanced deflection method considers the interaction between axial forces and bending moments while ignoring shear contributions, and it is thus suitable for efficiently analyzing simple uniaxial or biaxial load cases at relatively small computational costs. The sophisticated 3D FE model was developed to provide more in-depth insights into the behavior of FRP-RC arches. This model effectively captures complex load interactions (e.g., combined effects of axial load, shear load, and bending moment) and the bond-slip relationship between FRP rebars and the surrounding concrete. The model was validated using the test results and was subsequently employed in a parametric study on FRP-RC arches, considering a wide range of parameters that may affect their structural behavior. The results of the parametric study have laid a solid foundation for the design of FRP-RC arches to suit various structural demands. |
| Rights: | All rights reserved |
| Access: | open access |
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