Ductile fiber wrapping for seismic retrofit of reinforced concrete columns

Abstract

An experimental study was performed on fiber wrapping to strengthen RC columns with insufficient moment capacity and ductility. In pseudo-seismic test of four columns with a circular cross section, the test variable was fiber type: none, carbon fiber (CF), polyethylene terephthalate (PET), and combined use of CF+PET. PET has high tensile strength and ductility, but very low elastic modulus. While a large area of PET typically needs to be used, the amount of PET actually utilized was about 50% of CF in terms of fiber axial stiffness (E f A f). All columns wrapped by CF and/or PET showed significantly improved strengths over the control column (121~143% of control column) while ductility also significantly improved (2.3~3.1 times the control column). Performance of PET was comparable to that of CF in terms of strength and ductility improvement while no sign of fiber rupture was observed at ultimate stage due to excellent ductility intrinsic with PET.

Modification of epoxy binder with multi walled carbon nanotubes in hybrid fiber systems used for retrofitting of concrete structures: evaluation of strength characteristics

“…These two stages usually govern the ultimate properties of the concrete and the MWCNT incorporated FRP. Control specimens exhibit failures at the end of the initial stage itself due to its brittle nature [ 46 ]. On the contrary, MWCNT incorporated FRP confined specimens after yielding shows ductile mode of failure.…”

“…It was clear that HSBFRP and CFRP wrapped specimens survived more in the second and final stage exhibiting their better ductile and yielding properties. Thus, reducing the probability of catastrophic failure [ 46 ].

Figure 13 Axial stress-strain curves of specimens confined with different FRP systems.

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Evaluation of Hybrid Fiber Multiscale Polymer Composites for Structural Confinement under Cyclic Axial Compressive Loading

“…However, recently, an emerging trend has been the usage of natural fibers in FRP composites as a replacement for conventional synthetic fibers. In fact, natural fibers such as sisal, jute, abaca, and flax fiber, which have moderate tensile and flexural properties, when used in fiber reinforced polymers were effective in retrofitting concrete columns [14][15][16]. The usage of natural fibers in strengthening application is considered to be a renewable and sustainable solution.…”

Confining effects of circular concrete tests reinforced PET fiber

“…The increase of strength and ductility by sheet reinforcement is effective in columns with small lateral displacement, but for columns that require large displacement due to big earthquakes, it cannot be expected that sheet reinforcement would offer sufficient ductility. For reinforcing materials like CF, GF, or aramid fiber do not have sufficient material properties to resist large displacement (Donguk et al 2015;Mander, Priestley, Park 1988;Moon Kwan 2006). Therefore, this study aimed to identify the strength and ductility improvement by polyethylene terephthalate (PET), and to examine the characteristics of PET fiber compared to the existing reinforcing materials like CF sheets or GF sheets so as to determine whether PET fiber can be used for construction projects as a reinforcing material.…”