Doctor of Philosophy
School of Civil, Mining, and Environmental Engineering
Widiarsa, Ida Bagus Rai, FRP-wrapped square RC columns under eccentric loading, Doctor of Philosophy thesis, School of Civil, Mining, and Environmental Engineering, University of Wollongong, 2014. http://ro.uow.edu.au/theses/4073
Reinforced concrete (RC) structural members like columns can experience deterioration caused by many factors such as concrete cracks, corrosion of steel reinforcement, imperfect structural design, damages caused by seismic load, increase of applied load and other factors. Due to these deficiencies of the concrete columns, a strengthening method by wrapping columns with fibre reinforced polymer (FRP) composites has been used widely. Studies on FRP-wrapped concrete columns have been undertaken for many years. Most of the studies investigated columns under concentric loads, whereas only a few studies investigated columns under eccentric loads. Moreover, among the studies on FRP-wrapped concrete columns under eccentric loads, most of them concerned concrete columns with a circular cross section. Only a few studies investigated concrete columns with square or rectangular cross sections. Contrarily, most concrete columns in the field have square or rectangular cross sections and may also resist eccentric loads. This study presents an investigation of the behaviour and performance of carbon fibre reinforced polymer (CFRP)-confined square RC columns under eccentric loading. The axial and flexural behaviour of the columns were investigated experimentally and analytically.
In order to fulfil the objectives of this study, an experimental study was conducted on square RC columns wrapped with CFRP composites. A total of sixteen short column specimens with the dimensions 200 × 200 × 800 mm were cast and tested. Twelve specimens were tested under compression loading and four specimens were tested under flexural loading. The influence of number of CFRP layers, magnitude of eccentricity and fibre orientation were studied. The specimens were divided into four groups: no layer (unwrapped), wrapped with one layer, wrapped with three layers and wrapped with two layers after the application of one layer of vertical CFRP strap. For each group, the specimens were tested under concentric loading, 25 mm eccentric loading, 50 mm eccentric loading and pure flexural loading. An analytical study was also undertaken by proposing FRP-confined strength models.
The experimental results showed that CFRP wrapping enhanced the load carrying capacity and performance of concrete columns, except the columns that were wrapped with one layer of CFRP where no significant enhancement of maximum load was obtained. A more significant enhancement on maximum load was obtained by CFRP wrapping on eccentrically loaded columns compared to concentrically loaded columns. The strength models proposed in this study showed better performance than the existing strength models. Furthermore, the proposed strength models yielded good predictions in estimating the axial load capacity of the CFRP-confined concrete columns.