The behavior of FRP-confined short concrete columns subjected to eccentric loading

Abstract

Many researches were carried out in the past on the column confined by fiber reinforced polymer (FRP) under concentric loading, which was found that confinement greatly enhance the strength and ductility of column. However, the loading of columns may not be perfectly concentric due to different reasons, in which the column is subjected to eccentric loading. In recent years, many people tried to predict the response of column by simply using the stress-strain equation for concentric loading. Until now, only one stress-strain model was developed to account for behavior of FRP-confined column under eccentric loading with parameters correctly identified. Thus, this study was developed based on the existing model. This study adopted another loading method to investigate the performance of columns under eccentric loads and compare with the existing model. 70 columns were tested and reported in this thesis. Three primary parameters were introduced in the experimental program, which were axial load ratio, confinement ratio and concrete grade. The relationship between the parameters was studied by expressing the experimental data in terms of moment curvature curves and N-M interaction diagrams. The relationship between the lateral strain and longitudinal strain was also studied, which could demonstrate the effectiveness of FRP in enhancing the capacity of column. Based on the experimental result, comparisons were made to the prediction by Wu and Jiang’s stress-strain equation by using section analysis. Great disparity was observed between the predicted curve and the experimental curve. It was found that the prediction from the model overestimates the moment capacity of the column. However, the reason for such a great difference needs detailed analysis in the future study. A preliminary conclusion could be drawn that the stress-strain behavior of column was load path dependent, as seen from the comparison with the existing experimental result.