BEHAVIOR OF REINFORCED CONCRETE COLUMNS CONFINED BY FRP UNDER ECCENTRIC LOADS

Abstract

FRP-confmed concrete columns benefit from a confming effect due to restraint of the lateral expansion. This effect increases the strength and the ductility ofthe concrete confined by FRP shell for case of centric load, as given by many researchers. However, more research work is necessary in order to investigate experimentally the behavior of R.C. columns confmed by FRP under eccentric loads, as it seems that axially loaded columns do not exist in practice and that is why eccentrically loaded columns may be more representative.

This thesis deals with the effect ofload eccentricity on the ultimate load and ductility of confined columns with different height to depth ratio. Thirty R.C columns were tested and their results were analyzed. An analytical model is proposed for analysis of columns subjected to eccentric loads, also empirical equation based on experimental results is proposed, which can be used to determine the ultimate load ofFRP-confined concrete columns under eccentric loads tacking into account load eccentricity as well as height to depth ratio. Note that, we can not use any of the models given by many researchers which have been proved for case of centric loaded columns, as all these models based on a constant vertical strain of concrete along the column depth, while, in case of eccentric loading the vertical stress of concrete is no longer constant.

The proposed method of analysis is verified by comparing the prediction to experimental data published by different researches, as well as the present experimental work . Based on the finding, design guidelines are suggested.

Based on the proposed model, a computer program was designed specially to suite the unique response of FRP-confined concrete circular sections. In the same program we combine the design recommendations with the proposed design expressions to introduce a design program can be used to design FRP-confined short columns and piles, also an example for the proposed design procedure is given. A list of computer program is given in appendix "A".