Available guidelines do not provide design procedures for the general case of retrofitting\nreinforced concrete (RC) columns using fiber reinforced polymer (FRP) sheets subjected to\nsimultaneous bi-axial flexural and axial loads. In many practical cases, columns essentially undergo\nsimultaneous axial force and bi-axial bending moments, especially in in-situ construction. This paper\nsuggests a simplified design method based on the equivalent uni-axial moment concept to calculate\nthe required number of layers FRP sheets for retrofitting RC square columns. The proposed procedure\nis then verified against available bi-axial moment and axial force test data found in the literature.\nResults demonstrate that the proposed procedure is appropriate for practical applications with\nacceptable accuracy. It also appears that retrofitting RC square columns by longitudinal fiber\narrangement is only effective for columns with tension-controlled behavior, while transverse and\ncombined longitudinal-transverse arrangements are more effective in enhancing the load bearing\ncapacity of both the compression- and tension-controlled columns. A design example will also\nbe presented.
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