Abstract
Available guidelines do not provide design procedures for the general case of retrofitting reinforced concrete (RC) columns using fiber reinforced polymer (FRP) sheets subjected to simultaneous bi-axial flexural and axial loads. In many practical cases, columns essentially undergo simultaneous axial force and bi-axial bending moments, especially in in-situ construction. This paper suggests a simplified design method based on the equivalent uni-axial moment concept to calculate the required number of layers FRP sheets for retrofitting RC square columns. The proposed procedure is then verified against available bi-axial moment and axial force test data found in the literature. Results demonstrate that the proposed procedure is appropriate for practical applications with acceptable accuracy. It also appears that retrofitting RC square columns by longitudinal fiber arrangement is only effective for columns with tension-controlled behavior, while transverse and combined longitudinal-transverse arrangements are more effective in enhancing the load bearing capacity of both the compression- and tension-controlled columns. A design example will also be presented.
Highlights
There are a number of situations where an increase in structural capacity or rehabilitation of reinforced concrete (RC) columns are required
This paper proposed a simplified design procedure for calculating the required number of fiber reinforced polymer (FRP)
Analysis results indicate that fibers with transverse orientation lead to enhancement of strength in the compression-controlled region of the interaction curve of the column and longitudinal fibers cause an increase in strength in the tension-controlled region
Summary
There are a number of situations where an increase in structural capacity or rehabilitation of reinforced concrete (RC) columns are required. From a ductility capacity point of view, notable biases are typically observed between theoretical models and experimental results [12,13] This may be due to the fact that eccentric loading conditions significantly affects the ultimate axial strain of the confined column, an issue that is of great significance for predicting deformation capacity of retrofitted. This guideline deals with the subject of retrofitting of RC columns under axial loads without direct attention to biaxial moments It seems that current design procedures consider primarily the increase in axial load capacity of RC columns merely due to the increase in compressive strength of concrete resulting from confinement effects of FPR sheets. The proposed procedures will be illustrated through a case study along with it will be validated against experimental results
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