Evaluation of moment distribution in continuous fiber-reinforced polymer-strengthened concrete beams

Fiber-reinforced polymer (FRP) strengthening offers many well-documented benefits for the retrofit of existing reinforced concrete (RC) structures. The main drawback in using FRP for such applications, however, is the reduction in ductility capacity after strengthening. This loss in ductility has led worldwide codes to not consider redistribution of bending moments in continuous FRP-strengthened RC beams. This implies that an unstrengthened continuous RC beam that was previously designed under assumptions of moment redistribution (MR) and is to be strengthened with FRP must now be redesigned according to full elastic distribution of bending moments. This could lead to onerous conditions in such strengthening applications. This paper sets out a rationale for the possible appropriate use of redistribution principles for FRP-strengthened beams. Analytical results show that if a section can develop a curvature ductility capacity greater than 2.0, it is likely that redistribution in the order of at least 7.5% can be achieved. These results are presented and further discussed in this paper. © 2008, American Concrete Institute