Experimental and numerical assessment of the effectiveness of FRP-based strengthening configurations for dapped-end RC beams

This paper presents experimental and numerical assessments of the effectiveness of strengthening dapped-end reinforced concrete beams using externally bonded carbon fiber reinforced polymers (CFRPs). The research was prompted by a real application, in which the dapped-ends of several precast/prestressed concrete beams developed diagonal cracks due to errors during assembly. Hence, the dapped-ends were strengthened on-site using CFRP plates to limit further crack opening. In the empirical phase of the study, four similar specimens were tested: one unstrengthened reference specimen, two strengthened with high-strength CFRP plates, and one with high-modulus CFRP sheets. The specimens strengthened with plates had slightly higher load carrying capacity than the reference element, but failed by debonding, while the specimens strengthened with sheets showed no increase of capacity and failed by the fibers rupturing. Nonlinear finite element analysis of the specimens under the test conditions indicated that: (a) debonding is more likely to occur at the inner end of dapped-ends and (b) the capacity could have been increased by up to 20% if the plates had been mechanically anchored.The research work was partially supported by research Grant type A No. 27688/2005, awarded by the National University Research Council, Romania. The authors would also like to thank SIKA Romania Corporation for offering the composite systems used in the experimental tests

Assessment of the strengthening effectiveness of EBR and NSM techniques for beams’ dapped-end by FEM analysis

This document presents the work related to the assessment of the effectiveness of strengthening reinforced concrete (RC) dapped-end beams using carbon fiber reinforced polymers (CFRP). Several non-linear finite element analyses were performed using different strengthening configurations, from the simplest solutions to the more complex ones in which different application schemes were overlapped. The work is focused on evaluating the strengthening systems, considering the ultimate capacities they can lead to and the failure modes involved. There were modeled 17 different strengthening configurations. While some of them provided a marginal increase in the ultimate load that can be applied, several of them provided significant load bearing capacity increase. The observed failure modes ranged from a sudden failure of the whole strengthening system up to the desired progressive failure of the individual components of each strengthening system