Abstract
This paper reports the effects of carbon fiber-reinforced polymer (CFRP) length on the failure process, pattern and crack propagation for a strengthened concrete beam with an initial notch. The experiments measuring load-bearing capacity for concrete beams with various CFRP lengths have been performed, wherein the crack opening displacements (COD) at the initial notch are also measured. The application of CFRP can significantly improve the load-bearing capacity, and the failure modes seem different with various CFRP lengths. The stress profiles in the concrete material around the crack tip, at the end of CFRP and at the interface between the concrete and CFRP are then calculated using the finite element method. The experiment measurements are validated by theoretical derivation and also support the finite element analysis. The results show that CFRP can significantly increase the ultimate load of the beam, while such an increase stops as the length reaches 0.15 m. It is also concluded that the CFRP length can influence the stress distribution at three critical stress regions for strengthened concrete beams. However, the optimum CFRP lengths vary with different critical stress regions. For the region around the crack tip, it is 0.15 m; for the region at the interface it is 0.25 m, and for the region at the end of CFRP, it is 0.30 m. In conclusion, the optimum CFRP length in this work is 0.30 m, at which CFRP strengthening is fully functioning, which thus provides a good reference for the retrofitting of buildings.
Highlights
The applications of carbon fiber-reinforced polymer (CFRP) for strengthening concrete structures have recently received considerable attention
Experiment measurements and finite element (FE) analyses were performed on concrete beams strengthened with various lengths of CFRP bonded onto the bottom of a beam subjected to 20 kN loading applied to the central point
(3) The failure mode for strengthened concrete beams varies with CFRP length
Summary
The applications of carbon fiber-reinforced polymer (CFRP) for strengthening concrete structures have recently received considerable attention. Various methods are extensively used for strengthening concrete structures, especially for flexural members; these methods include the use of additional steel parts, external pre-stressing of parts and reducing or bridging the gap between supports [1,2,3,4] These methods generally require considerable economic cost and consume a great deal of time. CFRP is high in strength and rigidity, as well as having a low specific weight This material has widely been applied in structural engineering for the retrofitting and strengthening of reinforced concrete (RC) beams and steel beams (both of them are similar in flexural behavior). The research [10,11]
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