Behavior of Coupling Beams Strengthened with Carbon Fiber Reinforced Polymer Sheets

In this research, using the results of 6 tests, the effect of Carbon Fiber Reinforced Polymer (CFRP) sheets on the behavior of reinforced concrete coupling beams of shear walls is studied. First, in the experimental part of the study, four coupling beams with different reinforcements were manufactured and tested. Then, after the failure of the specimens, two of them were rehabilitated and strengthened with CFRP sheets, and retested. Four specimens were constrained longitudinally in order to evaluate the effect of the slab diaphragm on the coupling beam behavior. In each test, the applied load and the displacement of the coupling beam were measured. Test results show that the CFRP sheets can increase the shear strength of the conventional reinforced coupling beams. The Canadian Institute ISIS equations are in agreement with the test results of the strengthened beams. The assumption of a major diagonal crack instead of 45 degrees inclined cracks due to shear forces results in a better prediction of the strength of coupling beams. Based on the results of this study, the effect of longitudinal constraint may not be remarkable for the strength of coupling beams with conventional reinforcements. The rehabilitated and strengthened coupling beams with CFRP sheets can achieve appropriate strengths even larger than those of original beams. However, their stiffness decreases.