| Six isolated and simplified reinforced concrete (RC) beam-column joint specimens were tested in order to study the behavior of the RC frames' beam end zones before and after strengthening. The specimens were subjected to controlled deterioration under cyclic loading first until yielding of the reinforcement. Then, they were strengthened with RC jacketing and bonding steel plates respectively. The investigated test parameter of the specimens strengthened by RC jacketing were connection types between the new reinforced bars and the column. Eventually, the rehabilitated specimens were retested under low cyclic loading. The loads and displacements of the beam end as well as the steel or plate strain were measured in detail; and furthermore, crack patterns and failure model of the specimens were also observed during the test.Comparison including the cracking, yielding and ultimate loads of the beam, load-displacement curve, envelop curve, the ductility and energy-dissipation capacity were made between the response of the specimens before and after strengthening. Test results indicated that the yielding loads of the specimens after strengthening were improved from 12.3 percent to 17.2 percent and the improvement of specimens rehabilitated by jacketing was higher than that of the bonding steel plates one.In this thesis, the major behaviors of the rehabilitated RC joints were studied theoretically which contained the flexural and shear capacity of the beam at the ends, the shear capacity of the joint core, shear stress of the interface and the shear stress transfer mechanism from beam to the column. Analytic results were also compared with the test results. Furthermore, factors that affect the rehabilitation were studied for the sake of further study and application.Suggestions for design, construction and for further research were presented based on the whole study.
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