Experimental Study on Rehabilitated RC Beamcolumn Connections Under cyclic Loading

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Post-earthquake investigations into damaged structures generally showed that in many cases, damages of RC frame structure were localized in beam-column connections which might have led to partial or total collapse of the building. It was observed that the exterior beam-column connections had suffered more in comparison to the interior ones. The failure of these connections during past earthquakes opened a new research direction in the field of repair of damaged structures. Research in this area is essential as engineers in seismic-prone regions often face the task of analyzing and designing repair or strengthening works for damaged buildings. Thus, it is difficult to decide always whether to discard the damaged structure or to rehabilitate the same for retrieving the lost capacity without any quantitative guidance. After an earthquake, a building may suffer damages and depending on the overall level of structural integrity, it can be rehabilitated by repairing or strengthening the damaged areas. Several methods of rehabilitation on RC beam-column connections damaged during earthquake have been reported. Each of these methods possesses its own practical limitation. The effectiveness of any rehabilitation / strengthening techniques however depends on the treatment provided to the fragmented concrete in the damaged region. Hence, in this study an effort has been focused on rehabilitating the affected damage zone of RC beam-column connections by employing different rehabilitation strategies depending on extent of damages. Several experimental studies have been carried out to evaluate the behavior of rehabilitated RC beam-column connections under cyclic loading. However, no record could be found where the comparative studies covering various deficiencies were addressed together. Further, the nature and extent of damage in a structure during an earthquake depends on the characteristic of loading. Thus, a holistic approach was initiated to cover different deficient cases of RC beam-column connections with different loading characteristic so as to gather a comprehensive knowledge about the behaviour of these connections. Generally, severely damaged structures are thought to be irreparable and are abandoned in spite of huge economic loss. To ensure further usability of the distressed or damaged structure, effective and reasonable techniques are needed to be investigated for rehabilitations of the damaged structures for post-earthquake usage. Some of the researchers conducted tests on beam-column connections without considering the effect of size of the tested specimens. Moreover, most of the investigators conducted tests on scaled down models. The results of scaled down models cannot be used directly for prototype implementation in actual field as the size of specimen plays an important role. Available theories of material behavior that predict size effects are receiving increasing attention in the technical literature. Concrete is a heterogeneous material, which is generally full of micro cracks. Upon loading, these micro cracks propagate and the accumulation of such micro cracks leads to failure of specimens. It is well established that the mathematical modeling of such behavior should be based on the theories of fracture mechanics. Material models based on fracture mechanics can predict a size effect, if geometrically similar specimens.
Supervisor: A. Dutta AND S. K. Deb