Retrofitting of Beam Column Joints Using Confined High Performance Hybrid Fiber Reinforced Concrete

Abstract

Presently, various multi storey buildings are serving to the societies which were constructed before the implementation of seismic codal guidelines. The change in occupancies of building, amendment in codal provisions and to meet the present seismic demand, there is an urgent need for up-gradation of these structures. In the past, various methods, such as steel plate adhesion, jacketing, and fiber reinforced polymer (FRPs), have been successfully deployed to retrofit the pre-seismically detailed structures. Nonetheless, the demerits associated with these techniques depict the limitation in the performance of the retrofitted BCJ. The initial damage level also significantly governs the retrofitting strategies and affects the performance of the retrofitted BCJ. The newly developed high performance hybrid fiber reinforced concrete (HP-HFRC) revealed excellent properties (post-elastic ductility, strain hardening, higher tensile strain, higher bond strength and durability) which are expected from the retrofitting materials. Hence, it can be used as a new retrofitting material. Moreover, in past studies, much attention was not paid to the fact that what is the initial damage level of the beam-column joint before the time of retrofitting. Therefore, the present study explores the possibility of using HP-HFRC in the retrofitting of beam column joint which is initially damaged to different damage levels. In the study firstly, the HP-HFRC is developed using trial and error method and fresh, mechanical and durability properties were evaluated. Thereafter, the design mix is refined using Andreasen and Andersen (AandA) packing model. The fresh, mechanical, durability and microstructural properties are evaluated after 28 days of curing and are further used for retrofitting the initially damaged beam column joint. In the second phase of the study, sixteen beam column joint specimens are cast and set of two specimens are tested as control specimens for each retrofitting strategy.