Seismic Retrofitting Of R.C. Structures Using Buckling restrained Braces

Abstract

Revision in standard specifications for building design is a continuous process. Advancement in material technology, understanding about behaviour of structural systems, construction technology, tools for analysis and design as well as availability of data related to hazards lead to modifications of standards. Old buildings which are not complying the requirements of revised standards need to be retrofitted. To satisfy the lateral strength requirement of existing Reinforced concrete buildings the seismic retrofitting techniques are to be implemented to enhance the behaviour of the building under future earthquake. Since last few decades buckling restrained braces (BRB) have become increasingly popular as lateral force resisting element because of its capacity of improving the strength, the stiffness and the energy dissipating capacity of the structure. Present study aims to understand behaviour of buckling restrained brace and its implementation in building for performance enhancement. In this study 6 storey Reinforced concrete framed structure is considered. Modelling and Analysis of building is carried out using ETABS software. Design of a building is carried out as per IS 456:2000 and IS 1893 Part 1(2016). To examine the capacity of the existing building Non linear static analysis procedure is used and deficient members are identified. Subsequently with incorporation of buckling restrained braces with different geometric configurations the response of a building is evaluated. Comparative study between Ordinary Concentric Braced Frame (OCBF) and Buckling Restrained Braced Frame (BRBF) is also carried out to understand the advantage of buckling restrained braces. Nonlinear Time History Analysis (NLTHA) and Incremental Dynamic Analysis (IDA) of building is carried out for retrofitting of building using buckling restrained braces. From the study it is found that buckling restrained brace proves to be better alternative for seismic retrofit technique in terms of increased energy dissipation, reduced top story displacement, reduced inter story drift and increased stiffness. In order to understand behaviour of buckling restrained brace an experimental study is carried out. Experimental results are compared with that obtained from Euler's buckling theory. Further experiment is carried out on reduced scale bare portal frame and portal frame with buckling restrained brace to verify the behaviour of Buckling Restrained Brace Frame (BRBF)