Whenever a member of a structure becomes structurally deficient, it becomes vulnerable to the existing load and for the additional loads that it may be subjected to in the coming future. Since columns are the most important structural element, the structural retrofit of columns, relative to other structural elements is of prime importance. This study intends to investigate the performance and behaviour of an RC column jacketed with Reinforced Concrete columns under axial loads. The objective of this paper is to find out the efficiency of RC jacket in enhancing the strength of an existing RC column. A mathematical design based upon Indian Standards codes has been designed to identify the behaviour of jacketed RC columns. This has been followed by a finite element based numerical simulation using the same material properties as used in the process of designing. The simulation has been done in ABAQUS software with appropriate contact modelling. The analytical model considers that there is no bond slippage between the existing and new concrete surface i.e. the bond between the existing and new concrete is assumed to be perfect. This perfect bond between the surfaces has been modelled by using appropriate constraints in ABAQUS software. The finite element models show fair agreement with the designed values in terms of ultimate capacity and failure mode. The load bearing capacity enhancement of the RC jacketed column has been found to increase substantially. The enhancement capacity results obtained from the finite element software differs about 16-25% from the design values.

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Existing buildings may need to be strengthened to avoid the damage related to structures due to an increase in floor loads, inadequate detailing, a timely revision of design codes, etc. [1−3]. Retrofitting requires modifying an existing structure to make it more durable and resilient for the desired use. Several techniques for strengthening the existing buildings, such as enhancing the stiffness, improving discontinuity or irregularity in the distribution of stiffness of a building, have been examined and analysed in recent years. In the construction field, Reinforced Concrete (RC) is still the most widely used material being used [4]. Load bearing members such as beam and column largely utilises concrete and steel. But, due to poor construction practices and deterioration of materials, such members sometimes need to be strengthened. This paper covers the strengthening of RC columns. Various techniques such as RC jacketing, steel jacketing, Fibre Reinforced Polymer (FRP) jacketing exist which are being used worldwide to strengthen the columns [2]. *Author for correspondence One of the most influential techniques to retrofit the column is RC jacketing. This type of strengthening improves the axial, shear strength, and flexural capacity of columns, however, the increase in ductility is relatively less [2]. Secondly, it is easy to construct and install, therefore, is the most widely used technique of retrofitting all over the world. Besides RC jacketing, steel jacketing is also a widely used technique to strengthen the columns. Seismic performance of RC columns strengthened by externally wrapping the steel plates resulted in an increased bearing capacity of about 80% than the unstrengthened column [5]. The use of steel tubes as a retrofitting tool on the slender RC column has been proven to be very effective in enhancing the load bearing capacity, ductility and stiffness [6]. The effect of steel jacketing on the seismic performance of a 6 story RC building by jacketing the columns was investigated [7]. The results of the same indicated that the axial and flexural strength of an individual column increases by 184% and 261%, respectively, whereas the lateral strength of the building increases by 127% and 74% along X and Y direction respectively. Apart from RC and steel jacketing, another technique that has become the hotspot of strengthening practices is