Investigation of reinforced concrete jacketed columns under different loading conditions

Abstract

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