The strength of reinforced concrete columns, strengthened by reinforced concrete jacketing under loading

Reinforced concrete (RC) jacketing is the most widespread method of columns strengthening. The design of such strengthening requires consideration of additional factors. Among them is the impact of the load supported by the existing structure during strengthening on the future performance of the strengthened structure. Determination of the impact of that factor is the main objective of this research. To achieve this RC column specimens were strengthened after preliminary loading to different levels and tested to failure. All specimens had identical geometrical and mechanical characteristics and were tested as pinned columns subjected to eccentric loading. Different load values applied prior to strengthening represented the only variable parameter. During tests dial indicators were used to measure linear deformation of reinforcement and concrete. Measurements were taken from jacketing and strengthened columns. Deflections along the column length as well as crack development were also monitored. RC jacketing is a very effective strengthening method that allowed us to achieve up to 290% of strength increase. Strengthened columns appeared to work as monolithic structures. No displacements, cracks or adherence loss between columns and jacketing was noticed, even though no interface preparation methods were used to increase bonding between the new concrete and the column. Experimental strength of test specimens was close to calculated values. Maximum deviation equaled 10%.

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