An Investigation of Seismic Retrofit of Columns in Buildings Using Concrete Jacket

Abstract eng:
The columns in a typical reinforced concrete multi-storeyed building in India, especially with an open ground storey, are found to be deficient to resist seismic forces. One option of retrofitting the columns is to jacket them with concrete. The conventional analysis of a jacketed column investigates the strength based on interaction diagrams for the composite section or for some equivalent section. The present study investigates the performance of columns jacketed by a certain scheme of reinforcement. First, prism specimens with new concrete cast against the sloping faces of old concrete were tested under compression (slant shear test) to study the interface between old and new concrete. Second, column specimens were tested under pure compression, eccentric compression and pure bending to study the effect of jacketing on the strength. Finally, beam-column sub-assemblages with reference and retrofitted columns, were tested under monotonic and cyclic lateral loads in presence of constant vertical loads. From the tests, it was found that the lateral strength, ductility and energy absorption capacities of the retrofitted specimens were higher than the corresponding reference specimens as per prediction. A lamellar analysis was used for the prediction of the moment versus curvature behavior of a retrofitted column section. An incremental nonlinear approach was used to predict the lateral load versus displacement behavior of the retrofitted sub-assemblage tested under monotonic lateral load. The scheme of strengthening a column is explained with reference to the practical considerations of an existing building.

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