Background to the Monolithicity Factors for the Assessment of Jacketed Reinforced Concrete Columns

The paper presents the background to the expressions adopted in the new Eurocode 8—3 for jacketed reinforced concrete columns. These are based on the commonly adopted concept of monolithicity factors (ratios of resistance of the jacketed section to that of an identical monolithic one). These factors are derived here in two ways: (i) by fitting experimental results for jacketed columns and (ii) by an extended parametric study of substandard reinforced concrete (R/C) members that were retrofitted by adding R/C jackets, analysed using a model developed by the authors that takes into account slip at the interface. Apart from the cross-section geometry and the thickness of the jacket, parameters of the investigation were the material properties of the core cross-section and the jacket, as well as the percentage of longitudinal reinforcement of the jacket and the percentage of dowels placed to connect the existing member to the jacket. It was found that the parameter that had the most visible effect on these factors was the normalised axial load (ν). The finally adopted factors are either simple functions of ν or constant values.

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