Numerical Modeling of the Flexural Behaviour of Substandard Columns Reinforced with RC Jackets

This paper aims to present the results of a finite element modelling (FEM) study on the flexural behaviour of Reinforced Concrete (RC) columns retrofitted with RC jackets. The RC jacketing technique is widely used to improve the structural performance of substandard RC columns. However, the relative slip between the old and new concrete can have a significant impact on the flexibility and strength of the retrofitted column, and limited studies have investigated numerical modeling strategies to address this. The proposed FEM approach uses fiber-section beam elements connected by a non-linear interface, and the results highlight the difference from the usual assumption of monolithic behaviour. The monolithic assumption is a common hypothesis in International Technical codes forRCjacketing design and is affected by empirical factors knownas monolithicity factors, which are difficult to assess. The study also presents the development of a software package that performs static non-linear analysis of RC jacketed columns and evaluates the actual monolithicity factor by using the OpenSees finite element framework and Matlab for a user-friendly Graphical User Interface (GUI). The fiber-section approach models the flexural performance of the column, and the bond between the old and new columns is considered through a distribution of non-linear springs.