Modelling steel jacketed RC columns: Remarks by experimental-numerical comparisons

The recent large use of nonlinear seismic assessment techniques requires the definition of highly reliable computational models. The retrofitting or strengthening of RC columns by steel angles and battens is a commonly adopted technique, used to improve strength and deformation capacity of existing RC buildings. In the case of steel angles not directly loaded, the numerical definition of the cross-section model has to be handled carefully since it is affected by more uncertainties. The vertical load carried by the angles is a function of the lateral confinement pressure, the cohesion and the friction coefficient between the materials, parameters which are not always easy to predict. The paper discusses the numerical implementation in OpenSees of RC jacketed sections models, giving practical solutions to properly account for the above mentioned issues. In order to validate the predictive capacity of the model, the numerical results are compared with the outcomes of an experimental campaign carried out by the authors. Some final modelling remarks are given by the observation of the results of experimental tests and numerical simulation