Effect of Damping in Nonlinear Dynamic Analysis of Existing Reinforced Concrete Buildings

Nonlinear Response History Analysis (NRHA) is the most accurate method for predicting the building response under strong ground motions. The results of these analyses depend on many factors such as the ground motion selection, the structural modelling strategies (frame vs solid models, lumped or distributed plasticity models) and the damping models used. The definition of the damping models and their influence on the structural response to date is one of the most complex, uncertain and least studied elements. This is partly due to the difficulties in understanding the mechanical meaning of the damping models. This paper focuses on the comparison between two of the most widely used damping models: the Modal and the Rayleigh damping. A representative Italian 6-storey existing reinforced concrete building designed for gravitational loads only is studied, with and without infills. In both cases, NRHAs are carried out using 20 pairs of ground motion records selected for a return period of 475 years. The results of the two damping approaches are compared to evaluate their impact on the overall response of the case-study building