CALIBRATION AND VALIDATION OF AN OVERDAMPED DISPLACEMENT ADAPTIVE PROCEDURE FOR SEISMIC ASSESSMENT OF INFILLED RC FRAMES

The main part of the existing buildings in the Mediterranean area is extremely vulnerable to seismic actions. Since a complete renewal of the building heritage is not possible, the seismic assessment of existing structures has gained importance to identify the structural deficiencies and design the most appropriate retrofit interventions. Nonlinear dynamic analysis is widely recognised as the most accurate tool to predict the seismic behaviour of structures. However, it has high computational cost and is not suitable for professional purposes. To provide a tool that reliably assesses the seismic behaviour of structures, with an acceptable computational burden, nonlinear static methods of analysis have been developed. This paper proposes a multimodal adaptive procedure named overDamped Displacement Adaptive Procedure (D-DAP) for seismic assessment of RC frames. The D-DAP is ruled by two main parameters: the value of top displacement adopted as step size and the number of modes of vibrations deemed significant for the determination of the load vector. Furthermore, the D-DAP is equipped with an equivalent damping law to consider the increase of the energy dissipation due to the cumulated damage in both structural and non-structural members. The goal of this paper is to determine the values of the displacement step size and the number of modes of vibration necessary to achieve a suitable accuracy by means of the D-DAP. In addition, a new equivalent damping law is calibrated considering also infilled frames. In fact, nonlinear static analysis provided in literature are not optimised to estimate the nonlinear behaviour of infilled frames, despite the well known influence of infill panels on the structural response. A parametrical investigation that includes frames with and without infills is con ducted. A set of 54 RC frames have been designed to be representative of existing buildings with various levels of seismic deficiencies and analysed. The adopted research methodology assumed the response obtained by Incremental nonlinear Dynamic Analysis (IDA) as target.