Mechanical modelling of exposed column base plate joints under cyclic loads

Abstract

ABSTRACT Dealing with steel Moment Resisting Frames (MRFs) the current European seismic design rules suggest, in case of severe earthquakes, to enforce the formation of plastic zones in members or joints. When joints are the main source of energy dissipation, a thorough knowledge of their inelastic behaviour is needed. This is the reason why, in past years, many efforts have been devoted to the study of the static and seismic response of connections. However, as well known, traditionally, the main efforts of the scientific community have been devoted to beam-to-column joints, neglecting the seismic behaviour of column bases which, indeed, count a significantly lower number of experimental and numerical investigations. Within this framework, in this paper, in order to provide a contribution towards a better understanding of the seismic response of base plate joints, the possibility to model their rotational cyclic behaviour by means of the so-called component method is examined. This approach in case of load reversals requires the development of the following steps: i) identification of the main sources of deformability, resistance and energy dissipation; ii) characterization of the single components; iii) model assembly. Therefore, starting from previous studies concerning the monotonic and cyclic behaviour of the single components, a mechanical model able to predict the cyclic response of exposed base plate connections is proposed. The model is validated against cyclic tests on exposed base-plate joints presented in this work or taken from technical literature. The comparisons show a satisfactory accuracy of the developed model.