Assessment of existing steel frames with infills under multiple earthquakes

Many existing steel multi-storey frames in Europe were designed prior to the provisions of modern seismic design codes; therefore, they often exhibit low resistance to earthquakes due to their insufficient energy dissipation capacity. However, the current framework for assessing existing structures in EC8-3 is inadequate and should be reviewed. Particular attention should be paid to the contribution from masonry infill walls as they significantly affect the modal properties and the lateral stiffness of structures. To this end, two 3D models of a two-storey steel moment-resisting frame were developed to assess the applicability of the current framework in EC8-3 to the infilled structures under multiple earthquakes through nonlinear analyses. The modelling of masonry infill walls was achieved through a macro-model using equivalent diagonal struts. The ground motions utilised during the analyses took the records of the recent 2016 Central Italy earthquake sequence. As part of the project HITFRAMES, this paper serves as a preparation for the experiment to be conducted in Greece.