Seismic assessment of existing steel frames with masonry infills

Abstract

Many existing steel moment-resisting frames were constructed before the provisions of modern seismic codes; therefore, they are likely to exhibit high vulnerability to earthquakes due to their inadequate ductility design, hence low energy dissipation capacity. Public concern has been raised about the development of a reliable code-based framework for assessing existing structures, however, previous research has shown that the current European code EC8–3 may not be sufficient and requires urgent improvements. Particular attention should be paid to the contribution from infill walls in steel buildings, especially those made of masonry, and beam-column connections, as they play a significant role in the structural performance under earthquakes. To this end, an updated assessment procedure, which is an extension of the current procedure in EC8–3 but with several improvements to the non-linear analysis methods, is proposed in this paper and is applied to an existing steel building as a case study. The building is a three-storey steel moment-resisting frame located at Amatrice in Central Italy, which survived the recent 2016–2017 Central Italy earthquakes. Refined 3D models of the case study building, which account for the effects of infill walls and column panel zones, were implemented in a refined finite element platform. The effects of masonry infills on structural components, such as beams and columns, were investigated through non-linear analysis methods. The results emphasise the significance of including masonry infills in the numerical model for seismic assessment especially when an optimised retrofit solution is needed.