Abstract
Nowadays, many buildings with steel Moment Resisting Frames (MRF) are built in seismic zones when seismic codes are at its early stages of development, and as such, these structures are often designed solely to resist lateral wind loads without providing an overall ductile mechanism. On the other hand, current seismic design criteria based on hierarchy of resistance allow enhancing the structural ductility and controlling the structural plastic behaviour. Therefore, seismic design criteria might also be beneficial to improve the structural robustness. In order to investigate this issue for steel MRF, a parametric study based on pushdown analysis and on the Energy Balance Method is described and discussed in the present paper. With this regard, the following cases are examined: (i) MRF not designed for seismic actions and (ii) MRF designed for seismic actions. The investigated parameters are (i) the number of storeys, (ii) the interstorey height, (iii) the span length, (iv) the building plan layout and (v) the column loss scenario. Results show that the low-rise and long span structures are the most prone to progressive collapse and that the elements in the directly affected zone of the wind designed 8 storey structures respond in the elastic range. Structures designed according to the capacity design principles were found to be less robust than wind designed structures that are characterized by strong beams and weak columns. The number of elements above the removed column and size of beam cross section were found to be key parameters in arresting progressive collapse.
Highlights
Low/medium rise steel Moment Resisting Frame (MRF) structures designed only for lateral wind actions are typically characterized by weak column/strong beam assemblies, owing to the need to limit lateral drifts
The results show that the 10 m span structures present lower values of Reserve Strength Ratio (RRSR) than the 6 m span ones
For the four storey structures, the results indicate that the type of lateral load design scenario is not a distinguishing factor in terms of ductility
Summary
Low/medium rise steel Moment Resisting Frame (MRF) structures designed only for lateral wind actions are typically characterized by weak column/strong beam assemblies, owing to the need to limit lateral drifts. Seismic design criteria currently recommended by modern codes (e.g. the EN 1998-1 [1]) lead to frames with strong column / weak beam arrangements, which are obtained by applying capacity design principles, where a component resistance hierarchy is established in order to form an overall ductile mechanism. In order to guarantee this performance, the dissipative zones (e.g. the beams in case of moment resisting frames) should develop plastic hinges that are characterized by strain hardening [2 - 10]. The non-dissipative zones (e.g. the columns) should be designed to resist the maxima effects developed into the plastic hinges [7, 10]. The necessary level of detailing to improve the robustness of buildings in case of column loss scenarios remains an open issue
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
