Seismic Resilience of Multistorey Dual-Steel Building Frames
Seismic resistant building frames designed as dissipative structures must allow for plastic deformations to develop in specific members, whose behaviour has to be predicted by proper design. Members designed to remain elastic during earthquake, such as columns, are responsible for robustness of the structure and prevention the collapse, being characterized by high strength demands. Consequently, a framing solution obtained by combining HSS and MCS, is natural. The robustness of structures to severe seismic action is ensured by their global performance, in terms of ductility, stiffness and strength, e.g. the “plastic” members of MCS – (S235 to S355) will dissipate the seismic energy, acting like “structural fuses”, while the “elastic” members (HSS – S460 to S690), provided with adequate overstrength, will have the capacity to carry the supplementary stresses, following the redistribution of forces after appearance of plastic hinges. Such a structure is termed dual-steel structure. When braced frames of removable MCS dissipative members are used, such as the links in EBF, Buckling Restrained Braces in CBF or Shear Walls in MRF systems, the elastic HSS part of the structure has a beneficial restoring effect after earthquake enabling to replace the “fuses”. That’s why such a structural solution can be characterized as seismic resilient.