I.11.20: Design recommendations for dual moment – eccentric braced frames with replaceable links

Abstract

ABSTRACTModern seismic codes allow for inelastic deformation in dissipative zones during design earthquakes, accepting damage to the relevant structural parts to a certain extent. Experience has shown that repair work is needed after moderate to strong earthquakes. To obtain a seismic resilient structural system means to be easily repairable. For a given structure, to be repairable, after an earthquake, it must be calibrated by design to concentrate the inelastic deformations into the removable dissipative members, only, and after their removal, avoid permanent (residual) drift. To obtain re‐centring capability in a structure with eccentrically braced frames (EBFs) and removable dissipative members, a dual structural configuration is used, which combines EBFs and moment‐resisting frames (MRFs). If the more flexible MRFs are kept elastic – high strength steel might be used on this purpose, they would provide the restoring force necessary to re‐centre the structure upon the removal of the damaged removable links (the dissipative members). First, this paper summarises the experimental validation of technical solution and re‐centring capability of a dual EBFs with replaceable links, based on a full‐scale experimental testing programme performed at the European Laboratory for Structural Assessment (ELSA) at the Joint Research Centre (JRC) in Ispra, Italy. Secondly, with a numerical model, calibrated on these test results, parametric studies have been performed with the aim to offer a base for drafting specific design recommendations. These recommendations include prequalification procedures for the links.