DESIGN CRITERIA AND MODELLING OF RE-CENTRING DUAL ECCENTRICALLY BRACED FRAMES

Abstract eng:
Conventional seismic design philosophy is based on dissipative response, which implicitly accepts damage of the structure under the design earthquake and leads to significant economic losses. Repair of the structure is often impeded by the permanent (residual) drifts of the structure. The repair costs and downtime of a structure hit by an earthquake can be significantly reduced by adopting removable dissipative members and providing the structure with re-centring capability. The paper presents application of this concept to a dual structure, obtained by combining steel eccentrically braced frames (EBFs) with removable bolted links and moment resisting frames (MRFs). The solution was validated experimentally using component and system tests. Structural design of re-centring eccentrically braced frames can be performed using conventional code-based approach, but some additional criteria need to be considered. Among these are (1) providing moment resisting frames with a minimum strength in order to obtain a dual frame; (2) checking the re-centring capability by keeping the moment-resisting frames in the elastic range and constraining plastic deformations to replaceable dissipative members; (3) choosing an appropriate behavior factor and (4) designing the connections of replaceable links to allow re-placement. Moreover, due to limitations of simplified code-based approach, nonlinear pushover or time-history analyses are recommended to validate the intended structural performance. Modelling approach of the system for nonlinear static and dynamic analysis is presented, and the results of seismic performance assessment are presented.

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