The widespread use of damped braces is closely related to the availability of simplified yet reliable design procedures along with the new generation of seismic codes based on the performance-based design. On the other hand, the seismic retrofitting of a reinforced concrete (r.c.) framed building goes through a proper evaluation of the structural behaviour before failure and sensitivity to damage. In fact, lack of knowledge on strength and stiffness degradation may not be compensated for in the following calculation of a passive control system. A Displacement-Based Design (DBD) procedure to proportion hysteretic damped braces (HYDBs) is proposed in order to take into account the effects of the seismic degradation of a structure that needs to be retrofitted. To this end, a hysteretic model based on plastic and damage mechanisms is adopted to describe the inelastic response of r.c. frame members. Then, nonlinear seismic analysis of a single-degree-of-freedom system, equivalent to a multidegree-of-freedom model of the structure, is used to generate the capacity boundary curve by means of the hysteretic model defined starting from the initial backbone curve. Two-, four- and eight-storey r.c. framed structures, representative of low-, mid- and high-rise r.c. framed buildings, are designed for a medium-risk seismic zone of a former Italian code. These structures are then to be retrofitted by inserting HYDBs to attain performance levels imposed by current Italian code in a high-risk seismic zone. Different retrofitting solutions are compared, considering for each retrofitted structure: i) variable damper ductility coupled with constant frame ductility; ii) variable frame ductility coupled with constant damper ductility. The effects of different damage levels and different damage evolution laws are also investigated.
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|Titolo:||DISPLACEMENT-BASED DESIGN OF DAMPED BRACES FOR EXISTING R.C. BUILDINGS WITH DEGRADING SEISMIC RESPONSE|
MAZZA, Fabio (Corresponding)
|Data di pubblicazione:||2019|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|