A Displacement-Based Design (D.B.D.) procedure is adopted for the retrofit of framed structures by inserting hysteretic damped braces (HYDBs) in order to attain, for a specific level of seismic intensity, a designated performance level. To check the reliability of the design procedure, two six-storey buildings are considered as having steel and r.c. framed structures, which, originally designed in a medium-risk seismic region, have to be retrofitted as if in a high-risk seismic region. To avoid high deformability of the steel structure at the damage limit state (SLD) and brittle behaviour of the r.c. structure at the life-safety limit state (SLV), two retrofitting structural solutions are examined: additional diagonal braces; HYDs supported by the additional diagonal braces. Nonlinear dynamic analyses under real ground motions are carried out by a step-by-step procedure. The frame members and the HYDs are idealized by a bilinear model; an elastic behaviour is considered for the braces.
SEISMIC UPGRADE OF A R.C. BUILDING WITH DISSIPATIVE BRACES
The paper illustrates the design and execution of seismic retrofit of a building with reinforced concrete structure, through the use of metal braces with integrated viscous damper. The work is part of a larger project that also included works by expanding the classroom through the use of stilts, closed with drywall that do not interfere in the structural behavior of the building. The economy and the possibility of working without closing the buibing, are its salient features. The cost of structural works was in fact of 190,000 € plus VAT and charges, amounting to less than 170€/sqm. A sum much less than the cost of traditional interventions (400€/sqm).
This paper is available in Italian only.
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