A New Design Procedure Based On The Realistic Definition Of Seismic Input

Nowadays seismic codes require to design structures using ground motion estimates resulting from a probabilistic seismic hazard analysis (PSHA). Focusing on the limits of this approach, in this work a new seismic Performance Based Design (PBD) process is presented. The acceleration response spectrum at a given site is defined by means of the envelope obtained from a large number of realistic ground motions simulated using the Neo Deterministic Seismic Hazard Assessment (NDSHA) method. This response spectrum is defined “Maximum Deterministic Seismic Input” (MDSI) and represents an upper bound level to the spectral accelerations at a given site. The MDSI response spectrum can be developed both at the bedrock (MDSIBD) and at the free surface, thus including the site specific effect (MDSISS). This process supplies realistic synthetic seismograms that allow to run accurate time history analysis. In the proposed Performance Based Design procedure every structure needs to resist to the site specific maximum deterministic (MDSISS) level of seismic input, at least at the collapse prevention level of performance. The importance of the structure (risk category) is taken into account limiting the acceptable structural damage under the MDSISS level of seismic input and not reducing it. The procedure has been just applied, in its essence, to real cases represented by relevant (e.g. schools) buildings of the Trieste province.