Seismic Analysis of Light Secondary Substructures via an Extended Response Spectrum Method

The seismic survival of relatively light non-structural attachments may be important in practice as the earthquake resistance of the main structural system. In this chapter, aimed at overcoming some drawbacks of existing procedures, a new combination rule is formulated and numerically validated for the response spectrum analysis of Light Secondary Substructures (LSSs), whose definition is hereby rigorously established. The main advantages of the proposed approach are: i) the eigenproperties involved in the computations are those of the decoupled substructures, assumed to be fixed to their own bases, i.e. even though the combined Primary-Secondary (P-S) system is in general non-classically damped, the required eigenproperties are real-valued quantities; ii) the new combination coefficients incorporate the effects of frequency tuning and different damping in the two components; iii) the elastic response spectrum for just a single value of the viscous damping ratio is required, and this spectrum can be selected as the reference one provided by the seismic code.