Passive Structural Control
In this chapter, structural control techniques aimed at reducing the vulnerability of existing or new structures, built in medium and high seismic risk areas, are described. The description is focused on the passive control and, in particular, on the pass
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Passive Structural Control
Abstract In this chapter, structural control techniques aimed at reducing the vulnerability of existing or new structures, built in medium and high seismic risk areas, are described. The description is focused on the passive control and, in particular, on the passive supplemental energy dissipation techniques. The effectiveness of the largest and most popular dissipation devices, such as hysteretic and viscous, by highlighting the significant reduction of seismic demand on the main structure to be protected through the evaluation of earthquake damage indices is briefly described.
1.1 Structural Control Techniques After several destructive earthquakes in recent years in Italy (Friuli 1976, Campania and Basilicata 1980, Marche and Umbria 1997, L’Aquila 2009 and Emilia 2012), the need to redefine the design strategies and codes for the structures sited in high seismic risk areas has been highlighted. Deaths from earthquakes are almost always associated, as in the case of landslides, to damage suffered by buildings, dams, bridges and other human settlements. Unfortunately, the seismic events are characterized by a frequency that is difficult to predict and quantify in space and time due to the randomness of various seismological factors. An average of about 200 high magnitude events occur every decade, of which 10–20 % in the oceanic crust without causing problems to human settlements. Others occur in areas far from the cities and settlements and likewise cause very few problems. The biggest problems arise when an earthquake strikes densely populated areas. It is useful, at this point, to introduce the concept of risk. The risk is the threat to any property or the area’s activities following the occurrence of a phenomenon of assigned intensity or return period TR. It can be expressed as the product of three terms: R¼PV E
ð1:1Þ
where P is the probability of occurrence of a phenomenon characterized by a return period (the return period is the average number of years that elapses P. Castaldo, Integrated Seismic Design of Structure and Control Systems, Springer Tracts in Mechanical Engineering, DOI: 10.1007/978-3-319-02615-2_1, Springer International Publishing Switzerland 2014
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1 Passive Structural Control
between two successive events of equal intensity), V is the vulnerability of the exposed properties and depends mainly on the type of infrastructure and services in the area; finally, E (exposure) represents the value of the goods exposed. The risk can be reduced in general by acting on one of the three term. However, in the case of seismic events, it is evident that it is not possible to act on the frequency of occurrence, i.e. on the dangerousness. Vulnerability is the only factor that the codes, design criteria and design strategies can reduce. Structural damage observed during several seismic events clearly demonstrates that the structural design determines the response of a building to the event. A structure characterized by a global symmetry and regularity both in elevati
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