SEISMIC PROTECTION SYSTEM
  1. GENERAL
The conventional anti-seismic design of structures relies on their strength, namely on their
capability of withstanding the effects of seismic vibrations (e.g., for buildings, increasing
inertia forces from their base to their top and interstory drifts). Such a design may save the structure from collapse but, it cannot avoid damage to the structural elements and especially, the nonstructural ones, including the building contents (i.e. human beings, in addition to objects). Nowadays, this sure damage is worldwide recognized to be quite a serious problem for all kinds of structures, but especially, as far as buildings are concerned, for the strategic and public ones: among the first, this is the case of hospitals, emergency management centers
and all other structures which should remain fully functional (i.e. absolutely undamaged)
during and after earthquakes also, (e.g. bridges), in order to ensure an adequate emergency
management; among the second, it is the case of schools and other highly populated
buildings[4]. Extensive research has been conducted to develop strategies and systems for protecting the structure from seismic hazard.
  1. SEISMIC PROTECTION SYSTEM
In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken in the last three decades to develop the structural control concept into a workable technology. Each has distinct working principle, although all have a single goal, which is to protect the structure. Intensive research has been conducted to reduce structural response caused by dynamic effects. As a result, many structural control concepts have been evolved for this purpose, but quite a few of them have been implemented in practice. There are a number of motivating factors for conducting this research. They include: (i) reduction of undesirable vibrational levels of flexible structures due to unexpected large environmental loads; (ii) retrofitting existing structures against environmental hazards; (iii) protecting seismic equipment and important secondary systems; and finally, (iv) providing new concepts of design of structures against environmental loading[5].
Seismic protection systems can be classified according to the following: