Modal Performance Factor Testing Procedure for Base Isolation Systems

SITUATION Almost indisputable belief that base isolation hardware should separate a building from shaking ground just by definition is extremely appealing. The examples are numerous. Sometimes, it was even stated that seismic forces in base isolated structures could be reduced by factor of 66 in comparison with conventional construction (Tajirian et al. 1990), though the degree of promised mitigation may vary. It is 10-20-fold per Rodwell et al. 1990, 7-fold per Bailey & Allen 1988 and Zayas et al. 1990, 5 to 10-fold per Volkinburg 1991, 5-fold per Amin & Mokha 1995, 6-fold per Bachman 1995, 5 to 10-fold per Buckle (Prendergast 1995). Although different in the specifics, all mentioned researchers and engineers predicted a sizable reduction of seismic forces in the buildings equipped with base isolators.