COMPARATIVE SEISMIC PERFORMANCE OF A BASE CONTROL SYSTEM BASED ON MEASURED AND CALCULATED RESPONSES

Finite element (FE) models of two similar buildings, one constructed with a traditional fixed-base foundation and the other provided with a Base Control System (BCS), were developed and calibrated. The two instrumented buildings, which are practically identical 3-story reinforced concrete structures, are located in Mendoza, Argentina. The accelerometers recorded the response due a 5.7 magnitude earthquake that shook the buildings on August 5, 2006. The BCS, developed by Gerb GmbH in Germany, consists of a combination of helicoidal springs and viscous dampers. The numerical models were used to carry out a comprehensive comparison of the seismic response of the two buildings and to evaluate the performance of the isolation system. Commercial finite element software was used to calculate the response due to the recorded seismic excitation in time domain, considering the non proportional damping due to the viscous dampers as a nonlinear load term. After the FE models were calibrated, the response time histories of both buildings were compared. The response examined were the acceleration at different levels, the base displacements, the axial forces and bending moments on different columns and the base shear. The results showed that the BCS was able to reduce the accelerations and internal forces in the isolated building to less than one third of the values corresponding to the rigid base structure.