Assessment and code considerations for the combined effect of seismic base-isolation and viscoelastic dampers

To propose an initial formulation for the passive control section of the Turkish Earthquake Code, the impact of base isolation and viscoelastic dampers on a four-story reinforced concrete (RC) frame building was considered under various one-dimensional earthquake excitations. Both statically equivalent seismic load methods (comparing Turkish Earthquake code with Uniform Building Code) and linear time history analyses were applied to the RC building based on a portion of the 1999 Kocaeli Earthquake ground motion record (modified to possess predominant spectral periods of T1=0.13 sec and T2=1.43 sec). Effective peak ground acceleration was set to 0.40g representing hard and soft soil conditions, respectively. Time history variations of upper column displacements and bending moments were compared, as well as story drift ratios. Reductions of the fixed-base case displacements and column bending moments were obtained of up to 73% under base-isolation, up to 25% with viscoelastic dampers, and up to 83% (with a unified response reduction factor) when both devices were both present.