Direct displacement-based design approach for isolated structures equipped with supplemental fluid viscous damper

In this paper, direct displacement-based design (DDBD) approach is extended for the isolated structures equipped with supplemental fluid viscous damper (FVD) while this method can be also implemented for the isolated structures without supplemental FVD. The design process has been developed based on a non-iterative manner whereas a complexity from preliminary design to iterative design process can be found in previous DDBD approaches. To validate the proposed method, three steel moment-resisting frames with four, eight and twelve stories are designed using this method. Nonlinear time-history analysis has been performed under a far-field record set including twenty-two earthquakes and a near-field record set including fourteen earthquakes. The results show that the isolated frames without supplemental FVD have effective performance under far-field earthquakes. Therefore, the proposed design method can be employed as effective design approach for isolated structures. However, their performance is not very reliable under near-field earthquakes because base isolation system originally does not have effective performance under near-field earthquakes. Seismic performance of isolated frames equipped with FVD shows that their peak response is less than target drift under both far-field and near-field earthquakes and these frames have effectively achieved the desired performance levels related to both superstructure and base isolation levels. Therefore, the developed DDBD approach can be introduced as an effective design method for isolated structures equipped with supplemental FVD.