Isolator level in height of seismic isolation system with semi-active control

Recently, buildings with an isolation device installed in middle story have been constructed. However, an adequate isolation layer level in height of a mid-story isolated building has not been established, and this causes a restriction on design of a plan of a mid-story isolated building. To reduce this restriction, semi-active controlled systems are compared to observe response characteristics. Regarding a control law, velocity feedback based on bilinear optimal control is used. Based on time history analysis with a 30-DOF system, response differences with respect to a position of an isolation layer is studied. It is observed that semi-active control scheme can be used to reduce the absolute acceleration of a roof and the deformation of an isolation layer. On the other hand, much attention must be paid to behavior of a lower structure under seismic excitation in design.