Hybrid identification method for multi-story buildings with unknown ground motion: Theory

Simultaneous identification of both structural parameters and ground motion of an earthquake-excited structure by using measured structural response time histories only has received great interests in recent years. However, this paper demonstrates through a multi-story shear building that the structural parameters and the ground motion cannot be uniquely identified when the absolute forced structural response time histories are used directly. A hybrid identification method is thus proposed for the problem concerned. The hybrid identification method first identifies the structural parameters above the first floor of a multi-story shear building using the least-squares method after the corresponding parametric identification equation is established. The minimum modal information is then introduced to find the structural parameter of the first floor of the building to eliminate the non-uniqueness problem. After all the structural parameters are identified, the unknown earthquake-induced ground motion is finally constructed by solving a first-order differentiation equation. To enhance the capability of the hybrid identification method against measurement noise, an amplitude-selective filtering procedure is also proposed. Numerical example demonstrates the feasibility and efficiency of the hybrid identification method and the effectiveness of the amplitude-selective filtering procedure. The restriction of the proposed methodology in real application and future research on this topic are also pointed out.