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. A hybrid identification method is proposed in this paper 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. 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. A series of shaking table tests were also conducted on a building model under different kinds of ground motion to experimentally examine the proposed hybrid method. Absolute acceleration responses at all floors of the test building were measured and integrated to obtain velocity and displacement responses. All the measured and integrated responses are then analysed using the hybrid identification method with a shift-average procedure to identify the stiffness and damping parameters as well as to reconstruct the unknown seismic input. The experimental results indicate that the hybrid identification method is potentially a promising technique for structural parameter and seismic excitation identification of multi-story buildings using output measurements only.
