Severe seismic damage can be occurred in the position of significant changes of the vertical stiffness of the large chassis structure, and the mid-story isolation system can effectively solve the problem of significant changes of stiffness and mass between the chassis and the tower. A large number of numerical analysis studies have been conducted to investigate the performance of mid-story isolation structure. However, there has been a lack of experimental studies on mid-story isolation structure, and the study of the lateral-torsional coupling effect of the mid-story isolation structure with large chassis and eccentric tower has not been reported. Therefore, in order to guide the seismic design of the project, seismic response and the lateral-torsional coupling effect of the mid-story isolation structure with large chassis and eccentric tower are studied. A large chassis structure (single tower) with significance of typical engineering application and eccentric tower is established at the zone of fortification intensity 8, in which the chassis has 2 floors and the upper tower has 6 floors, the plane area ratio of the upper tower to the chassis is 1:2.4 and the ratio of the tower height to the tower width is 1:3,I that is consistent with the typical features and conditions of such large chassis structure. According to this prototype structure, the simplify and the scaled model is built. A shaking table test and a numerical analysis are conducted by two-dimension ground motion input, and compared the results of the shaking table test and the numerical analysis. The acceleration and story drift of each story of the model are obtained. The experimental results show that the seismic response of the structure is reduced obviously by using mid-story isolation technology. Through the analysis of experimental data, it is known that the ratio of acceleration reduction and the ratio of story drift reduction for upper tower are 83.13% and 81.18% or more (Y-dir) when peak ground acceleration is 0.60g. However, the acceleration response of the chassis increases. The ratio of acceleration reduction is between -12.69% and -24.07% (Y-dir) and the ratio of the story drift reduction is between 15.53% and 17.15% (Y-dir), so the vibration control effects of the chassis is poor. When peak ground acceleration is 0.60g, the model of the upper tower remains elastic stage but the chassis leads to the elastoplastic stage at 0.40g, and the second layer displacement of the chassis is significantly larger than that of the first layer. The results of the numerical simulation analysis for the lateral-torsional coupling effect analysis of the mid-story isolation are verified by the shaking table test. Compared with the seismic model, it can be concluded that the torsional angle of the chassis is reduced by 2/3, the torsion response of the isolation story is larger but not transmitted into upper tower, the interstory torsional angle of the tower tends to zero, and the torsional coupling effect between the tower and the chassis is not obvious. Therefore, the mid-story isolation technology is an effective method to reduce torsion effect for the building (single tower) with large chassis and eccentric tower.
