Different from previous researches which mostly focused on linear response control of seismically excited high-rise buildings, this study aims to control nonlinear seismic response of high-rise buildings. To this end, a semi-active control strategy, in which H∞ control algorithm is used and magneto-rheological dampers are employed for an actuator, is presented to suppress the nonlinear vibration. In this strategy, a modified Kalman–Bucy observer which is suitable for the proposed semi-active strategy is developed to obtain the state vector from the measured semi-active control force and acceleration feedback, taking into account of the effects of nonlinearity, disturbance and uncertainty of controlled system parameters by the observed nonlinear accelerations. Then, the proposed semi-active H∞ control strategy is applied to the ASCE 20-story benchmark building when subjected to earthquake excitation and compared with the other control approaches by some control criteria. It is indicated that the proposed semi-active H∞ control strategy provides much better control performances by comparison with the semi-active MPC and Clipped-LQG control approaches, and can reduce nonlinear seismic response and minimize the damage in the buildings. Besides, it enhances the reliability of the control performance when compared with the active control strategy. Thus, the proposed semi-active H∞ control strategy is suitable for suppressing the nonlinear vibration of high-rise buildings.

This study proposes a new structural design of the first-story isolation system in reinforced concrete (RC) structures. Compared to the conditional buildings with independent columns, this new design integrates the independent columns with beams to increase the seismic capacity of the building by increasing the integrated stiffness of the coupled columns and the stability of the isolation system. The seismic responses of the proposed structure and the corresponding isolation effect were investigated by performing a series of numerical simulation and shaking table tests on a typical 7-story RC frame structure. The structure models were subjected to four earthquake waves with two PGAs (peak ground acceleration) of 0.30 g and 0.40 g for seismic analysis regarding the peak acceleration and inter-story displacement. Both simulation and testing results showed that the story acceleration and inter-story displacement of the superstructure in the isolated model decreased significantly. While the substructure below the isolation layer had a negligible decrease of acceleration. The connection of beams with concrete columns significantly increases the seismic capacity of the RC frame buildings compared to non-isolated frame buildings. The coupled beam-column connections could thus be potentially adopted in the practical first-story isolation system to avoid the requirements of large column stiffness and large column size.

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This study aims to better understand the seismic responses and isolation effect of a first-story, independent, column-top isolation structure with concrete frames. A series of shaking table tests and a numerical simulation were performed on a seven-story reinforced concrete–framed structure with first-story isolation, using rubber bearings. A non-isolated, structural model was used as a reference for comparison. The testing and numerical results showed that the story acceleration and inter-story displacement of the superstructure in the isolation model were significantly reduced, indicating the good damping effect of the isolation system. This system, which composed of rubber bearings, could absorb most of the seismic energy. The inter-story displacement of the substructure in the isolation model was also significantly reduced, while the acceleration was slightly reduced. The horizontal deformation of the column was not severe, and the seismic capacity of the substructure was higher than that of the superstructure. It is suggested that to guarantee the seismic security of reinforced concrete–framed structures with the first-story column-top isolation under extremely rare strong earthquakes, the stiffness of columns in the substructure should be further strengthened. Moreover, it is effective and reasonable to adopt the first-story column-top isolation method to improve the seismic capacity of reinforced concrete–framed structures with a weak first story.

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