## 1 Introduction  
The conventional base isolation method with rubber bearing is fundamentally a damping technology. It has the advantages of obvious damping effect, safety, reliability and low cost, and hence has been widely used in a number of low-rise buildings [1; 2; 3]. However, the isolation structure with the rubber bearings will normally have a large isolation layer deformation during rare earthquakes. In order to control the displacement of the isolation layer, more isolation bearings are generally embedded into the isolation layer system. After adding some stiffness and damping for the isolation layer, the acceleration of the superstructure and the displacement of the layer may be enlarged, sometimes even in low-level earthquakes [4; 5]. This excessive acceleration will cause equipment damage in certain buildings, such as hospitals, communication centers, government buildings, etc. Moreover, articles falling in the building may cause secondary damages [6]. The need for security protection for the overall structure to mitigate such damages has led to the development of novel isolation technologies [7; 8; 9]. The mitigation of secondary damages is one of the design objectives in the present study.  
Magnetorheological (MR) damper is a variable damping controller with excellent performance, which has been demonstrated by many research cases either experimentally or practically. It has the characteristics of a damping force in wide range, rapid response and requires little energy input. It has been widely used in hybrid or semi-active controlled structures [10; 11; 12; 13]. In broader applications, MRD has been applied in protecting civil infrastructure systems against severe earthquake and wind loading [14], in semi-active seat suspension systems and in payload launch vibration isolation of a spacecraft [15; 16]. [PERSON] et al. proposed a coupled building control scheme interconnecting the inline floors of two closely spaced adjacent buildings with semi-active Magnetorheological (MR) dampers [17]. It was noted that the control scheme is quite effective in response mitigation of both the buildings under a wide range of ground motions [18]. The efficacy of this smart system in reducing structural responses for a wide range of loading conditions was demonstrated in a series of experiments [19]. Amongst various control devices, seismic base isolation has proved to be a time tested method and semi-active MR dampers have also emerged as a very attractive proposition for a control device [20]. [PERSON] found that when the semi-active control is suitably designed and implemented, the seismic performance of the structure can be significantly improved [21]. A series of large scale experimental tests was conducted on a mass equipped with a seismic base isolation system that consists of high-damping rubber bearings and an MR damper [22; 23]. Researchers have been exploring various approaches of seismic hazard mitigation of closely spaced adjacent buildings, by way of employing various control devices [24].  
This study will focus on the base isolation control system using MR damper and rubber bearings with the high-order single-step algorithm (HSA) [25]. HSA is known to be well-suited for real-time control applications due to its excellent capability in high-speed computation and fast convergence. The new structural vibration control involves the use of two control strategies, namely, continuity and switch control. In this paper, both the numerical simulation and experimental test were subjected to seismic waves with different characteristics and intensities. The research work establishes a theoretical and experimental basis for the novel isolation system applications.