## 1 Introduction  
The soil-structure interaction (SSI) is well-known as a dynamic coupling phenomenon between soil and structure under seismic loading [1; 2]. In engineering practice, a free-field (FF) motion, recorded in soil at a distance far away from the structure, could be preliminarily regarded as a foundation input motion (FIM) for structure analysis [3]. However, an earthquake acceleration recorded in the free-field generally differs from the FIM. Thus, soil-foundation-structure interaction (SFSI) has been recently considered to estimate seismic response of a structure [4; 5; 6]. [PERSON] and [PERSON] [7], and [PERSON] et al. [8], have proposed mathematical solutions for the vibration of foundations, either embedded or buried with an inclined load. SFSI is attributed to two distinct mechanisms: (1) Kinematic interaction (KI) of soil-foundation, and (2) inertial motion (II) of structure that re-affects response of the foundation [2; 4; 5; 9; 10; 11; 12; 13]. Due to the global explosion in demography and the development of megacities, many structures constructed are surrounded by various sized buildings with different dynamic characteristics. Previous investigations have reported that significant changes of the near-field motion, due to the dynamic response of structures [14]. Such changes also affect the response of structures located nearby, this is called the structure-soil-structure interaction (SSSI) phenomenon [4; 15; 16; 17; 18; 19]. Therefore, it is essential in engineering practices to explore SSSI effects to avoid unexpected damage in structure when another structure is placed nearby, as SSSI effects are not considered in modern seismic design codes [20; 21; 22]. [PERSON] and [PERSON] [19], in their pioneering work, have analytically investigated SSSI effects for a group of two and three buildings in a 3D scheme, using a simple model composed of masses and springs connection. Other works of [PERSON] and [PERSON] [23], [PERSON] and [PERSON] [24], and [PERSON] and [PERSON] [25] have been performed to study two-dimensional seismic problems of two or more infinite shear walls with a scenario of vertically incident harmonic SH-waves propagation. They have observed some detrimental effects on structure response during an earthquake when a target wall is located adjacent to a larger and heavier one. More recently, [PERSON] et al. [26] and [PERSON] et al. [27] performed a large-scale force vibration test for a cluster of NPP and found that the appearance of Control Building can result in a decrease in Reactor Building response in the vicinity of the structures' resonant frequency. [PERSON] et al. [28] and [PERSON] [29] have conducted back-analysis for the above large-scale force vibration tests, using SASSI program and couple boundary element method and finite element method. Their results suggest that: (1) SSSI effects occur near the peak response; and (2) SSSI could be associated with structural properties. Some numerical or experimental studies have also been performed to find key factors controlling SSSI effects in a configuration group of two structures, including the distance between two foundations and the characteristics of an adjacent structure, such as relative mass, height, and natural frequency. [PERSON] et al. [17]; [PERSON] [30]; and [PERSON] and [PERSON] [18] have numerically demonstrated that a massive structure can have detrimental SSSI effects on a lighter structure. On the other hand, [PERSON] et al. [16], [PERSON] et al. [31], and [PERSON] et al. [32] have used a discrete model and demonstrated that SSSI effects between two and three single-degree-of-freedom (SDOF) structures could be controlled by height or fixed-base frequency ratios between structures. They found that the response of short structure increased when taller structures with lower in fixed-base frequency were located in close proximity. [PERSON] et al. [4] and [PERSON] et al.