Moreover, through the comparison of the responses of unbraced frames resting on soft soil considering fixed base buildings as well as considering SSI, it can be concluded that the SSI significantly increases the interstorey drifts and decreases the base shear [42]. Indeed, the necessity of considering SSI increases as the shear wave velocity and shear modulus of the soil decrease [43; 44; 45]. Also, considering nonlinearity is important in SSI problems to obtain results with acceptable accuracy [46]. Because considering SSI can change the structural dominant frequency and lead to a mistuned mass damper, [PERSON] et al. [47; 48; 49] developed advanced versions of mistuned mass dampers to adjust to the effects of considering SSI, to control human-induced vibrations, as well as to control the vibrations of base-isolated buildings. It is worth noting that several methods have been proposed for the numerical evaluation of the response of vibrating buildings taking into account SSI [45; 50; 51]. Also, several methods have been proposed for the experimental evaluation of the response of vibrating buildings taking into account SSI using the shaking table tests (see [52; 53], for example). More details were reported in the literature, providing an in-depth description of considering SSI experimentally, describing the necessary procedure and equipment for the consideration of the SSI, including creating the physical model [54] and the soil mixture [55]. Furthermore, previous studies confirm that bounding is significant in the case of SSI as well as in the case of soil-pile-structure interaction [56; 57]. Several contradictory results about the effects of the SSI on the response of colliding buildings have been reported in the literature. It was found that bounding with SSI leads to the increase in the displacements, shear forces, and impact forces in some studies (see [56; 58; 59; 60; 61; 62; 63], for example). However, in some other studies (see [64; 65], for example), it was found that bounding with SSI leads to the decrease in the displacements, shear forces, and impact forces. The contradictory results referred to several factors that were overlooked in these studies, such as the soil type, since the effects of the soil type have been ignored in some studies and the fact that these studies considered different soil types. Recently, [PERSON] et al. [66; 67; 68] studied the effect of the soil type on the response of buildings experiencing floor-to-floor bounding during earthquakes. Five soil types have been considered in the investigation, as defined in the ASCE 7-10 code [69], i.e., hard rock, rock, rock, very dense soil and soft rock, stiff soil, and soft clay soil. The results of the study show that bounding is more significant for the buildings founded on the soft clay soil than for buildings founded on stiff soil, than for buildings founded on very dense soil and soft rock, and finally for buildings founded on the rock and hard rock. Indeed, [PERSON] et al. [70] studied the effects of the soil type on the response of buildings experiencing floor-to-column pointing where special attention has been paid to the shear demands of the impacted column (the column experiencing the hit from the top slab of the shorter building). The same five soil types have been taken into account. It was found that the shear demands of the impacted column significantly increase due to collisions. Also, it was found that the impacted column experiences higher shear demands for buildings founded on the soft clay soil than for buildings founded on the stiff soil, than for buildings founded on very dense soil and soft rock, and finally for buildings founded on the rock and hard rock. Moreover, [PERSON] et al. [71] studied experimentally (using the shaking table tests) the effects of the soil type on the response of colliding buildings. Two steel-storey buildings with different dynamic properties have been considered in the case of bounding as well as the no-pounding case. Four seismic gaps and five earthquakes have been considered in the study.