## 1 Introduction  
The meizoseismal area in southwest China is rich in water energy resources [1], and therefore the problem of selecting sites for high dams and large reservoirs is \"difficult to avoid\". Moreover, some of the high dams that have been built, are under construction, or in the planning stage are located near the seismic fault zone [1], which is subject to complicated rules of near-fault ground motions. Near-fault earthquakes occur within 20 km of the fault and include displacement and velocity pulses, as well as permanent ground displacement [2; 3; 4], additionally, their characteristics are remarkably different from those of far-fault earthquakes. Several major earthquakes in the last twenty years, such as Northridge (1994), Kobe (1995), Chi-Chi (1999), and Iran (2003), and especially the Wenchuan earthquake in China (2008) and the earthquake in Haiti (2010) have confirmed the remarkable impact of velocity pulses contained in near-fault seismic records on building damage [5; 6; 7; 8; 9]. At present, based on the time-history method and the theory of the response spectrum, the latest \"Code for seismic design of hydraulic structures of hydropower project\" (2015) of China does not distinguish between the near-fault seismic records and far-fault seismic records. In addition, most of the current studies on near-fault ground motions were based on the uniform seismic excitation method and assumption that the wave was propagating along a vertical direction [10], because the vertical direction is the weakest and critical direction in dam structures. However, this assumption did not fully consider the elasticity of foundation and the structure-soil interaction. It is now generally accepted that the traditional uniform seismic motion input method would overestimate the response of the dam [11]. Moreover, many studies have confirmed that quite different responses in infrastructures can occur under the non-uniform motion caused by oblique incidence [12; 13; 14]. According to the current research status, it is necessary to further analyze the behavior of a dam under near-fault earthquakes. The influence of the incidence angle of the seismic waves on various dam bodies should also be taken seriously. RCC (roller-compacted concrete) has been widely used in engineering due to its structural and construction advantages [15; 16], and the joint construction of RCC with other materials has become the future development trend [17; 18]. However, material properties and deformation characteristics of CC (conventional concrete) and RCC are significantly different from each other, and high deformation gradients tend to occur at the interface under seismic excitation. In addition, currently, the dynamic behavior of combined dam structures subjected to obliquely incident seismic waves is rarely considered. Therefore, it is of great significance to study the dynamic response of the combined dam structures under the oblique incidence of near-fault ground motions. Some scholars have done related work on the dynamic characteristics of dams to near-fault ground motions. [PERSON] et al. [19; 20; 21] focused on the dynamic response of different types of dams under near-fault ground motions and far-fault ground motions, and they indicated the dynamic analysis of structures under different near-fault earthquakes should be evaluated. [PERSON] and [PERSON] [22] took into account the rock interactions of a dam-water-sediment-foundation system and analyzed elastoplastic behavior of the dam under near-fault and far-fault seismic records. They concluded the near-fault earthquakes were more destructive than the far-fault earthquakes. [PERSON] et al. [5; 23] studied the plastic damage response of the dam-reservoir-foundation system of the Koyna dam under near-fault and far-fault earthquakes and pointed out the important effect of near-fault earthquakes on dam damage. [PERSON] et al.