To investigate the variability of ground motion characteristics (GMC) with the angle of seismic incidence (ASI) and the impact of seismic incident directionality on structural responses, first, a large-scale database of recorded ground motions was used to analyze the causes of GMC variability due to the seismic incident directionality effect (SIDE). Then a single-mass bi-degree-of-freedom system (SM-BDOF-S) with different types of symmetrical sections was selected to explore the influence mechanism of SIDE on the seismic responses. The results illustrated that the GMC has substantial variability with the ASI, which is independent of the earthquake source, propagation distance, and site condition, and exhibits complex random characteristics. Additionally, a classification method for ground motions is proposed based on this GMC variability to establish a criterion for selecting ground motions in seismic analysis considering the SIDE. Moreover, for an SM-BDOF-S, the response spectral plane is proposed to explain the transition behavior of spectral responses that are very similar among different stiffness ratios, but divergent for different types of ground motions. The influence of SIDE on structures is determined by their stiffness and stiffness ratio in the x- and y-directions, as well as the type of ground motion.

中文翻译：

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地震入射方向性对单质量双自由度系统地震动特性和响应的影响

为研究地震动特性（GMC）随地震入射角（ASI）的变化以及地震入射方向性对结构响应的影响，首先利用大型地震动记录数据库分析了地震动的成因。由于地震入射方向性效应（SIDE）的变化。然后选择具有不同类型对称截面的单质量双自由度系统（SM-BDOF-S）来探索SIDE对地震响应的影响机制。结果表明，GMC与ASI存在较大的变异性，与震源、传播距离和场地条件无关，呈现出复杂的随机特征。此外，基于该GMC变异性，提出一种地震动分类方法，建立考虑SIDE的地震分析地震动选择标准。此外，对于 SM-BDOF-S，提出了响应谱平面来解释谱响应的过渡行为，这些谱响应在不同刚度比之间非常相似，但在不同类型的地面运动中是发散的。SIDE 对结构的影响取决于它们在结构中的刚度和刚度比。X- 和是的- 方向，以及地面运动的类型。