# 3.5.7: 自然振动 (Natural Vibrations)

如果用户想知道结构振动的方式和频率，请使用**“NaturalVibrations（自然振动）”**运算器（如图图3.5.7.1）。长度为$$10m$$的简支钢梁IPE100上中跨点质量的第24种自然振动模式。

通过其材料重量得出的值，可将梁和桁架的质量输入自然振动的计算。Karamba3D对梁元素使用一致的质量矩阵。而对于桁架和壳体单元，则采用集总方法。

在节点处，可定义附加质量（请参阅第[3.1.11](/chinese_1_3_3/3-in-depth-component-reference/3.1-model/3.1.11-point-mass.md)节）以模拟诸如近似混凝土板（通常在高层建筑中占大多数）的效果。假定这些质量仅具有平移惯性。

Karamba3D 以最大分量为1的方式缩放产生的振动模式$$\vec {v\_i}$$：它们作为结果案例附加到模型上，可以通过**“ModelView（模型视图）”**运算器查看。模态质量和参与因子的计算是基于以上述方式缩放的模态位移。

![图3.5.7.1：长度为10 m的简支钢梁IPE100上中跨点质量的第24种自然振动模式。](/files/-M9XuTVoOaHh_CxXJVFE)


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