> For the complete documentation index, see [llms.txt](https://manual-1-3.karamba3d.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://manual-1-3.karamba3d.com/chinese_1_3_3/3-in-depth-component-reference/3.3-cross-section/3.3.7-eccentricity-on-beam-eccentricity-on-cross-section.md).

# 3.3.7:  梁上偏心率、断面偏心率 (Eccentricity on Beam and Cross Section) 🔷

![图3.3.7.1：梁相对于其两个终端节点连接线的偏心放置](/files/-M9XuT6Xpnst73jP2aFZ)

梁和桁架单元的横截面力与连接横截面质心的线有关。当横截面发生变化时，其质心位置也极有可能发生位移。如果元件主要由弯矩加载，通常可忽略这种偏移。不过，在法向力存在的情况下（例如：考虑柱子时），质心位置的变化会导致附加的弯矩，这对于构件的横截面设计可能是决定性的。

在Karamba3D中，有两个可以用于处理质心偏移的运算器（请参见图3.3.7.1）：一个作用于梁，另一个作用于横截面。当两个定义的变量在一个元素上重合时，它们将进行加法组合。这样，用户可定义不同尺寸的横截面系列，例如，其上侧位置位于同一水平。

可直接定义带有**“Eccent-CroSec”**运算器的横截面局部偏心率：**“EcceLoc”**输入端口需要定义一个相对于局部梁轴偏移的矢量，其输入值以厘米为单位。其中，“x”代表纵向梁轴，“y”代表水平梁轴，“z”代表垂直粱轴  （请参见[3.1.14](/chinese_1_3_3/3-in-depth-component-reference/3.1-model/3.1.14-orientate-element.md#orientate-beam) 节）。使用**“Generate Cross Section Table（生成断面列表 ）”**运算器可将质心偏移的横截面存储在横截面列表中，从而可以在其他项目中重复使用。

与横截面变量相比，**“Eccent-Beam”**运算器有一个附加输入端口：**“EcceGlo”**允许用户定义相对于全局坐标系的梁的偏心率($$cm$$) 。


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