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  2. 结构3D
  3. 技术提示: 如何使用刚性链接对偏心载荷进行建模

技术提示: 如何使用刚性链接对偏心载荷进行建模

Applying eccentric loads (off-center loads) to members

What is an eccentric load?

An eccentric load is any load that is not applied to the centroid 成员的. In finite element analysis, 点荷载, 分散负荷, and other forces are generally applied to the centroid of the section (即. the geometric center of the section). 然而, in certain scenarios you may wish to apply a force off center – 例如, applying a load to the flange of an I-beam, rather than the web. Assuming this is a lateral load, this will create a torsional force and an overall different loading behavior in the member.

How to apply eccentric loads to a model

Here we’ll take you through an example of how you can use 刚性链接to apply such an eccentric load. By using Rigid Links, we can transfer the load from the centroid of the member to a different location. 刚性链接 are extremely useful for this sort of work, as it automatically calculates the resultant moment and other forces from one location to another.

Head over to S3D and create a new model. 下一个, select the pen tool in the right panel or by tapping V. Click once to place the first node at the origin, then draw upward about 2m (6.5英尺) to create a column. 

Down in the corner by the coordinate system, 点击 秒1: 没有定义的, then in the left panel, 点击  建造者 to open section builder. Choose a column section, for this tech-note I have selected an Australian 150UC23.4, this is about a 6×6 I section for our imperial friends. In the left panel, click supports and add fixed support at Node 1.

Now we will add another member so we can create an eccentric load that induces torsion and another that creates a buckling effect on our column.

To see the orientation of your column, click the visibility icon on the right panel and select 3D会员. Use the pen tool to draw a 300mm (1英尺) member in the X direction from the top of the column. 如果 “3D memberis switched on, you will see this member uses the column section. Click the new member, then in the left panel, change the type attribute to 死板的 然后点击 申请.

Your model should look similar to the below:

Click Point Loads in the left panel. Fill out the attributes with the following values:

  1. 节点编号: 3
  2. 从量级: -5 (If your model uses the Y-axis as vertical, add this value to Y Magnitude instead).
  3. 负荷组: Buckling Load

Click apply and the point load will be added to the model. The Point Load ID will increment to 2 (新) so add another load to create torsion in the column:

  1. 节点编号: 3
  2. 和量级: 2 (If your model uses the Y-axis as vertical, add this value to Z Magnitude instead).
  3. 负荷组: Torsion Load

节点 3 of your model should now look something like the following.

Run the solver, then open render modethe cube icon in the right panel. Change the drop-down in the left panel to Buckling load, the deflection scale to Auto, and the Member Results dropdown to 位移总和. You can now see how the first eccentric load is causing a buckling effect. 


Note that if you would like to see a finer subdivision of the member you can go to 设定值 hip-delete-未使用 解算器, change the 每个会员的评估点 to a suitable number and run solve again.

Now change the dropdown from Buckling LoadTorsion Load 和 会员结果Torsion Stress. 在这种情况下, the member will appear grey as the torsion load is consistent throughout the member.



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