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  4. TechTip: リジッドリンクを使用して偏心荷重をモデル化する方法

TechTip: リジッドリンクを使用して偏心荷重をモデル化する方法

Applying eccentric loads (off-center loads) メンバーへ

What is an eccentric load?

An eccentric load is any load that is not applied to the centroid メンバーの. In finite element analysis, 点荷重, 分布荷重, and other forces are generally applied to the centroid of the section (つまり. the geometric center of the section). しかしながら, in certain scenarios you may wish to apply a force off center – 例えば, 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 リジッドリンク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. リジッドリンク 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. 次, 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フィート) to create a column. 

Down in the corner by the coordinate system, クリック Sec1: Not Defined, then in the left panel, クリック  ビルダー 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メンバー. Use the pen tool to draw a 300mm (1フィート) member in the X direction from the top of the column. もし “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 堅い をクリックします 適用する.

モデルは次のようになります。:

左側のパネルで [点荷重] をクリックします。. 属性に次の値を入力します:

  1. メンバーがいます: 3
  2. マグニチュードから: -5 (モデルが Y 軸を垂直として使用している場合, add this value to Y Magnitude instead).
  3. 負荷グループ: Buckling Load

Click apply and the point load will be added to the model. ポイント ロード ID は次のように増加します。 2 (新着) so add another load to create torsion in the column:

  1. メンバーがいます: 3
  2. そしてマグニチュード: 2 (モデルが Y 軸を垂直として使用している場合, add this value to Z Magnitude instead).
  3. 負荷グループ: Torsion Load

ノード 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 変位合計. You can now see how the first eccentric load is causing a buckling effect. 

eccentric-buckling

Note that if you would like to see a finer subdivision of the member you can go to 設定 右から左に、選択ボックス内に完全に含まれている要素のみが選択されます ソルバー, change the メンバーごとの評価ポイント to a suitable number and run solve again.

Now change the dropdown from Buckling LoadTorsion Load そしてその メンバーの結果Torsion Stress. この場合, the member will appear grey as the torsion load is consistent throughout the member.

eccentric-torsion

Notice that the contour scale in the top left still shows the magnitude of torsion that the column is experiencing.

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