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Load Combinations

Use custom Load Combinations or import from relevant Design Codes in Structural 3D

Load Combinations (LC’s) are a linear function of multiple load cases and are used when designing structures in conjuncture with building codes. Each Load Case within an LC is multiplied by a Load Factor, adjusting the weighting of that load type in combination with others. Building Codes require the use of LC in design to ensure a safe response from a structure experiencing the maximum possible loading conditions.


Adding/Editing Load Combinations

To start, Load Combinations can be added by clicking the Load Combos button within the main menu as shown:

load combo 1

Note: the Load Combinations window will only let you edit the Load Factors for Load Groups you have already assigned. To learn more about how Load Groups work in conjuncture with Load Cases, read the previous article about Load Groups.

Once you are on the load combinations menu you can add a custom name for each LC, which is given an ID, and each involved load groups contributing factor, as shown above. Users can now add Load Combinations manually by entering the aforementioned fields and hitting Apply for each Load Combination.

Load Combinations can be viewed and edited using the Load Combinations Datasheet, which can be accessed by clicking the button on the top right-hand corner of the Load Combos menu (looks like a spreadsheet). The Load Combinations Datasheet supports the same functionality as other spreadsheet software. To learn more about Datasheets in Structural 3D, read about the Datasheets Software Documentation.

load combo 3

Note: Users can clear all Load Combinations using the Clear button within the Load Combos Datasheet.

Importing Load Combinations from Design Codes

Users can import Load Combinations from a variety of different Building Codes across the globe. To start, click on the Design Codes button while in the Load Combos menu, as shown in the image above. A large prompt will come up where you can start editing the options to get the intended Load Combinations.

First, (shown in red), select the governing country and the relevant design code. Then, (shown in blue) if you haven’t already, assign specific load cases to the load groups you have applied to your structure. Finally, (shown in green), toggle all or some of the Load Combinations you would like to import in the project:

load combo 2

Importing/Editing Load Combinations from a Spreadsheet

Sometimes, users will have a compilation of Load Combinations stored in a 3rd party spreadsheet application (like Excel). Instead of importing the Load Combinations from the design codes or inputting them each time, users can simply Copy and Paste their load combinations from any other spreadsheet software. Simply use the Copy and Paste commands to copy and paste the Load Combinations into the Load Combinations Datasheet in Structural 3D.

Note: The columns will need to be in the same order in the 3rd party spreadsheet as shown in Structural 3D. After pasting into the Datasheet, make sure to hit Apply.

load combo 4

Envelope Load Combinations

Along with your user-defined (or imported) load combinations, the solver will also add some envelope cases to make it easier to review the results. Envelope Load Combinations display the absolute worst case result for each member and compile them into one neat set of results. For instance, say member 1’s worst shear case is 1.4D, the Envelope Case will display that result for member 1.

The software will add the following envelope cases:

  • Envelope Min – Minimum results (i.e. negative results)
  • Envelope Max – Positive results (i.e. negative results)
  • Envelope Absolute Max – Will take the absolute maximum of the above two results

Here is a sample of some of the load combinations you might expect to see returned from the solver:

envelope max load combinations show the worst case scenario for each member

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