Define Load Combinations dialog
Used to specify a load case that combines results of analysis performed for different primary load cases.
For more information about Load Combinations, refer to TR.35 Load Combination Specification.
Setting | Description | ||||||||||
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Load No. | Specify an integer value to define a new load case combination. This number is automatically incremented. | ||||||||||
Name | Specify a Name for the load case combination. | ||||||||||
Type |
There are three types of combinations possible:
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Factor | The load factor coefficient, b, used for the square root value of the sum of the squares. | ||||||||||
Default |
Indicates the default value of the load factor, a (or c, in the case of a SRSS combination), for any load case moved from the Available Load Cases to the Load Combination Definition. Load factors may be changed from the current default by selecting the entry in the Load Combination Definition. |
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SRSS Component |
(Active only when the SRSS type is selected) The SRSS load combination type allows a mixture of algebraic combination with an SRSS combination. Select this option to for the load to include it as a SRSS in lieu algebraic addition. |
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Generate Combination |
(Active only when either the SRSS or ABS type is selected) Se this option to generate 1 - 64 load combinations for each combination of degrees of freedom at member ends to create load envelopes for positive and negative analysis results for SRSS and Absolute load combinations. |
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Available Load Cases list |
Lists all of the previously created Primary Load Cases or Load Combinations in the current input file. Tip: Double clicking any load case or
combination will add it to the Load Combination Definition list.
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Load Combination Definition list |
Entries here represent the Primary Load Case, load factors, and SRSS component (if any) which will make up the Load Combination. |
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List Operators |
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Example
Thus, for example, if you want to create a combination case called 101, which combines the absolute values of the results of cases 7 and 15, factored by 1.5 and 1.64 respectively, the command would be
LOAD COMBINATION ABS 101
7 1.5 15 1.64
From the Create New Load Combination dialog:
- Select the ABS option.
- Select load case 7 in the Available Load Case list.
- Specify a Default factor of 1.5 and move it to the right pane by clicking on the > button.
- Repeat this process for case 15 with a factor of 1.64.
- Click Add.
The table shown below illustrates the Load Combination logic for Algebraic and SRSS types assuming that the Primary Load Cases are L1, L2, and L3.
Primary Load Case | Factor | Combine Algebraically? | SRSS? | SRSS Factor | Resulting Combination Formula |
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L1 | 0.75 | Yes | No | n/a | 0.75(L1) + 0.75(L2)+1.33(L3) |
L2 | 0.73 | Yes | No | n/a | |
L3 | 1.33 | Yes | No | n/a | |
L1 | 1.0 | No | Yes | 1.2 | |
L2 | 0.4 | No | Yes | 1.2 | |
L3 | 0.4 | No | Yes | 1.2 |