# Combinations & Envelopes \[FEA]

## Items

This object serves multiple purposes, including **filtering** staged construction results by **load type**, extracting **incremental**/**cumulative** results from staged construction analysis, and combining transient loads such as wind loads, live loads to identify the most critical load effects.

**Envelope\[Yes/No]:** If the "Envelope" option is set to "Yes," the component will find the critical case from the cases specified in the "Cases and Factors" column. However, if only one result case is defined in this column, selecting "Yes" or "No" for the envelope will not affect the results.

If the "Envelope" option is set to "No," the linear result combinations will operate by summing the results of multiple cases specified in the "Cases and Factors" column. Factors can be applied to the cases to achieve a weighted linear combination, but it is recommended to increase the loads according to the factors defined in AASHTO under limit states part. These factors should only be used if any increase needs to be made to compute the unfactored loads, such as including splice and other steel girder attachments by increasing the dead load by 5 percent. However, if only one result case is defined in this column, selecting "Yes" or "No" for the envelope will not affect the results.

**Extreme Effects(Transient Loads)\[Yes/No]:** Selecting this option will exclude the selected result case from the combination if its value in the enveloped column is positive for minimums or negative for maximums. It is recommended to select "No" for permanent loads and "Yes" for transient loads. Choosing EE=Yes for permanent loads may lead to incorrect results since the result may be excluded from the maximum or minimum results.

**Incremental\[Yes/No]:** If "**no**" is selected, the **cumulative** results from the selected stage will be extracted. If "**yes**" is selected, the **incremental** results from the selected stage will be extracted.

**Load Type Filter\[None/Dead Load/Imposed Dead ….]:** If the "Filter By Load Type" option is set to "None," the component will extract the incremental or cumulative results from the selected stage without filtering it according to load types. However, if it is set to "Dead Load," the component will extract only the incremental or cumulative dead load results and exclude other load types such as imposed dead or wearing surface results from the selected stage. This option filters the results according to the load type. It is crucial to ensure that the load types are correctly assigned to the stages for accurate results extraction.

**Case 1:** The selected result case is the one that will be used in the computations. It is also possible to use other combinations as input for another case here.

**Factor 1:** Factor of the selected case.

**Case 2:** The second result case to include in the combination.

**Factor 2:** Factor of the second case.

**Case 3:** The third result case to include in the combination.

**Factor 3:** Factor of the third case.

**Case 4:** The fourth result case to include in the combination.

**Factor 4:** Factor of the fourth case.

**Case 5:** The fifth result case to include in the combination.

**Factor 5:** Factor of the fifth case.

## More Items A

Additional cases 6-10 follow the same pattern as Cases 1-5 above. Use these when the combination requires more than five result cases.

**Case 6:** The sixth result case to include in the combination.

**Factor 6:** Factor of the sixth case.

**Case 7:** The seventh result case to include in the combination.

**Factor 7:** Factor of the seventh case.

**Case 8:** The eighth result case to include in the combination.

**Factor 8:** Factor of the eighth case.

**Case 9:** The ninth result case to include in the combination.

**Factor 9:** Factor of the ninth case.

**Case 10:** The tenth result case to include in the combination.

**Factor 10:** Factor of the tenth case.

## More Items B

Additional cases 11-15 for combinations requiring a large number of result cases.

**Case 11:** The eleventh result case to include in the combination.

**Factor 11:** Factor of the eleventh case.

**Case 12:** The twelfth result case to include in the combination.

**Factor 12:** Factor of the twelfth case.

**Case 13:** The thirteenth result case to include in the combination.

**Factor 13:** Factor of the thirteenth case.

**Case 14:** The fourteenth result case to include in the combination.

**Factor 14:** Factor of the fourteenth case.

**Case 15:** The fifteenth result case to include in the combination.

**Factor 15:** Factor of the fifteenth case.

## More Items C

Additional cases 16-20 for combinations requiring the maximum number of result cases.

**Case 16:** The sixteenth result case to include in the combination.

**Factor 16:** Factor of the sixteenth case.

**Case 17:** The seventeenth result case to include in the combination.

**Factor 17:** Factor of the seventeenth case.

**Case 18:** The eighteenth result case to include in the combination.

**Factor 18:** Factor of the eighteenth case.

**Case 19:** The nineteenth result case to include in the combination.

**Factor 19:** Factor of the nineteenth case.

**Case 20:** The twentieth result case to include in the combination.

**Factor 20:** Factor of the twentieth case.