Result Extraction Cases [SIG]

This object serves multiple purposes, including defining unfactored result cases for AASHTO-based combinations, 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.

The Result Extraction Cases generated through this process will be utilized in the "Limit States" section.

When selecting result cases from a Staged Construction Analysis, there are several options available to extract 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.

Filter By Load Type[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.

Once results are extracted from a staged construction analysis using the incremental and filter by load type options, the envelope and extreme effect options can be used to specify how the results will be combined in a combination.

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. For example, when dealing with temperature loads, there are usually two cases to consider: expansion and contraction. The user has the option to add these cases to single result extraction case and choose the envelope as "Yes." Another scenario to take into account is the deck pouring sequence, which may consist of multiple stages. Some of these stages might have a maximum bending moment greater than the final stage. To consider those maximum values, the user can combine all deck pouring stages into a single result extraction case and select the envelope option as "Yes" to identify and utilize the critical one. You can observe both examples in the screenshot below.

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(Dead, Wearing Surface…) and "Yes" for transient loads(Temperature, Wind on Structure, Wind on Live, Live Load, Braking, Centrifugal…). Choosing EE=Yes for permanent loads may lead to incorrect results since the result may be excluded from the maximum or minimum results.