Hello LEAP team,
While creating my own Load combination Groups by copying from an original load comb group (already available in LEAP). I noticed that even though I've created specific load group combination for Strength I, III, and V for example. The software incorrectly uses all Wind loads cases to generate the load combinations to be later used by the analysis/design. This issue creates unnecessary load combinations, which would slowdown the analysis/design of bridge components (bent cap, column, and footing). Furthermore, it will incorrectly use a load combination with the incorrect wind force (based on different wind speed) and most probably over designing the component.
Here is a simple example to explain the issue.
After creating the wind load (WS) cases using the Auto generator features. We would end up with 4 WS load cases ...
So using, the original load combination Groups III and V. We would end up with 8 load combinations.
However, when using my own (personalized) load combination group. Which in this example, it was created from copying the load factors from the original load combination group and ONLY changing the ETA multiplier (importance factor as per AASHTO for example)... Also, I noticed that the LABEL has to be different . Perhaps, if the LABEL can be the same, the software would use the Load group with the same LABEL to correctly create the load combinations.(see below)
The software creates a total of 32 load combinations (4 times more load combinations cases in this simple example) and uses ALL the Wind load cases even though the wind load cases were created based on specific wind speed. As previously mentioned, this would affect the design of the element (cap, column, footing) and also would slowdown the analysis due to additional (unnecessary) load combinations.
Thanks
Please let us know which version of LBC you are working on.
Users can delete the load combinations which is not required for the analysis design purpose.
There were improvements done to the load combination generation of wind load (WS) cases.
The current release version is
For more information related to Leap Bridge Concrete program please check the wiki articles in the below mentioned Bentley Communities link.
https://communities.bentley.com/products/bridge_design___engineering/w/bridge_design_and_engineering__wiki/15933/leap-bridge-concrete-main-page
here is the version I am using
regarding you suggestion of deleting the unwanted load combination.. I would agree that for my simple example, it is obvious to identify the unwanted ones and delete them .. however, if we consider multi wind direction (60, 45, 30, etc) and generate the load combination .. just with 2 Load groups ..
we would end up with 288 load combinations to go thru and delete the unwanted ones. NOT SO SIMPLE this time.
I am not using the version you have since I need to stay compatible with other users/clients. Therefore, please run this test on your computer and let me know.. remember that the issue only appear when considered a Personalized load group .. in my case, I copied from an original load group and ONLY changed the ETA multiplier factor ... everything else stayed that same ...
Thank you.
Current LEAP Bridge Concrete version does have the this limitation for new Load Groups (with modified eta factors). We currently have enhancement request filed for the request (332700) so that the new load groups behave the same as the default load groups when load combinations are generated.
Until this enhancement is implemented the only work around currently we have when using the new load groups (with modified eta factor) is delete the extra loads that generated. Or the other option is to use the default load groups and then Edit each load combination and modify the eta factor.
For more information related to Leap Bridge Concrete program please check the wiki articles in the below mentioned Bentley Communities link:
Thank you for the clarification.
Hopefully this improvement will be included soon.