Seismic effect- irrigation channel

[shashank_b]

i am currently designing an irrigation channel which requires application of compression springs along with seismic loads. i have defined seismic loads first (load no. 4). i have used repeat load cases to combine all the loads(

https://files.engineering.com/getfi...c-48bc-87ad-8afa4ceba722&file=load_cases.jpg)

In summary, i can see the moments being introduced due to seismic forces but it seems they are not being combined with other load cases. For eg. the forces summary for load cases excluding and including seismic forces is exactly the same (

https://files.engineering.com/getfi...b478f527564b&file=load_case_with_seismic.jpg,

https://files.engineering.com/getfi...559d45330b&file=load_case_without_seismic.jpg

)?

i am unable to exactly pin point the problem as to why earthquake effect is not combining?

 

[WARose]

Could you post the STAAD file? (Or preferably, the text of the Edit file.)

 

[shashank_b]

My staad code file is attached here (

https://files.engineering.com/getfi...-49ef-9325-0d0711620037&file=STAAD_file.docx)

 

[WARose]

Could you paste the text of the edit file into a post? I cannot get this to work.

[red]EDIT: Never mind.....I was able to get it. Will get back to you.[/red]

 

[WARose]

Ok I think the issue is your seismic load. You are using some sort of generation command that I don't recognize. On my end, I changed that to a self-weight in the X-Direction and it combined the load cases just fine.

When I ran it with the command you are using, it gave the following warning in the output file:

**WARNING: IF THIS UBC/IBC ANALYSIS HAS TENSION/COMPRESSION
OR REPEAT LOAD OR RE-ANALYSIS OR SELECT OPTIMIZE, THEN EACH
UBC/IBC CASE SHOULD BE FOLLOWED BY PERFORM ANALYSIS & CHANGE.

So that may be your issue. It may be just faster to work up a percentage of self-weight and do what I was talking about before.

By the way, are you certain you need a seismic load here? I've never seen one on a trench before. (Of course, then again, I haven't done that many in high seismic zones.)