Loading on underground arch/dome

[Euler07]

Hi all,
Firstly, thanks for any help on this. Please see the image below.

I'm just wondering if anyone has any ideas on loading an arch or dome which is being covered in sand? I was thinking of just super imposing the vertical and horizontal load. The vertical load would be a simplified triangular shape. The horizontal load would be the Rankine load distribution for active soil pressure.

Do you think is going on the right track? Thanks.

 

[IDS]

What size structure are you looking at, and is it an arch or a dome?

Analysing a buried arch as a free standing structure with symmetric loading is likely to give very misleading results.

For an arch structure the simplest way to get realistic results is to include the foundations and the backfill in a 2D plane strain analysis, with non-linear material properties for the soil elements. Also model the construction process, with unequal fill levels either side and application and removal of compaction loads.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Euler07]

Hi IDS, thanks for the help. It is technically a dome but with a large cut-out at the front and smaller cut-outs between. I thought to look into arch action for the front section as a verification, and use a full model of a dome (with cut-outs) for the rest. It is essentially the same as a buried dome house with an open front.

The largest diameter is around 8m with 3m ceiling. The sand will be about 0.5m on top.

I've been looking at this document: "Design and Analysis of Underground Reinforced-Concrete Arches". It has load diagrams on page 18 to 21.

https://usace.contentdm.oclc.org/digital/api/collection/p266001coll1/id/1906/download

Do you think a possible approach would be modelling the whole dome with simplified loading and then modelling a 2d section with 2D plane strain analysis and soil elements as you say? A problem is that modelling soil elements needs specialised software. Thanks.

 

[bugbus]

I can see you're based in Australia

Not sure what type of arch/dome you're looking at but there is an Australian Standard for buried corrugated metal structures (AS 2041) which talks about the loading assumptions, etc. One of the bigger suppliers of buried corrugated metal arches is Roundel, who are pretty helpful if you have specific questions.

 

[IDS]

Do you think a possible approach would be modelling the whole dome with simplified loading and then modelling a 2d section with 2D plane strain analysis and soil elements as you say? A problem is that modelling soil elements needs specialised software. Thanks.

Yes, I think that would be a reasonable assumption. I use Strand7 for my FEA. It works well, and has good facilities for staged analyses.

bugbus - I haven't used that standard, but I'd be cautious about using a code written for corrugated steel structures, which are very flexible and have different behaviour under soil loading.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Euler07]

Thanks guys, I'll go with that.