Dear Fellow Stressers!!

I have encountered in the Geotechnical report a certain value of tank settlement at the edge of the tank. There are two set of values given.
The first one is showing (TBH-01 to TBH-06) which shows 22mm (TBH stands for Tank Bore Hole). The second one is showing "Lower Bound Limit" showing 50mm.

I want to understand the meaning of "Lower Bound Limit" in the Geotechnical Report?

As stress engineer, which of the value above will you consider?

Cheers,

The ultimate bearing capacity is related to bearing stress which causes- by shear failure- a sudden catastrophic settlement of the foundation. It can be investigated using the limit (or bound) theorems considering ideal plastic models; they can be used to give upper and lower bounds on the predicted collapse load.

Thanks Mariog.

In this case, do we need to consider it in stress analysis of piping?

Warm Regards,

The geotech reports I've seen have known the proposed tank diameter/weight and said the expected settlement is x, or possible options depending on tank size/ranges.

Just ask the geotech report writer what settlement you should assume.

You'll have to ensure the piping has sufficient flexibility to account for the settlement (through expansion joints or other methods) and that the tank nozzle loads are acceptable.

Unless your Project is not a special one- subject to high risk analysis, you need to consider settlement under Serviceability Limit State (SLS) and you need not to consider bound analysis results. Normally, SLS must be defined in your Project by Civil. I suggest also to investigate with Civil whether your specific tank layout needs to account for settlement under the group of tanks.

Thanks Mariog and anubis. Civil group is not confirming my query so I'll just take the highest number.

Cheers!!!

I have found on the Geotech report the difference between Modulus of Subgrade Reaction considered in the Finite Element Analysis. The 49mm settlement is using a Modulus of Subgrade Reaction of 1E6 KPa/m while the 22mm settlement is using a Modulus of Subgrade Reaction of 4.3E7 KPa/m. This explains the difference between the two values.

Warm Regards,

A good article on the subject, explaining also the basis.
https://www.newcastle.edu.au/__data/asse...Old-Problem.pdf

Thanks Mariog for that very nice article. I have e-mailed directly to the originator of the geotechnical report a query thru our project manager and hoping for their valuable response.

Cheers!!