Max allowable foundation settlement! 1

[engr567]

What is the maximum allowable foundation settlement (total settlement and differential) for a building with (3) wood floors, (1) concrete transfer slab, and (2) garage floors below? Is there any literature on this? Does ACI talk about the maximum allowable foundation settlement in a building design? I would appreciate your help.

 

[Bagman2524]

There is no maximum allowable settlement specified in any codes that I'm aware of. You have to check how your calculated settlement will affect the serviceablilty/function of your structure and check that your foundation is structurally adequate for any differential settlement.

 

[ishvaaag]

Spain's codes MV-103 and then its re-encarnation NBE AE-88, that governed building loads for 4 decades had some provisions for that, Table 8.8 Asientos generales admisibles (Maximum allowed settlements) stated that the permissible total settlements were, for wood structures, checking that no disorganization appears nor in structure nor foundations,

Sandy soils 50 mm
Clayey Soils 75 mm

Since 2005 the current standing code CTE (Código Técnico dela Edificación, that has undergone already two main revisions) has sections on this, obviously in the intent defined by Bagman.

Download the

DB-SE C: Cimientos

from the site

http://www.codigotecnico.org/index.php?id=33

And see sections 2.4.3, 4.4 and Appendix F.1.2

 

[BigH]

India codes also have limiting settlements - 40 mm I believe for total - but, in my view, if proper analyses are done and you can show that settlements over that are not detrimental, then you should be able to argue exceeding. it is not the total settlement that usually governs - but the differential - which may be because of two adjacent footings that have different loads which results in different settlement-time (consolidation) levels - or even the same load but applied at different times or the same load with the soil properties varying (thickness, inherent property variation).

 

[drile007]

Eurocode:
A) Maximum relative rotation 1/500
B) Total settlement 50mm

 

[engr567]

Is there any provision on ACI or IBC?

 

[jike]

There is no code guidelines that I know of but there are various recommendations and guidelines. I will scan a couple and post those.

Total settlement (the whole building settling the same amount) will generally affect only site drainage and building access.

Differential settlement can cause cracking, buckling, misalignment of equipment, tilting, pipe ruptures, tripping hazards, etc.

 

[jike]

Attached are a couple reference documents that will give various guidelines for allowable settlements. The first one must be from the foundation book written by Sowers; don't know the title. Second one looks like it might be from a government publication.

I hope this helps!

 

[engr567]

thanks jike.

 

[BigH]

One must be careful - large settlements can be accommodated without damage; yet very small settlements cannot be accommodated without damage. Example - high speed paper machines where there is a differential settlement tolerance of 10 mm in 125 m (on one of my very old projects); large clarifiers where undo tilt makes them not act "so good". Allowable settlements (whether by code, guideline or structure requirements) need to be understood on a project by project (and even foundation by foundation) basis.