Soil spring stiffness 1

[learner100]

Hello All
Could someone please explain why do we provide soil spring for structure for analysis, or the main purpose of it
Bye

 

[rowingengineer]

To provide an estimate of soil/structure interaction.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[learner100]

Hi rowingengineer
Thanks but how we can verify it by using in staadpro or any other FEM software,kindly explain in brief
I have this details with me
bearing capacity = 200KN/m2
allowable settlement = 10mm
FOS = 2
Bye

 

[KootK]

You probably want a range to work with, not a single value. NEHRP's design brief on mat foundations provides some guidance. As tempting as it is, I wouldn't try to calculate the soil stiffness from the values that you quoted. Get the stiffness straight from your geotechnical engineer if you have one.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[DaveAtkins]

KootK is correct, but in a pinch, here is what I have done:

The allowable bearing pressure provided by a geotechnical engineer is generally based on limiting settlement to an acceptable value. So, bearing pressure is related to settlement.

In your case, the allowable bearing pressure (200 kN/m2) is directly correlated to a settlement of 10 mm.

Thus, your soil spring constant would be 20,000 kN/m3.

DaveAtkins

 

[rowingengineer]

Dave, your relationship could only be correct for small pad footings and the 10mm you refer to is only correlated for a specific set of circumstances, as such I would go with KK suggestion and get the geo engineer to provide the stiffness.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[KootK]

Out of curiosity, if we took the DIY approach, would the FOS not factor in somehow? 400 kN/m^2

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[pikku14]

I'd recommend having a read of this presentation which has some really good practical tips on using soil springs:

http://australiangeomechanics.org/pdf/20130814-UseAndAbuseOfSpringsToModelFoundations.pdf

KootK: Yeah I think it would. The 400kPa is the "real" value, although I've always varied springs from 50% to 200% of the given value anyway to be sure the structure isn't too sensitive

 

[KootK]

Excellent reference Pikku -- thanks for sharing it. The OP may find ACI 336.2 relevant as well.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[learner100]

Thanks Pikku for this excellent reference