maximum allowable settlement\differential settlement
maximum allowable settlement\differential settlement
(OP)
Dear Experts
i am structural engineer and i am working now on a EPC contract project (the contractor is the client)and he gave me the bearing capacity around (130 to 180) KN/m2 with allowable settlement 50mm , the thing is that he want to squeeze the geo-technical specialist to increase the allowable settlement around (75 to 100)mm to increase the bearing capacity and he need my approval, my question is, there is any reference in any codes controlling the maximum value of the allowable settlement or it's depend on the geo-technical specialist evaluation .
note :the building is precast bearing walls with hollow core slabs .
i am structural engineer and i am working now on a EPC contract project (the contractor is the client)and he gave me the bearing capacity around (130 to 180) KN/m2 with allowable settlement 50mm , the thing is that he want to squeeze the geo-technical specialist to increase the allowable settlement around (75 to 100)mm to increase the bearing capacity and he need my approval, my question is, there is any reference in any codes controlling the maximum value of the allowable settlement or it's depend on the geo-technical specialist evaluation .
note :the building is precast bearing walls with hollow core slabs .
Thank you





RE: maximum allowable settlement\differential settlement
Also, just because the contractor is your client, don't yield to his non-engineering opinion for an engineering issue. He might be placing cost saving ahead of structural safety. You can't do that!
RE: maximum allowable settlement\differential settlement
the design of supper structural precast wall and slabs by vendor and he does not have any problem to increase the settlement may be because all of the connections will be hinged (not monolithic) , so if there is no limitations in any codes or standards control the settlement i can't reject his suggested.
Thank you
RE: maximum allowable settlement\differential settlement
Mike
RE: maximum allowable settlement\differential settlement
the thing is that , i don't know under which forum i can put this thread, and sorry for repeating and interruption .
Thank you
RE: maximum allowable settlement\differential settlement
These are made up numbers; however. We use the loads from the structural engineer to inform our settlement calculations. These loading numbers have all sorts of live load assumptions and the live load does not represent a sustained condition that will lead to settlement, in all honesty. We (some that is) often just take that load and run the numbers!
Along the way, I did pick up an industrial client. My client liaison was an architect that actually wore his thinking cap. He also wanted cost-effective design. In that instance, he just allowed us to deliver a design that showed a paper settlement of less than 3 inches.
There was never a problem.
f-d
ípapß gordo ainÆt no madre flaca!
RE: maximum allowable settlement\differential settlement
Also, what are the size of your footings for the given allowable bearing pressure of 130 to 180 kPa? I assume that the soils are medium dense sandy soils but depending of the size of the footings you can replace some soils with engineered granular fill to get higher bearing pressures. Check also the groundwater levels if you go with the soil overexcavation/replacement option...
RE: maximum allowable settlement\differential settlement
the type of footings are strip footing (inverted beam) and i main soil is silty sand , also i have about 5 meter fill and the ground water table is very far from the surface .
Thank you
RE: maximum allowable settlement\differential settlement
Shooting for 3" of settlement is not a good idea, IMHO...
Dik
RE: maximum allowable settlement\differential settlement
not the contractor will fill when he will start construction , i know what you mean , you mean the soil will take the full settlement from the over burden pressure of fill before the foundation loads so it will not effect on the soil capacity .
Thank you
RE: maximum allowable settlement\differential settlement
RE: maximum allowable settlement\differential settlement
dik....that's not a humble opinion....that's a correct one! Three inches of settlement is ludicrous. If you have 3 inches of settlement, you're bound to have an inch of differential, just from imbalance of loading! I've seen structures fail with less!
RE: maximum allowable settlement\differential settlement
Being opinionated has been a failing of mine since I was a kid... and my wife keeps telling me I have no tact... but, what does she know <G>.
Dik
RE: maximum allowable settlement\differential settlement
Opinionated? Yep...have the same failing....and the same spousal opinion!
By the way SWMBO is obviously not reading this!
RE: maximum allowable settlement\differential settlement
The oft-cited maximum settlement limit of 1-inch total and 3/4-inch differential in most geotechnical reports goes back to Peck about 50 years ago and has little basis in reality.
RE: maximum allowable settlement\differential settlement
You get the unhappy face of the day.
Most dissatisfied clients and lawsuits are not due to structural resilience, or lack thereof, but concrete cracking.
RE: maximum allowable settlement\differential settlement
I just can't take this at face value.
If generally-accepted practice is to design for 1-in, then your statement is correct. If the client is knowledgeable and elects to evaluate risk-reward, then it's neither good or bad. It's an informed decision that may be just fine (i.e., a good idea).
So, your statement only makes sense if you don't have a discussion that includes the geotechnical engineer, the owner and the structural engineer.
f-d
ípapß gordo ainÆt no madre flaca!
RE: maximum allowable settlement\differential settlement