Factor of Safety for Uplift -Tension Piles
Factor of Safety for Uplift -Tension Piles
(OP)
Hi All ,
According to ASCE , Service Load Combination for uplift check =0.6D+U , this would produce factor of safety 1.67
When using tension Piles to resist uplift , normaly factor of safety for skin friction =3.0 .
As a result of this , we end up getting global factor of safety =1.67*3.0 = 5.0 which is extremely high.
Would be appreaciated to hear your input in this Gentlemen.
Regards
According to ASCE , Service Load Combination for uplift check =0.6D+U , this would produce factor of safety 1.67
When using tension Piles to resist uplift , normaly factor of safety for skin friction =3.0 .
As a result of this , we end up getting global factor of safety =1.67*3.0 = 5.0 which is extremely high.
Would be appreaciated to hear your input in this Gentlemen.
Regards






RE: Factor of Safety for Uplift -Tension Piles
RE: Factor of Safety for Uplift -Tension Piles
One thing that kills me about current ASD... I'm supposed to pretend that 40% of my dead load is not even there, when it is. How could this ever represent a true loading condition?
Which brings me to another point... What do engineers out there use for dead load? Actual dead load , or the dead load allowance? Strictly speaking, codes define dead load as "the weight of materials of construction incorporated into the building". Because of the definition, I think most engineers use actual dead load only when checking against uplift. It is my opinion that the 0.6 multiplier was originally intended to be the fraction of dead load allowance that was likely to actually be there. Now it's morphed into pretending somehow that real dead load, like dead weight of a structure, dead weight of soil, dead weight of a footing or pile cap, etc. is not there. Dead weight of soil especially kills me. Is this really a "construction material"? I'm interested to know what others think.
ahmedhegazi - I'm also interested to know where you came up with the safety factor of three against uplift. I thought it was normally two.
RE: Factor of Safety for Uplift -Tension Piles
He also made some arguments against using the 0.6D + U calculation bu that mostly revolved around the self weight of the footing and soil.
RE: Factor of Safety for Uplift -Tension Piles
RE: Factor of Safety for Uplift -Tension Piles
RE: Factor of Safety for Uplift -Tension Piles
RE: Factor of Safety for Uplift -Tension Piles
There is an interesting discussion in this thread, which pertains mainly to metal buildings. Most engineers, when designing for uplift, design the base connection for 0.6D + W. In this case, the "D" only includes the superstructure and not weight of the footings or soil.
ash060's discussion talks about this. What's the point in providing all the weight in the footing preventing uplift, when the connections aren't designed for it.