Pile Lateral Capacity Check

[rfd23]

Hi,

I am doing CFA piles. We have large lateral loads due to high winds. I am writing what i think should be. Please comment on it if this is right or wrong or too conservative.

Geotech. gave us lateral capacity table of pile. I am writing a part of it.
serv.lat. load Capacity Ser. Def.(mm) Ser. mom u/s PC
125 2.0 229
175 (max) 3.4 347

Now suppose I have a 100 KN of Lateral load on my pile. By interpolation pile will have about 200 KN-m moment on top.

Now my check should be

Happ/Hallow+Mapp/Mall < 1.0
100/175+200/347 < 1.0

OR

Since My H app< Hall So my Pile will be ok.
Keep in mind I am checking, here, only lateral deflection criteria to see pile fail due to lateral deflection or not.

I will strength check separately.
P/Pall+M/Mall < 1.0

Please comment on this. I am really confused on this issue.
Thanks

 

[msquared48]

Any chance of reducing the load to the pile by using any lateral bearing on your grade beam system - if you have one?

Mike McCann
McCann Engineering

 

[shin25]

You really need to consider the verical load and moment due to lateral load acting together. If the combined stress due to these two components are less than allowable then your design is ok. Lateral load also needs to be considered as shear load and shear capacity needs to be checked as well.

 

[vincentpa]

Get the program L-Pile to get the shears and moments in the pile and design using the interaction. The Geotech should really be giving you the shears and moments in the pile given the loading you provide. That is their job not yours to determine the shears and moments in piles. If you want a theoretical approach, ACI has a document on drilled piers which has a procedure for lateral analysis. I imagine it is similar for steel piles. The USACE has a few programs out there that are free to analyze piles and pile groups for lateral load but you should really leave it up to the Geotech because that is supposed to be their specialty and their job.

 

[rfd23]

Tanks to everybody for their valuable feedback.

msq-I have both situations some time i have set of two piles combined by grade beam to other set of piles and some time 4x4 group alone.

I will perform strength check on pile for rebar and x-section capacity as H/hall+p/Pall+M/Mall < 1.0
Hall= 2*phi*(fc')*.5=Shear Capacity of section
similarly Pall and Mall.

I am concerened with soil failure. Pile can fail in two ways.

1. Soil fails -which is deflection more than permissable range (this is usually 0.25 in for lateral)
2. pile section fails (rebar and concrete)

I am trying to check ist criteria. In this check should I use H/Hall+M/Mall <1.0 as shown above in the start of my question.

 

[J1D]

H/Hall+M/Mall < 1.0 is the typical check equation for soil lateral load resistance.

Hall and Mall are given by geotechnical consultants. They are the loads to cause 0.25" (typically) lateral deflection when applied separately.