Structural Design of Pile Caps and Piles

[Ahmed A. Alamin]

Should i design R.C piles structurally as columns? If so; piles are normally too long " will the pile be classified as slender column?" What is the effect of the surrounding soil ?..Also, pile caps are normally analayzed and designed using strut and tie models, is there any software capable of doing this. I watched youtube videos of peeple using CSI Safe for pile caps and piles design,and they didn't clarify this. Finally what are piles end conditions at the tip and at the connection with the cap will it be pinned or what?

 

[MIStructE_IRE]

Leave it to the geotech guys. Piles are always specialist design items in my country

 

[canwesteng]

Disagree that Geotech guys should design the piles. Piles are designed as short columns for axial and flexural loads, the surrounding soil can be modelled as a spring. You can use any 3D FEA software to make strut and tie models, and then just crunch the numbers outside of the software after the fact.

 

[r13]

Pile design is a coordinated efforts between the structure engineer and geotechnical engineer. Structural project engineer needs to provide loading information (structural reactions), and the geotechnical engineer will size the pile, determine pile length, and obtain pile reactions. The structural engineer is responsible for the design of pile cap, cap - pile connection, and pile reinforcing. CSI is a good source for pile cap design. In the US, L-Pile is usually used for pile design.

 

[MTNClimber]

Although I prefer retire13's approach, I have found that it is location specific. Sometimes the geotech provides the input parameters for pile design in the soils report and other areas the pile is sized by the geotech. If you gave a pile design to a geotech in Colorado, there's a good chance they wouldn't know where to to start.

 

[r13]

Agree with MTNClimber, as I've seen both.

 

[BridgeSmith]

We'd really like to hand off sizing the piles (drilled shafts in our case) to a geotech, except we don't have any at the DOT, so the Geology guys do half of the work (soil properties, stiffnesses & capacities) and us structurals do the other half (sizing shafts, determining stability and loads, structural design of the shafts and cap). We take the soil properties and loads into All-pile or L-pile, iterate the size, get the max moments and do the structural design of the shafts and cap.

Fixity in the soil is determined from the All-pile or L-pile output. The shaft is generally considered fixed at the top, unless we provide a hinge at the shaft-to-cap interface.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[jdonville]

RC piles (I am assuming you are talking about bored piles) are not necessarily the same as columns. Piles get lateral support from the surrounding soil. Unless the surrounding soils are pure crap or are anticipated to scour, the piles should be treated as laterally supported in the as-installed condition. If these are piles to be installed by driving, then there are additional considerations to handle the driving stresses.