Analysis of a pile group with Raker Piles

[pgnair1]

Hi,

Currently I am working on a Equipment Support Foundation with heavy horizontal forces both under operating and Seismic cases. The foundation system is of 400 sq precast piles - 36 M long ( vertical capacity 900 kN and lateral capacity 50 kN ). The pile design is governed by the lateral pile capacity and it has been decided to go in for raker piles to reduce pile numbers.

Can somebody explain how should the contribution of the raker pile to resist lateral load is to be taken in the design . Is it that the horizontal component of the axial load in the pile to be taken as resisting the lateral load and the difference between the two to be resisted by the other piles ? Also if rakers at either end of the group are inclined in opposite directions, do we only consider the raker piles under compression only resisting the lateral load or both tension and compression piles together??

Is there are any definitive article or book which covers pile group analysis with raker piles subjected to vertical and horizontal loads as well as moments ?

Thanks

 

[DRC1]

See Liu & Evett Soils and Foundations. The pile can be designed as a 2 force member with the horizontal component resisting lateral load. This was a common method before computers and is still an acceptable method. Today the computer allows mor elegant solutions, but this method is fast and serviceable. If there is suffient overturning moment in the foundation, such that the back piles go into tension, and the piles have sufficient capacity in tension, then the horizontal componet can be used, otherwise, only the front batter piles can be used. For construction considerations batters are usually 3:12 or less unless drilled in minipiles are used.