In BS 8110 and BS 5400 Pt.4, there is provision of nominal reinforcement for columns. However, for pile design the requirement of nominal reinforcement may not be necessary.

Firstly, as piles are located underground, the possibility of occurrence of unexpected loads on piles is quite less. 

Secondly, shear failure of piles due to severe collision is not critical to the structure . 

The failure of piles by buckling due to fire is also unlikely because fire is rarely ignited underground.

However, the suggestion of provision of nominal reinforcement to cater for seismic effect may be justified. Reference: J P Tyson (1995).