Introduction
Pile-caps are elements that transfer the actions from the superstructure of a building, bridge etc., into piles. They can be considered to be a form of pyramid truss that spreads the axial and bending forces from a vertical element into the piles on which the pile caps sit. Another way to describe them would be as a transfer structure that accommodates tolerances of the piles and spreads the axial force from a concentrated column or wall into one or more piles.
This Technical Guidance Note concerns the design of pile-caps for small groups of piles e.g., 2–4 piles. It relies on the strut and tie method to determine the amount of reinforcement required in the pile-cap; which is
dependent upon the depth of the cap, the magnitude of the axial load being placed upon it, the cap’s concrete strength and the pile size and spacing. Larger pile-caps are influenced by diff erential settlement across the base, which complicates their analysis and design. As such, these aspects of pile-cap design will be covered in a future guidance note.