Handbook of Civil Engineering Calculations

FIGURE 20. Real and dummy piles.

Stating the equation for the length L' of the dummy pile, equate the displacement Ax in
the equivalent pile group to that in the actual group. Or, Ax = SL'IAE = SL^3 /SEL

AL^3

V~ (38)

2. Replace all fixed supports in the given pile group with
   hinged supports
   Add the dummy piles. Compute the lengths of these piles by applying Eq. 38.


3. Determine the axial forces induced in the equivalent pile group
   Using the given load, apply Westergaards construction, as described in the previous cal-
   culation procedure.


4. Remove the dummy piles; restore the fixed supports
   Compute the bending moments at these supports by applying the equation M= SL.

LOAD DISTRIBUTION AMONG PILES FIXED

AT TOP AND BOTTOM

Assume that the piles in Fig. 19a may be regarded as having fixed supports both at the
pier and at their bases. Outline a procedure for determining the axial load and bending
moment induced in each pile.