3107F.3.3.2 Displacement Capacity

A distinction shall be made between a pier-type pile, with a long unsupported length and a wharf-landside-type pile with a short unsupported length between the deck and soil. The effective length, L, is the distance between the pinned deck/pile connection and in-ground fixity as shown in Figure 31F-7-15. For pier-type (long unsupported length) vertical piles, three simplified procedures to determine fixity or displacement capacity are described in UFC 4-151-10 [7.12], UFC 3-220-01A [7.13] and Chai [7.14].

In order to determine fixity in soft soils, another alternative is to use Table 31F-7-8.

The displacement capacity, Δ, for a pile pinned at the top, with effective length, L, (see Table 31F-7-8 and UFC 4-151-10 [7.12]), and moment, M, is:

(7-35)

where:

Assuming linear curvature distribution along the pile, the allowable curvature, ϕ_a, can be established fromml:

(7-36)

where:

ε_a = allowable strain limit according to Section 3107F.3.3.3

c = distance to neutral axis which can be taken as D_p/2, where D_p is the diameter of the pile

The curvature is defined as:

(7-37)

The maximum allowable moment therefore becomes:

(7-38)

The displacement capacity is therefore given by:

(7-39)