The capacity of steel piles is based on allowable strains corresponding to the desired performance criteria and design earthquake.
When the plastic hinge forms in-ground, the plastic hinge length may be determined using Equation (7-21) [7.5]:
D = pile diameter
PLASTIC HINGE LENGTH FOR STEEL PILES [7.5]
|CONNECTION TYPE||Lp AT DECK (in.)|
The following limiting value applies:
Strain at extreme-fiber, εu ≤ 0.035
The maximum allowable strain may not exceed the ultimate value defined in Section 3107F.2.6.4. Table 31F-7-7 provides limiting strain values for each performance level, for both new and existing structures.
Steel components for noncompact hollow piles (DP/t < 0.07 × E/fy) and for all nonseismic loading combinations shall be designed in accordance with AISC 325 [7.10].
The procedures of Section 3107F.2.5.7, which are used to establish Vdesign are applicable to steel piles.
The shear capacity shall be established from the AISC 325 [7.10]. For concrete filled pipe, Equation (7-15) may be used to determine shear capacity; however, Vpile must be substituted for Vs.
t = steel pile wall thickness
fy,pile = yield strength of steel pile
c0 = distance from outside of steel pipe to center of hoop or spiral
[All other terms are as listed for Equation (7-18)].