(1) Design load. The applied design load per pile Qd from equation 2-1 is
(2) Structural capacity. The unfactored structural capacity Qcap is fy Ay = 36 x 21.4 = 770.4 kips. From Table 2-1 Φpf = 0.85 and Fe = 0.78. The factored structural capacity is FeΦpfQcap = 0.78 x 0.85 x 770.4 = 508.4 kips > Qd = 182.2 kips. Table 2-3 indicates that the allowable stress qa = 10 ksi qa Ay = 10 x 21.4 kips > Qd = 182.2 kips.
(3) Buckling capacity. A flexible cap unbraced at the top is to be constructed for the pile group. The Els = (1/4) x 1 ksi = 0.25 ksi because the spacing is three times the pile width. The equivalent length Leq for the constant Els = 0.25 Ksi from equation 2-4a for the minimum Ip of the X-X axis is
The minimum critical buckling load Qcb from equation 2-3d is
The Qcb = 201 kips > Qd = 182.2 kips. Buckling capacity is adequate.
Table 1-3 Standard H-Piles; Dimensions and Properties (AISC 1969)
Table 2-1 Tolerances in Drilled Shaft Construction.