### Design Example - Driven Piles.

**Table 1-3.**This pile is made of A36 steel with fy = 36 ksi, Ep = 29,000 ksi, and pI = 729 in.^4 for the X-X axis and 261 in.^4 for the Y-Y axis. Dead load QDL = 40 kips and live load QLL = 60 kips. Load factors FDL = 1.3 and FLL = 2.17. Free-standing length above the ground surface is 10 feet. The soil is a clay with a constant modulus of horizontal subgrade reaction Els = 1 ksi. Spacing between piles is three times the pile width.

**(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.

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