Timber Piles - Structural Design.

Representative allowable stresses for pressure-treated round timber piles for normal load duration in hydraulie structures are given in Table 2-6.

(1) Working stresses for compression parallel te the grain in Douglas Fir and Southern Pine may be increased by 0.2 percent for each foot of length from the tip of the pile to the critical seclion. An increase of 2.5 psi per foot of length is recommended for compression perpendicular to the grain.

(2) Values for Southern Pine are weighted for longleaf, ash, loblolly, and shortleaf.

(3) Working stresses in Table 2-6 have been adjusted to compensate for strength reductions due lo conditioning and treatment. For piles, air-dried or kiln-dried before pressure treatment, working stresses should be increased by dividing the tabulated values as follows:

Pacific Coast Douglas Fir:          0.90
SouthemPine:                             0.85

(4) The FS for allowable stresses for compression parallel to the grain and for bending are 1.25 and 1.3, respectively (International Conference of Building Officials 1991).

Table 2-6  Allowable Stresses for Pressure-treated 

Round Timber Piles for Normal Loads In Hydraulic Structures.