2001 ASD Supplements - unprotected PDF - American Wood Council

ASD TIMBER POLES AND PILES SUPPLEMENTPP-73.2.3 BearingFor parallel to grain (end bearing):Allowable bearing design capacity parallel to grainfor timber poles are computed based upon the followingequations:where:P g′ = F g′AF g′ = F g(C DC tC u)For perpendicular to grain:Allowable bearing design capacity perpendicular tograin for timber poles and piles:where:C b is 1.0P ⊥′ = F c⊥′AF c⊥′ = F c⊥(C tC uC b)for bearings of any length at the ends of amember, and to all bearings 6" or more inlength at any other location, and as stated in3.2.9 otherwise.3.2.4 Load Duration Factor, C Dor fire retardant chemicals. The impact load duration factorshall not apply to connections.3.2.5 Temperature Effect Factor, C tEnd-use temperature conditions, other than those definedin Section 2.3.4 of NDS, require use of the temperatureeffect factor, C t . Temperature effect factors for polesand piles exposed to sustained temperatures between therange of 100°F to 150°F are provided in Table 3.3.3.2.6 Untreated Factor, C uIf preservative treatment is necessary, poles and pilesshall be treated in accordance with American Wood PreserversAssociation standards. The Untreated Factors providedin Table 3.4 apply for poles and piles that are eitherair-dried prior to treatment or are not treated.3.2.7 Single Pile Factor, C spTabulated compression parallel to grain and bendingdesign values for timber piles assume use of piles in clusters.The corresponding single pile (load sharing) factoris 1.0. For design of single piles, reduction factors providedin Table 3.5 shall be applied.3DESIGN ADJUSTMENT FACTORSAll tabulated design values except modulus of elasticity,E, shall be multiplied by load duration factors, C D ,as specified in 2.3.2 of NDS (see Table 3.2). Load durationfactors greater than 1.6 shall not apply to structuralmembers pressure-treated with water-borne preservatives3.2.8 Critical Section Factor, C csTabulated compression parallel to grain design valuesat the tip of a pole or pile shall be permitted to beincreased as shown in Table 3.6 to account for strengthTable 3.1 Applicability of Adjustment Factors for Poles and PilesLoadDurationFactorTemperatureFactorUntreatedFactorSizeFactorSinglePile FactorColumnStabilityFactorCriticalSection FactorBearingAreaFactorF c ' = F c C D C t C u – C sp C P C cs –F b ' = F b C D C t C u C F C sp – – –F v ' = F v C D C t C u – – – – –F c⊥ '= F c⊥ – C t C u – – – – C bE' = E – C t – – – – – –F g ' = F g C D C t C u – – – – –AMERICAN FOREST & PAPER ASSOCIATION