2001 ASD Supplements - unprotected PDF - American Wood Council

PP-8DESIGN ADJUSTMENT FACTORSincreases as the critical section becomes further from thetip. Critical section factors, C cs , are independent of taperedcolumn provisions in Section 3.7.2 of NDS and bothshall be permitted to be used in design calculations.3.2.9 Bearing Area Factor, C bTabulated compression design values perpendicularto grain, F c⊥ , for timber poles and piles shall be permittedto be multiplied by the bearing area factor, C b , specifiedin NDS section 2.3.10. Table 3.7 provides bearingarea factors for the indicated bearing length on such smallareas as plates and washers.3.2.10 Wet Service Factor, C MTabulated design values apply to wet or dry serviceconditions.Table 3.2 Frequently Used Load Duration Factors, C D1Load Duration C D Typical Design LoadsPermanent 0.9 Dead LoadTen years 1.0 Occupancy Live LoadTwo months 1.15 Snow LoadSeven days 1.25 Construction LoadTen minutes 1.6 Wind/Earthquake LoadImpact 2 2.0 Impact Load1.Load duration factors shall not apply to modulus of elasticity, E, nor to compression perpendicular to grain design values, F c⊥ , based on a deformation limit.2.Load duration factors greater than 1.6 shall not apply to structural members pressure-treated with water-borne preservatives or fire retardant chemicals. Theimpact load duration factor shall not apply to connections.Table 3.3Temperature Effect Factor, C t, for Poles and Piles Exposed toSustained Elevated TemperaturesDesign ValuesEOther Propertiesand ConnectionsIn ServiceMoisture ConditionC t100