2001 ASD Supplements - unprotected PDF - American Wood Council

ASD WOOD STRUCTURAL PANELS SUPPLEMENTSP-214.4 Creep Adjustment Factor, C CWood-based panels under constant load will creep (deflectionwill increase) over time. For typical constructionapplications, panels are not normally under constant loadand, accordingly, creep need not be considered in design.When panels will sustain permanent loads which will stressthe product to one-half or more of its design capacity, allowanceshould be made for creep. Limited data indicatesthat under such conditions, creep may be taken into accountin deflection calculations by applying the applicablefollowing adjustment factor (C C ) to panel stiffness EI. SeeSection 4.5 for additional adjustments related to servicemoisture conditions, for which EI is cumulative with theadjustment for creep.4.5 Moisture Effect Factor, C MDesign capacities apply to panels under moisture conditionswhich are continuously dry in service; that is, whereequilibrium moisture content is less than 16%.Adjustment factors for conditions where the panelmoisture content in service is expected to be 16% or greaterare as follows (see NDS Section 9.3.3):Table 4.3Moisture Condition Plywood OSBDry 1/2 1/216% MC or greater 1/2 1/6Table 4.4Reference CapacityCreep Adjustment Factor, C CMoisture Effect Factor, C MC MStrength (F bS, F tA, F cA, F s(Ib/Q), F vt v) 0.75Stiffness (EI, EA, G vt v) 0.854DESIGN ADJUSTMENT FACTORS4.6 Preservative TreatmentCapacities given in Tables 3.1 through 3.4 apply withoutadjustment to plywood pressure-impregnated withpreservative chemicals and redried in accordance withAmerican Wood Preservers Association (AWPA) SpecificationC-9 or Specification C-22. However, due to theabsence of applicable treating industry standards, OSBand COM-PLY panels are not currently recommended forapplications requiring pressure-preservative treating.4.7 Fire Retardant TreatmentThe information provided in this Supplement does notapply to fire-retardant-treated panels. All capacities andend-use conditions for fire-retardant-treated panels shallbe in accordance with the recommendations of the companyproviding the treating and redrying service.APA – The Engineered Wood Association