EWPAA Structural Plywood and LVL Design Manual - Engineered ...

Application of Structural memberAll structural elements in houses. All secondary structural elements in structuresother than housesPlywood CapacityFactor, ΦPrimary structural elements in structures other than houses 0.8Primary structural elements in structures intended to fulfil an essential service orpost disaster functionTABLE 5.6: Capacity Factor, ΦFactor k 1 – Load DurationThe k1 duration of load factor given in TABLE 5.7 allows for the time dependant nature of thestrength of timber. A timber member subjected to a short term load without failure may failover time if the load is sustained. The k 1 factor allows for the reduction in the strengthcapacity of the plywood member when subjected to long term loads. For loadcombinations of differing duration, the appropriate k 1 factor is that for the shortestduration load.Type of Loadk1Permanent loads (50+ years duration)0.57Live loads on floors due to vehicles or people applied at frequent butirregular intervals (5 months total duration)0.80Live loads applied for periods of a few days and at infrequent intervals(5 days total duration)0.94Impact or wind loads (5 seconds duration) 1.00Wind gust 1.15TABLE 5.7: Duration of Load Strength Modification Factor0.90.75Factor k 6 – Ambient temperature factorThe ambient temperature factor relates temperature effects in buildings to geographicallocations and is taken as k 6 = 1.0 for normal structures, except for coastal regions ofQueensland north of latitude 25°S and all other regions of Australia north of 16°S. For theseregions strength is modified by taking k 6 = 0.9. If floods are due to cyclonic winds thentemperature modification may not be required.Factor k 7 – Factor for length and position of bearingThe k 7 bearing factor given in TABLE 5.8 may be used to increase the bearing capacityperpendicular to the grain for bearing lengths less than 150mm along the grain when thebearing length is 5mm or more from the end of the member.AS1720.1-1997AS1720.1-1997Clause 2.4.4Length of bearing of Member (mm) 12 25 50 75 125 150 or moreValue of k7 1.85 1.60 1.30 1.15 1.05 1.00TABLE 5.8: Factor for Length and Position of Bearingk 12– Stability factor for plywood loaded in the plane of the panelThe k 12 factor allows for the reduction in strength due to buckling of plywood diaphragmsloaded in-plane. The ratio of the plywood diaphragm depth to plywood thickness iscritical in determining whether the diaphragm will buckle. TABLE 5.9 gives k 12 factors fortypical diaphragm depths and plywood and plywood thicknesses when diaphragm lateral edgesare supported and subject to uniform edge forces.AS1720.1-1997Appendix J29