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

13.3 Modification Factors – Nailed and Screwed ConnectorsThe modification factors discussed herein allow adjustments to be made to the CodeCharacteristic Strength values (Q k ,N) to account for the various influencing designparameters.Capacity Factor(φ)Capacity factor (φ) given in Table 2.6 of AS 1720.1-1997 differs in magnitude to those formembers and is generally less. This reduction is due to their being more contributingfactors, each of which is more difficult to quantify.Duration of load factor (k 1 )Duration of load factor (k1) for connections also differs from those values given for solidmembers. TABLE 13.3 lists the duration of load factors for connections.Load Type Source Duration k1Dead loadsgravity permanent 0.57Long term live loads furniture and partitions permanent 0.57Frequent live load occupancy or vehicle 5 months 0.69Infrequent live loads crowds, construction 5 days 0.77Ultimate wind gust from AS/NZS 1170.2 gust 1.30Earthquake loads from AS 1170.4 5 second 1.14Regular snow loads alpine regions 5 month 0.69Rare snow loads Sub-alpine regions 5 days 0.77TABLE 13.3: Connection duration of load factorsIn connection design a critical load combination, i.e. the one giving the highest D L , can befound from the relationship:whereDLN *D L =k1= duration of load parameter for the strength limitstate;N* = Design action for the connection due to theapplied loads;k 1= duration of load factor for the shortest durationload in the combinationD L performs no other function in the design process other than to identify worst loadingcase for the strength limit state.Grain orientation factor (k13)Grain orientation factor (k13) for Type 1 nailed and screwed joints, irrespective of loaddirection, is k 13 = 1.0. For nails and screws into end grain k 13 = 0.6. FIGURE 13.1 (a) and (b)show examples.Shear plane factor (k 14 )Shear plane factor (k14) accounts for the number of shear planes penetrated by aconnector. FIGURE 13.3 (a) and (b) show examples of k 14 for Type 1 connections. k 14 = 1 and2 for FIGURE 13.3 (a) and (b) respectively.Head fixity factor (k 16 )Head fixity factor (k16) relates to the amount of nails and screw head fixity offered by themember containing the connector head. FIGURE 13.5 (a) shows a fully restrained nailhead by virtue of its being driven through an interference hole in the steel side plate. Thisarrangement forces the nail to deform in double curvature under load which increases the192