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

Type of JointSeasoned TimberUnseasoned Timber(no transverse restraint)Unseasoned Timber(transverse restraint)Values of k17na≤4 na=5 na=10 na=15 na≥161.0 1.0 1.0 1.0 1.01.0 0.95 0.80 0.55 0.50.5 0.5 0.5 0.5 0.5TABLE 13.6: Values of k 17 for bolts and coach screwsThe designer must closely examine the joint configuration to assess the likelihood of some of the timberelements drying out (if unseasoned) during their design life.If all of the timber elements of the system are seasoned, and remain so, there should be no problems withrestraint stresses.When one member of a system can shrink and the lateral movement of that member is restrained throughconnection to other members which are stable, as shown in FIGURE 13.9, extraneous stresses will beinduced into the system.FIGURE 13.9: Lateral restraint stresses13.14 Bolted connection Design – Methodology• Sketch or draw to scale a typical connection which will allow the angle of the force to the grain,acting on the bolt for each member of the joint, to be determined. This will allow the joint type to beidentified.• Select k 16 based on whether the bolts pass through tight fitting holes in steel side plates (ifnecessary) or otherwise.• For each force component parallel or perpendicular to the grain match the configuration to adiagram of FIGURE 13.8. This allows b eff to be determined, hence Q skl and/or Q skp the sum of theindividual characteristic loads for the system, can be found.• Select a connector diameter based on analysis, availability, etc.;• Determine the characteristic strength for:o angle of bolt reactive force to the grain, i.e. parallel or perpendicularo b eff for each member/bolt interface;• Evaluate modification factors except for k 17 which has to be assumed conservatively initially forinclusion in the relationship:Φ N j= Φk 1 k 16 k 17 nQ sk205