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

Because of the obvious difficulty associated with having to attempt an analytical check of the rackingdeflection of a dwelling it is essential:“satisfaction of the strength limit state results in automatic satisfaction of theserviceability limit state”.The strength limit state for EWPAA test panels has been established by determining the racking load at adeflection limit of height/100. To ensure a reserve of strength:• strength limit state defined by height/100 must be > 0.8 x ultimate racking load.To fully quantify the racking load variables requires:• strength limit state to be ≥ 1.5 x serviceability limit state.The bracing topic will be discussed further in Error! Reference source not found. on Shearwalls andDiaphragms.7.11 Structural Plywood Lightweight Roofing SystemsTongued and grooved structural plywood in combination with overlayed waterproof membranes or shinglesis used as lightweight, flat or curved roof systems in residential, light commercial and industrial buildings.Design information including installation and fixing details for non-trafficable roof systems arecontained in the EWPAA design manual Featuring Plywood in Buildings. TABLE 7.2 gives minimumstructural plywood thicknesses for rafter or truss spacings for non-trafficable roofs. For trafficable roofsystems the plywood must be designed as a floor in accordance with the EWPAA flooring designmanuals detailed previously in this chapter. Design issues for structural plywood used in lightweightroofing systems are similar to those detailed for structural plywood flooring. Structural plywoodroofing should be spanned with the face veneer grain direction parallel to the span to maximise theplywood capacity. Support spacings should be selected to suit the plywood sheet length, such thatthe ends of the sheet land on a support.Rafter or Truss Spacing Minimum Allowable Plywood Thickness (mm)(mm) F8 F11 F14800 13 12 12900 16 15 151200 19 17 16TABLE 7.2: Minimum Structural Plywood Thickness and Support Spacing for Non-TrafficableRoof Systems Supporting Lightweight Roofing (20 Kg/M2)7.12 Structural Laminated Veneer Lumber (LVL) FramingMembersEWPAA / JAS-ANZ certified structural LVL and structural plywood webbed, LVL flanged, I-Beams areseasoned, engineered timber members that are dimensionally accurate, with very consistent, definedengineering properties. The high structural reliability and consistent performance of these engineeredproducts means they have highly predictable strength and deflection characteristics and therefore canbe designed for use in single member, load critical applications, with confidence. Their high strength toweight ratio and the availability of long lengths (12+ metres) facilitates handling and installation onsite. Additionally, being timber, these products can be nailed, screwed and fixed with timber fastenersas well as sawn, drilled or otherwise modified using conventional carpentry tools.Design Issues for LVL Framing MembersLVL is a generic descriptor used to define a product fabricated from veneers laminated with adhesive, inwhich the grain direction of the outer veneers and most of the inner veneers is in the longitudinaldirection. The mechanical properties of structural LVL are based on the properties of the parent materialused in fabrication and are therefore specific for each manufacturer’s product. The manufacturer’s brand63