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

For a nailed only plywood sheathed, timber framed shearwall these force components result in thedeformations shown in FIGURE 9.13.FIGURE 9.13: The two major racking deflection componentsIn the nailed only bracing system it is nail group stiffness (or lack thereof) whichdominates panel response. This is opposed to in-plane sheathing torsional rigidity (GJ) asexpected in the shear component diagram of FIGURE 9.13 or the flexural rigidity (EI) of thesheathing which is of significance when buckling becomes an issue.The nailed only system also offers certain advantages, e.g.:• failure is gentle resulting in fairly large deformations compared to the rapidcatastrophic failure associated with glued joints;• offers the possibility of designing a plastic moment joint and its associatedadvantages where seismic loads occur.The classical stiffness relationship for a nailed only plywood sheathed, timber framedbracing panel is given by:c ⎡ IxIy⎤k = ⎢ ⎥(9.1)h2⎢⎣Ix+ Iy⎥⎦where:hI xI yIxIyIx+ Iyc= height of the bracing panel;= second moment of area of the nail group aboutthe X-axis, see FIGURE 9.13;= second moment of area of the nail group aboutthe Y-axis;is equivalent to the second moment ofarea (I) for the panel and can be seen tobe entirely dependent upon nailingdensity;= takes into account material aspects and isequivalent to the modulus of elasticity (E).110