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

• resist any bending induced by the sheathing being connected to the top or bottom of thesemembers.Hence, perimeter members can be subjected to combined bending and direct axial compressive forcesand must be designed accordingly.By sandwiching the sheathing into the perimeter members with half of the perimeter member above andhalf below the sheathing, eccentricity will be eliminated and the perimeter members will be subjected to axialcompression only.Since membranal stresses result in boundary shears along the perimeter member these shears can beresolved to determine sheathing stresses. The principal forces in the shell are compressive forces c,parallel to the direction of the convex parabola and tension forces t, parallel to the direction of theconcave parabola shown in FIGURE 12.17.FIGURE 12.17: Resolved components of the tension and compression forcesThe following lists the nomenclature applicable to FIGURE 12.16 and FIGURE 12.17a = length of sidea’ = length of the horizontal projection of aC = total compression force in perimeter memberc = principal compressive force in sheathing / metreF = resultant of the vertical reaction R and the horizontal thrust HH = horizontal thrusth = vertical distance from a support to the highest point of the shellk = inclined distance from a support to the mid-point of the length l 1 = length along longitudinal axis2= length along transverse axisR = vertical actiont = principal tension force in sheathing per metres = boundary shear force per metre172