| 303, top-quality acrylic latex house paint systems
provide best performance (see page 47). Face-checking (separations
between fibers parallel to the grain of the face veneer) can be expected on non-overlaid
plywood which is exposed to the outdoors, even when Finished. If a smooth, check-free
surface is desired, use medium Density Overlay (MDO) plywood. APA Panel Roof Diaphragms
With only slight design modifications, any APA panel roof deck
system described in the previous sections will also function as an engineered diaphragm to
resist high wind and seismic loading. A diaphragm's ability to function effectively as a
beam, transferring lateral loads to shear walls, is related to the quality of the
connections. Nailing is critical since shears are transmitted through these fasteners.
Common nails provide required strength. Other nail types may be used when their lateral
bearing values are considered in the design. Load-carrying capacity is highest when the
diaphragm is blocks. Where 1-1/8" roof panels s are desired, such as for Heavy Timber
construction (see page 64), shear values for 19/32" panel are
used. Blocked shear values of r 1-1/8" panel may be obtained by specifying stapled
T&G edges. Staples shall be 16 gauge, 1" long with a 3/8" corn, driven
throughout the T&G edges 3/8" from the join so as to penetrate the tongue Staples
shall be spaced at one-half of the boundary nail spacing for Cased 1 and 2, and at
one-third the boundary nail spacing for Case 3 through 6, as illustrated in Table 32. Table 32 gives panel and fastening
recommendations for roof diaphragms. Panels and framing are assumed already designed for
perpendicular loads. To design a diaphragm, follow these steps:
1. Determine lateral loads and resulting shears.
2. Determine nailing schedule. Consider load
direction with respect to joints.
3.Compute chord stress due to bending moment.s
Provide adequate splices. Check deflection. Check anchorage of boundary framing (e.g.,
chords) to walls.
For information about developing higher diaphragm shears than shown
in Table 32, contact APA.
|
