Roof Diaphragm Shear

Since the framing will be spruce pine fir with sg 0 42 the shear values from table 2 must be adjusted according to footnote a.

Roof diaphragm shear.

The term diaphragm is usually applied to roofs and floors. The brackets allow the use of continuous ridge venting in blocked diaphragms by replacing the boundary nailing between the roof sheathing and the ridge board ridge beam that is lost due to the gap required for venting. A shear wall however is a vertical cantilevered diaphragm. The maximum diaphragm shear in the roof diaphragm is.

In structural engineering a diaphragm is a structural element that transmits lateral loads to the vertical resisting elements of a structure such as shear walls or frames. Shear nailing of the roof diaphragm north south the diaphragm loaded in the north south direction has been selected to illustrate the design of a wood structural panel roof diaphragm. The roof diaphragm is oriente d horizontally and carries loads to the endwall shear wall and then to the foundation. The side walls carry the load to the roof diaphragm on top and the foundation at the bottom.

In building design these loads are typically caused by wind and seismic events although earth and water can exert lateral forces as well. Shear diaphragms are commonly used in buildings as a means of transmitting lateral loads. The allowable shear capacities in tables 2306 2 1 1 and 2306 2 1 2 are permitted to be increased 40 percent for wind design. Sheathed elements such as walls and a roof covere d with panels and tied together provide additional strength to the building.

Diaphragms are typically horizontal but can be sloped such as in a gable roof on a wood structure or concrete ramp in a parking garage. The diaphragm forces tend to be transferred to the vertical resisting elements primarily through in plane shear stress. Af pa sdpws shall be met and wood structural panel diaphragms are permitted to resist horizontal forces using the allowable shear capacities set forth in table 2306 2 1 1 or 2306 2 1 2. A diaphragm is a flat structural unit acting like a deep thin beam.

A similar design is required in the other orthogonal direction east west but is not illustrated here. While the diaphragm shear stiffness development is similar for both mca and steel deck institute s sdi diaphragm design manual the only difference is the panel edge term k. The shear walls may also be known as vertical or cantilevered diaphragm s. Allowable stress design asd will be used.

These construction systems can be used when designing a building for lateral loads such as those generated by wind or earthquakes. V n s wl 247 72 212 plf 2b 2 42 v e w wl 180 42 52 plf 2b 2 72 3.