Roof Wall Diaphragm

Specifically the ibc irc wfcm and icc 600 provide prescriptive shear wall details and designs that may be applied when certain basic conditions are met.

Roof wall diaphragm. 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 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. In figure 1 wind pressure on the walls parallel to length l act on the building. Diaphragm action is an additional capacity of the panel to transfer the lateral loads to the outside edges of the panel to the eave for roof panels and to the ground for wall panels. Wood frame structure shown lateral wind load 30 psf 2x rafters and studs find.

At the roof level these wall reactions turn the load in the roof system in the plane of the roof. Assuming a flexible roof diaphragm determine the forces in walls a b c and d for north south loading. Learn more about the force transfer around openings ftao method of shear wall analysis including downloadable ftao design tools. Diaphragm and shear wall example given.

This horizontal element is known as the diaphragm. Because this building has one story assume that the seismic weight is concentrated at roof level. The roof and foundation support the vertically spanning wall and consequently pick up the developed horizontal reactions. Table 2304 6 of the 2006 ibc lists the minimum thickness of wall sheathing and.

A shear wall however is a vertical cantilevered diaphragm. The term diaphragm is usually applied to roofs and floors. Use apa sheathing tables in x305 peter von buelow university of michigan tcaup slide 19 of 28. The diaphragm itself does not have a bracing unit rating but is used when bracing lines exceed 6m separation.

Gypsum board diaphragm ceilings shall be in accordance with section 2508 5. Similar changes to 2306 3 for shear walls. If a larger opening is unavoidable this must be in the middle 1 3rd of the diaphragm. Double diagonally sheathed lumber diaphragms shall be designed and constructed in accordance with af pa sdpws.

Figure 1 illustrates the basic concept for a roof and wall diaphragm. 2306 2 4 gypsum board diaphragm ceilings. Protrusions are permitted but cut outs for walls or sky lights are not. A diaphragm is a flat structural unit acting like a deep thin beam.

Strength and stiffness of a diaphragm depends on the panel properties the span arrangements and the quality of the connections. Also assume the mass is evenly distributed over the entire roof. The diaphragm forces tend to be transferred to the vertical resisting elements. The basic shape of a ceiling diaphragm is square or rectangular 1 1 or 1 2.