Design Cantilever Floor Diaphragm

The term diaphragm is usually applied to roofs and floors.

Design cantilever floor diaphragm. A diaphragm is a flat structural unit acting like a deep thin beam. I can see no good reason this wouldn t work and it would basically eliminate the need for bracing this. Cantilevered diaphragms sdpws 08 rigid wood frame diaphragms shall be permitted to cantilever past the outermost supporting shear wall a distance lc of not more than 25ft or 2 3 of the diaphragm width w whichever is smaller. Limiting it to one story simplifies the example while allowing a comprehensive explanation of an open front diaphragm design.

If rectangular diaphragm no support condition c full cantilever no exterior wall support no significant exterior wall support. A shear wall however is a vertical cantilevered diaphragm. A design example of a wood cantilever diaphragm designers of modern low rise and mid rise multi family buildings often face challenges due to fewer opportunities for shear walls at exterior wall lines e g more glass and larger openings increased building heights and multi story shear wall effects. Therefore induced unit shears and chord forces used in terms 1 2 and 3 of the deflection equation are calculated using strength level design loads.

I m designing a small attachment single level 900 sf to an existing steel building to save on bracing i d like to design the roof diaphragm as a cantilever see attached sketch traditional method on left proposed method on right. Of importance is the in plane rigidity of the diaphragm relative to the walls or frame elements that transmit the lateral forces to the ground figure 4 29. These construction systems can be used when designing a building for lateral loads such as those generated by wind or earthquakes. 7 diaphragm types rigid diaphragm behaves as a fully rigid body d diaphragm 2d shearwalls inherent and accidental torsion considered in design flexible diaphragm behaves as a series of simple beams d diaphragm 2d shearwalls no torsion tributary loading to vertical resisting elements shear walls.

To design as cantilever most load goes to corridor walls. Double cantilever diaphragm and help engineers better understand the code and standards issues associated with these types of structures. This method of analysis can also be applied to multi story structures. Design rigidity means relative rigidity.

Strength level design loads can be estimated by multiplying the allowable stress design seismic loads shown in figure c4 2 2 3a by 1 4.