Open Front and Cantilever Diaphragms - The Analysis of Irregular Shaped Structures - page 229

F i g u r e 6.16 Transfer diaphragm loading diagram.
If shear walls are placed at the corridor wall lines only, grid lines 2 and 3, a
minimum eccentricity is required to be applied in accordance with ASCE 7-05
Section 12.8.4.2.
Many of the designs for open front and cantilever diaphragms submitted for plan
review are incomplete. The designs typically do not provide the means for the loads to
get to interior supporting walls and seldom include calculations for the deflection of the
diaphragm. Common practice has been to design the longitudinal shear walls and
determine the diaphragm nailing requirements only. The torsional force to the end
walls and confirmation of complete load paths are often not checked, because it is
assumed that loading in the transverse direction will apply a greater force to the end
walls and will control the design. All the examples presented in this chapter clearly
show that this approach provides only a partial analysis. A complete analysis should
also include the following:
• The establishment of continuous load paths in both directions
• Correct collector, strut, and chord placement
• Determination of the collector, strut, and chord forces and their connections
• Diaphragm deflection calculations
• Special nailing requirements at the transfer areas
Open front and cantilever structures can be very complex and demand the utmost
respect and attention from the designer. Even simple open front structures are subject
to considerable damage if improperly designed.