Diaphragms With End Horizontal Offsets - The Analysis of Irregular Shaped Structures - page 150

F i g u r e 3.40 Diaphragm delection.

At grid line 5 (above B),

F 5 = ( 420 + 300 20 )() = 14 400 , lb compression

B

The force diagram closes.
Diaphragm deflection (see Fig. 3.40): The double end notched diaphragm has three
different depths due to the offsets at each end and should be analyzed as a single-span
beam with three different moments of inertia. The complete method of calculating
the deflection of irregular-shaped diaphragms was presented in Example 3.1. It
should be expected that the diaphragm just examined would have questionable
performance, especially with respect to deflection. The performance can be improved
by adding interior shear walls which would increase redundancy, shorten the span,
and reduce the demand on each of the individual shear walls. It would also resolve
some of the deflection issues.
Optional layouts (see Fig. 3.41): Optional layouts are available assuming there is flexibility
in the architectural design. In the first option, an interior shear wall is installed at grid line 2.
The resulting configuration produces a simple rectangular diaphragm on the left of grid
line 2 and a single notched diaphragm on the right side of line 2. Adding an additional
shear wall at grid line 5 would remove the notch condition and simplify the analysis.