Diaphragms With Intermediate Offsets - The Analysis of Irregular Shaped Structures - page 169

4.3 Optional Layouts

Example 4.1 assumed that shear walls supporting the diaphragm were allowed at grid
lines 1 and 5 only. Shear wall locations are often controlled by the floor plan layout.
However, the engineer usually has considerable flexibility for the utilization and place-
ment of those walls in the lateral-force-resisting system. The goal of the engineer should
be to optimize the lateral-force-resisting system by strategically placing walls to elimi-
nate discontinuities and irregularities, thereby creating some redundancy into the sys-
tem. As an example, review Fig. 4.5. The diaphragm in Example 4.1 can be simplified by
adding a shear wall at grid line 3. This creates two separate diaphragms, as shown at the
bottom dimension line of the figure. Diaphragm 1 is a notched diaphragm, which
requires a transfer diaphragm and remains a complex diaphragm, unless the collector at
grid line B from 1 to 2 is used as a part of the diaphragm chord and the section below is
considered as a nonfunctioning part of that diaphragm. The reduced span proportion-
ately reduces the magnitude of the collector and chord forces. Diaphragm 2 becomes a
simple diaphragm. A collector or interconnection tie is required at grid line 3B to provide
some degree of continuity and to prevent separation at the reentrant corner, in accor-
dance with IBC 2 Section 1614.4. The structural configuration becomes further simplified
if an additional shear wall is added at grid line 2. The diaphragm is then broken down

F i g u r e 4.5 Optional layouts.