Complex Diaphragms With Combined Openings and Offsets - The Analysis of Irregular Shaped Structures - page 303

F i g u r e 8.20 Analysis in longitudinal direction.
The main diaphragm section lies between grid lines 5 and 9 from A to E. The
diaphragm section is supported by the shear walls at grid lines A and E. The distribution
of shears through this section is complicated due to the presence of the intermediate
offset at grid line E from 7 to 8. The diaphragm shears on the right side of grid line 5
must be transferred to the shear walls through the 50 ft and 25 ft sections between C and
E designated as sections A and B, respectively. Both sections A and B have full-length
shear walls. This section of the diaphragm can be analyzed similarly to the intermediate
end notch in Example 4.3. However, section A will draw more load because of the
increased depth (50 ft) and stiffness over section B, so an alternate method of analysis
will be presented for consideration. Since the collector at grid line C does not extend to
grid line 5, most of the shear applied to section A must be transferred into the wall by the
section between grid lines 6 and 7. Transfer diaphragm TD2 is used to resist and transfer
the disrupted chord forces of sections A and B at the corners of the notch.
Determine the load distribution into the diaphragm segments (see Fig. 8.21): Assume that
seismic controls with the following design criteria:
Seismic response coefficient C s = 0.14 (ASD).
Roof plus tributary wall dead load DL = 30 psf.
The strip load will be distributed to each section in accordance with its depth.