The Portal Frame - The Analysis of Irregular Shaped Structures - page 465

designed using the perforated wall method or force transfer method must comply with
the aspect ratios provided in AF&PA SDPWS 5 Table 4.3.4 and Figs. 4D through 4F.
Portal wall were developed to provide a wall system that allows a minimum wall pier
width of 16. This creates aspect ratios up to 7.5 : 1, which exceeds those allowed by code
for shear walls. Portal frames are not narrow shear walls because, unlike shear walls,
they resist lateral forces by means of a semirigid moment-resisting frame and by flex-
ure. For this reason, the wall aspect ratio requirements of the code do not technically
apply and therefore must fall under IBC Sections 104.11, 104.11.1, and 104.11.2. These
code sections allow alternate materials, designs, and methods of construction and
equipment that are deemed by the building official to be satisfactory and to comply
with the intent of the code. Supporting data, as required by code, can be provided by
valid research reports or by testing performed by an approved testing agency. Portal
walls are covered under IBC Section 2308.9.3.2 as “Alternate Bracing Wall Panel
Adjacent to a Door or Window Opening.” IBC Fig. 2308.9.3.2, shown in Fig. 13.3, sum-
marizes the prescriptive framing requirements for one- and two-story portal frames
for both the IRC and the conventional construction section of the IBC. The minimum
F i g u r e 13.3 IBC Figure 2308.9.3.2, alternate braced wall panel adjacent to a door or window
opening. ( Courtesy of the International Code Council, Inc. (ICC), Washington, D.C. )