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The program implements the design provision from AWC Special Design Provisions for Wind and Seismic 3.1.1.1., that was formerly also in IBC 2306.2.1 for editions 2006 and earlier.
This changes the repetitive member factor Cr for moment design of wall studs so that it based upon wall stud size. The system factors from the table in SDPWS 3.1.1.1, with factors ranging from 1.5 for 2 x 4 studs to1.15 for 2 x 12 and higher.
It also applies this factor to the stiffness EI used for deflection analysis, even though the Cr factor is not ordinarily applied to E for deflection, as per NDS Table 4.3.1. The Cr is applied to EI used for both "live" and total deflection, where "live" includes wind loads. It is not applied to the E'min value or the stiffness EI'min used for buckling calculations.
A checkbox in Column mode is used to indicate whether the member meets the sheathing requirements of SDPWS 3.1.1.1. The modified Cr factor is applied when the following are true:
The modified Cr factor is applied only to design for those load combinations which contain a wind load. Other load combinations use the 1.15 system factor. If the dead load governs over the wind load, then the D-only load combination with the reduced Cr factor will govern. This is the same principal under which the highest KD factor in all the loads in a load combination is applied.