Internal Action Combination Factor — Kc,i
AS/NZS 1170.2:2011 • Clause 5.4.3 and Table 5.5
Select the number of effective surfaces whose wind pressures contribute together to the structural action being checked. The internal surfaces of the building are counted as one surface where internal pressure is effective.
Internal pressure action combination factor
Kc,i = 1.00
No combination reduction.
2011 edition check: Internal surfaces are not counted as an effective surface when |Cp,i| < 0.2. The selected number refers to surfaces contributing to the same action effect, not the total number of walls and roofs on the building. The 0.8 minimum for Ka × Kc,e concerns external factors; it is not an additional minimum applied to Kc,i. For negligible internal pressure, Table 5.5 may identify Kc,i = 1.0 as not an effective surface.