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KD used for load combinations
As per 5.3.2.3, the program uses the largest KD from Table 5.1, for any of the loads in a combination, except when the 5.3.2.2 permanent load factor is applied. Therefore the combinations with higher KD’s are balanced against those with more loads or higher load factors.
Short-term loads - For the combinations that include wind or earthquake loads, the short-term load is considered the dominant variable load and the 1.15 factor for it is used. The long-term load duration factor from 5.3.2.2 does not apply to these combinations.
Standard term loads - If no wind or earthquake loads are included, then the 1.0 factor for snow and live loads is dominant unless the conditions in 5.3.2.2 are met, in which case the long-term load duration factor is used.
Long-term loads - Load combinations with long-term loads in combination with standard-term loads have the standard-term load factor = 1.0 except when the conditions in 5.3.2.2 apply. When only long-term loads exist in a combination the permanent factor 0.65 applies.
Long-term loads in Sizer are dead loads, dead loads due to soil, hydrostatic loads and sustained live loads due to storage or liquids in tanks.
Load Combinations when Live and Sustained Live are Present
The program creates separate load combinations containing other permanent loads plus Ls or Lt, but without L, in addition to those load combinations containing Ls or Lt + L. This is because the load combination with Ls or Lt but without L could govern over the load combination with Ls or Lt and L, because of the lower KD factor for permanent loading, 0.65 vs. 1.0.