Nested Load Combinations in RISAFoundation

RISAFoundation includes the ability to utilize “nested” load combinations. Currently, the Load Combinations spreadsheet in RISAFoundation is limited to ten columns of Basic Load Cases (BLCs) and Factor combinations. However, there are times where you may need to include additional entries to your Load Combination. To do this, you can simply “nest” your load combinations.

This means that if you need more than eight BLC entries in a single load combination, you can define the common BLCs (such as Self Weight, DL, and/or LL) in one load combination that you can then reference in the other load combinations. Entering “Lnn” in the BLC field will include all the BLCs (and their factors) from the load combination on line “nn” of the spreadsheet, thereby “nesting” the combination. This can also be used to simplify your input.

Note: When a Factor is assigned to the “nested” BLC line, it will be applied to all the entries in the nested combination. For example, in the image above, the DL in LC2 has a Factor of 1.2, whereas the “nested” combination (LC2) has a Factor of 1.5. This means that the two Factors will be multiplied together, resulting in an overall factor of 1.2*1.5 = 1.8 to the DL. This is why it is important to consider all factors listed when using the nesting feature.