According to ASCE 7-22 [1], a number of different load cases must be considered in the design of both primary and secondary structural members. For the example shown below—a three-span PEMB with ten bays and continuous purlins—the frame design requires consideration of 5 roof live load cases, 3 snow load cases, and 8 wind load cases, while the purlin design requires 1 roof live load case, 16 snow load cases, and 8 wind load cases, in addition to other applicable load cases such as dead load, live load, and crane load (if present). 

MkaPEB carefully accounts for all of these load cases in the generation of load combinations and in the structural analysis and design of both main and secondary members.

However, because calculating these loads and accurately applying them to the individual members requires significant computational effort, structural engineers often neglect some of these load cases. Such omissions can significantly affect both the weight and the safety of the final design compared with a fully code-compliant design.



References:

[1] American Society of Civil Engineers. "Minimum design loads and associated criteria for buildings and other structures." American Society of Civil Engineers, 2022.