More column in rigid frame?

ppd exam 3 , one question is asking the challenge of steel rigid frame and the correct answer “Columns may be required where undesirable”. explaination is “A rigid steel frame may require more columns than other, longer spanning systems in such areas as the lecture hall”
rigid frame span 30-150’ , isn’t that long span? why would it need more column??

designer decide to use exposed steel frame , another answer(wrong) mentioned finish my be hard to achieve, even though exposed has no finish ,but code might not them to be exposed . does this not count ?

Hi @xurubi ,

We will see if we can help get this cleared up for you.
@coachchrishopstock can you please dig into this further?


Hi @xurubi and thanks for the question!
The correct answer ‘Columns may be required where undesirable’ is correct because, compared with other long span structural systems, rigid steel frames have more columns. They also generally are built in a modular fashion, with regular spacing of columns as opposed to being able to place them as the design dictates.
Regarding finish, I wouldn’t read further into the question than the prompt states. No information is given about a required finish per the building code, so I would not assume one is required. The prompt notes that the structure will be exposed for aesthetic reasons, therefore the answer about ‘achieving a finish’ is incorrect because no finish will be applied, per the prompt.