roof joist design

huangyhg

roof joist design
i just want to find out how other engineer in the industry has been specifying special open web steel joist with snow surcharge, additional concentrated loads due to roof top units, architectural elements, uplift, etc.  i have been getting mixed feedback from joist supplier, some would perform the design based on loading specified in the structural specs, some prefer engineer to specify a kcs joist (if applicable), etc.
what is your experience and thoughts on this matter?  any input would be appreciated.
lutein:
fwiw, i tend to use kcs joists as much as possible. the dominant local joist suppilier (vulcraft) has indicated a preference for them, and i can size them much faster than getting bogged down in drawing a lot of different joist loading diagrams for each case that might arise.
just my preference. nothing scientific about my approach at all.
i prefer kcs for rtu's. this allows flexibility.
i use special joists for drifted snow although i sometimes wonder how if these ever get turned end for end in the field.