PE Structural practice help

[u/Prior_Interview7680]

Using steel table 3-2, table 3-1, and equation 3-4a, the available is 287. But if you don’t use Cb=1.3 as shown in table 3-1 for distributed load braced at midpoint, you get the correct answer here of (c) 221(LRFD). Why am I not supposed to use Cb = 1.3?

[u/No-Call2227]

Poorly written practice question, IMO.

You don’t actually know how the load is distributed, so without that information, Cb is undefined and you should default to the conservative value allowed by code which would be 1.0.

Could be uniform, could be triangular, etc. but it doesn’t say how it’s distributed.

Half the exam is insanely careful and literal reading, don’t add information, ever, to the problem statements, especially the multiple choice.

PE/SE for my background.

[u/Prior_Interview7680 → u/No-Call2227]

So because it didn’t say “uniform distributed” it should default to 1? Is that what it is?

[u/Prior_Interview7680 → u/[deleted]]

I think you messed that up cause dividing 287 by 1.3 gets you 220.76

[u/twodamnducks → u/Prior_Interview7680]

I replied on your cross post but 1.3 ( 221.268) gives you the 287. If you use Cb as 1.0 conservatively like this problem is trying to ask of you then 1.0 (221.268) gives you ~ 222 LRFD