Lr for Channel Capped S shape

[swearingen]

I've been banging my head on this one, working through the 13th manual for a rail beam and I'm pretty sure my answer isn't right. Using the equation at the bottom of page 16.1-50 in the 13th AISC, I have:
rt = 0.614
E = 29000
FL = 31.3
J = 696.5
Sxc = 105
ho = 14.3 (rough calc)

I'm getting 1068" or 89 feet! Any ideas on where I'm screwing up would be helpful...

Of course, any tables for S15x42.9's capped with C10x15.3's would be even better...

As a check, I ran equation F2-6 with a W14x82 (similar depth and top flange width) and got 397" or 33'. I know my capped S should have an Lr longer than this, but not 2 1/2 times longer.

 

[UcfSE]

Check all your units.

Try giving us some informaiton on how you got r_t, F_L, h_o, and so on. The more we have the easier it is to help trouble shoot.

 

[swearingen]

Sorry - idiotic mistake - I used polar moment of inertia instead of torsion constant for J. A common booboo...

 

[swivel63]

that was the first thing that jumped out at me....J seemed to high