LTB parameters for rafters and columns

[MUHANNAD.ABU_ABDO]

i'm designing steel portal frame with span 41 meter , i followed BS Code in design , my hand calculations indicates that the sections obtained from robot is bigger than the ones that obtained from manual calcs . my thoughts are the problem is in the LTB parameters although i defined the spacing between purlins as intermediate restraint but still get the same problem ! Could you help me to clarifying this discrepancies ? 

Note that the sections obtained from manual calcs are 

UB 533X210X122 For Rafters 
UB 610X229X140 For Columns 

Here's the link to model 
https://drive.google.com/open?id=1_za0jtCLe0NwCninhsA2CGgqqMUU9ojC

Thanks in advance 

[Artur.Kosakowski]

Hi @MUHANNAD.ABU_ABDO

Could you attach the manual calculations for selected rafter / column and combination?

[MUHANNAD.ABU_ABDO]

it's not available right now . it's in the office ! But i can attache the Reference that i followed which include worked example !

Thanks in advance 

[MUHANNAD.ABU_ABDO]

Please check my hand calculation which indicates the problem with sections obtained from robot !

thanks in advance  

[Artur.Kosakowski]

Hi @MUHANNAD.ABU_ABDO

I  will not be able to run through the design of the whole structure. Let's try to focus on a single rafter and see what is different. To start with could you indicate a single rafter and check if the governing load combination produces similar internal forces for this member as those you used to design it manually? If yes, which bar and load case should I look at. If the forces are different this is the first thing to look and make sure they are coherent.

[MUHANNAD.ABU_ABDO]

lets take rafters no 7&8 in the second bay .. the negative moment at the top of the column is 992 KNm and the apex moment value is 408 KNm , 

by mnauka calcs
although the required moment capacity of rafter Mpr is 648.9 KNm which is satisfied to section  UB 533X210X92 with moment capacity equal to 652 KNm , So the section capacity i used is satisfactory !

i guess the problem is with LTB my thoughts are in defining rafter parameters Ly,Lz is disabled and we define LTB for upper flange and lower flange in this case robot should divided the rafters into parts equal to the purlin spacing ( For Upper Flange ) and For Lower Flange will be the distance between torsional restraint is that true ? where's the problem ?