U-frame Analysis necessary even after designing everything in STAAD?

Question

Hi all, 
 
 I have modeled a Steel Foot Bridge with Lattice Truss structure. I find all the members passing checks (* except few diagonal flats failing in Cl. 6.2.9.1 which is not necessary in this case, to be ignored.) 
 I will be doing Connection design manually. 
 
 My question is Do I still need to do a U-Frame analysis manually ? as is customary in BD or EU codes? 
 Please check my model which is attached herewith. 
 
 Regards 
 Mahesh 
 Teignmouth.std

Sye · Accepted Answer

Generally for calculating properties for built up sections or non standard sections, you can use Section Wizard which is also integrated with STAAD.Pro. These sections can be formed using a combination of standard sections and plates and Section Wizard would be able to calculate the properties for you and also export it to an external user table file which can be imported into STAAD.Pro. 
 
As far as Cw calculation is concerned, design codes like AISC 360-05 or 10 provides values in the property tables but these are for standard shapes. AISC design guide 9, engineering text books like Formulas For Stress and Strain by Raymond J. Roark are some other documents that I can think of, which has some information on the Cw. I am not aware of tools that can be used for non standard shapes.

Sye · Answer

I did not see any issues with the model. The only thing that is missing is a LOAD LIST command before both the strength and the serviceability checks just to ensure that strength check is done for the combination 7 and serviceability check is done for load combination 6. Modified file is attached. 
 I am not too familiar with the standards you mentioned and so cannot comment on whether a U Frame analysis is mandatory or not. However my personal take on this is, a properly substantiated 3D analysis is much more accurate than any manual analysis. 
 Teignmouth_rev.std

Sye · Answer

In Section Wizard, the user can assemble any section of his/her choice or draw any shape. Calculating the properties like shear areas and terms like TB, TD etc. for such shapes can be quite tricky and while the software tries to come up with a reasonable estimate for these terms, the user should always check these terms before exporting the section and also make changes if required. Recent versions of the product, mention this as a warning at the bottom of the export dialog box as shown in the screenshot below. 
 In this case the zero values reported for Ay and Az mean that the software is not able to come up with a value for these terms. So you should go ahead and specify these yourself. If the export is already done, you can always directly open the upt file and edit the appropriate values. Section 5.19.8 of the technical reference manual lists the order in which the terms are defined in the upt for a general type section.

Sye · Answer

I am not able to replicate this. The Ix and HSS seem to come to STAAD.Pro fine. One thing that I would suggest is to use smaller unit like cm or mm instead of meter for the cross sectional properties. So try this first and if you still face the issue, zip the .upt file and the section wizard file (.sec ) together and upload it.