Bolt Thread

[tmgczb]

In recent design, ratio for 1 vertical brace connection for TEEUB146 section reached 0.89(<0.85 required, otherwise perform separate check, maximum separate check ratio<1).
This is a truss member.
The capacity given in standard drawing is 246kN and actual tension is 220kN.
In RAM, the separate check proved the actual ratio is 0.85<1.
Is this case safe or not?



It is not good but true that my ability to calculate steel connection is 0 but only clicking the softwares.
In this case I checked Chinese Code, the shear capacity of 1 bolt differs from location of failure point: shank or thread.
So I sent an email to Vendor of Steel Fabrication, I want to know if the bolt we use is of full length or part thread.
They replied: their product complies with ASTM F3125.
In ASTM F3125, it says

But is their any detailed description about it?
Thank you for reading my thread, and looking forward to your reply.

 

[human909]

It is not good but true that my ability to calculate steel connection is 0 but only clicking the softwares.

I'll give you credit for your honesty. But that is all.

Your role as an engineer is to assess this connection and make an informed professional judgment that it is suitable. By your own admission you don't seem to be in the position to do so.

Maybe some friendly people who know this software and this CHECK issue might help you. But it won't fix the fundamental issue highlighted above.

 

[Struct123ure]

This is one of those situations, where you pull up a reliable reference (usually a textbook) and start to read form the beginning of the chapter. It will take you a while, it will be tedious, you will need to do this both at work and outside of work (depends on when you need to respond by) and figure this out for yourself.
Sit down and design this connection from scratch taking a conservative first pass. I suspect it will fail and you will take a second pass and a third slowly optimizing the design and getting and understanding for the variables.

 

[HDStructural]

Agreed with what others have said.

You asked about F3125 bolts and their threads. For F3125 type A325 bolts, there are type N bolts which are essentially fully threaded so the shear plane is for the reduced threaded section. Type X bolts do not have threads in shear plane so they have a higher strength.

Additionally, in your screenshots, it appears that the T brace has the same capacity in compression as it does in tension based on the loads and the utilization ratios. That should not be the case, the compressive capacity should be much less than the tension capacity, assuming it is unbraced from end to end.