1 1/4 Pipe Post to 1 1/2" Stringer Flange

[connectegr]

We have designed stair and handrail for years. And for the entire time we have discussed the weld of the post to the stringer flange. A standard detail is 1 1/4" pipe (standard or XS) to an MC12x10.6. I know there are channels intended for this purpose with wider flanges, but they are not popular due to cost or availability (???).

I am again debating with a customer the design of an all around fillet weld of the pipe to the stringer flange. I see this done everywhere, even in the lobby of my own office. But, an all around weld is not possible within the requirements of AWS. (see attached) In an effort to be open minded I reviewed the calculations (of another engineer) in which all that is required is a 1/4" fillet weld "all-around". The calculations use the circumference of the pipe for the weld design and the point stress in the pipe. How??? Also the detail does not account for the slope of the stringer, or the acute angle and obtuse angle where the welds are applied. Again, How/Why???

I have tried to design the welds using the actual arc length available on the flange of the channel. And I can adjust the weld sizes for Z-loss and the obtuse angle. But, even an XS pipe is not adequate for the point stress.

Am I missing something?

http://www.FerrellEngineering.com

 

[ToadJones]

Not sure what is meant by "point stress in the pipe".
What load is being used in the calc?

 

[slickdeals]

You bring up a question that I have tried to find an answer myself. I think a 1/4" all around fillet weld on a 1-1/2" pipe is probably not going to work for strength requirements if designed using the elastic vector method. Do you agree?

One of the fabricator's response to how you get an all-around weld was........"I will heat up the pipe during welding, bring in a sledge hammer and then I will get an all-around weld". Obviously the pipe is no longer circular. That was the end of my discussion with him.

There was a modern steel article on this very topic not too long ago.

http://www.modernsteel.com/Uploads/Issues/February_2009/022009_Feb09_Handrails_web.pdf

 

[connectegr]

For reference, I have attached a detail we have used. I admit it is more difficult than a fillet.

Especially when other engineers are telling fabricators an all-around fillet is adequate.

http://www.FerrellEngineering.com

 

[hokie66]

That looks good, but how does the channel web take the bending?

 

[connectegr]

slickdeals
For 42" posts and 4' spacing, 200lbs concentrated load. A 1/4" fillet will not work, unless you use the full circumference of the pipe. Which is not actually welded.

I have seen the article that you attached. They show an HSS to the stringer flange. But, this also has problems. The thickest HSS 1 1/2" is 3/16". BTC-P4 partial pen.: f = 1/8". If welded in the field, probably SMAW (stick) E = S - 1/8" = -1/16". In the shop with BTC-P4-GF (GMAW/FCAW) E = 1/16. Not much strength.

http://www.FerrellEngineering.com

 

[connectegr]

hokie66
NAAMM does not consider the web or flange bending at the posts. I have seen details with stiffeners at each post, but I think that is conservative. We have discussed this, but I have not seen any examples.

http://www.FerrellEngineering.com