Existing steel tubing purlins need to be extended 2

[delagina]

I have existing purlins made of steel tubing. It needs to be extended 3' overhang. What is the best BOLTED moment connection detail for this? Since it's a purlin it has existing roof. They want roof extended 3' overhang.

This cannot be field welded for a couple of reasons.
I work inside a plant. Welding requires hot work permit which they (boss) prefer not to do. Electrical guys don't want any field welding done because it may cause issues with the existing electrical equipment that the roof/shed is covering.

The detail I have come up is shop weld a plate inside a new tubing purlin, with about 1' of plate protuding out. Then shove in the protruding plate inaide the existing purlin and bolt it.

 

[MikeHalloran]

The details are left as an exercise for the reader?


Mike Halloran
Pembroke Pines, FL, USA

 

[dik]

It can work with the moment being taken by a couple of bolts 9" apart or whatever. With tolerances, it can wobble a bit. Use a circular 'hole' bit (one with hacksaw teeth) to drill... a lot easier than using a regular bit.

Dik

 

[robyengIT]

I don't like the plate (the holes in the plate will we threaded ?). I would prefer as per attached sketch

 

[delagina]

Roby, unfortunately existing tubing is the smallest it's HSS 2x1x3/16.

 

[XR250]

You could probably get 1/4x2" x say 24" steel plate and use it on the outside of each face as a splice. Pre-drill it for some #12 Tek5 Screws. I imagine the numbers could be made to work out.

 

[dik]

XR250:

Tek 5 is a better solution...

Dik

 

[delagina]

Thinking of using 1/4" bolt instead of screw. Why should I use Tek screw instead?

 

[hoshang]

I don't like the plate (the holes in the plate will we threaded ?). I would prefer as per attached sketch

https://files.engineering.com/getfile.aspx?folder=59b38d4a-adf2-4abb-9022-2

Roby, unfortunately existing tubing is the smallest it's HSS 2x1x3/16.

I would suggest using steel tube (instead of plate) as preferred by robyengIT, but outside the existing purlin (steel tube) and extension (steel tube).

 

[delagina]

Hoshang, i'll check with our roofing guya if that will not cause issues with uneven roof.

 

[XR250]

Thinking of using 1/4" bolt instead of screw. Why should I use Tek screw instead?

Might be easier to install as it is a one sided connection, You don't have to worry about drilling straight holes in the tube steel.

 

[berkshire]

You could try 2 1/2 x1 1/2 with .188 wall as an outside sleeve. You may have a problem with 1/4" wall depending on the tubing tolerances it may be a drive on fit. Through bolting may be preferred . Tek screws tend to break off at the heads if the people installing them are too heavy handed.
B.E.

You are judged not by what you know, but by what you can do.

 

[delagina]

I'll use bigger HSD as sleeve as long as it will not have issues with uneven roof. Shouldn't purlins have same top of steel? I'll check with our roofing contractor. I prefer thru bolt for stronger connection.

 

[CANPRO]

Would it be any easier to slide in new purlins beside the existing? If they're only 2" deep, it can't be that far back to the next interior support...You could use some kind of banding or clamp system to fasten the new purlin to the existing purlin and/or to whatever supports the purlins.

 

[delagina]

I just realized I may not be able to use a bigger HSS as sleeve because I will hit the existing purlin support. Purlin is welded to support and only have a few inches overhang.

 

[CANPRO]

Also, if you're detailing a sleeved connection with HSS don't forget that there may be a weld seam on the inside. If you're sleeving something into the existing, double check the inside of the tube.

 

[robyengIT]

1 - smallest size (existing one)
2 - few inches overhang
3 - issue with uneven roof (purlin outside)
Therefore the only possibility (the most similar to an inside purlin) is to place 4 (at least 3 - the one on top no because of uneven roof due to the head of the bolt) plates with through bolts horizontal and TEK screw on bottom
PS : welding the plates can cause a gap between the 2 purlins (can be a problem for the bending moment)

 

[hoshang]

I just realized I may not be able to use a bigger HSS as sleeve because I will hit the existing purlin support

The detail I have come up is shop weld a plate inside a new tubing purlin, with about 1' of plate protruding out. Then shove in the protruding plate inside the existing purlin and bolt it

Shop weld a plate inside a new tubing purlin, with about 1' of plate protruding out. Then shove in the protruding plate inside the existing purlin at top. Cut top plate from a bigger HSS and use the bigger HSS as sleeve at bottom and sides

 

[Tmoose]

"I just realized I may not be able to use a bigger HSS as sleeve because I will hit the existing purlin support. Purlin is welded to support and only have a few inches overhang."

It appears Pictures and as-built drawings of the actual installation ASAP would help everyone with this endeavor.

 

[XR250]

Tek screws tend to break off at the heads if the people installing them are too heavy handed.

Anyone who is too heavy handed can break anything. Does this mean we should never spec TEK screws?