Square HSS with crack in corner 1

[archeng59]

thread507-508096

I read the referenced thread regarding some 10x10 tubes with a crack in the corner. I was asked to look at some 4x4x1/4 tubes in a building that is not my design. The tubes are used as hangers for an elevated running track in a wellness center. New construction. The steel framing has been in place for about a year. The contractor noticed the cracks after the steel framing was painted a light gray. There is some sidewall bulging adjacent to the crack. No connections are near the crack, which is located about 4 ft from the end of each tube.

The first thought was the crack was caused by freezing water but the contractor said the tubes were not stored on-site during cold weather. The fabricator said the tubes were shipped to the job site shortly after being received, cut to length and slots cut for gussets at each end. The fabricator said the tubes were not stored at their shop during cold weather. So, freezing water inside the tubes does not appear to be a cause unless it happened at the mill.

My thought is the cracks formed when the tubes were formed and the cracks were not noticed until after the tubes were painted gray. I checked the capacity of the tubes versus loading and they are nowhere near being over-stressed.

Are the tubes still ok to remain in place since they have adequate capacity to support the imposed loads? In my opinion, yes, but would like another opinion. Can the cracks be repaired? I'm concerned about welding the cracks closed and causing other problems.

 

[dik]

any close up pictures?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Once20036]

Is the steel galvanized?

 

[desertfox]

Hi

Some detailed pictures may help us to help you.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[archeng59]

Tubes are not galvanized. I am currently reviewing possible torsional effects of bolted connection between bottom of tube and floor beam. Crack in photo is 1/32" wide x 10 inches long. The other affected column is similar.

 

[dik]

Can that be a rolling problem. Was that cracked before fabrication?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[EdStainless]

Is that corner just very rough or is that actually a weld?
I would fully expect to see similar cracks in other tubes from that lot.
I don't like it. What happens when it gets 2-3' long?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[dik]

It looks like a rolling problem. I'm not sure what loading condition could cause that separation unless frozen water within.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dold]

Not sure about the cracks, but it looks like they forgot to add a web member to the bar joists where the hanging columns are attached?

 

[sbisteel]

Hung directly under a mechanical duct, oops!

 

[desertfox]

Hi archeng89

Agree with others in that it looks like a manufacturing problem and this post gives a recommendation for a repair.

thread507-389009


Sometimes he cracking can be caused the sawing of tubes to length if heat is used, see this site:-

https://www.cumic.com/sept-8th-2020-stop-cut-edge-cracking-in-steels.html

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[dvd]

These are some references from the Steel Tube Institute -

CHARPY V-NOTCH TOUGHNESS OF HSS

HSS Damage Due to Water Infiltration and Freezing

The literature on water infiltration has some discussion on repair at the bottom of p.2.

 

[dauwerda]

A higher resolution picture might help, but is that crack even in the HSS? It looks to my like there is some sort of covering on the front of the HSS in that picture. Am I the only one that thinks this looks like a caulk joint?

It could just be the outside radius of the HSS also, but hard (for me) to tell in that picture.

 

[archeng59]

dauwerda, what's difficult to see clearly in the photo are vertical steel pickets for the handrail. The portion you circled is the edge of the picket closest to the tube.

dold, I commented on the lack of bracing for the bottom chords of the joists at the hanger locations. I was told that the joist fabricator designed the bottom chords to support the hanger loads. It looks unusual to me, too.

 

[archeng59]

Many of you noticed the lack of bottom chord reinforcing at the tube hanger locations. Apparently, enough people (including me) made comments about it during site visits that the EOR decided that something should be done. He issued a detail showing several steel angles welded to the joists chords around the ducts. Thought some of you would like to know.

Regarding the cracked tubes: the steel fabricator, erector and contractor all stated that the tubes were not stored in a manner that would allow water to freeze inside the tubes. No comment from the mill. The tubes are not galvanized, so the hot-dipping process did not cause the bulging and cracks. Design check calculations show the tubes are not over-stressed. I recommended that a hole be drilled at each end of the crack to prevent propagation. The Owner wanted the cracks welded, which will be done after the holes are drilled. All of the framing is being shored to take the load off of the joists for installation of the reinforcing angles. The tube welding will be done during the joist "repairs".

Thanks for all the input.

 

[XR250]

Many of you noticed the lack of bottom chord reinforcing at the tube hanger locations

Seems like a lot of load for those bar joists to manage. Has that been checked?

 

[XR250]

Also, if they were intended to carry that point load, wouldn't the manufacturer already have put a vertical or diagonals there?

 

[EdStainless]

If they weld make sure that they grind them out and weld and not just try to cover them.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[archeng59]

XR250, the joist question has been raised in the past and was raised during my site visit. It is my understanding that the joists were designed to support the loads imposed by tube hangars. I am not the EOR for the project, so I don't know for certain that is the case. I am a third party engineer asked to inspect the cracked hangars. That said, apparently enough questions have been asked that the joist fabricator is currently working with the contractor to shore the floor framing at each hangar and is installing supplemental web members at the hangar locations. It is my understanding that the supplemental web members are not required, but are being installed because questions have been raised.