Crack in an Angle Corner

[marinaman]

I've got an angle member (4x4x3/8) that has two fitted stiffeners (shop welded) in it. The angle is 12" long. The angle is used to provide force continuity between members subject to either tension or compression. See the sketch.

I called for each angle leg to be welded, three sides.

The angle is in place. Now, the testing service has called me and said that a couple of the angles have a crack in the corner of the angle.

The calculated loads are nowhere close to the amount of weld I have on the angle.

Could this be a case where the angle underwent thermal changes when being welded and cracked the corner? Its been in the 30's in terms of temperature here lately.

I'm baffled as to why the angle would crack.

 

[KootK]

Is the angle galvanized? Is there stiffener weld in the "k area"?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[marinaman]

The angle is not galvanized.

The stiffeners are fitted stiffeners. I would say there probably is weld in the "k" area.

What are you thinking?

 

[JAE]

I wonder if after welding the stiffener plate resisted the shrinkage of the two orthogonal legs as the pieces started cooling and simply pulled the two legs of the angle apart.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[marinaman]

I'm confused by the situation.

I've stiffened angles before without any issue.

They've only been in place a few weeks, so I know it's not fatigue.

It has to be forces developed during welding of the stiffeners, or, internal forces developed when the stiffened angle had its legs welded on all three sides.

I've searched everywhere and can not find any literature about why not to do this.

 

[Ron]

This looks more like a deficiency in the rolled angle, brought out by the welding. The stiffeners and the welding of the angle are, in my opinion, insufficient to place enough thermal stress in that location to cause the cracking. I think you have a metallurgical anomaly in the angle itself.

Have the angle cross-sectioned and polished through the crack and you will likely see the problem.