Denny's Sign Failure 8

[dik]

https://www.ctvnews.ca/world/toweri...gh-wind-killing-1-injuring-2-others-1.6239328

Was it removed before an investigation... seems a little hasty.

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

-Dik

 

[Alistair_Heaton]

i know where your coming from tug but to me the two plates are still a married item be it by rust and the 4 bolts.

The failure is the circular butt weld with more than likely zero weld prep through paint in the pissing rain and zero grinding to remove end of runs and zero NDT to see if the chimp doing it could light a cigarette never mind put a full penetration butt weld in.

I say this as someone that through some sort of alignment of the planets and other extremely unlikely and unbelievable to coincidences was handed a 7G occluded stainless TIG welding approval by a Lloyds welding inspector. Which apparently covers everything else!!!

It was a days laugh to be honest for me to give me production experience. Did it and the energy monitor came back in limits.... bombed it no voids, porosity or slag occlusions.... sharpies and impact came back in limits. Are you ever going to use this cert? Am I F...... Signed and presented in the workshop canteen to a colossal amount of humour. The charge hands giving noise to the youngsters saying that 22 year old white collar prat can stick two bits of metal together....

And no I never used it but I can still TIG stainless and thin plate.. but it takes ages and absolutely loads of gas. Quite how I managed to stay inside the energy monitor limits I don't know, which was the normal way us graduates failed I really don't know but I was told you were low compared to the experienced time served guys. I just said must be because I am Aberdonian and tight with money.... LLoyds dude said it was interesting watching you work but please promise me that you will never use the qualification because we both know you don't have a clue what your doing. Shock hands on that point...

To note this qualified me for Nuclear primary circuit pipe welding unrestricted.

A year later i worked with a proper shipwright in Yarrows and the steel excellent centre. That man just need to stroke metal with his hand for it to flow into its intended form and wave his magic wand and the residual stress would evaporate. We also had two lads in the army unit i was in that were also ship yard and they were the only ones in Scotland qualified to weld thick plate amour in the British army. And I learnt a lot from them. A good weld is more about the preparation and planning than when the stick comes out the oven.... And if they were anything to go by the meat pies in the stick oven are a key ingredient to a good weld.

 

[spsalso]

"I don;t think there is anything left on the pole."

In the picture I posted, I see a big square thing on top of the pole.


spsalso

 

[Brian Malone]

This is being discussed on a message board run by sign fabricator/installers.

https://www.signs101.com/threads/dennys-sign-kills-2.171500/

1/25/23 update: it appears this message board has removed the Denny's sign thread

 

[spsalso]

"I'm not suggesting the weld that caused this artifact is on the contact faces even on this plate. The lower plate is welded to the circular column. The contact pressure at the faces of the two plates is the same. Therefore, the effects caused by warping of the lower plate during welding could translate into the bottom face of the upper flange."





I do see that the lower plate might have warped as you describe, as a result of the original fabrication. IF that caused the exposed parts of the lower plate to warp "downwards", then that could have generated a gap around the edge up to the round central portion that would have allowed easier water ingress.

Without more evidence, I can't go farther than "maybe".



spsalso

 

[spsalso]

"The failure is the circular butt weld..."

But the circular butt weld held. The bolt attachment failed, in some way.



spsalso

 

[driftLimiter]

The plate on the top of the pole remains in the pictures I am seeing. Looks like we have two bolts rupture (tension side perhaps?) the two bolts remaining in the plate are the compression side.

Sign's baseplate seems in decent condition (unreformed).

But as others have said bolts seem fairly small diameter. Combination of moisture and cyclical loading over all these years with little (probably no) maintenance. I suspect this is the failure mode.

The spacing, number, and size of bolts kind of suggests to me they weren't supposed to be permanent. But seems like they were the main load carrying element to resist the overturning of the sign.

Best guess is that this structure would be a Risk Category II structure.
But the wind load is quite a bit higher than a normal building because its a freestanding sign.

 

[spsalso]

"The plate on the top of the pole remains in the pictures I am seeing. Looks like we have two bolts rupture (tension side perhaps?) the two bolts remaining in the plate are the compression side."

Yup. What I find interesting is that the two "compression" bolts appear to have pulled through the lower mounting plate, rather than snapping off.


spsalso

 

[driftLimiter]

Yes I was curious about that as well, Perhaps that low edge distance also had some fatigue cracking and ruptured the cap plate of the mast near the bolts as well.

Would like to see a photo of what the plate up there looks like.

 

[JStephen]

On the two-plates and the circular paint pattern- makes me wonder if at some point in the past, maybe the pole was replaced?

 

[driftLimiter]

Maybe plate was re-used. Maybe the majority of the compression stresses was in a circular profile and this stopped the rust encroachment from happening as quickly as it did from the outsite.
Loss of bearing material on the outward edges of the plate could contribute to additional movement under cyclical loading.

 

[Alistair_Heaton]

just because there is a big square thing on a pole doesn't mean the square is attached to anything. look at the failure surface. it tells no lies.

using a bit of 10mm plate to prevent anyone seeing anything i have use in the past.... And I will use something similar in 2 months time to prevent building control seeing that my rafter roof is going to have 4 x 200mm SS 8mm screws attaching them to the ceiling plates. When the architect wants 6 x mild steel chemical anchors into aerated concrete ceiling panels with 40mm separation.

 

[driftLimiter]

I hear you but I'm not seeing any evidence of weld along that circular profile. Low quality pictures is not definitive, but still I would expect to identify some remnants of weld Also the geometry and the bolts suggests it would be difficult to even make that weld (impossible)?

 

[Alistair_Heaton]

I must admit I am thinking pants American metal, poor weld prep in the field, poor welding definition getting it up for minimal cost and make it look nice.

IRstuffs pic looks like its has been carrying load with paint on with a low O2 environment internally outside rusty. And there are 2 plates sandwiched.

 

[Alistair_Heaton]

there is pretty limited evidence for chewing gum welds onto plate in my experience. And if the welds are not taking load why bother with them use silicone sealant that can move

 

[LionelHutz]

Yes, yes, keep posting American hate there. They are too stupid to know how to weld right after all. /s

 

[SwinnyGG]

I must admit I am thinking pants American metal, poor weld prep in the field, poor welding definition getting it up for minimal cost and make it look nice.

There is zero chance any of this assembly was welded in the field.

 

[Alistair_Heaton]

I think actually the USA has less of a problem with practical skills than Europe. The kids are just not interested in doing dirty jobs over here. So its mainly a migrant skill set.

UK lost most of ours back in the 80's/90's with the transfer of the economy to service industry. And them shutting the high quality steel industry down. There are a few aging bubbles still left but mostly they are gone. Back in the 80's kids used to leave school at 16 and the next day start an apprenticeship. That doesn't seem to happen any more. Industry not interesting in investing and the kids not interested in doing it. Glasgow there were literally hundreds of young welders taken on every year. Now they can't fill the available slots.

I think you have a lot more fabrication shops dotted about as well. Gone are they days when you could find a blacksmith to knock something up.

 

[dik]

There is no American hate here... even Canada has a few warts...

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

-Dik

 

[driftLimiter]

I agree with Swinny that this would not be a field weld at that height.

I am thinking we had poorly proportioned bolted connection. Maybe meets the calc (static no fatigue probably) but just poor detail and oversight, lack of redundancy.
Then the rusting on the plates could have increased the slop in the connection, contributing to additional bolt stress, and increased fatiguing.

At the instant of failure I proposed bolt rupture in tension, followed by overturning of the sign, leading to bolt tear out of the plate (low edge distance, and rusted/fatigued steel already).

Seems like the biggest things missed are fatigue and coating. And of course inspection/maintenance.

Will be interested to see if they ever found those missing bolts, and what the cap plate looks like post-failure.

 

[IRstuff]

Given the current size of the holes and the two visible bolts, I think bolts simply broke through the holes; the two still attached to the sign broke through the bottom plate, and the other two broke through the top plate.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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