Sign hung issue

[Dagger]

Saw this on a gig.
I drew a pic. See attached image please.

1) sign hung ( eyebolt, shackle, GAC choked on top truss)


2) after 3 hours we saw thst the sign frame bent. see RED in image (2)


Theories?

 

[Amiers]

Sign was to heavy for the frame. Someone tried to hang from it and didn’t tell no one.

 

[Dagger]

I did a FBD (attached image)

For the sign to NOT Bent ,
The Top Frame would have to withstand a force of 175 lbs??
I am thinking correctly?

 

[egilson1]

Not quite. If the sign in the frame weights 350lbs, and we hung it on a single center point, that would be 350lbs in the middle of the 6’ frame. So the 6’ frame needs to support 350lbs at center. We know that a beam typically has a CPL of 50% of the UDL. So the top of your frame needs to be strong enough to support a 700lbs UDL even though the sign only weights half that. My guess is the “designer” missed the CPL to UDL relationship.

 

[Dagger]

700 lbs thats for single vertical hitch in center.

How strong would the fram have to be if its hung like in the image with 2 verticals?


Edit* disregard question i think understand *

 

[Dagger]

can someone point out the right answer this question please

 

[egilson1]

Well, you’ve got 2.5 ton of load on an eye. A shoulder eyebolt at 0-45 degrees has a strength of 70% of the rated WLL. So we 8now the 2.5ton eye is out. What’s 70% of the 3ton? The 5ton?

 

[Dagger]

I dont quite understand ...But after looking at yours can i think of it this way.

I am using sling angle factor( i have been learning sling angle factor the last few days)

5T / 2 x . 1.15 = ~ 2.9T

Sling angle tension is 2.9T on one leg . So answer WLL on eyehook is 3 T. (?)

 

[tdrga]

I dont quite understand ...But after looking at yours can i think of it this way.

I am using sling angle factor( i have been learning sling angle factor the last few days)

5T / 2 x . 1.15 = ~ 2.9T

Sling angle tension is 2.9T on one leg . So answer WLL on eyehook is 3 T. (?)

The question asks about the eye hook, not eye bolt(s). The minimum rating for the eye hook should be 5T since it has a 10,000 lb load. No information provided as to safety factor required, so that 5T rating will only ensure that the eye hook should not fail at the 10,000 lb load with no margin for safety.

-Todd

 

[Chase P.]

In the hook illustration, doesn’t the side force of the two cables on the hook need to be accounted for? The hook is rated for that force in a single point vertical lift.

Todd, I’m with you, there’s no safety margin at all.

Also, does it bug anyone else that the cables are drawn without thimbles? I get that the cables are not the point, but still... If you’re going to draw the shoulders on the eyebolts, give the same detail to the cables!

 

[DuckJordan]

In the hook illustration, doesn’t the side force of the two cables on the hook need to be accounted for? The hook is rated for that force in a single point vertical lift.

Todd, I’m with you, there’s no safety margin at all.

Also, does it bug anyone else that the cables are drawn without thimbles? I get that the cables are not the point, but still... If you’re going to draw the shoulders on the eyebolts, give the same detail to the cables!

In construction rigging most of the steel is used for a single job site and then discarded if in bad condition. They aren't in the same situation as theatrical and arena rigging where the steel needs to last 8 months or more on the road.

As for the hook, its rating needs to be 5T to lift that load. Now there are additional questions to be asked such as how much of an angle those steel are pushing that hook as well as some other questions but from the information provided 5T would be the correct answer.

 

[kicknargel]

You do need to consider the bridal angle. If that angle approached zero (fully horizontal) the tension on the cables and hook would approach infinite. I've not checked Dagger's sling angle math, but if correct then the hook would need to support both of the 2.9T loads, which is more than any multiple choice option on the quiz.

I'm a little concerned about this thread, because there are some wrong answers to rigging questions.

 

[joe2you]

How / where is the sign attached to the frame? End points of the frame? Equally distributed across the frame?
Where are the eye bolts in relation to the sign attachment points?

 

[derekleffew]

You do need to consider the bridal angle.

Especially when there are multiple grooms.

 

[Dagger]

You do need to consider the bridal angle. If that angle approached zero (fully horizontal) the tension on the cables and hook would approach infinite. I've not checked Dagger's sling angle math, but if correct then the hook would need to support both of the 2.9T loads, which is more than any multiple choice option on the quiz.

I'm a little concerned about this thread, because there are some wrong answers to rigging questions.

I found this.

2.9 T times 2 is incorrect i think

 

[Dagger]

How / where is the sign attached to the frame? End points of the frame? Equally distributed across the frame?
Where are the eye bolts in relation to the sign attachment points?

It was just a frame 8x 5 . Two eyebolts on top 6' apart

It was just like my drawing.

 

[tdrga]

I found this.
View attachment 19051

2.9 T times 2 is incorrect i think

What are these questions from? An online exam?

 

[Dagger]

Practice tests from crosby.

 

[TimMc]

You do need to consider the bridal angle. If that angle approached zero (fully horizontal) the tension on the cables and hook would approach infinite. I've not checked Dagger's sling angle math, but if correct then the hook would need to support both of the 2.9T loads, which is more than any multiple choice option on the quiz.

I'm a little concerned about this thread, because there are some wrong answers to rigging questions.

The correct answer to the test question is D - none of the above. As you point out, Nick, if the 2.9 tons per leg is correct, the hoist hook is under rated for the proposed lift.

 

[tdrga]

The correct answer to the test question is D - none of the above. As you point out, Nick, if the 2.9 tons per leg is correct, the hoist hook is under rated for the proposed lift.

I'm going to disagree. The eye hook (assuming it is a Crosby product since it is a Crosby exam) is rated for a 5T capacity as long as the included angle of the bridle does not exceed 90 degrees. The angle of the bridle at the hook is 60 degrees (equilateral triangle = each angle is 60 degrees).

The eye bolts do need to take into account the additional load due to sling angle, but the eye hook is already rated for the sling angle given in the example.
See the Crosbly application note for hooks attached.
-Todd