Hoist ring capacity 1

[972wpff]

I need some direction in determining the capacity of a hoist ring mounted on the ceiling of a 35-ft diameter concrete tunnel. The hoist ring is welded to an embeded piece of channel steel, which is anchored by 4x 16" #8 rebar with tails, offset 7'-6" from the tunnel centerline. The ring is bevel welded to the channel steel such that it is vertical. The hoist ring is A36 steel, 1.75" diameter, in a u-shape with the legs being 6" long and the radius of the half-circle being 6" (total height of the u being 12"). Old design documents (1960's) say the design capacity of the hoist ring is 8,000 lbs. but I would like to figure out how they came to that conclusion given that the anchorage and channel steel has a much greater capacity.

Thanks for looking.

 

[racookpe1978]

Probably, they used a conservative "concrete anchor" capacity and weld capacity at each joint, and used a factor of safety on the 8,000 entire written capacity as 5.0x. That 5x is standard OSHA "below-the-hook" safety now.

So, assume the design load was 40,000 lbs. Now look at the rating.

 

[chicopee]

Looking thru my Crosby manual, an alloy steel oblong ring with an identical design specifications as your ring, lists a working load limit of 52,100 lbs which is 1/6 th of the minimum ultimate load. The material thought, is forged alloy steel, weldless, quenched and tempered. Obviously Crosby material cited is stronger than the A36 material, so, I have to believe that as part of the 8000 lbs rating which seems low to me, certain considerations were made such as the strength of the weld to the steel channel, the weigh of the steel channel and the anchoring design between the steel channel and the concrete roof. Also it is possible that taken into consideration would be side loading on the hoisting ring.

 

[972wpff]

Thanks rackookpe1978, I suspect that a generous factor of safety such as the 5 for OSHA that you cited plays a role.

Thanks chicopee, I suspect that the possiblity of loading at angles other than 0° may also play into this. By Crosby manual, are you referring to The Crosby Group products? If so, what product number/catalog are you referring to? I briefly looked on

http://www.thecrosbygroup.com

and didn't see a match to the hoist ring I am researching.

 

[chicopee]

It is labeled as A-342 weldless alloy master link found in section titled links and rings. Here is the Crosby link

http://www.thecrosbygroup.com/html/default.htm#/