load factors on lifting 2

[nsjxs]

Anyone knows load factors in lifting?

 

[271828]

Lifting what?

 

[JAE]

It depends upon the yield stress of your biceps.

 

[271828]

Hey, I was just looking the other day at footstep force waveforms. I think there's a load factor of about 1.2 for walking, LOL. 2 or 3 for sprinting--load factor being dynamic force peak / static weight.

That's like "lifting" oneself--does that count?

 

[JAE]

I just finished a quick run, 271828, and it was definitely uplifting. It's just so dang nice outside.

 

[271828]

It's beautiful here too.

Stuck inside doing a project however. I'm comically behind.

 

[swivel63]

well, i just hit the weights and i'd say i'm at 150% yield right now.

<== can barely life my arms to type

 

[hokie66]

nsjxs,

These fellows are having a bit of fun at your expense, but seriously, just make your question more specific and someone will probably be able to help you. As to 271828, if he didn't spend so much time on this site, maybe he wouldn't be so comically behind.

 

[JAE]

Yes, you can tell that 271828 takes engineering seriously - the handle is all numbers

nsjxs, I'd second hokie66 - It's Saturday and we're just relaxing a bit - just post more details about your question and I'm sure we'll all tackle it.

 

[271828]

LOL Hokie66, I need to decompress a few times a day. This place is perfect for a structural fanatic, LOL.

The point is well taken, though.

My problem is one of over-commitment. I just can't say no. Dissertation proposal, then consulting work, then writing papers, conferences, committee work, etc. I actually said no to a really interesting project yesterday and was very proud of myself!

271828 comes from my little girl. Her name starts with E, so I called her "Little E" which morphed into e, which is of course the base of the natural log. I couldn't use a handle with a decimal point, hence the name.

 

[JAE]

Alright so you're not just a techno-geek-nerd-numbercrunching-engineer-with-no-life-outside-...uh...engineering.

You're a daddy. Be sure to give little "e" a hug tonight and read her a story!

 

[JStephen]

There's an ASME standard for under-the-hook lifting devices, and it requires a factor of safety of 3 with respect to yielding, if I remember correctly. Seems like slings are normally limited to 1/5 the breaking load or so- mandated by OSHA.

 

[nsjxs]

i guess 271828 and JAE are one of engineers who are very proud of themselves who believes they know everything.

I got an answer from JStephen. Thanks.

 

[271828]

Sorry nsjxs, no offense or disrespect was intended. You asked a question without enough details to answer, then didn't show up for almost a day. We were all just having a little fun on a Saturday.

 

[mrMikee]

The way I've done it in the past is the 1/3 yield or 1/5 ultimate as mention by JStephen. If you want more info there's a guide published by the AISC(?) that is very helpful. It's been mentioned a few times in threads during the last year but I can't seem to find it now.

JAE and 271828, it doesn't hurt to have some fun now and then, IMHO.

Regards,
-Mike

 

[nsjxs]

thanks mrMikee

just thinking about how factor of safety in lifting should be considered.

3 is usualy considered by most engineers and maybe this is because of the following:

-uncertainty of load would be a factor of 1.6
-dynamic factor of 1.25
-and a factor again of 1.5 which I think this includes material strength reduction

Im not certain of how the 3 is got but if someone got answers i'll be very thankful

sorry for my choice of words. its just that I'm not really good in english. And I'm also a young engineer so I havent got enough experience yet.

 

[mrMikee]

nsjxs,

It's been a long time since I read thru the AISC material on lifting beams so I can't really remember the reasoning behind their recommendations. My first job after my engineering degree was in a plant engineering department where one of my responsibilities was lifting devices. I started using the 1/3 factor simply because that was the way they did it. Later after doing more research I added the 1/5 factor of safety. I think the 1/5 is useful to prevent the use of materials not ductile enough to go into a gradual yielding when overloaded.

One cause of impact is the result of the lifting speed of hoists which can be determined using several of the crane specs. You could check the following site for either the CMAA#70 spec or the Monorail spec.

http://www.mhiastore.org/category.cfm?Category=16

-Mike

 

[ChipB]

mrMikee has got it. I just did one last week:

1/2% for each foot/minute of the working load, not to be taken less than 15% or more than 50%.

Do a search for MH27.1-2003 which is the monorail spec.

 

[Lcubed]

nsjxs,
If you multiply the three factors you mentioned in your post of May 20, you get 3.
Regards,
Lcubed

 

[shipwright]

What type of load and lifting appliance are you considering?
A shipyard gantry lifting 1000 ts or a crane in a marina to lift dinghies? I would recommend you to have a look in the Codes for lifting appliances used by Lloyd's or DNV or any other national design codes.