Lifting capacity of existing bridge crane

[mike20793]

I've got a project where the client is asking me to come up with a lifting capacity of an existing bridge crane. I have the existing structural drawings and I know the runway beam and cap channel sizes and the crane rail, but for reasons I can't get into, I do not have any other information about the existing bridge crane and I will not be able to get any information. Is there a way I can determine an approximate bridge weight and hoist and trolley weight? I know I will probably have to get in touch with some manufacturers, but does anyone have any rules of thumbs or existing catalogs or something similar that might get me started? Since I don't have access to the site, the client has asked me to approximate (to the best of my ability) the missing weights.

The runway beams are simply supported, 40 ft spans, and are W21x44 with C15x33.9 with a 40# ASCE rail. The bridge span is 30 ft. Thanks in advance.

 

[EdStainless]

I take it that this crane does not have a rating, and that it has not been tested, and that there is no insurance involved?
With what you have you might be able to generate a rating for the support system.
But the bridge and hoists are a critical part that you know nothing about.
Rails that will support 50t don't matter with a pair of 10t hoists.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[mike20793]

Thanks. That is in essence what I am doing, figuring a lifting capacity for the structure. The client is fully aware we cannot determine the actual lifting capacity with such lack of information on the crane itself.

 

[Lomarandil]

If you're not using some dynamic factor on the lifted load, ccouldn't you analyze the structure and provide a maximum allowance that would include both the mechanical lifting hardware and the lifted load?

 

[WARose]

One question I would ask them at the outset is: “What rating are you looking for?” (I.e. what are you trying to pick up?)

You can run through the structure and see what the limit of everything is.....but (based on my experience) a lot of times they have a number in mind.......and having that in mind is good while evaluating everything.

 

[mike20793]

Thanks for the input. To expand a bit further, I know the weight of what they want to lift. They just want to know if they can lift it or not, which is pretty easy to assess if I have the bridge weight and the hoist and trolley weights. No one expects the existing crane to work, but they want to know how off it is so they can price whether it's cheaper to refine the process and reduce the load for what they are lifting, strengthen the existing crane rails and upgrade the crane, or remove everything and replace it altogether. So they are fairly comfortable with me assuming the weights, however I'd like to be as accurate as possible since we do repeated work with this client. The problem is exacerbated since this client deals with highly confidential material and they really really really don't like to give out any specific information. They currently aren't letting us even do site visits and are asking us to work within the constraints. So my only option may be as Lomarandil suggested and give a maximum allowance including the lifting hardware.

 

[canwesteng]

That's what I do on design drawings - state the max corner wheel load (without impact), minimum wheel spacing, and a max lifted load. I think what youre client is after is similar in this case, since after all they aren't giving you access to the crane.

 

[TLHS]

Without actual crane information, I'm not sure what you're supposed to do. Right away, I'd be putting huge factors of safety on things and be expecting them to load test to certify. If they're already pretty sure that it won't work, then the load reductions you'll have to put in to account for any approximations is going to put it well into the range where it's not possible to modify their process to suit the equipment.

Will you be able to do a field visit at some point? You could theoretically tell them that you'll rate the steel based on available information, but if that comes out okay you'll have to come out and figure out what other information is available for the equipment.

The other option, I guess, is to load rate the steel and then load test by incrementally adding weight until the equipment breaks or you prove that it can lift what you want plus an appropriate factor?

 

[MikeHalloran]

I thought it was a US Federal law that bridge cranes need to carry a big sign specifying their capacity in tons, and are required to lift a somewhat larger proof load once a year.

Has anyone bothered to look up at the crane itself?



Mike Halloran
Pembroke Pines, FL, USA

 

[mike20793]

I need to go back to the client and make it more clear that I can't rate the structure for a lift capacity but I can rate it for a total load. They originally asked if I could assume the weights and I thought maybe I could through manufacturer's tables or something similar. After getting some good feedback I don't think that's the right way to approach this problem.

 

[FLCraneBuilder]

Ref the structure capacity:
need know:
Grade of steel beam and Cap channel steel
Proposed vertical wheel loads
Proposed Lateral loads
Wheel spacing

I can tell you that this section will not take much load @ 40' bay spans, the W21 has a narrow flange and fails quickly for sidesways web buckling AND tension

the tension limit is why you will need to know grade of steel - but one can assume anything built before 2000 has a good chance of being A-36. Channels were still often Gr 36 up to around 2010

AISC has a downloadable program that runs the beams for you

It works fairly well

Regarding Cr capacity, simply identifying the manufacturer & model # of the hoist would be a really good start
I assume is a package hoist so, there is likely a label on it somewhere


Regards

 

[CTW]

See if the attached document helps.

 

[jimstructures]

Note the Whiting Crane Manual is a Third Edition and a Fourth Edition has been released and a Fifth Edition was talked about but never released as far as i know. The Whiting Crane Manual is for very heavy duty cranes, Class F at least used for very heavy work. i.e. picking up Locomotive engines, etc.

Look for a DeMag, Herrington, Kone or Gorbel crane catalog for more moderate lifts.

As noted above the 40' bay length is going to have a very low capacity. Normal bay lengths are 20', 25' & up to 30' bay lengths.

Jim

 

[TLHS]

As a general aside, CISC puts out a pretty good document on the design of crane supporting steel. It's free and can be found here:

http://www.cisc-icca.ca/files/publications/techpubs/design/craneguide/CraneGuide2E5P.pdf

It's targeted to the Canadian steel code, CSA S16, but it's pretty code portable, I think, and contains useful general information.