# Crane barge stability

Discussion in 'Stability' started by JeffVDM, Jan 1, 2019.

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### JeffVDMJunior Member

Good day,

First of all Happy New Year and the best wishes.

I am a student in my second year civil engineering. For a project beyond or area of expertise we have to make stability calculation sheet for a specific crane barge.

The barge is 9 m wide and 34 m long. On the barge is a mobile crane on tracks with it specific maximum load diagram. Only thing is when the barge trims due to load the maximum load can not be readed out of the specs of the crane.

Our project consist of calculating the maximum load the crane can lift from a specific point at 8 meters in front of the barge. We know the ballast and weight distribution of the barge.
The second part of the project is to implement the calculation in an Excel sheet where we can calculatie other situations with.

After a lot of research we have not been able to find any consistent source where the theoretical background is explained. Most of the sources we have found are older and the use of symbols is not consistent.
We have found 2 newer books, but those are prettige expensive, and it is not for sure that we will be able to use them.

Can some of you point us to a couple of good excessive sources that descrkbe the complete process of the stability calculation of a crane barge?
Idealy the source starts from a very basic approach, because naval design is completely new to us. Though we are familiar with the design of rigid structures like buildings.

Kind regards,
Jeff

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### Tiny TurnipSenior Member

Hi Jeff and Adam- and welcome.
I am no engineer, and cannot directly answer your question. However, using the forum search with appropriate terms should yield a lot of interesting background- I know there is a lot of relevant maternal on crane barge stability here.
And there will be responses from people far better equipped to answer your enquiry than me soon. In the meantime, here is a thread about a crane barge accident with which you are probably familiar. There is extraordinary footage of the actual event, and a few pages into the thread, I linked a video about the Mammoet active water ballasting barges, which are impressive.

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### HeimfriedSenior Member

I doubt that such a source exists because the beginners in naval architecture will start with the hydrostatics of a ship (or floating body). And when they have to calculate cranes there is no more need of the basics. May be I'm wrong.

But hydrostatics is quite simple if you understand the basic ideas of it and if your given barge has a hull with simple geometry it is easy to calculate.
If you are dealing with basics yet, this may help:
Ship Stability - Introduction to Hydrostatics and Stability of Surface Ships https://www.marineinsight.com/naval-architecture/ship-stability-introduction-hydrostatics-stability-surface-ships/

To get a graphic idea of what happens, if a boat takes up a load, this may help:
Berechnung der Schwimmlage von Booten http://www.bootsphysik.de/index.php
(top right is the button "English", the buttons "i" are leading to information, some hydrostatic values are also provided, after changing load, use "find equilibrium")

Last edited: Jan 3, 2019
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### jehardimanSenior Member

First of all, while putting a land based crane on a barge is fairly common, it is really one of the most dangerous things you can do. There are several reasons for this
1) Most land based cranes are not designed for side or leading loads. Boom failure or house kingpin failure can occur. This is important to remember because the changes in list and trim during load movement is exactly the same as giving the boom a side or leading load.
2) Land based mobile cranes are designed for vertical static support only. Because the crane is just sitting the barge structure this leads to two separate issues. First, the outrigger/tread toe point loads can exceed the lifted load by a factor of 5 or more, resulting in deck punch through of deck beam failure (We once actually measured the outrigger load of a 90 ton P&H mobile lattice boom crane to determine if we could use it on a pier. For all maximum loads at reach, the crane was effectively balanced on one outrigger; i.e. the weight of the entire crane, counterweight, and load was on one 2ft x 2ft pad). Second, if the crane is somehow restrained, the crane frame will be loaded in a condition it was not designed for.
3) Again, land based mobile cranes are designed for vertical static support only. The coefficient of friction of the tracks/out riggers with the steel deck is considerably less than the expected shore based one.

Though I haven't seen an accident study of the aforementioned barge/crane accident at the Juliana Bridge in the town of Alphen aan den Rijn, the video shows that all three of the above happened.

As for the stability calculation, it is straight forward for the barge and the crane. What you need to remember is that the load, below the hook rigging, the hook, and any paid out hoist wire is applied as a weight centered on the top sheave. This significantly raises the apparent CG of the crane/barge combo, especially when boomed up; i.e. you can be stable when boomed down, but bringing the boom up will cause a capsize. Once you have assure yourself of adequate stability throughout the lift, you can then go back and calculate boom side load, friction, etc.

Also, FWIW, you are doing yourself a disservice to think of concepts as specific symbols. When you start poking around in the old dusty dark spots of engineering to find a road not taken 100 years ago, you will find a lot of inconsistency in nomenclature.

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As already noted above, it is just a simple methodical process.
Firstly you need to obtain a set of hydrostatics for the barge at the given loaded displacement. Since it is a box, this should be easy enough to calculate.

From the loading conditions of the barge, you the have a location (lever) of the weight being lifted from the details of the crane position relative to the barge and then use a series of assumed weights (for lift), this is the crane lift moment. In the case of your barge, depending upon the location of the crane along the length of the barge, this will be a trim and/or list. This "moment" can then be simply laid over, as a straight line (assumed - but in reality it is not) onto the GZ curve for the barge - which you have obtained from your hydrostatics. The results being a series of curves laid over the GZ curve. Like this:

Then you can calculate/ascertain the values of the roll/trim angles and the residual stability under the curve created by the crane lift moment versus established codes of compliance.

Not overly difficult, just time consuming - good luck.

Last edited: Jan 1, 2019
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### Squidly-DiddlySenior Member

I'd start with FREE Student Edition of Autodesk Inventor, and make a simple crane and do motion simulations, particularly when the load is swung out.

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### DolfimanSenior Member

Here is a memoire about a crane barge project by a student, inc. a chapter 6 on stability, the various angles and areas under the stability curve to check, the wind to take into account, .....by hoping this can be helpful :
https://dumas.ccsd.cnrs.fr/dumas-01291445/document

TANSL likes this.
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### CDBarrySenior Member

What is the criteria for safe load?

For example, 46 CFR Subchapter S has criteria for lifting vessels toward the end of the Subchapter that might be applicable.

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### JeffVDMJunior Member

Thank your for this very helpful and clear source! The info is very helpful. Unfortunately like many, the stability calculations are done via software.

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### TANSLSenior Member

If you wish, send me more information about your crane and what you need, through a PM. I will do the calculations and I will explain what is done, how and why.

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### JeffVDMJunior Member

Hi TANSL,
Thanks a lot! I don't seem to find the feature on the site to PM you. How can I PM you?
Kind regards, Jeff

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### JeffVDMJunior Member

Thanks for this info! Can you also point us to a source which describes these 3 problems?

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### jehardimanSenior Member

1926.1437 - Floating cranes/derricks and land cranes/derricks on barges. | Occupational Safety and Health Administration https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.1437

I would expect that there is an EU standard also. Pay particular attention to the following paragraphs.

and

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dear Jeff,