Lateral Motion of A Frame

[mrcasper]

Guys,

I have an A Frame that is moving laterally, I need some advice on how to limit lateral motion its experiencing when out to see.

I'm attaching some drawings here and some pictures.

Any advice?

Thank You

 

[paddingtongreen]

You didn't get a structural engineer to design this, DID YOU? this structure was doomed to sway from inception.

You don't give limits, can you cross brace between the verticals, that would be easiest and most effective, it could improve the design parameters for the verticals as well but the calculation should be performed by someone who knows what she is doing. To make it a rigid frame would increase the demand for an experienced structural engineer.



Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[ishvaaag]

If you want the device go rigid with the ship, the support itself needs be rigid enough first, and then the device. If it is slender as it seems, the different modes of vibration can show at specific exciting frequencies either from machinery or sailing/wave action, and displacements become more noticeable. A proper analysis may require to analyze beyond the base itself. The general recommendation is to make everything stiffer and firmly attached to the vessel.

 

[mrcasper]

@paddington
yes, it was contracted to a design firm.
Some bracing was done but its limited by cables running between the beams.

@ishvaag
for each leg, the web is 'sandwich' between two 1" plate which goes between 1" pad eye on either side.

The Ibeam is used for a jumbo piston corer (JPC), and its experiencing both shock loads when it hits the bottom and also due to sea motion.

We're considering shortening the length of the A frame by 4', currently at 27' and also fabricating a guide for the JPC.

Still fishing for ideas/suggestions

Thank You

 

[gab1414]

I would have to agree with paddington green in that the frame should have been designed with cross bracing between the two vertical columns, however if there are space constraints associated with doing this perhaps gusset plates on the corners would provide rigid connections and provide a small amount of lateral stability.

 

[mrcasper]

We've decided to shorten the A Frame by 6' as well as add more bracing as long as it doesnt interfere with the cables running between the vertical columns

thanks everyone.

still encouraging suggestions

 

[hokie66]

First suggestion...stop calling it an "A Frame", because it definitely is not. Where's the "A"? The whole thing is unstable.

 

[mrcasper]

Good point there, that what the geotechs call it, so the jargon was created

It works well on land based trials but when u factoring the pitch of the boat and bad weather, things start to move.

We've been having some very bad weather