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Re: Crane Runway Bracing Vibration

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Isn't it the buckling mode vibration of the angle bracing, if I understood
correctly ?

In my view, when crane starts and stops - it transmit a horizontal
acceleration or deceleration - longitudinal forces - which come as  axial
forces in the bracing.

I think horizontal strut alone would solve the problem. or you can add
vertical brace in another brace - also, you can try to soften the
acceleration at starting and stopping by restricting maximum speed ?
It would seem a serious problem to me, if not worked upon quickly - because
if there is some residual deformation in angle and it again tries to buckle
- it can really buckle.

On Fri, Jun 6, 2014 at 6:46 AM, Gary L. Hodgson and Assoc. <
design(--nospam--at)hodgsoneng.ca> wrote:

> Fellow listers,
> I have a problem that I have never run into before. I designed a free
> standing crane rwy for a 30 ton EOT crane.  The column centres are approx
> 28.5 ft, with only 5 bays and the columns are braced about the weak axis 
> by X-bracing in one bay (at centre of rwy, both sides) consisting of 
> L6x4x5/16 with the long leg horizontal, connected by a bolt where the 2 
> angles cross. When the crane starts up and starts travelling down-aisle, 
> the bracing vibrates to the annoyance of the customer and his workers. The 
> vibration is out of the plane of the X-bracing. This does not happen if 
> the crane starts elsewhere, and just passes over the braced bay.
> First, I had the existing bracing pulled tighter - did'n't work. Next,
> I added reinforcing angles i.e, boxed the angles but that did not solve 
> the problem.  My next attempt will be to add a horiz strut between the 
> columns and then connect that to the X-bracing with a short length of angle 
> to the centre of the X-bracing so it will prevent or decrease the amount 
> of out-of -plane motion.
> Can any of the members suggest another solution?
> Gary

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