increasing height of a current jib crane by 11 inches 2

[Monkeyboy5067]

I have a jib crane that is currently installed on a concrete floor below is what we followed for installation, the current jib crane mounting plate is 248mm x 248mm.

We want to add 11 inches of height to the beam - how do we do this? secondly we would like to get a structural engineer to review this and provide us with a stamped drawing as we would like this to be safe and done properly.

Please let me know if anyone is interested for a reasonable fee, we are located in Vancouver BC

Fundamental for the boom:
Level, extracted, vibration-free foundation plate.
Dowels according to the technical specifications of the manufacturer
with Fischer FHB dyn. shear connector
4x FHB - A dyn M16 x 125/25
Concrete thickness min. 170 mm ®
Concrete strength class min. B25 and max. B55 DIN 1045
or min. C20/25 and max. C50/60 DIN EN 206
input torque: 4.4 kNm
Vertical force: 2,3 kN

 

[dik]

Jib cranes usually have a mounting bracket the jib 'beam' attaches to. This is usually in the top few feet of the jib crane 'column'. It's a matter of cutting the column below this point, adding your 11" with a section of similar material and dimensions and connecting the new part with a CJP weld top and bottom. Extending the crane column by 11" should have little or no effect on the connection forces.

The column should be checked for the added length as a cantilevered beam-column. Missed that.

I don't know if there are seismic implications; if there are, they should be minor.

The moment at the base of the jib crane is missing; this is often the critical loading.

It's a fairly simple project. You should be able to find a local engineer that can do the work,

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[3DDave]

"The column should be checked for the added length as a cantilevered beam-column. Missed that."

Isn't the ideal/naive condition for these that the moment is constant through the column?

I suppose there is some additional deflection in the additional 11 inches, but that doesn't seem as if it should contribute much.

If it's used for other than vertical loads - that would be worth examining.

Of course I am picturing the sort that is essential a tall post with a cylinder slipped over and some rollers to reduce friction rather than the ones that look like little cranes with variable angle arms.

 

[dik]

Other than the connection of the jib to the post... there's moment at the top and one at the base... what's to influence that in between? Not naive. Treated as a beam-column with a uniform load full length.

Other than moving the object on the jib or the load hitting the end stop they are not generally used for horizontal load... My SMath program includes these loads as well as a 10deg angle load. These would increase the moment, but likely little added effect. They should be checked.

Jib beam is checked for LTB...

Jib cranes often only have a limited horizontal angle... not 350 360. Most have a bracket at the top that the jib rotates on.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[3DDave]

I wasn't sure what you wanted to check. For small perturbations it's the very nearly the same moment before and after and whatever the design did before it should still do, pending the use of a competent means of creating the extension.

I was just saying naive as the moment changes if the beam deflects, changing the acting radius and therefore the moment, not that it's simple. For example - if the length of the column was increased to 100 feet, the naive analysis doesn't detect what will certainly be that column nodding in the breeze.

 

[dik]

The typical posts are usually between 10' and 20' long, generally less than 15'. Jib cranes can be in a fairly 'brutal' environment and a really detailed design is generally unwarranted. Often overdesigned a tad; design is not 'skimped' on to save a couple of bucks. They are not normally part of production but any downtime can cost more than any savings.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[human909]

An increase of 11 inches for your 'jib' sounds like you really are asking too much.

After using many useless products advertised to me online I finally found one that work and was happy with a 3 inch increase... So was my wife.

Um.... I'll show myself out.
[flush]

 

[dik]

Sorry... I read it was the column to be extended... a little easier task.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik