C-Beam durability - strength - capacity

C-Beam durability - strength - capacity - bearing load

Could you tell me if I could hang 400kg in the centre of C beam. It will be supported on both of its ends. The width of the beam - 80 mm, the overall length 3 metres.

I am gonna use it for engine lifting...

thank you.

How thick is the metal?

6 mm

It will depend a bit on the orientation of the C section, and how it is held at either end.

so... I just need an answer guys, if you know how to calculate it just do it for the vertical and horizontal position, by the way it is gonna be placed horizontally.

As for the mounting it is going to lie on the other C sections bolted to the wall.

What is the depth (height) of your beam? For a deflection and stress calculation we need to calculate the central moment of inertia (I), from the beam dimensions, then calculate deflection, based on load, span and how it is held up. I assume from the above that it is just resting on another beam, so we can assume that it is simply supported.
Once you know your load, I and span, and assuming you lift from the center of the beam, the deflection will be :-

deflection = (load x length^3)/(48 x E x I)

where E is the elastic modulus for steel (assuming its a steel beam) aprox = 210 E9 (210 GPa)

Max stress in the beam will be roughly = MY/I, where
M = half the span x engine weight x 9.81
Y = half the height of the beam

as long as the stress is below about 200 000 000 N, then you should be ok.

This figure is very conservative, as I don't know what material spec you are using.

Or..... let me know the beam height, width, material thickness, span and engine weight, and I'll let you know.

Phil

I would say no from that info given. I take it the 80mm is the vertical height if the beam is laying like this>> [

I'd be looking at a bit around 6"x3" for that.

Did a bit of FEA at lunchtime.......

assumed 80 wide by 120 high, simply supported, weight centrally slung on a 25mm sling.

Displacement (image 1) is about 18mm at the flange edge. Expect the whole beam/engine to drop by about 10-12mm.

Max stress (Von Mesis, image 2) is at the upper flange edge where the strap goes over the edge. Approx 260 MPa, so rather high for this application. I'd expect to see some permanent bending to the upper flange edge.

Phil

Would you use the C beam that way? I would have used it more like a n beam or poss a U beam but gone for a larger side wall length. Not sure if that would be stronger or not just looks better. Failing that get a I joist.


justme

n beam would have less localised deflection and stress, but the overall drop would be greater, assuming the same dimensions as above. I beam or box section would be the ideal choice.

Could always stitch weld 2 [ sections. ][ would improve things, but [] would be better for the straps not going over the edge.

Phil

i assume with n beam the danger is the sides bow out (or in) creating a flat sheet & it all buckles. Welding in a few braces to stop this would increase load capacity & deflection I guess.

Justme

yep, that would be the failure mode.

thank you for your input, a lot of professional help here, I did still something different, bought a double T beam, cut it in half, welded together. It is 7 mm now and the center part is 1 cm thick. It will be OK

Chanel is its strongest in that position.

You could spread the load nearer the ends by using 2 strops, dropping down into a single for lifting, spaced further apart.

storm monkey said:

Did a bit of FEA at lunchtime.......

assumed 80 wide by 120 high, simply supported, weight centrally slung on a 25mm sling.

Displacement (image 1) is about 18mm at the flange edge. Expect the whole beam/engine to drop by about 10-12mm.

Max stress (Von Mesis, image 2) is at the upper flange edge where the strap goes over the edge. Approx 260 MPa, so rather high for this application. I'd expect to see some permanent bending to the upper flange edge.

Phil

Click to expand...

Thats very fancy Phil. We have an old boy we ring and he either says yup, or shakes his head and says no the beam will bend. I'd like to think he has something like what you have here. Neat.

To be honest, FEA is a little overkill for this job, but I couldn't be bothered to work out the central moment of inertia for a C-beam. Simple hand calcs are fine for most application, and would have been fine for an I beam, with less localised deflection due to the lift strap. FEA comes into its own with complex shapes and multiple load paths.

The above took about 8 mins to complete, and was done in Pro/E and Mechanica. My "proper" work, designing and analysing a new front loader arm for a backhoe laoder, has invilved models that take over a week to make work properly, with multiple moving parts and various load cases. A little more complex, and way beyond hand calcs.

Phil