structure strength
structure strength
(OP)
hi all,
I have a sold mild steel round bar of 40 mm diameter and 850 mm length. this bar is subjected to a load of 1500 kg at the middle. i have already tried the the bar and i know that it can take the load applied to it. however i need to show the calculation in order to get it load certified. can anyone help to put in correct direction.
I have a sold mild steel round bar of 40 mm diameter and 850 mm length. this bar is subjected to a load of 1500 kg at the middle. i have already tried the the bar and i know that it can take the load applied to it. however i need to show the calculation in order to get it load certified. can anyone help to put in correct direction.






RE: structure strength
How are the ends supported?
How was your 1.5 tonne load applied, do you have bearing along the length spreading the load?
What is your limiting deflection?
Based on the figures (assuming simple support mid span point load) above I get a bending stress of about 500MPa, which is significantly greater than the yield stress of mild steel.
RE: structure strength
RE: structure strength
Don't be suprised if they won't certify it, as Ussuri said the bending stress is very high.
RE: structure strength
OP ... are the kgs mass or force (weight) ?
RE: structure strength
RE: structure strength
RE: structure strength
RE: structure strength
the bending stress is MR/I.
I = pi/64*D^4
you should get a stress of 500 MPa, which is pretty high for nominal stell, as noted above.
the simple beam is an assumption, says there's no moment transferre at the ends (into your frame). fully fixed ends (making the beam doubly cantilevered) reduces the moment to 1/2; but now some moment is loading your frame so if they're asking you for an analysis of the beam, they're probably also going to ask for an analysis of the frame.
btw, if they're fussy, they might want to see you account for the weight of the beam.
any reason you went with a bar, rather than an I-beam ? bar was what was lying around (readily assessable) ??
RE: structure strength
are you sure that the I equation is correct? because i cant manage to get the 500 MPa value. is there any chance that you could include the calculation please. so i can try it for different bar diameter to suit the load.
RE: structure strength
I=(pi/64)*D*D*D*D
RE: structure strength
RE: structure strength
M = PL/4 = 14.7*0.85/4 = 3.123kN-m
For a 40 mm bar, Z = 10,666 mm3
If Fy = 248MPa, Mp = 2.64kN-m (no good)
If Fy = 350MPa, Mp = 3.73kN-m (won't fail, but not much Safety Factor)
Try 50mm bar...Z = 20,833 mm3
Mp = 5.17 for Fy = 248 (looks okay)
As TXStructural has said, this is pretty basic stuff. The certifying company should know how to perform the calculation. Otherwise, their certification doesn't mean much.
BA
RE: structure strength
depends on (the fixity of) the supports ...
RE: structure strength
Hadn't thought about that. You may be right.
BA
RE: structure strength
RE: structure strength
RE: structure strength
Basic SI units are Newtons and Metres.
All you need now is to show that the yield strength is over 660 MPa.
RE: structure strength
What design code are you checking against?
What is your deflection under load, and what is your deflection limit?
Shear check (although not a problem but your calcs should at least show you considered it and ruled it out)
How are you attaching it? Welded, if so what about the weld capacity? Slotted through holes, if so how thick is the material, do you have any bearing issues?
How is your load attached, are there any issues with the detailing that need checked? The simplification above uses a point load which I doubt you actually have.
Is the structure you are fixing to adequate. No point sizing your rod to take 1.5 tonnes if the thing it is attached to fails at 500kg.
In reality none of these may be an issue, but if someone submitted a set of calculations to me for verification and all they contained was bending check then I would start asking questions about the competency of the designer. The usual approach would be a single line stating that it is not critical and explain why.
RE: structure strength