Flange Strength Calculation
Flange Strength Calculation
(OP)
Hello,
I wonder if anyone can give me some help. I am trying to determine the strength of a flange which is subject to an external bending moment. The flange is rigidly supported at the necked portion and has a bending moment applied at the flange face. In essence it is similar to a pipe flange which has being subjected to an external bending moment. I have looked into various piping textbooks and Roark's but cannot seem to find anything. If anyone could point me in the right direction this would be most appreciated.
Thanks
I wonder if anyone can give me some help. I am trying to determine the strength of a flange which is subject to an external bending moment. The flange is rigidly supported at the necked portion and has a bending moment applied at the flange face. In essence it is similar to a pipe flange which has being subjected to an external bending moment. I have looked into various piping textbooks and Roark's but cannot seem to find anything. If anyone could point me in the right direction this would be most appreciated.
Thanks






RE: Flange Strength Calculation
RE: Flange Strength Calculation
Your bending moment = PL
Consider some effective width of your flange depending on how the load is applied. If it is from a pipe clamp, I would take about 3" of flange in bending.
Your section modules Sx= bd^2/6 where b=3"(assumed tributary of flange); d= flange thickness
Your bending stress is of course M/S.
Your allowable bending stress will be 0.75*Fy. If not sure about the beam run with 36 ksi for a steel beam, and allowable bending stress of 27 ksi.
Not sure how heavy your load is, but the beam itself should also be verified for possible torsional loading and additional stresses to the bottom flange from the bending applied since you're introducing bi-axial bending. If you can, apply the load to the existing beam at the 1/3 point instead of midspan and the additional check can most likely be avoided.
RE: Flange Strength Calculation
Thanks again.
RE: Flange Strength Calculation
If you're applying a torque to the flange, then the critical section is the pipe beyond. Apply statics to your pipe section where Sx = pi (d^4-d1^4)/32d
use same principle of M/S.
RE: Flange Strength Calculation
If it is applied by a weld around the perimeter, the weld will carry a variable line load. The line load will cause variable bending moments around the flange plate which will result in variable bending stress in the plate with maximum value at 90 or 270 degrees to the applied moment vector and zero at 0 or 180 degrees to the moment vector.
If the moment is applied in some other way, the above will not be true.
BA
RE: Flange Strength Calculation
RE: Flange Strength Calculation
The bolt array is presumably a bolt circle. The number and size of bolts needs to be specified as well as the diameter of the bolt circle.
Are the flange faces tightly abutting? If so, you will have prying action which amplifies bolt tensions and makes the analysis extremely complicated.
On the compression side of the flange, bolts will not be carrying any load. Compression will be carried by bearing on the contact surfaces of the flanges.
Analysis would be tedious and difficult by hand. It could be performed using finite element methods. There may be simplified approximations as well, but I am not aware of any.
Perhaps the mechanical guys could be of more help.
BA
RE: Flange Strength Calculation
'Design of Tension Circular Flange Joints in Tubular Structures', by: Cao & Packer. [1st quarter, 1997].
The article appears to focus on flange to flange connections, but I would assume it could be adapted for other conditions. (I'm not sure if you have pipe to pipe, or pipe to concrete, or whatever.)
RE: Flange Strength Calculation
Thanks for the reference I will also have a look at this.
RE: Flange Strength Calculation
If so there is a publication for monopole structures and there base plates that may be applicable. Let me know if this is your problem and I'll see if I can find the publication.
EIT
www.HowToEngineer.com
RE: Flange Strength Calculation
http://www.towernx.com/downloads/Technical_Manual_...
BA
RE: Flange Strength Calculation
EIT
www.HowToEngineer.com
RE: Flange Strength Calculation
Bending in the flange could then be approximated by considering the maximum bolt force acting eccentrically to the fillet between flange and pipe. The resulting moment would act over a chord length equal to bolt spacing reduced by the factor Dp/Dc where Dp and Dc are pipe outside diameter and bolt circle diameter respectively.
The above would be a pretty crude but conservative way of checking the strength of flange.
BA
RE: Flange Strength Calculation
The reference I mentioned has some design aids/charts that speeds things up. (In fact they have some in the elastic range and plastic.)
RE: Flange Strength Calculation
This leads me to believe that the NRX formulations for ungrouted round base plates cannot be used unmodified or perhaps need a sensitivity study. The NRX relations for a base plate bolted to concrete likely neglect flexibility of the concrete which is like having a mating flange that is much stiffer than your flange which we have already said may be unconservative.
Somehow I think an FEA solution is the simplest approach unless you have a very specific empirical formula.
RE: Flange Strength Calculation
BA
RE: Flange Strength Calculation
Thanks for the responses guys the information is great.
RE: Flange Strength Calculation
https://www.google.ca/url?sa=t&rct=j&q=&am...
BA