I-Beam Bending Strength
I-Beam Bending Strength
(OP)
I am currently working with a Pillar Type Jib Crane. It appears that its cantilevered S-Beam was damaged at some point in time by a load that was applied to the end of the beam and at the bottom flange, perpendicular to the length of the beam. The beam has yielded from this torsional force and it appears the web has bent to make a radius (on one side of the web the flanges are closer together, on the other side of the web the flanges are farther apart). This deformation is tapered down the length of the beam and the fixed end of the beam has minimal deformation.
Is there a method to determine how much the bending strength of the beam about its strong axis has been reduced?
Is there a way to technically justify that this beam needs to be replaced or its use be continued?
Any help would be greatly appreciated.
Is there a method to determine how much the bending strength of the beam about its strong axis has been reduced?
Is there a way to technically justify that this beam needs to be replaced or its use be continued?
Any help would be greatly appreciated.






RE: I-Beam Bending Strength
RE: I-Beam Bending Strength
This particular Jib Beam seems to have been built with a high Factor of Safety with respect to bending among the strong axis of the beam, for which its use was intended. Replacing the Beam seems very impracticable if the bend of the beam only slightly effects its strength.
RE: I-Beam Bending Strength
RE: I-Beam Bending Strength
IFRs is right, proofloading would be the best and less controversial way to prove it still works. I can not think on any theoretical approach that would work.
Is there a way to technically justify that this beam needs to be replaced or its use be continued?
I can not think on a way to justify its use technically, replacement yes, it is out of tolerance, it defformed plastically, out!
Another thought. Have you considered heat straightening? Have you considered adding stiffeners to maintain flange distance?
If it was my crane though, proof load or replacement
RE: I-Beam Bending Strength
1. Depends on the rotation, the hoist may not be working with lift weight.
2. Torsion to both the arm (beam) and the support connection.
I wouldn't allow the operation without any corrective measures. Replace the beam seems a small price to pay.
And, yes, lifting devices are usualy designed with amber safety factors build-in, check with ASME code, as it governs the jib crane design.
RE: I-Beam Bending Strength
RE: I-Beam Bending Strength
RE: I-Beam Bending Strength
RE: I-Beam Bending Strength
Trust his judgment.
Mike McCann
MMC Engineering
RE: I-Beam Bending Strength
is this a welded section ?
RE: I-Beam Bending Strength
Maybe my description of how the deformation occurred is not completely accurate. Ignore that because we really don't care how the deformation occurred, rather if the beam is usable or not.
I believe this beam is as rolled.
RE: I-Beam Bending Strength
i suspect that some mgmt type is leaning on you to "show it good", and it probably is good ! (which the test would show). Analytically it sounds like a I-beam with one flange rotated ... something that is easy enough to analyze (re-calc I). but is the beam still straight ? what internal stresses result from the "accident" ?
RE: I-Beam Bending Strength
RE: I-Beam Bending Strength
RE: I-Beam Bending Strength