Strengthenning of an H-shape against torsional moment
Strengthenning of an H-shape against torsional moment
(OP)
Hi every body,
I faced a rather rare problem of an H-Beam under torsional moment togehter with bending and shearing force. The designer seemingly designed it to resist against flexure and shear, as maximum nominal shear stress in the web is 0.38Fy, very close to the maximum alloeable 0.4Fy. A relatively large amount of torque is applied to the section which is indifferntly ignored during the design process. The end conditions are fixed to column by means of end plate bolt connections, friction type. Analysis show that shear stress in the web due to torsion may exceed twice the allowable, so does the bending in the flanges due to warping torsion. I made some kind of strengthening, but have no theoretical base. I'l be glad to know about your view points. If anyone is expert in this, I can send him detailed information and drawings. Thanks a lot.
I faced a rather rare problem of an H-Beam under torsional moment togehter with bending and shearing force. The designer seemingly designed it to resist against flexure and shear, as maximum nominal shear stress in the web is 0.38Fy, very close to the maximum alloeable 0.4Fy. A relatively large amount of torque is applied to the section which is indifferntly ignored during the design process. The end conditions are fixed to column by means of end plate bolt connections, friction type. Analysis show that shear stress in the web due to torsion may exceed twice the allowable, so does the bending in the flanges due to warping torsion. I made some kind of strengthening, but have no theoretical base. I'l be glad to know about your view points. If anyone is expert in this, I can send him detailed information and drawings. Thanks a lot.





RE: Strengthenning of an H-shape against torsional moment
RE: Strengthenning of an H-shape against torsional moment
1- To fail due to excessive shearing stress, a catastrophie.
2- To form a torsional plastic hinge as a result of yielding in some sections. The structure is under vibration, as it is a screening tower for row material. This vibration may cause plastic fatigue in the yielded section after certain number of cycles and may cause fracture. As you see the risk is so high and I can't leave anything to chance. To have a figure, the shearing force is 60tones and is coupled with 7.1 ton-m torsion and about 45 ton-m of flexure. The section is HE-A600, 7m long.
RE: Strengthenning of an H-shape against torsional moment
In any case, if you are to support this load in primary torsion, of necessity you will need to conform to some code, or at least good practice. It is obvious that if the torsional strength of the supporting beam is what is in question, you may convert your supporting H in a box (with the original H within) by adding vertical plates parallel to the web, between tips of flanges. This at the proper size should solve any bending, shear torsion problem at the supporting beam level. Of course the new forces may affect to the girder supporting the bunker and the columns wehre the then new box would be fixed, themselves needing further redesign. In reality, I in this see more than anything a resizing problem, finding more difficult how to ascertain the effect of the heavy vibration you announce, that to be dealt with no doubt requires either quite precise code-speified procedures or at least empirical knowledge of when the built items start to show structural distress. This would be for me the more difficult part, and in absence of such reliable information, I would say a mere modest impact factor wouldn't satisfy to me, since the fatigue-stress concentration aspects may be very relevant. This would convert your subassemblage in the target of analysis by the specialized fatigue analysis software packages out there.
RE: Strengthenning of an H-shape against torsional moment