Bolt Prying Question (Underhung beam connection)

[JD P.E.]

I understand the basic prying concepts and calcs. However, I am connecting this monorail under two beams and this version of prying came to mind. Does this practically exist or does the stiffness of the monorail/web prevent meaningful prying in this manner? I figure the flange/web would "flex" on the supporting beams preventing this, but if you had stiffeners wouldn't it pry in this direction?

 

[KootK]

1) I would think that the primary source of flexibility that would tend to alleviate the prying would be the twist in the supporting beams. Wide flange beams are pretty flexy when it comes to twist

2) Pursuant to [1] I might only be concerned about this if the cross beam were installed close to the girder supports where significant torsional restraint is present. And this likely is not the case.

3) In principle you are not wrong. There will be some degree of prying for the reason that you've identified. I just don't think that it will be of the same order as the bolt prying situations that we commonly consider as a part of connection design.

 

[rb1957]

Prying is the local flange bending. You stop prying with tension fittings. There would be a small bending (moment) from the ends of the beam, partially fixed ends, but less than local prying.

 

[human909]

As the others say. The local prying dominates, probably by an good order of magnitude or two.

Consider the stiffness of the segment between the two bolts along the plane of the WEB of the monorail compared to the stiffness perpendicular to the web. The former had a depth of say 300mm, the latter has two flanges each with a depth of 16mm or similar.

I can some hand calcs on this problem exact problem and also ran it on IdeaStatica. The prying forces are very much there and should be considered. But normally for a monorail your flanges are going to be decently thick anyway for the crane wheels.