Prying loads on bolts. 1

[jaggmi]

We have a piece of equipment with steel side frames of a given distance from each other; 1.25 thk plates parallel to each other with cross bars. We need to mount this on top of a similar piece of equipment with a side frame to side frame distance a few inches wider or narrower than ours. A solution we have tried is to bolt an adaptor plate to the top of each side frame that steps inboard or outboard a few inches to provide a platform for the next piece of equipment. The best description I can give it to imagine cantilever that is very short and very wide and bolted along the wide edge. We have approached this assuming that if the moment due to the eccentric load (load at the end of the cantilever X cantilever length) is less than what is required to open the joint we are ok. Spanning the side frames with a beam is not always possible due to machine function.

jaggmi

 

[boo1]

jaggmi want is the question

 

[jaggmi]

My question above relates to 1) the practice of using bolts in a configuration where a prying load is the main load being resisted. 2) If this practice is ok is our assumption about using a pre-stress value on the bolt that keeps the joint closed is a good guide for designing such a joint?

 

[CoryPad]

1) This practice is discouraged because the eccentric loading decreases joint force resistance and increases the chance of damaging the bolt.

2) If you must use this configuration, then yes you design with the pre-stress that prevents joint opening. This topic is covered in VDI 2230, Systematic Calculation of Bolted Joints available at:

http://www.beuth.de

 

[vonlueke]

Is VDI 2230 available in English? Our librarian claimed it's available only in German, but I wonder if I should ask them to check again. Thanks.

 

[CoryPad]

VDI 2230 is available in English - I have the 1986 translation, although a new one is supposed to be published very soon.