Guides for bolt diameter and length against plate thickness?

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Discussion Overview

The discussion revolves around the design regulations and guidelines for selecting bolt diameter and length in relation to the thickness of connected plates, particularly in structural applications. Participants seek clarity on whether specific standards exist and share insights based on their experiences and knowledge.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant inquires about design regulations or codes that specify relationships between bolt diameter/length and plate thickness, noting difficulty in finding relevant information in Eurocodes 3.
  • Another participant suggests that any plates can be connected with any size bolts, emphasizing that the critical factor is the load that the plates and bolts must support, rather than the sizes themselves.
  • A participant mentions a British/EU Standard for bolted connections that could be useful, providing a link to a resource.
  • One participant shares a rule of thumb from a friend, recommending that the bolt diameter should be approximately equal to the plate thickness, citing an example of connecting 12 mm plates with M12 bolts.
  • Another participant describes a specific case involving two steel beams with different flange thicknesses and seeks advice on the appropriate bolt diameter for this connection, mentioning the load conditions on the cantilever beam.
  • A participant points out that there are regulations regarding the maximum hole diameter that can be drilled in the HEB140 beam before it loses structural integrity, suggesting that this diameter could inform the choice of bolt size.
  • Reference is made to "The Mechanical and Metal Trades Handbook," which provides information on maximum hole diameters for specific beam types, suggesting that an M20 bolt might be suitable for the discussed application.

Areas of Agreement / Disagreement

Participants express a range of views on the relationship between bolt sizes and plate thicknesses, with some suggesting rules of thumb while others emphasize the importance of load considerations. No consensus is reached on specific regulations or best practices, and multiple competing views remain.

Contextual Notes

Participants note that the discussion is influenced by the specific structural requirements and regulations that may vary by region or application. There is mention of potential limitations in the information available regarding Eurocodes and other standards.

Raf76
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Hi,
I tried to find design regulations/codes that specify relations between bolt diameter/bolt length against connected plate thicknesses. I couldn't find that in Eurocodes 3. Can someone help me with info where to find those regulations ?

Example: can we connect 5 mm plates using M24 ? or vise versa, i.e. connect 32 mm plates with M8 ?
what about bolt length ?,
is there any helpful regulations to go through ?
Thanks in advance.
 
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Hello Raf76, Welcome to PF.

You can connect any plates with any size bolts, because you did not specify a load that tries to push, split or tear the two plates apart.
As far as I know there are no regulations on sizes, but on the loads that need to be supported by said plates and bolts.
A diagram of your intended setup and some sizes could be useful.
 
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Raf76 said:
Hi,
I tried to find design regulations/codes that specify relations between bolt diameter/bolt length against connected plate thicknesses. I couldn't find that in Eurocodes 3. Can someone help me with info where to find those regulations ?

Example: can we connect 5 mm plates using M24 ? or vise versa, i.e. connect 32 mm plates with M8 ?
what about bolt length ?,
is there any helpful regulations to go through ?
Thanks in advance.
Hello, Raf. There is a British/EU Standard for bolted connections in structural design which might be useful:
http://www.steelconstruction.info/The_Green_Books
 
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Lok,
Thank you for your reply.
I have reached the same answer you proposed after many hours of searching. But one of my friends has advised as a rule of thumb, he said, to use the same plate thickness as bolt diameter or something nearby. As example to connect 12 mm plates with M12. It could be logical!.
By precise case is that I wanted to connect two steel beams together using bolts. Big beam which is a part of platform HEB700 with flange thickness of 32 mm and the small beam is HEB140 with flange thickness of 12 mm. This small one is a cantilever (i.e. connected only to HEB700) and carrying some 0.5 KN on three directions at the free end of it.
The question here was the choice of the bolt diameter. Regards.
 
Thanks tech99
 
Raf76 said:
Lok,
Thank you for your reply.
I have reached the same answer you proposed after many hours of searching. But one of my friends has advised as a rule of thumb, he said, to use the same plate thickness as bolt diameter or something nearby. As example to connect 12 mm plates with M12. It could be logical!.
By precise case is that I wanted to connect two steel beams together using bolts. Big beam which is a part of platform HEB700 with flange thickness of 32 mm and the small beam is HEB140 with flange thickness of 12 mm. This small one is a cantilever (i.e. connected only to HEB700) and carrying some 0.5 KN on three directions at the free end of it.
The question here was the choice of the bolt diameter. Regards.
In this case there are regulations. Mostly there is a maximal accepted hole that you can drill in the HEB140 before it loses it's structural properties. Why not make that your bolt diameter? As the biggest is clearly the best.
The Mechanical and Metal Trades Handbook (aka "the BIBLE" for all but the meaning of life) tells us of a maximal hole diameter of 21mm (For an IPB140 as designated in the "DIN 1025-2 (1995-11)". So a M20 sounds nice. And the other HEB 700 will not care.
 
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Lok said:
In this case there are regulations. Mostly there is a maximal accepted hole that you can drill in the HEB140 before it loses it's structural properties. Why not make that your bolt diameter? As the biggest is clearly the best.
The Mechanical and Metal Trades Handbook (aka "the BIBLE" for all but the meaning of life) tells us of a maximal hole diameter of 21mm (For an IPB140 as designated in the "DIN 1025-2 (1995-11)". So a M20 sounds nice. And the other HEB 700 will not care.
Thanks for your reply.
I have checked and will use your advice. :)
Kind regards.
 

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