# Rivet pitch determination

1. Feb 21, 2014

### ozzolins

Hi guys!

I have assignments and we are trying to get to reasonable value for more than 2 days and still nothing...

Okay..

problem is:
https://imagizer.imageshack.us/v2/705x238q90/191/6qqd.png [Broken]

picture of the plate:
https://imagizer.imageshack.us/v2/412x395q90/835/7u81.png [Broken]

F = 2500 N (orthogonal to the plane)

Thickness is 0.8 mm

E modulus = 72400 MPa

K (0.9*c) = 1.89

We got Area with value of: 553812mm^2 = 0.5538 m^2

We keep getting value of 4.4 meters, isn't that too much???

Last edited by a moderator: May 6, 2017
2. Feb 21, 2014

### SteamKing

Staff Emeritus
Given that the structure is only 1.5 meters long and 0.4 m wide, yes, a rivet spacing of 4.4 m is too much.

You should show all of your detailed calculations.

3. Feb 21, 2014

### ozzolins

Here are the calculation steps:

https://imagizer.imageshack.us/v2/585x597q90/30/0jso.png [Broken]

[I hope the step where I calculate area is straight-forward, it's just basic geometry]

E modulus was given in 72400 MPa, but it's the same as 72400 N/mm^2 right?

Last edited by a moderator: May 6, 2017
4. Feb 21, 2014

### SteamKing

Staff Emeritus
I don't understand your calculation of the area of the plate to be riveted.

I think you treat the area of plate at each end separately, which will give two different rivet pitch values.
You then select the smaller pitch value to use at both ends.

In any event, the lap width at one end is 65 mm and 110 mm at the sloped end. Remember, the rivets must resist tear out in shear, so the shear area involves the thickness of the plate being riveted, rather than the area of the overlap.

5. Feb 21, 2014

### ozzolins

Ok, I kind of gave you misleading info. I forgot to mention that in grey areas rivets cannot be placed because this box will be put into bending machine and in these places it will be clamped. Furthermore, there will be stringers inside the box and rivets will be bolted through them (so in parallel to 1500mm side). So it would be like slightly simplified version of this (this is not our design, this is just for showing concept):

https://imagizer.imageshack.us/v2/499x462q90/23/lirr.png [Broken]
Sorry, CATIA drawing is not ready yet.

We are planning to put 7-9 stringers in total and 2-3 ribs.

That is why I calculated the area of whole sheet face. But apparently area is the only value that can be wrong in my equation.

Last edited by a moderator: May 6, 2017
6. Feb 21, 2014

### SteamKing

Staff Emeritus
It's better if you can arrange your longitudinal stringers to have the same transverse spacing top an bottom. With that arrangement, you can tie the ends of the stringers together to make a longitudinal frame. Similarly, you want to make the transverse frames supporting the top and bottom plates line up and tie together with the stringers supporting the side plates. Although the skin carries its share of the shear and bending loads, you want the stringers to tie together also so that they can support the plating effectively.

It's not clear from the drawings you have so far how the end plates join with the side plates of the top and bottom plates. Although it may not be desirable to locate rivets around the ends of the box, the plates must be joined together in some fashion.

7. Feb 21, 2014

### ozzolins

Well, we have some restrictions for this project so we decided to use two ribs (in the middle) and 8 stringers - in the corners between plates and 2x2 stringers on top and bottom plates as shown in picture. Box ends will be open, so no plates there. But still question remains.. How to determine rivet pitch? Everything else seems ok. This is irritation design so we will be able to make changes afterwards if there are too many stringers, but river pitch must be calculated precisely cause we should prevent structure from inter rivet buckling at 2.5 kN.

8. Feb 21, 2014

### SteamKing

Staff Emeritus
I guess what you are saying then, you want to know what rivet spacing would be suitable for attaching the stringers to the plating.

I'm not sure what 'irritation' design is. Perhaps you mean the design can go thru several 'iterations'.

9. Feb 22, 2014

### ozzolins

Exactly, I need max possible spacing between rivets for attaching stringers to the plate.

Sorry, yeah, that was a stupid typo. :D

10. Feb 23, 2014

### ozzolins

Please, anyone? Still trying to find out where my mistake is.