How to calculate tension force for scattered bolt on plane

[enotyphoon]

Please find the attached (http://s23.postimg.org/ropds44ob/Capture.jpg). I know how to get the shear force for each bolt using bolt analysis. But I don't know how to get the tension/compression force of the bolt when it position is not symmetric.

*I already download some excel from internet, but not sure how of how the formula for tension is obtained.(http://s18.postimg.org/nsovgux55/Capture.jpg). searching for original formula before it got as above formula.

Edit: Yb in the second pics is Zb

 

[PhanthomJay]

Tension or compression in bolts would be the same as the symmetric case for the loading shown, but with some small torsional shear stresses. See the following link for more detail:
https://www.physicsforums.com/threads/bolted-connection-loads.806484/#post-5065853

 

[enotyphoon]

Tension or compression in bolts would be the same as the symmetric case for the loading shown, but with some small torsional shear stresses. See the following link for more detail:
https://www.physicsforums.com/threads/bolted-connection-loads.806484/#post-5065853

However, from excel result that I have downloaded from engineering edge showed that the value of tension is varying when I change the bolt in z-direction (force(P) applied above plane(distance=y) with direction along x-axis, hence creating Mz=Py). If I'm applying the basic formula same as shown in thread you gave, supposedly tension/compression developed due to moment in z-axis is same although I change the bolt in z-direction.

 

[JBA]

The last post in the above referenced thread states: "Great. I think I got the forces down, just divide the forces by the total bolt area, which is total tensile stress area for the tensile x load and shear stress area for the shear y and z loads.". Alternatively, be sure to use the bolts' thread minor diameter when calculating the area for the the tensile stress on the tension bolts.

 

[PhanthomJay]

The moment Mz is 80 and the outer bolts have tension or compression loads of 80/4(2) = 10 N. No load on center bolts.

 

[enotyphoon]

The answer is 10 when using the formula given. However this excel spreadsheet shows otherwise, the value is 10 only if I put the bolt symmetrical (the 1st column bolt).
If I deviate the bolt as figure above (which is not symmetrical in the first row). The value become 9.10. Here I attached link to excel of bolt group.

http://s000.tinyupload.com/?file_id=09997040759162842171

you can see the formula for axial load at cell S5. So right now I'm confuse which one to follow, But if there is conservative method, please do tell.

*the axis shown is using y-x coordinate. the z axis from the original pics is y-axis in this excel.
this excel is downloaded from http://www.calculatoredge.com/structural/boltgrp.htm

 

[PhanthomJay]

My analysis assumed a rigid base plate such that all bolts an equal distance from the neutral z axis share the same loads under Mz bending moments. I am unsure how that excel calc works, but it indicates less than 10 N load on some bolts and more than 10 N load on others, and non-zero middle bolt loads, implying to me that calcs are based on principal axes rather than the centroidal neutral axes. It's been 50 years since I last fooled with principal axes. I use a factor of safety instead.