revolutio
Structural
- Nov 17, 2016
- 2
Long time lurker, first time poster.
I'm writing an algorithm at the moment to calculate the shear forces on bolts for monopole bases under a combination of pure shear and torsion. For a circular bolt pattern the equations are straightforward, but because the bolt pattern can also be square, I need a method that can handle both. There's plenty of reference material online (the attached, for example), however they only seem to handle a case of torsion in a bolt group by simplifying to M = Pe.
Imagine you have a 10 m steel utility pole with a square base plate with 8 bolts in a symmetric square pattern. At the top we have an element introducing eccentric loading at the top due to wind, leading to a combination of direct shear at the base (let's call it V) and torsion in the shaft (T) which is then resisted by the bolts in shear. With reference to the attached document, Px and Py are the components of the overall moment, M = Pe. But in the case of the utility pole, there is also V (which can be further broken down into Vx and Vy).
My statics is rusty, though what I expect is the bolt in one corner will have a higher net shear higher than the rest (as the direct shear and torsion acting together), and on the opposite corner, the bolt should have the lowest net shear (as the torsion will be acting against the direct shear). With that in mind, I was hoping you might be able to provide some clarification on which of the following is the correct modification of the the formulas in the reference document to account for this?
1. Px = Vx and Py = Vy
2. Px = Vx + T/e and Py = Vy + T/e
3. Something completely different...
I'm aware there's another method using the instantaneous centre of the bolt group, but I'd like to make sure I've grappled with this one first.
I've been stuck on this for a few hours, so any tips would be appreciated...
I'm writing an algorithm at the moment to calculate the shear forces on bolts for monopole bases under a combination of pure shear and torsion. For a circular bolt pattern the equations are straightforward, but because the bolt pattern can also be square, I need a method that can handle both. There's plenty of reference material online (the attached, for example), however they only seem to handle a case of torsion in a bolt group by simplifying to M = Pe.
Imagine you have a 10 m steel utility pole with a square base plate with 8 bolts in a symmetric square pattern. At the top we have an element introducing eccentric loading at the top due to wind, leading to a combination of direct shear at the base (let's call it V) and torsion in the shaft (T) which is then resisted by the bolts in shear. With reference to the attached document, Px and Py are the components of the overall moment, M = Pe. But in the case of the utility pole, there is also V (which can be further broken down into Vx and Vy).
My statics is rusty, though what I expect is the bolt in one corner will have a higher net shear higher than the rest (as the direct shear and torsion acting together), and on the opposite corner, the bolt should have the lowest net shear (as the torsion will be acting against the direct shear). With that in mind, I was hoping you might be able to provide some clarification on which of the following is the correct modification of the the formulas in the reference document to account for this?
1. Px = Vx and Py = Vy
2. Px = Vx + T/e and Py = Vy + T/e
3. Something completely different...
I'm aware there's another method using the instantaneous centre of the bolt group, but I'd like to make sure I've grappled with this one first.
I've been stuck on this for a few hours, so any tips would be appreciated...
