Basic Forces & Bolts: Getting Started on Homework

In summary, the conversation discusses the distribution and calculation of forces on bolts and plates in a tower structure. There is confusion about the loading on the cables and the number of foundations, but there are two possible methods for finding the shear force on the bolts. Friction is not considered a reliable factor in calculations.
  • #1
el_diablo549
11
0

Homework Statement


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Homework Equations


sum of forces in x and Y = 0
sum of the moments at a point = 0
Ffr = normal force * friction coefficient

The Attempt at a Solution



Im just trying to make a start, I am struggling to wrap my head around the basics with this question. Do you guys think I have simplified my fbd too much and I am not sure how the force is distrubuted amoung the bolts and the plates and whether to include the distance between bolts in the first fbd or to add it into the calcs of each individual plate.
Not after answers just want to check I am on the right path

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  • #2
You have the correct approach, except that there are 2 foundations on the bearing side and 2 on the uplift side, so your numbers for the load on each bolt will need to be divided by 2. But the problem statement is unclear when it mentions all cables torn on one side, so you'd have to multiply the FT load by 6 to account for 6 phase conductors , I guess, and it would be slightly conservative to apply that load all at point m. Looks like Earth wires are assumed not to carry any of the unbalanced load.
 
  • #3
thanks for the reply, the question is mostly aimed at bolts and threaded fasteners So I am not too worried about the forces on the cables etc I just need to get it right for my calcs. I think what they implied by saying one side broken is either front or back that way the force would be in one direction instead of opposite.
 
  • #4
Well ok but you can't find the load on the bolts if the problem is unclear as to what loading to use for the cable tensions. If the resultant load of the cable tensions on one side is 12 kN directed as shown and applied at the center of the tower body at 25 m from the base, then your calculations for the tension in the bolts on the uplift side is off by a factor of 2 because there are 4 foundations not 2.
 
  • #5
yer I've fixed that one up thanks
 
  • #6
In the real world, at least consider the torque on the tower if cables on one end of the crossarms fail and the diagonal cables on the other end of the crossarms also fail.
 
  • #7
What about the frictional force and shear force of the bolts? two methods of thinking either the frictional resistance of the tower is 114*0.17 = 19.38 therefore to reach equilibrium the frictional resistance the combined plates create needs to equal 90.39-19.38 = 71.01kN and each bolt is 71.01/4 = 17.52

Or

friction on left side = (202-57) *0.17 = 24.65 and right side is (316.95 + 57) *0.17 = 63.57 and divide each number by 2 to find for each plate
 
  • #8
el_diablo549 said:
What about the frictional force and shear force of the bolts? two methods of thinking either the frictional resistance of the tower is 114*0.17 = 19.38 therefore to reach equilibrium the frictional resistance the combined plates create needs to equal 90.39-19.38 = 71.01kN and each bolt is 71.01/4 = 17.52

Or

friction on left side = (202-57) *0.17 = 24.65 and right side is (316.95 + 57) *0.17 = 63.57 and divide each number by 2 to find for each plate
I never count on friction, there is really none available on the uplift side anyway. I'd design the bolts to take all the shear equally.
 
1.

What are the basic forces and bolts?

The basic forces refer to the fundamental forces in physics, which include gravity, electromagnetism, strong nuclear force, and weak nuclear force. Bolts are mechanical fasteners that are used to hold two or more objects together.

2.

Why is it important to understand basic forces and bolts?

Understanding basic forces and bolts is essential for engineers and scientists to design and build structures and machines that can withstand different forces and stresses. It also helps in understanding the principles behind various natural phenomena.

3.

How do you calculate the forces acting on a bolt?

The forces acting on a bolt can be calculated using the principles of Newton's laws of motion and equations of equilibrium. The external forces and moments acting on the bolt can be balanced with the internal forces and moments within the bolt to determine its strength and stability.

4.

What are some common types of bolts used in engineering?

Some common types of bolts used in engineering include hex bolts, carriage bolts, lag bolts, and eye bolts. Each type of bolt has a specific shape and purpose, and the choice of bolt depends on the application and the forces it will be subjected to.

5.

What are some tips for getting started on homework involving basic forces and bolts?

Some tips for getting started on homework involving basic forces and bolts include reviewing the principles and equations related to forces and bolts, understanding the problem statement, and using diagrams and free-body diagrams to visualize the forces and their directions. It is also helpful to practice solving similar problems and seeking help from peers or instructors if needed.

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