Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
(OP)
I'm an engineer and we are installing a piece of equipment we recently purchased. It has some pretty large moment loads and I want to find the tension on the anchor bolts. But don't have a lot of experience in this type of application I'm more of automotive engineer than a structural guy. I found an example problem online that is very similar but don't know how to actually solve for the the 4 bolts tension. Here is what the example is. a Base plate has a moment of 10 kips at 12" off center and the base plate is 12" long the bolts are 2" and 10" from the from the pivot edge of the plate and there are 4 bolts. If you relate that into an equation you have 120In-Kips=(xkips*2inches*2bolts)+(ykips*10"*2bolts). They showed a diagram giving the tension per bolt as 5.77 kips on the bolts 10" away and 1.15 kips on the bolts 2" away so I already had the answers for my "x" and "y". But They said under the diagram a simple calculation can be performed to find these tensions - then didn't show the math. Can anyone please show me how they solved for these tensions?






RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Check the AISC site. It has some base plate manuals that you can download - possibly #1 - I don't remember.
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Can you provide a sketch or give us the link to the example your looking at.
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
The second equation or relationship you need to solve for ‘x’ and ‘y’ is based on their assumption that the base is very stiff. Thus, it rotates about the front edge as a rigid body, so the elongation of the bolts, or the load each takes, will be in a ratio of 2 for the front bolts and 10 for the back bolts, or 1:5. In other words y = 5x, should be plugged into your moment equation to solve for ‘x’. As others have mentioned there can be more to this base plate problem than the simplified approach above, depending on the stiffness/rigidity of the machine base or foot. Dig out your old Engineering Mechanics and Strength of Materials text books, so should have a basic understanding of what you are doing on this kind of problem, before you do it.
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
I have attached a solution for you.
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Your welcome!
desertfox
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Finding Bolt Tension on a machines base plate when the machine is eccentrically loaded