John, for the life of me I cannot find the thread where you gave me some ideas about the width of a-frame braces beneath the bridge. You had a formula for the amount of loss in structural integrity per unit of spread of the a-frame.
I'm not putting that question well, but maybe you can read my mind? And refresh me on the subject? The reason being that I'll be working with a somewhat longer bridge, and would like to spread the a-frame out longer than the plans I have.
Thanks!
Question for John Parchem
-
Dave Bagwill
- Posts: 5951
- Joined: Tue Dec 13, 2011 7:44 pm
Question for John Parchem
-Under permanent construction
-
John Parchem
- Posts: 2749
- Joined: Fri Dec 23, 2011 8:33 pm
- Location: Seattle
- Contact:
Re: Question for John Parchem
From me? Sounds sort of technical,deadedith wrote:John, for the life of me I cannot find the thread where you gave me some ideas about the width of a-frame braces beneath the bridge. You had a formula for the amount of loss in structural integrity per unit of spread of the a-frame.
I'm not putting that question well, but maybe you can read my mind? And refresh me on the subject? The reason being that I'll be working with a somewhat longer bridge, and would like to spread the a-frame out longer than the plans I have.
Thanks!
I would ignore all of that and just make the brace a bit taller as the braces stiffness increases proportional to the cube of its height. So a little height a lot of stiffness.
If you really want it. ...
If I remember my physics Force falls off COS(angle). If you think about a brace that is straight into the load angle of 0 Cos(0) = 1 so full strength. If you had a brace 90 degrees to the load COS(90) = 0 (no support). The in between follows a sign wave. I am not 100% certain that braces follows this equations I am basically pulling it from my behind. The reason I think this is correct is that as you rotate the brace it is providing bracing strength in the cross dimension. These type of things usually follow a sign wave. You can just type in COS(angle) in bing or google to perform the calculation.
If you want to see the relative effect of the change you want to make from the center line measure the angle of the brace on the original plan
and calculate COS(angle) save that result. Measure the new angle and calculate COS(New angle) Subtract the new value from the old and divide that value by the old and multiple by 100 and use will have the percentage of strength with your new angle.
-
Dave Bagwill
- Posts: 5951
- Joined: Tue Dec 13, 2011 7:44 pm