Statics problem?
Statics problem?
(OP)
Hi there,
I need some help accurately calculating the compression forces in the members Cy and Cx shown in the attached image. I know how to calculate the compression in 2D triangles but not sure what to do when the object becomes 3D (includes the z axis). If it helps the cables attached to the frame are inclined at 45 degree angles to the vertex (z axis).
I calculated an estimate of the compression forces to use in my design, however I am looking to learn a more accurate calculation methodology for this current project along with all future projects.
Any help will be appreciated.
[img ]
- Psyche
I need some help accurately calculating the compression forces in the members Cy and Cx shown in the attached image. I know how to calculate the compression in 2D triangles but not sure what to do when the object becomes 3D (includes the z axis). If it helps the cables attached to the frame are inclined at 45 degree angles to the vertex (z axis).
I calculated an estimate of the compression forces to use in my design, however I am looking to learn a more accurate calculation methodology for this current project along with all future projects.
Any help will be appreciated.
[img ]

- Psyche






RE: Statics problem?
Then use methods of joints to solve the truss system. Find the force in one of the diagonals and then you can find the force in each of the horizontal members.
Results should look something like this...
RE: Statics problem?
RE: Statics problem?
@BUGGAR Thank your the advice, I actually used that method originally in the estimate calculation, I just wasn't sure if that was the correct way to go about it. However, I got very similar results to Trenno so must be correct.
RE: Statics problem?
http://files.engineering.com/getfile.aspx?folder=3...
Try this I solved a problem very similar to yours.
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: Statics problem?
RE: Statics problem?
RE: Statics problem?
The upside to this is that your problem is now only two-dimensional rather than three-dimensional
RE: Statics problem?
diagonal = sqrt(6.1^2+2.5^2) = 6.6m
height = diagonal/2 = 3.3m
length of cable = sqrt(3.05^2+1.25^2+3.3^2) = sqrt(2)*3.3 = 4.66m
vertical reaction = 215kN/4 = 53.75 kN
load in cable = 4.66/3.3*53.75 = sqrt(2)*53.75 = 76kN
load in long side = 3.05/4.66*76 = 3.05*53.75/3.3 = 49.74kN
another day in paradise, or is paradise one day closer ?
RE: Statics problem?
RE: Statics problem?
As stated above by Denial, it is possible for only two slings to be engaged (although it would likely be three to "balance" the load).
As stated by racookpe1978, you could eliminate this concern with chainfalls but at my company we refuse to use chainfalls because we consider them mechanical and prone to failure. For high risk heavy lifts, we would either size the rigging lengths, or add shackles to make up the extra lengths. It can be iterative depending on how accurate your COG was determined.
Or you could just size it so that two of the slings can take the entire load. Offshore lifts would be sized so that 75% of the entire load could be handle by one sling.
RE: Statics problem?
RE: Statics problem?
RE: Statics problem?