Restraints of crane
Restraints of crane
(OP)
Hello!
I am new to the forum, but need some help.
I am currently working on a project where i am designing a movable container crane. The design is fairly simple and resembles a straddle carrier or mobile boat lift. I am currently working on the structural analysis and for one of the load cases i am simulating a crash. I have the energy balance and spring constant down but i am having some trouble defining the restraints of the "wheels". The case is that the crane is colliding with one leg. My proposition per now is this:
3 legs free in x,y and locked in z. 1 leg locked in x,y,z and rotation. I have a feeling this is not the best solution but as i said i am having some trouble coming up with something that works better.
I am new to the forum, but need some help.
I am currently working on a project where i am designing a movable container crane. The design is fairly simple and resembles a straddle carrier or mobile boat lift. I am currently working on the structural analysis and for one of the load cases i am simulating a crash. I have the energy balance and spring constant down but i am having some trouble defining the restraints of the "wheels". The case is that the crane is colliding with one leg. My proposition per now is this:
3 legs free in x,y and locked in z. 1 leg locked in x,y,z and rotation. I have a feeling this is not the best solution but as i said i am having some trouble coming up with something that works better.





RE: Restraints of crane
RE: Restraints of crane
I'd suggest supporting each wheel on 3 rods of some stiffness and constraining the far ends of the rods; to give the wheels finite stiffness. Then ask yourself "could some of these wheels move?".
another day in paradise, or is paradise one day closer ?
RE: Restraints of crane
RE: Restraints of crane
another day in paradise, or is paradise one day closer ?
RE: Restraints of crane
i suggest to leave that 1 leg that hits an object free to rotate in whatever direction it wants, even torsion so to say
RE: Restraints of crane
RE: Restraints of crane
another day in paradise, or is paradise one day closer ?
RE: Restraints of crane
RE: Restraints of crane
then simulate and find out xyz deflections and 3 rotations of the leg
So look at this problem as if the crane is in rest and a object hits that one leg
RE: Restraints of crane
Constraining all 4 points in z is an acceptable compromise (saying the flat base remains flat) and constrains 3 freedoms (Fz, Rx, Ry). So you need 2 x and 1 y (or 1 x and 2 y) to take out the other 3 freedoms (Fx, Fy, and Mz).
Better than hard (infinitely stiff) nodal constraints is to apply a finite stiffness at each support. My suggestion is three orthogonal rods at each support point, and hard constrain the far ends of these rods.
another day in paradise, or is paradise one day closer ?
RE: Restraints of crane
Then only add a collision force at one leg.
Then simulate and conclude what deflections and stresses that one leg will show.
Your method of adding orthogonal rods will also work by the way.
RE: Restraints of crane
another day in paradise, or is paradise one day closer ?
RE: Restraints of crane