I have been designing the barrier system for V8 a race in Australia.
For the concrete barriers the calculations were pretty straight forward. We assumed that 4 - 3 barriers would act together through catenary action to resist the load. I assumed an inelastic collision between the car and the wall and determined system velocity. From there i used the weight of 4-3 walls and calculated the stopping distance of the wall due to the friction. I did the calculations for several situations and confirmed my results with the FIA standards which uses the same logic.
The problem occurred when designing the debris fences.
To calculate the load of the tire on the mesh I calculated an equivalent spring constant of the mesh, treating it as simply supported between the posts. From there I calculated how far the fence would need to deflect to take out the kinetic energy of the tire in an Inelastic Collision - (this combines the fences weight and the tires and gives a systems velocity which is resisted by its elasticity) . It came to be about 8 KN which is close to the FIA standards.
For the post I realized there is no way I can assume an inelastic collision and it would be much closer to perfectly elastic.
The question is how can I calculate my impulse loads on the posts?
Using conventional mechanics will give a ridiculous force because the deflection of such a stiff post is so small.
Say for a tire weighing 9 Kg with a velocity of 27 m/s.
Fence post will be CHS 114.3 * 3 spaced at 4 m.
Does anyone no of any standards or have experience in this area?
I have only been out of uni for 12 weeks so tread lightly lol.
For the concrete barriers the calculations were pretty straight forward. We assumed that 4 - 3 barriers would act together through catenary action to resist the load. I assumed an inelastic collision between the car and the wall and determined system velocity. From there i used the weight of 4-3 walls and calculated the stopping distance of the wall due to the friction. I did the calculations for several situations and confirmed my results with the FIA standards which uses the same logic.
The problem occurred when designing the debris fences.
To calculate the load of the tire on the mesh I calculated an equivalent spring constant of the mesh, treating it as simply supported between the posts. From there I calculated how far the fence would need to deflect to take out the kinetic energy of the tire in an Inelastic Collision - (this combines the fences weight and the tires and gives a systems velocity which is resisted by its elasticity) . It came to be about 8 KN which is close to the FIA standards.
For the post I realized there is no way I can assume an inelastic collision and it would be much closer to perfectly elastic.
The question is how can I calculate my impulse loads on the posts?
Using conventional mechanics will give a ridiculous force because the deflection of such a stiff post is so small.
Say for a tire weighing 9 Kg with a velocity of 27 m/s.
Fence post will be CHS 114.3 * 3 spaced at 4 m.
Does anyone no of any standards or have experience in this area?
I have only been out of uni for 12 weeks so tread lightly lol.
lease see FAQ731-376 for tips on how to make the best use of Eng-Tips.