Impact Force at Vehicle Crash

[harrytos23]

Good Morning,

I recently joined this forum. I am wondering if anybody here can share their knowledge on what things to consider, equations to used to calculate the Impact force of a 15,000 lbs truck driving at 50 mph. I am designing a bollard that needs to deal with these force and wanted to make sure that I will be using the right impact force. Thank you everyone.

There are online calculators but I don't trust it really well as it does not provide any explanations behind it for me to check.

 

[lucky-guesser]

F = M x A

Beyond that, things get really complicated, really fast.

Others may chime in, but whatever discussion is had it will be hard to take many numbers away from it.

 

[Stick.]

This has come up a fair bit in the past. Here's a search of the forum to get you started:

Search results for query: vehicle impact bollard

www.eng-tips.com

 

[Tomfh]

The masses and velocities involved here are well beyond the range where a simple “impact force” approximation applies. Attempting to solve this by hand is futile.

This is a complex problem involving numerous dynamic effects, including the crumpling and yielding of various components like the vehicle, bollard, footing, and the surrounding soil.

For scenarios like this, you want pre-engineered security bollards that have been specifically designed and tested for high-energy impact.

 

[HTURKAK]

harrytos23,​

I will suggest you to look Eurocode 1 Part 1.7

https://www.phd.eng.br/wp-content/uploads/2015/12/en.1991.1.7.2006.pdf

 

[LittleInch]

Good Morning,

I recently joined this forum. I am wondering if anybody here can share their knowledge on what things to consider, equations to used to calculate the Impact force of a 15,000 lbs truck driving at 50 mph. I am designing a bollard that needs to deal with these force and wanted to make sure that I will be using the right impact force. Thank you everyone.

There are online calculators but I don't trust it really well as it does not provide any explanations behind it for me to check.

Like Stick says in post #3 this has been discussed many times. What you are trying to do ( if this is no movement) is not feasible without design something like a concrete block 5m x5m x 5m. A "bollard" will not stop a truck at 50 mph. These sort of things all depend on how much deformation of both the vehicle and the post(s) you allow, but a lot of this is a very short duration deformation and is very difficult to calculate.

Look at this post and down at post 13 this seems to match your issue. https://www.eng-tips.com/threads/need-to-confirm-bollard-design-for-vehicle-impact.244205/

Remeber there are three pages to that post and it seems to have a lot of very good information. Key issue is how much deformation / crash zone can you accept. 3 to 20ft seems to be a good number to use and you end up with 8" diameter posts filled with concrete 3 to 5 ft apart buried 8 to 10 ft in the ground.

 

[LittleInch]

Good Morning,

I recently joined this forum. I am wondering if anybody here can share their knowledge on what things to consider, equations to used to calculate the Impact force of a 15,000 lbs truck driving at 50 mph. I am designing a bollard that needs to deal with these force and wanted to make sure that I will be using the right impact force. Thank you everyone.

There are online calculators but I don't trust it really well as it does not provide any explanations behind it for me to check.

Like Stick says in post 3 this has been nlloked at many times.
A good one is here https://www.eng-tips.com/threads/need-to-confirm-bollard-design-for-vehicle-impact.244205/ and go to post 13 and the second pages.

All depends on how much deformation and stopping distance you can take.

An 8" steel pipe concrete filled buried 6 ft or more in the ground seems to work well with a 3 to 5 ft spacing if you've got 20 ft of space to allow the deformation

This is a bit of repeat as the first didn't load properly.

 

[GeorgeTheCivilEngineer]

Need to be clear about what you want to do.

Resist the force without damage, or resist the force but destruction of the bollard is acceptable.

Generally, specifying a pre-designed and tested system is the easiest route out.

 

[JAE]

Specifying a pre-designed and tested system is the only route I believe.

 

[BridgeSmith]

Article 13 of the AASHTO LRFD bridge design spec has some information about the impact loading on railings, but most of is calculated using a 15 degree angle of impact. You might be able to extrapolate the force of a head on collision.

For unprotected pier designs, the spec requires a 600,000 lb loading for vehicle impacts, based on full-scale testing of the force exerted by a 72,000 lb truck traveling 50 mph and impacting a bridge pier, where the pier has to survive. You could scale that down to your truck, if your 'bollard' has to be intact after the collision.

Where the 'bollard' can be destroyed, things get more complicated, because the force is a function of the deceleration distance for the center of mass, which involves the deformation of the vehicle, as well as the deformation of the barrier.

Consider also, if this is adjacent to a public roadway, there are standards and regulations in place to minimize hazards to the occupants of vehicles, that may not allow you to erect something that's strong enough to withstand the force you want it to, because it would be too dangerous to the occupants of smaller vehicles, if they were to hit it. Inside the clear recovery zone for any public roadway, the rules regarding objects that could be a hazard are very strict.