You have extremely high forces anyway you look at this thing. I don't know the answer but it probably involves an energy equation. You have a bunch of kinetic energy in the system that has to be absorbed by yielding of the steel in the truck and the structure. Sounds like a very difficult problem.
the key will be your requirement to "resist" the impact. what does this mean in reality? Be so solid that it doesn't bend or actually be a protective barrier - but able to deform - to the thing behind it that really matters? You'll get a different answer depending on which of those it is?
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
The best method is crash testing, the second best method is non-linear dynamic finite element analysis, but for that to be worth anything it has to be modeled correctly, of course.
Other than those two onerous methods what will get get you in the game quickly is setting kinetic energy equal to work and solving for the force. But, to do that you have to know or decide over what distance it needs to be stopped, and the barrier has to have enough give and resistance to hold up over that distance. Once that's decided it's easy:
That is, set .5mv^ = Fd and solve for F. And watch your units, particularly if you're using the imperial system (i.e. divide pounds force by 32.2 ft/sec^2 to convert it into mass).
And as Excel noted, be prepared to see some large forces. Good luck.
Check out the Texas Transportation Institutue Research Report TTI-2-5-78-230-2. It can be downloaded on-line. It's rather dated but the theory and equations are still appropriate. I used it for the design of push walls inside a waste transfer station where front end loaders are used to load dumped waste for separation and handling for further processing or transport to a landfill. I developed a spreadsheet from the design examples in the report. The impact loading calculated is in the form of "g" forces. See if it helps.
to all,
thank you all for this super-speedy response
to IRstuff,
for this current job , I am designing a steel-sliding gate 9.00meter opening , and 1.50 or 2.00meter height approx.
its for an oil-terminal, and the oil company required high safety issues against terrorist attacks, one issue is designing this gate.
the gate is to provide zero penetration and I think to still remain functionable afterward.
I don't know whether I should consider the impact as frontal or at corner.
the owner wants the gate as in the attached in file, the one in the photo is 6.00 meter the one required is 9.00 meters
Ok, now we have some idea. Basically all the energy/deceleration is taken by the truck. At 80km/hr, (22 m/sec), assuming you crush the first 2m of the truck, thats about 220 m/s/s. F = M x A. = 1,650 kN. So about 85 tonnes force on each pillar - sounds about right. One hell of a big thick pipe. Add double for good luck.
Might be a bit difficult to open the gate after though.... A 7 1/2 tonne truck at 50mph is going to take some stopping.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Maybe I've got it wrong being so simplistic, but here goes:
Truck is travelling at 22m/sec. Truck stops in 2.2m (crumple zone/ destroyed cab - see the photo!) Therefore it takes about 0.1 sec. Therefore deceleration rate assuming constant deceleration is vel/time = 220m/sec/sec
Numbers seem to work out about right to me.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Thinking about this a bit more, you really want to make an entrance such that you can't get to that sort of velocity, i.e. a chicane or make the entrance such that you can't have a few hundred metres to accelerate to that sort of speed....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Tlycan:
Just some food for thought, no instant or profound solutions....
The variables needed to solve this problem are pretty tough to really put your finger on, so there may be a hundred numerical answers, non of them all right or wrong. The stopping or restraint devices designed for highways and the like have a large design component involved with stopping the vehicle without killing the occupants. That is absorbing a lot of energy, over some reasonably distance and period of time, so as to reduce high instantaneous impact forces. But, these aren’t your objectives, you want to stop the vehicle and don’t care about the damage to it or its driver. Notice in the picture you show, there is a good deal of cab damage above the elevation of the motor. You want to crumple a whole bunch of steel and sheet metal on the truck to absorb the energy, plus some on your gate. Start bustin up metal above and below the mass of the engine as quickly as possible, and then start stopping that concentrated mass too.
I think that having the gate be operational after the impact, may not be impossible, but is a pretty unreasonable design requirement. You can’t stop the gate from deforming and if so how can you pull it back into its slot, and will it operate properly after that. Why not work on a design which is fairly easily removable with available maintenance equipment, like fork lifts, front end loaders or a small truck crane. Use readily available components, like off-the-shelf WF beam shapes to span the 9m opening, so things can be replaced quickly, but not immediately. Heck, you’re going to spend a day gettin that busted up truck out of there. As your picture shows, two large conc. abutments and wing walls to take the impact. The gate slides through the one and locks into an 18" deep slot in the other, so it can deform quite a bit without disengaging. A track on the ground, may actually be a piece of RR rail, and chain drive pulling the gate either direction. This track system might be set in a 3'x5' deep reinforced conc. sill 9m long. In this sill you might also have some conc. filled pipes which could be pulled or pushed up 24-30" cantilevering out of sleeves in the conc. sill block, to start grabbing axles and underframe parts and bot. of the motor. Most of this stuff can be picked out in pieces and replaced, but straightening a bent gate may be quite a different matter.
What if this truck carries explosives that detonate at the gate, making room for the second truck to go through. Then the design is for blast resistance.
Truck is travelling at 22m/sec. Truck stops in 2.2m (crumple zone/ destroyed cab - see the photo!) Therefore it takes about 0.1 sec. Therefore deceleration rate assuming constant deceleration is vel/time = 220m/sec/sec
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