impact loads - navigation piles

huangyhg

impact loads - navigation piles
hi i’m designing some navigation piles (free ended, single laterally loaded piles) to protect a water inlet structure for a water treatment works.  the inlet is constructed on the river thames (uk). the design impact load from a vessel on the river is 100 tonnes at 2.5 meters/second. however i’m not quite sure to convert that force into kn.  any ideas please!

100 tonnes = 100000kg = 1000kn
momentum = p=mv  mass = 1000kn * 2.5 = 2500kn
hope this helps!

i would look at this in terms of energy, not momentum. equate the kinetic energy of the vessel to the energy absorbed by deformation of the piles. 0.5mv^2 = kd.
coming up with the spring stiffnes of your piles will require geotech input. if the soil strata are uniform it becomes a fairly straight forward problem. it may be worth looking at ductility of the system as well, depending on frewuency of occurence and the replacement cost of the piles versus the cost of piles large and deep enough to survive the impact.
also, 100 tonnes only equals ~1000kn when accelerated due to gravity. the acceleration due to a vessel hitting a pile will be at a much different rate.

the vessel is not accelerating, it's travelling at a constant velocity of 2.5m/sec, that's why i used the momentum equation.
the guy was asking to convert the force into kn.

also the acceleration due to hitting the pile would be 2.5m/s to 0, if we assume the pile does not move.
your equation des not seem to make any sense to me.
cheers
greg locock
not sure which equation your refering to, however both momentum and kinetic energy equations are correct.
to get the ke equation you simply intergate the momentum equ.
sorry, what i meant was that your arithmetic is correct, you are missapplying the equations.
cheers
greg locock
oh you mean when i wrote mass = 1000kn * 2.5 = 2500kn ?
yeah it didn't come out right! i meaning to write mass = 1000kn and v = 2.5m/sec, then apply the momentum equ.
sorry for poor description.

that is still a most unlikely solution to this problem. perhaps a search for impact loads might reveal the many threads on closely related subjects.
trust me, the complexities are immense.
cheers
greg locock
not sure why momentum is unlikely, sure you can go into the heavies of physics but as engineers we want the easiest solution.
you can calculate ke, deflection, stresses etc but i think the guy wanted to know how to convert one unit into another.