Shock Force

Forces Shock Loads Rock types History Bibliography

  A shock force is a word used to describe the sudden force that is applied to an object that suddenly accelerates or decelerates, such as a stop.  For example, when a rock climber falls he will exert a shock force on him/herself as he falls. Determining the shock force is very useful in certain safety situations.  In order to calculate shock force, you need to know a few things.  First, you need to know your own weight.  Then you need to know how far you think you will fall (this is useful for how far apart you should place your anchors).  The length of the cord is important along with what kind of rope you are using.  If the rope is dynamic, it has a large elasticity and there will be less of a shock force because the deceleration will be slowed down.  If the rope is static, the shock force will be much greater because there is no stretch in the rope.



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Shock  Load=Load×(1+sqrt(1+(2×FD×Area×E)/(Load×Length×12))Shock Load = Load × ( 1+sqrt{( 1+ (2 × FD × Area × E )/( Load × Length × 12 ))})

Load is the weight
FD is the Falling Distance
Length is the length of the rope
E is the elasticity
Area is the Diameter of the wire rope squared * Area Factor
For this example the area factor will be 0.416

Example: 

If a rope has a diameter of .25 inches and a 150 lb person falls 36 inches of a 40 foot long rope, with an elasthow much Shock Force is applied?

Area=.52*.416Area = .5^2*.416
Area=.104Area=.104

Shock Force=150(1+sqrt(1+(2*36*0.104*11500000)/(150*40*12))
Shock Force =  5339.65 lbs

This tells how much force is being put onto the safety harness and wire lanyard.

Here is a calculator to help determine the Shock Force: http://www.myoan.net/climbart/climbforcecal.html