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Need Help: Ground Reaction Forces of Human Jumping/Landing fromHeight

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  • Need Help: Ground Reaction Forces of Human Jumping/Landing fromHeight

    My name is Steve Fletcher and I am an Engineer for the U.S. Naval Facilities
    Engineering Command. We are doing testing of which I cannot fully disclose
    some of the details. I apologize if some of the following seems vague, but
    I will do my best to explain. A professor at Arizona State University was
    kind enough to point me to this Listserv to help solve my problem.

    We conduct a test on a type of structural flooring after it has been
    stressed in specified ways. The test is supposed to simulate a person
    jumping down onto the structure. We must ensure that the structure is
    capable of handling a 300 lb person jumping onto the surface after it has
    been stressed. There is the potential for people to be jumping from a
    maximum height of five feet (1.5m) onto the structural flooring and such is
    the height we drop the weight from. We currently use a 300 lb drop weight
    to do this. The "drop weight" is a welded steel structure that has two
    rectangular steel "feet" upon which it hits the landing surface. Under
    unstressed conditions, the structural flooring is rigid and does not visibly
    deflect upon the impact of a real human landing on it. The structural
    flooring may deflect a fraction of an inch, if at all.

    Some of my colleagues have called this method into question and are saying
    that it is not representative of a 300 lb person jumping onto this surface
    from a height of 5 feet. Being an engineer, I reviewed the physics behind
    this reaction and agree that this may be over-kill. I have done some
    research and have found limited information on this topic. Most of what I
    have found is the ground reaction forces on lighter athletes jumping from a
    height of 1'-2'. I found that the GRF of a female jumping onto a surface
    from a height of 0.47m is about 5.7 times their weight.

    My goal is to find the weight of a steel "drop weight" that generates an
    equivalent force to that of a 300 lb person landing on a rigid surface from
    a height of five feet.

    Another idea I had was to add springs to the drop weight to distribute the
    force over a length of time similar to a person's knees bending. The
    equivalent weight method is much more desirable.

    Thank you in advance for any insight you can provide.

    Steve Fletcher, E.I.T.


    Naval Facilities Engineering Command