When members of an offshore structure pass through the free surface, a
n impact load results which can not be calculated by use of Morison's
equation. The force is characterized as an impulsive load which is als
o not treatable through static analyses since even though the member m
ay be very stiff, its elastic properties have a profound effect on the
resulting stress. Anew design method for computing stress in cylindri
cal members due to impact is developed based on the energy principle w
hich is shown to agree well with experiments. Subsequent to initial im
pact the next peak in the stress is shown to be primarily a function o
f the Froude number. The method is quite general and is convenient for
application in design. Copyright (C) 1996 Elsevier Science Limited